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McKenzie T, Ayres N. Synthesis and Applications of Elastomeric Polymerized High Internal Phase Emulsions (PolyHIPEs). ACS OMEGA 2023; 8:20178-20195. [PMID: 37323392 PMCID: PMC10268022 DOI: 10.1021/acsomega.3c01265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 05/15/2023] [Indexed: 06/17/2023]
Abstract
Polymer foams (PFs) are among the most industrially produced polymeric materials, and they are found in applications including aerospace, packaging, textiles, and biomaterials. PFs are predominantly prepared using gas-blowing techniques, but PFs can also be prepared from templating techniques such as polymerized high internal phase emulsions (polyHIPEs). PolyHIPEs have many experimental design variables which control the physical, mechanical, and chemical properties of the resulting PFs. Both rigid and elastic polyHIPEs can be prepared, but while elastomeric polyHIPEs are less commonly reported than hard polyHIPEs, elastomeric polyHIPEs are instrumental in the realization of new materials in applications including flexible separation membranes, energy storage in soft robotics, and 3D-printed soft tissue engineering scaffolds. Furthermore, there are few limitations to the types of polymers and polymerization methods that have been used to prepare elastic polyHIPEs due to the wide range of polymerization conditions that are compatible with the polyHIPE method. In this review, an overview of the chemistry used to prepare elastic polyHIPEs from early reports to modern polymerization methods is provided, focusing on the applications that flexible polyHIPEs are used in. The review consists of four sections organized around polymer classes used in the preparation of polyHIPEs: (meth)acrylics and (meth)acrylamides, silicones, polyesters and polyurethanes, and naturally occurring polymers. Within each section, the common properties, current challenges, and an outlook is suggested on where elastomeric polyHIPEs can be expected to continue to make broad, positive impacts on materials and technology for the future.
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Affiliation(s)
| | - Neil Ayres
- N.A.:
email, ; tel, +01 513 556 9280; fax, +01 513 556 9239
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Valdoz JC, Johnson BC, Jacobs DJ, Franks NA, Dodson EL, Sanders C, Cribbs CG, Van Ry PM. The ECM: To Scaffold, or Not to Scaffold, That Is the Question. Int J Mol Sci 2021; 22:12690. [PMID: 34884495 PMCID: PMC8657545 DOI: 10.3390/ijms222312690] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 11/19/2021] [Accepted: 11/22/2021] [Indexed: 12/14/2022] Open
Abstract
The extracellular matrix (ECM) has pleiotropic effects, ranging from cell adhesion to cell survival. In tissue engineering, the use of ECM and ECM-like scaffolds has separated the field into two distinct areas-scaffold-based and scaffold-free. Scaffold-free techniques are used in creating reproducible cell aggregates which have massive potential for high-throughput, reproducible drug screening and disease modeling. Though, the lack of ECM prevents certain cells from surviving and proliferating. Thus, tissue engineers use scaffolds to mimic the native ECM and produce organotypic models which show more reliability in disease modeling. However, scaffold-based techniques come at a trade-off of reproducibility and throughput. To bridge the tissue engineering dichotomy, we posit that finding novel ways to incorporate the ECM in scaffold-free cultures can synergize these two disparate techniques.
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Affiliation(s)
| | | | | | | | | | | | | | - Pam M. Van Ry
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA; (J.C.V.); (B.C.J.); (D.J.J.); (N.A.F.); (E.L.D.); (C.S.); (C.G.C.)
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Auxetic Structures for Tissue Engineering Scaffolds and Biomedical Devices. MATERIALS 2021; 14:ma14226821. [PMID: 34832223 PMCID: PMC8621588 DOI: 10.3390/ma14226821] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/07/2021] [Accepted: 11/10/2021] [Indexed: 11/16/2022]
Abstract
An auxetic structure utilizing a negative Poisson's ratio, which can expand transversally when axially expanded under tensional force, has not yet been studied in the tissue engineering and biomedical area. However, the recent advent of new technologies, such as additive manufacturing or 3D printing, has showed prospective results aimed at producing three-dimensional structures. Auxetic structures are fabricated by additive manufacturing, soft lithography, machining technology, compressed foaming, and textile fabrication using various biomaterials, including poly(ethylene glycol diacrylate), polyurethane, poly(lactic-glycolic acid), chitosan, hydroxyapatite, and using a hard material such as a silicon wafer. After fabricating the scaffold with an auxetic effect, researchers have cultured fibroblasts, osteoblasts, chondrocytes, myoblasts, and various stem cells, including mesenchymal stem cells, bone marrow stem cells, and embryonic stem cells. Additionally, they have shown new possibilities as scaffolds through tissue engineering by cell proliferation, migration, alignment, differentiation, and target tissue regeneration. In addition, auxetic structures and their unique deformation characteristics have been explored in several biomedical devices, including implants, stents, and surgical screws. Although still in the early stages, the auxetic structure, which can create mechanical properties tailored to natural tissue by changing the internal architecture of the structure, is expected to show an improved tissue reconstruction ability. In addition, continuous research at the cellular level using the auxetic micro and nano-environment could provide a breakthrough for tissue reconstruction.
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Wang K, Kang L, Lu Y, Zhu Q, Jiang S, Yin R. Highly porous tissue scaffolds based on cyclic acetals with tunable hydrophilicity and degradation behavior. POLYM ADVAN TECHNOL 2021. [DOI: 10.1002/pat.5217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Kemin Wang
- School of Materials Science and Engineering Changzhou University Changzhou China
- School of Mechatronic Engineering and Automation Shanghai University Shanghai China
| | - Liangfa Kang
- School of Materials Science and Engineering Changzhou University Changzhou China
| | - Yuhui Lu
- School of Materials Science and Engineering Changzhou University Changzhou China
| | - Qifan Zhu
- School of Materials Science and Engineering Changzhou University Changzhou China
| | - Shan Jiang
- School of Materials Science and Engineering Changzhou University Changzhou China
| | - Ruixue Yin
- School of Mechanical and Power Engineering East China University of Science and Technology Shanghai China
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Sharma D, Singh J. Long-term glycemic control and prevention of diabetes complications in vivo using oleic acid-grafted-chitosan‑zinc-insulin complexes incorporated in thermosensitive copolymer. J Control Release 2020; 323:161-178. [PMID: 32283211 PMCID: PMC7299807 DOI: 10.1016/j.jconrel.2020.04.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/12/2020] [Accepted: 04/07/2020] [Indexed: 12/31/2022]
Abstract
Daily injections for basal insulin therapy are far from ideal resulting in hypo/hyperglycemic episodes associated with fatal complications in type-1 diabetes patients. Here we report a delivery system that provides controlled release of insulin closely mimicking physiological basal insulin requirement for an extended period following a single subcutaneous injection. Stability of insulin was significantly improved by formation of zinc-insulin hexamers, further stabilized by electrostatic complex formation with chitosan polymer. Insulin complexes were homogenously incorporated into PLA-PEG-PLA, a biodegradable thermogel copolymer, that instantaneously forms a subcutaneous gel-depot following injection. Chitosan polymer was hydrophobically modified using oleic acid prior to complex formation with insulin to enable distribution of oleic acid-grafted-chitosan‑zinc-insulin complexes into the hydrophobic core of PLA-PEG-PLA thermogel-copolymer micelles. In vivo, daily administration of marketed long-acting insulin, glargine, resulted in fluctuating blood glucose levels between 91 and 443 mg/dL in type 1 diabetic rats. However, single administration of thermogel copolymeric formulation successfully demonstrated slow diffusion of insulin complexes maintaining peak-free basal insulin level of 21 mU/L for 91 days. Sustained release of basal insulin also correlated with efficient glycemic control (blood glucose <120 mg/dL), prevention of diabetic ketoacidosis and absence of cataract development, unlike other treatment groups. Moreover, there was no sign of inflammation, tissue damage, or collagen deposition around depot site, suggesting exceptional biocompatibility of the formulation for long-term use.
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Affiliation(s)
- Divya Sharma
- Department of Pharmaceutical Sciences, School of Pharmacy, College of Health Professions, North Dakota State University, Fargo 58105, ND, USA.
| | - Jagdish Singh
- Deparment of Pharmaceutical Sciences, North Dakota State University, USA.
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Lipp L, Sharma D, Banerjee A, Singh J. In Vitro and in Vivo Optimization of Phase Sensitive Smart Polymer for Controlled Delivery of Rivastigmine for Treatment of Alzheimer's Disease. Pharm Res 2020; 37:34. [PMID: 31942651 PMCID: PMC6996875 DOI: 10.1007/s11095-020-2757-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 01/06/2020] [Indexed: 01/16/2023]
Abstract
PURPOSE Alzheimer's disease is a neurodegenerative disorder, and most common form of dementia afflicting over 35 million people worldwide. Rivastigmine is a widely used therapeutic for ameliorating clinical manifestations of Alzheimer's disease. However, current treatments require frequent dosing either orally or via transdermal patch that lead to compliance issues and administration errors risking serious adverse effects. Our objective was to develop a smart polymer based delivery system for controlled release of rivastigmine over an extended period following a single subcutaneous injection. METHODS Rivastigmine release was optimized by tailoring critical factors including polymer concentration, polymer composition, drug concentration, solvent composition, and drug hydrophobicity (rivastigmine tartrate vs base). Optimized in vitro formulation was evaluated in vivo for safety and efficacy. RESULTS Formulation prepared using PLGA (50:50) at 5% w/v in 95:5 benzyl benzoate: benzoic acid demonstrated desirable controlled drug release characteristics in vitro. The formulation demonstrated sustained release of rivastigmine tartrate for 7 days in vivo with promising biocompatibility and acetylcholinesterase inhibition efficacy for 14 days. CONCLUSION The results exemplify an easily injectable controlled release formulation of rivastigmine prepared using phase-sensitive smart polymer. The optimized formulation significantly increases the dosing interval, and can potentially improve patient compliance as well as quality of life of patients living with Alzheimer's disease.
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Affiliation(s)
- Lindsey Lipp
- Department of Pharmaceutical Sciences, School of Pharmacy, College of Health Professions, North Dakota State University, Fargo, North Dakota, 58105, USA
| | - Divya Sharma
- Department of Pharmaceutical Sciences, School of Pharmacy, College of Health Professions, North Dakota State University, Fargo, North Dakota, 58105, USA
| | - Amrita Banerjee
- Department of Pharmaceutical Sciences, School of Pharmacy, College of Health Professions, North Dakota State University, Fargo, North Dakota, 58105, USA.
| | - Jagdish Singh
- Department of Pharmaceutical Sciences, School of Pharmacy, College of Health Professions, North Dakota State University, Fargo, North Dakota, 58105, USA
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Sharma D, Arora S, Singh J. Smart Thermosensitive Copolymer Incorporating Chitosan-Zinc-Insulin Electrostatic Complexes for Controlled Delivery of Insulin: Effect of Chitosan Chain Length. INT J POLYM MATER PO 2019; 69:1054-1068. [PMID: 33012880 DOI: 10.1080/00914037.2019.1655750] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This work was designed to optimize thermosensitive copolymeric depot-based system for delivering insulin at a controlled rate for a prolonged period following a single subcutaneous injection. Intrinsic ability of insulin to form hexamers in the presence of zinc and electrostatic complexes with chitosan (CS) were explored for improving stability and release characteristics of insulin through the copolymeric depot. CS-zinc-insulin complexes were prepared using CS of different chain lengths (5, 30, 50, 200 kDa). Effect of different chain lengths of CS on the thermal stability, binding constant, and release profile of insulin was determined. Increasing chain length of CS demonstrated increasing thermal stability of insulin. However, higher chain length of CS adversely affected the release profile of insulin. Hydrolytic degradation analysis showed rapid degradation of copolymer in formulation containing higher chain length of CS (200 kDa)-zinc-insulin complexes, implying formation of bigger pores and channels in copolymeric matrix during initial release in this system. However, formulation containing smaller chain length of CS (5 kDa)-zinc-insulin complexes demonstrated slow copolymer degradation and sustained insulin release profile. Additionally, CS-zinc-insulin complexes were effective in preserving stability of insulin during the entire duration of release and storage.
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Affiliation(s)
- Divya Sharma
- Department of Pharmaceutical Sciences, School of Pharmacy, College of Health Professions, North Dakota State University, Fargo 58105, ND, USA
| | - Sanjay Arora
- Department of Pharmaceutical Sciences, School of Pharmacy, College of Health Professions, North Dakota State University, Fargo 58105, ND, USA
| | - Jagdish Singh
- Department of Pharmaceutical Sciences, School of Pharmacy, College of Health Professions, North Dakota State University, Fargo 58105, ND, USA
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Sarker MD, Naghieh S, Sharma NK, Ning L, Chen X. Bioprinting of Vascularized Tissue Scaffolds: Influence of Biopolymer, Cells, Growth Factors, and Gene Delivery. JOURNAL OF HEALTHCARE ENGINEERING 2019; 2019:9156921. [PMID: 31065331 PMCID: PMC6466897 DOI: 10.1155/2019/9156921] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 02/03/2019] [Indexed: 01/16/2023]
Abstract
Over the past decades, tissue regeneration with scaffolds has achieved significant progress that would eventually be able to solve the worldwide crisis of tissue and organ regeneration. While the recent advancement in additive manufacturing technique has facilitated the biofabrication of scaffolds mimicking the host tissue, thick tissue regeneration remains challenging to date due to the growing complexity of interconnected, stable, and functional vascular network within the scaffold. Since the biological performance of scaffolds affects the blood vessel regeneration process, perfect selection and manipulation of biological factors (i.e., biopolymers, cells, growth factors, and gene delivery) are required to grow capillary and macro blood vessels. Therefore, in this study, a brief review has been presented regarding the recent progress in vasculature formation using single, dual, or multiple biological factors. Besides, a number of ways have been presented to incorporate these factors into scaffolds. The merits and shortcomings associated with the application of each factor have been highlighted, and future research direction has been suggested.
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Affiliation(s)
- M. D. Sarker
- Division of Biomedical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK, Canada
| | - Saman Naghieh
- Division of Biomedical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK, Canada
| | - N. K. Sharma
- Department of Mechanical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK, Canada
| | - Liqun Ning
- Department of Mechanical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK, Canada
| | - Xiongbiao Chen
- Division of Biomedical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK, Canada
- Department of Mechanical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK, Canada
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Namdari M, Negahdari B, Eatemadi A. Paediatric nanofibrous bioprosthetic heart valve. IET Nanobiotechnol 2017; 11:493-500. [PMID: 28745279 PMCID: PMC8676244 DOI: 10.1049/iet-nbt.2016.0159] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 11/28/2016] [Accepted: 11/30/2016] [Indexed: 09/22/2023] Open
Abstract
The search for an optimal aortic valve implant with durability, calcification resistance, excellent haemodynamic parameters and ability to withstand mechanical loading is yet to be met. Thus, there has been struggled to fabricate bio-prosthetics heart valve using bioengineering. The consequential product must be resilient with suitable mechanical features, biocompatible and possess the capacity to grow. Defective heart valves replacement by surgery is now common, this improves the value and survival of life for a lot of patients. The recent paediatric heart valve implant is suboptimal due to their inability of somatic growth. They usually have multiple surgeries to change outgrown valves. Short-lived valve bio-prostheses occurring in older patients and younger ones who more usually need the replacement of its damaged heart with prosthesis led to a new invasive surgical interventions with an improved quality of life. The authors propose that nanofibre scaffold for paediatric tissue-engineered heart valve will meet most of these conditions, most particularly those related to somatic growth, and, as the nanofibre scaffold is eroded, new valve is produced, the valve matures in the child until adulthood.
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Affiliation(s)
- Mehrdad Namdari
- Department of Cardiology, Lorestan University of Medical Sciences, Khoramabad, Iran
| | - Babak Negahdari
- Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ali Eatemadi
- Department of Medical Biotechnology, School of Medicine, Lorestan University of Medical Sciences, Lorestan, Iran.
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Lee JW, Soman P, Park JH, Chen S, Cho DW. A Tubular Biomaterial Construct Exhibiting a Negative Poisson's Ratio. PLoS One 2016; 11:e0155681. [PMID: 27232181 PMCID: PMC4883790 DOI: 10.1371/journal.pone.0155681] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 05/03/2016] [Indexed: 11/18/2022] Open
Abstract
Developing functional small-diameter vascular grafts is an important objective in tissue engineering research. In this study, we address the problem of compliance mismatch by designing and developing a 3D tubular construct that has a negative Poisson's ratio νxy (NPR). NPR constructs have the unique ability to expand transversely when pulled axially, thereby resulting in a highly-compliant tubular construct. In this work, we used projection stereolithography to 3D-print a planar NPR sheet composed of photosensitive poly(ethylene) glycol diacrylate biomaterial. We used a step-lithography exposure and a stitch process to scale up the projection printing process, and used the cut-missing rib unit design to develop a centimeter-scale NPR sheet, which was rolled up to form a tubular construct. The constructs had Poisson's ratios of -0.6 ≤ νxy ≤ -0.1. The NPR construct also supports higher cellular adhesion than does the construct that has positive νxy. Our NPR design offers a significant advance in the development of highly-compliant vascular grafts.
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Affiliation(s)
- Jin Woo Lee
- Department of Molecular Medicine, School of Medicine, Gachon University, 7-45, Songdo-dong, Yeonsu-ku, Incheon, 406-840, Republic of Korea
| | - Pranav Soman
- Department of Biomedical and Chemical Engineering, Syracuse University, 318 Browne Hall, Syracuse, NY, 13244, United States of America
| | - Jeong Hun Park
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja dong, Nam-gu, Pohang, Gyeongbuk, 790-781, Republic of Korea
| | - Shaochen Chen
- Department of NanoEngineering, University of California San Diego, 9500 Gilman Drive, Atkinson Hall, MC-0448, La Jolla, CA, 92093, United States of America
- * E-mail: (SC); (D-WC)
| | - Dong-Woo Cho
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja dong, Nam-gu, Pohang, Gyeongbuk, 790-781, Republic of Korea
- * E-mail: (SC); (D-WC)
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Dennis SG, Trusk T, Richards D, Jia J, Tan Y, Mei Y, Fann S, Markwald R, Yost M. Viability of Bioprinted Cellular Constructs Using a Three Dispenser Cartesian Printer. J Vis Exp 2015:53156. [PMID: 26436877 PMCID: PMC4692613 DOI: 10.3791/53156] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Tissue engineering has centralized its focus on the construction of replacements for non-functional or damaged tissue. The utilization of three-dimensional bioprinting in tissue engineering has generated new methods for the printing of cells and matrix to fabricate biomimetic tissue constructs. The solid freeform fabrication (SFF) method developed for three-dimensional bioprinting uses an additive manufacturing approach by depositing droplets of cells and hydrogels in a layer-by-layer fashion. Bioprinting fabrication is dependent on the specific placement of biological materials into three-dimensional architectures, and the printed constructs should closely mimic the complex organization of cells and extracellular matrices in native tissue. This paper highlights the use of the Palmetto Printer, a Cartesian bioprinter, as well as the process of producing spatially organized, viable constructs while simultaneously allowing control of environmental factors. This methodology utilizes computer-aided design and computer-aided manufacturing to produce these specific and complex geometries. Finally, this approach allows for the reproducible production of fabricated constructs optimized by controllable printing parameters.
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Affiliation(s)
| | - Thomas Trusk
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina
| | | | - Jia Jia
- Department of Bioengineering, Clemson University
| | - Yu Tan
- Department of Bioengineering, Clemson University
| | - Ying Mei
- Department of Bioengineering, Clemson University
| | - Stephen Fann
- Department of Surgery, Medical University of South Carolina
| | | | - Michael Yost
- Department of Surgery, Medical University of South Carolina
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Bogni S, Ortner MA, Vajtai I, Jost C, Reinert M, Dallemagne B, Frenz M. New laser soldering-based closures: a promising method in natural orifice transluminal endoscopic surgery. Gastrointest Endosc 2012; 76:151-8. [PMID: 22726474 DOI: 10.1016/j.gie.2012.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 03/05/2012] [Indexed: 12/17/2022]
Abstract
BACKGROUND Complete closure of gastrotomy is the linchpin of safe natural orifice transgastric endoscopic surgery. OBJECTIVE To evaluate feasibility and efficacy of a new method of gastrotomy closure by using a sutureless laser tissue-soldering (LTS) technique in an ex vivo porcine stomach. DESIGN In vitro experiment. SETTING Experimental laboratory. INTERVENTIONS Histological analysis and internal and external liquid pressure with and without hydrochloric acid exposure were determined comparing gastrotomy closure with LTS and with hand-sewn surgical sutures. MAIN OUTCOME MEASUREMENTS Comparison of LTS and hand-sewn surgical gastrotomy closure. The primary outcome parameter was the internal leak pressure. Secondary parameters were the difference between internal and external leak pressures, the impact of an acid environment on the device, histological changes, and feasibility of endoscopic placement. RESULTS The internal liquid leak pressure after LTS was almost twice as high as after hand-sewn surgical closure (416 ± 53 mm Hg vs 229 ± 99 mm Hg; P = .01). The internal leak pressure (416 ± 53 mm Hg) after LTS was higher than the external leak pressure (154 ± 46 mm Hg; P < .0001). An acidic environment did not affect leak pressure after LTS. Endoscopic LTS closure was feasible in all experiments. Histopathology revealed only slight alterations beneath the soldering plug. LIMITATIONS In vitro experiments. CONCLUSIONS Leak pressure after LTS closure of gastrotomy is higher than after hand-sewn surgical closure. LTS is a promising technique for closure of gastrotomies and iatrogenic perforations. Further experiments, in particular survival studies, are mandatory.
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Affiliation(s)
- Serge Bogni
- Department of Biomedical Photonics, Institute of Applied Physics, University of Bern, Bern, Switzerland
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Gauvin R, Chen YC, Lee JW, Soman P, Zorlutuna P, Nichol JW, Bae H, Chen S, Khademhosseini A. Microfabrication of complex porous tissue engineering scaffolds using 3D projection stereolithography. Biomaterials 2012; 33:3824-34. [PMID: 22365811 DOI: 10.1016/j.biomaterials.2012.01.048] [Citation(s) in RCA: 349] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 01/27/2012] [Indexed: 01/27/2023]
Abstract
The success of tissue engineering will rely on the ability to generate complex, cell seeded three-dimensional (3D) structures. Therefore, methods that can be used to precisely engineer the architecture and topography of scaffolding materials will represent a critical aspect of functional tissue engineering. Previous approaches for 3D scaffold fabrication based on top-down and process driven methods are often not adequate to produce complex structures due to the lack of control on scaffold architecture, porosity, and cellular interactions. The proposed projection stereolithography (PSL) platform can be used to design intricate 3D tissue scaffolds that can be engineered to mimic the microarchitecture of tissues, based on computer aided design (CAD). The PSL system was developed, programmed and optimized to fabricate 3D scaffolds using gelatin methacrylate (GelMA). Variation of the structure and prepolymer concentration enabled tailoring the mechanical properties of the scaffolds. A dynamic cell seeding method was utilized to improve the coverage of the scaffold throughout its thickness. The results demonstrated that the interconnectivity of pores allowed for uniform human umbilical vein endothelial cells (HUVECs) distribution and proliferation in the scaffolds, leading to high cell density and confluency at the end of the culture period. Moreover, immunohistochemistry results showed that cells seeded on the scaffold maintained their endothelial phenotype, demonstrating the biological functionality of the microfabricated GelMA scaffolds.
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Affiliation(s)
- Robert Gauvin
- Center for Biomedical Engineering, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA 02139, USA
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Guo Z, Burley AC, Koelling KW, Kusaka I, Lee LJ, Tomasko DL. CO2bubble nucleation in polystyrene: Experimental and modeling studies. J Appl Polym Sci 2012. [DOI: 10.1002/app.36422] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Kretlow JD, Mikos AG. Founder's award to Antonios G. Mikos, Ph.D., 2011 Society for Biomaterials annual meeting and exposition, Orlando, Florida, April 13-16, 2011: Bones to biomaterials and back again--20 years of taking cues from nature to engineer synthetic polymer scaffolds. J Biomed Mater Res A 2011; 98:323-31. [PMID: 21714068 DOI: 10.1002/jbm.a.33154] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 04/28/2011] [Indexed: 12/11/2022]
Abstract
For biomaterials scientists focusing on tissue engineering applications, the gold standard material is healthy, autologous tissue. Ideal material properties and construct design parameters are thus both obvious and often times unachievable; additional considerations such as construct delivery and the underlying pathology necessitating new tissue yield additional design challenges with solutions that are not evident in nature. For the past nearly two decades, our laboratory and collaborators have aimed to develop both new biomaterials and a better understanding of the complex interplay between material and host tissue to facilitate bone and cartilage regeneration. Various approaches have ranged from mimicking native tissue material properties and architecture to developing systems for bioactive molecule delivery as soluble factors or bound directly to the biomaterial substrate. Such technologies have allowed others and us to design synthetic biomaterials incorporating increasing levels of complexity found in native tissues with promising advances made toward translational success. Recent work focuses on translation of these technologies in specific clinical situations through the use of adjunctive biomaterials designed to address existing pathologies or guide host-material integration.
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Affiliation(s)
- James D Kretlow
- Department of Bioengineering, Rice University, Houston, Texas 77251-1892, USA
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Bouten C, Dankers P, Driessen-Mol A, Pedron S, Brizard A, Baaijens F. Substrates for cardiovascular tissue engineering. Adv Drug Deliv Rev 2011; 63:221-41. [PMID: 21277921 DOI: 10.1016/j.addr.2011.01.007] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Revised: 12/26/2010] [Accepted: 01/14/2011] [Indexed: 12/29/2022]
Abstract
Cardiovascular tissue engineering aims to find solutions for the suboptimal regeneration of heart valves, arteries and myocardium by creating 'living' tissue replacements outside (in vitro) or inside (in situ) the human body. A combination of cells, biomaterials and environmental cues of tissue development is employed to obtain tissues with targeted structure and functional properties that can survive and develop within the harsh hemodynamic environment of the cardiovascular system. This paper reviews the up-to-date status of cardiovascular tissue engineering with special emphasis on the development and use of biomaterial substrates. Key requirements and properties of these substrates, as well as methods and readout parameters to test their efficacy in the human body, are described in detail and discussed in the light of current trends toward designing biologically inspired microenviroments for in situ tissue engineering purposes.
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Pabittei DR, Heger M, Balm R, Meijer HEH, de Mol B, Beek JF. Electrospun Poly(ɛ-Caprolactone) Scaffold for Suture-Free Solder-Mediated Laser-Assisted Vessel Repair. Photomed Laser Surg 2011; 29:19-25. [DOI: 10.1089/pho.2010.2779] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Dara R. Pabittei
- Department of Surgery, Academic Medical Center, Amsterdam, the Netherlands
- Department of Cardio-thoracic Surgery, Academic Medical Center, Amsterdam, the Netherlands
| | - Michal Heger
- Department of Experimental Surgery, Academic Medical Center, Amsterdam, the Netherlands
| | - Ron Balm
- Department of Surgery, Academic Medical Center, Amsterdam, the Netherlands
| | - Han E. H. Meijer
- Department of Mechanical Engineering, Polymer Technology Group, Technical University of Eindhoven, Eindhoven, the Netherlands
| | - Bas de Mol
- Department of Cardio-thoracic Surgery, Academic Medical Center, Amsterdam, the Netherlands
- Department of Biomedical Engineering, Cardiovascular Biomechanics Group, Technical University of Eindhoven, Eindhoven, the Netherlands
| | - Johan F. Beek
- Department of Biomedical Engineering, Academic Medical Center, Amsterdam, the Netherlands
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Nguyen C, Young S, Kretlow JD, Mikos AG, Wong M. Surface characteristics of biomaterials used for space maintenance in a mandibular defect: a pilot animal study. J Oral Maxillofac Surg 2010; 69:11-8. [PMID: 21055856 DOI: 10.1016/j.joms.2010.02.026] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2008] [Revised: 09/24/2009] [Accepted: 02/12/2010] [Indexed: 10/18/2022]
Abstract
PURPOSE The purpose of the present study was to evaluate the effect of implant porosity on wound healing between solid and porous implants placed within a bony mandibular defect with intraoral exposure. MATERIALS AND METHODS Solid poly(methyl methacrylate) (PMMA) implants similar to those used currently in clinical space maintenance applications in maxillofacial surgery were compared with poly(propylene fumarate) implants that contained a porous outer surface surrounding a solid core. A 10-mm diameter nonhealing bicortical defect with open communication into the oral cavity was created in the molar mandibular region of 12 adult male New Zealand white rabbits. Of the 12 rabbits, 6 received the hybrid poly(propylene fumarate) implants and 6 received the solid PMMA implants. At 12 weeks, the rabbit mandibles were harvested and sent for histologic staining and sectioning. RESULTS Gross inspection and histologic examination showed all 6 poly(propylene fumarate) implants to be intact within the defect site at the termination of the study period, with 3 of the 6 specimens exhibiting a continuous circumferential soft tissue margin. In contrast, 5 of the 6 PMMA-implanted specimens were exposed intraorally with an incomplete cuff of soft tissue around the implant. One of the PMMA-implanted specimens exhibited complete extrusion and subsequent loss of the implant. Fisher's exact test was used to compare the occurrence of oral cavity wound healing between the 2 groups (P = .09). CONCLUSIONS Although statistically significant differences between the 2 groups were not seen, our results have indicated that advantages might exist to using porous implants for space maintenance. Additional study is needed to evaluate these findings.
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Affiliation(s)
- Charles Nguyen
- Resident in Oral and Maxillofacial Surgery, Department of Oral and Maxillofacial Surgery, University of Texas Health Science Center at Houston, Houston, TX, USA
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Tavassol F, Schumann P, Lindhorst D, Sinikovic B, Voss A, von See C, Kampmann A, Bormann KH, Carvalho C, Mülhaupt R, Harder Y, Laschke MW, Menger MD, Gellrich NC, Rücker M. Accelerated angiogenic host tissue response to poly(L-lactide-co-glycolide) scaffolds by vitalization with osteoblast-like cells. Tissue Eng Part A 2010; 16:2265-79. [PMID: 20184434 DOI: 10.1089/ten.tea.2008.0457] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Bone substitutes should ideally promote rapid vascularization, which could be accelerated if these substitutes were vitalized by autologous cells. Although adequate engraftment of porous poly(L-lactide-co-glycolide) (PLGA) scaffolds has been demonstrated in the past, it has not yet been investigated how vascularization is influenced by vitalization or, more precisely, by seeding PLGA scaffolds with osteoblast-like cells (OLCs). For this reason, we conducted an in vivo study to assess host angiogenic and inflammatory responses after the implantation of PLGA scaffolds vitalized with isogeneic OLCs. MATERIALS AND METHODS OLCs were seeded on collagen-coated PLGA scaffolds that were implanted into dorsal skinfold chambers in BALB/c mice (n = 8). Two further groups of animals received either collagen-coated (n = 8) or uncoated PLGA scaffolds (n = 8). Animals that received chambers without implants served as controls (n = 8). Angiogenesis, neovascularization, and leukocyte-endothelial cell interaction were analyzed for 14 days using intravital fluorescence microscopy. RESULTS PLGA scaffolds with and without OLCs showed a temporary increase in leukocyte recruitment. At day 3 after implantation, a marked angiogenic host tissue response was observed in close vicinity of all scaffolds studied. At days 6 and 10, the angiogenic response was significantly higher (p < 0.05) in PLGA scaffolds vitalized with OLCs than in uncoated or collagen-coated PLGA scaffolds. The majority of OLCs, however, died within 14 days after implantation. CONCLUSION Our study demonstrates that PLGA scaffold vitalization with OLCs accelerates the angiogenic response in the surrounding host tissue. Bone substitutes created by tissue engineering may thus be superior to nonvitalized substitutes although the seeded cells do not survive for long periods.
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Affiliation(s)
- Frank Tavassol
- Department of Oral and Maxillofacial Surgery, Hannover Medical School, Hannover, Germany.
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Stella JA, D'Amore A, Wagner WR, Sacks MS. On the biomechanical function of scaffolds for engineering load-bearing soft tissues. Acta Biomater 2010; 6:2365-81. [PMID: 20060509 DOI: 10.1016/j.actbio.2010.01.001] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 12/18/2009] [Accepted: 01/04/2010] [Indexed: 11/16/2022]
Abstract
Replacement or regeneration of load-bearing soft tissues has long been the impetus for the development of bioactive materials. While maturing, current efforts continue to be confounded by our lack of understanding of the intricate multi-scale hierarchical arrangements and interactions typically found in native tissues. The current state of the art in biomaterial processing enables a degree of controllable microstructure that can be used for the development of model systems to deduce fundamental biological implications of matrix morphologies on cell function. Furthermore, the development of computational frameworks which allow for the simulation of experimentally derived observations represents a positive departure from what has mostly been an empirically driven field, enabling a deeper understanding of the highly complex biological mechanisms we wish to ultimately emulate. Ongoing research is actively pursuing new materials and processing methods to control material structure down to the micro-scale to sustain or improve cell viability, guide tissue growth, and provide mechanical integrity, all while exhibiting the capacity to degrade in a controlled manner. The purpose of this review is not to focus solely on material processing but to assess the ability of these techniques to produce mechanically sound tissue surrogates, highlight the unique structural characteristics produced in these materials, and discuss how this translates to distinct macroscopic biomechanical behaviors.
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Affiliation(s)
- John A Stella
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15219, USA
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Ni HC, Lin ZY, Hsu SH, Chiu IM. The use of air plasma in surface modification of peripheral nerve conduits. Acta Biomater 2010; 6:2066-76. [PMID: 20040388 DOI: 10.1016/j.actbio.2009.12.038] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 12/16/2009] [Accepted: 12/21/2009] [Indexed: 12/27/2022]
Abstract
Surface modification is a conventional approach in biomaterials development, but most of the modification processes are intricate and time inefficient. In this study, a convenient open air plasma treatment was employed to modify the surface of poly(d,l-lactide) (PLA). Chitosan and fibroblast growth factor 1 (FGF1) were sequentially grafted with the assistance of open air plasma treatment onto the PLA nerve conduits with designed micropores and surface microgrooves. Grafting of these components was verified by electron spectroscopy for chemical analysis. The modified nerve conduits showed enhanced ability in the repair of 10-mm sciatic nerve transection defects in rats. The sequential air plasma treatment can be a convenient way to introduce biocompatible (e.g., chitosan) and bioactive components (e.g., growth factors) onto the surface of biomaterials.
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Hashi CK, Derugin N, Janairo RRR, Lee R, Schultz D, Lotz J, Li S. Antithrombogenic modification of small-diameter microfibrous vascular grafts. Arterioscler Thromb Vasc Biol 2010; 30:1621-7. [PMID: 20466974 DOI: 10.1161/atvbaha.110.208348] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To develop small-diameter vascular grafts with a microstructure similar to native matrix fibers and with chemically modified microfibers to prevent thrombosis. METHODS AND RESULTS Microfibrous vascular grafts (1-mm internal diameter) were fabricated by electrospinning, and hirudin was conjugated to the poly (L-lactic acid) microfibers through an intermediate linker of poly(ethylene glycol). The modified microfibrous vascular grafts were able to reduce platelet adhesion/aggregation onto microfibrous scaffolds, and immobilized hirudin suppressed thrombin activity that may interact with the scaffolds. This 2-pronged approach to modify microfibrous vascular graft showed significantly improved patency (from 50% to 83%) and facilitated endothelialization, and the microfibrous structure of the vascular grafts allowed efficient graft remodeling and integration, with the improvement of mechanical property (elastic modulus) from 3.5 to 11.1 MPa after 6 months of implantation. CONCLUSIONS Microfibrous vascular grafts with antithrombogenic microfibers can be used as small-diameter grafts, with excellent patency and remodeling capability.
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Saxena AK, Baumgart H, Komann C, Ainoedhofer H, Soltysiak P, Kofler K, Höllwarth ME. Esophagus tissue engineering: in situ generation of rudimentary tubular vascularized esophageal conduit using the ovine model. J Pediatr Surg 2010; 45:859-64. [PMID: 20438914 DOI: 10.1016/j.jpedsurg.2010.02.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 02/02/2010] [Indexed: 12/21/2022]
Abstract
PURPOSE Esophagus replacement using the present surgical techniques is associated with significant morbidity. Tissue engineering of the esophagus may provide the solution for esophageal loss. In our attempts to engineer the esophagus, this study aimed to investigate the feasibility of generating vascularized in situ esophageal conduits using the ovine model. METHODS Esophageal biopsies were obtained from lambs, and ovine esophageal epithelial cells (OEEC) were proliferated. The OEEC were seeded on to bovine collagen sheets preseeded with fibroblasts. After 2 weeks of maintaining the constructs in vitro, the constructs were tubularized on stents to create a tube resembling the esophagus and implanted into the omentum for in situ tissue engineering. The edges of the omentum were sutured using nonabsorbable suture material. The implanted constructs were retrieved after 8 and 12 weeks. RESULTS The omental wrap provided vascular growth within and around the constructs as they were integrated along the outer surface area of the scaffold. After removal of the stents, the engineered conduit revealed a structure similar to the esophagus. Histologic investigations demonstrated esophageal epithelium organization into patches on the luminal side and vascular ingrowths on the conduit's outer perimeter. CONCLUSION Our study demonstrated the seeding of OEEC on collagen scaffolds and formation of a rudimentary conduit resembling esophageal morphology after in situ omental implantation. Vascular coverage and ingrowth in the periphery of the construct could also be demonstrated. These findings hold future promise for the engineering of the esophagus with improved microarchitecture.
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Affiliation(s)
- Amulya K Saxena
- Department of Pediatric and Adolescent Surgery, Medical University of Graz, A-8036 Graz, Austria.
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Abstract
Cardiovascular disease is the leading cause of mortality in the USA. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. While synthetic polymers have been extensively studied as substitutes in vascular engineering, they fall short of meeting the biological challenges at the blood-material interface. Various tissue engineering strategies have emerged to address these flaws and increase long-term patency of vascular grafts. Vascular cell seeding of scaffolds and the design of bioactive polymers for in situ arterial regeneration have yielded promising results. This article describes the advances made in biomaterials design to generate suitable materials that not only match the mechanical properties of native vasculature, but also promote cell growth, facilitate extracellular matrix production and inhibit thrombogenicity.
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Affiliation(s)
- Swathi Ravi
- Department of Surgery, Emory University, Atlanta, GA 30332, USA
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Yeh SK, Yang J, Chiou NR, Daniel T, Lee LJ. Introducing water as a coblowing agent in the carbon dioxide extrusion foaming process for polystyrene thermal insulation foams. POLYM ENG SCI 2010. [DOI: 10.1002/pen.21624] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Den Buijs JO, Lu L, Jorgensen SM, Dragomir-Daescu D, Yaszemski MJ, Ritman EL. Solute transport in cyclically deformed porous tissue scaffolds with controlled pore cross-sectional geometries. Tissue Eng Part A 2009; 15:1989-99. [PMID: 19196145 DOI: 10.1089/ten.tea.2008.0382] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The objective of this study was to investigate the influence of pore geometry on the transport rate and depth after repetitive mechanical deformation of porous scaffolds for tissue engineering applications. Flexible cubic imaging phantoms with pores in the shape of a circular cylinder, elliptic cylinder, and spheroid were fabricated from a biodegradable polymer blend using a combined 3D printing and injection molding technique. The specimens were immersed in fluid and loaded with a solution of a radiopaque solute. The solute distribution was quantified by recording 20 microm pixel-resolution images in an X-ray microimaging scanner at selected time points after intervals of dynamic straining with a mean strain of 8.6+/-1.6% at 1.0 Hz. The results show that application of cyclic strain significantly increases the rate and depth of solute transport, as compared to diffusive transport alone, for all pore shapes. In addition, pore shape, pore size, and the orientation of the pore cross-sectional asymmetry with respect to the direction of strain greatly influence solute transport. Thus, pore geometry can be tailored to increase transport rates and depths in cyclically deformed scaffolds, which is of utmost importance when thick, metabolically functional tissues are to be engineered.
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Affiliation(s)
- Jorn Op Den Buijs
- Physiological Imaging Research Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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Abstract
Surgical replacement of diseased heart valves by mechanical and tissue valve substitutes is now commonplace and enhances survival and quality of life for many patients. However, repairs of congenital deformities require very small valve sizes not commercially available. Further, a fundamental problem inherent to the use of existing mechanical and biological prostheses in the pediatric population is their failure to grow, repair, and remodel. It is believed that a tissue engineered heart valve can accommodate many of these requirements, especially those pertaining to somatic growth. This review provides an overview of the field of heart valve tissue engineering, including recent trends, with a focus on the bioengineering challenges unique to heart valves. We believe that, currently, the key bioengineering challenge is to determine how biological, structural, and mechanical factors affect extracellular matrix (ECM) formation and in vivo functionality. These factors are fundamental to any approach toward developing a clinically viable tissue engineered heart valve (TEHV), regardless of the particular approach. Critical to the current approaches to TEHVs is scaffold design, which must simultaneously provide function (valves must function from the time of implant) as well as stress transfer to the new ECM. From a bioengineering point of view, a hierarchy of approaches will be necessary to connect the organ-tissue relationships with underpinning cell and sub-cellular events. Overall, such approaches need to be structured to address these fundamental issues to lay the basis for TEHVs that can be developed and designed according to truly sound scientific and engineering principles.
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Affiliation(s)
- Michael S Sacks
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pennsylvania 15219, USA.
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Yang J, Yeh SK, Chiou NR, Guo Z, Daniel T, Lee LJ. Synthesis and foaming of water expandable polystyrene-activated carbon (WEPSAC). POLYMER 2009. [DOI: 10.1016/j.polymer.2009.05.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Shen H, Hu X, Yang F, Bei J, Wang S. The bioactivity of rhBMP-2 immobilized poly(lactide-co-glycolide) scaffolds. Biomaterials 2009; 30:3150-7. [DOI: 10.1016/j.biomaterials.2009.02.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2008] [Accepted: 02/02/2009] [Indexed: 10/21/2022]
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Abstract
Cardiovascular disease is the leading cause of mortality in the United States. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. Synthetic polymeric materials, while providing the appropriate mechanical strength, lack the compliance and biocompatibility that bioresorbable and naturally occurring protein polymers offer. Vascular tissue engineering approaches have emerged in order to meet the challenges of designing a vascular graft with long-term patency. In vitro culture techniques that have been explored with vascular cell seeding of polymeric scaffolds and the use of bioactive polymers for in situ arterial regeneration have yielded promising results. This review describes the development of polymeric materials in various tissue engineering strategies for the improvement in the mechanical and biological performance of an arterial substitute.
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Affiliation(s)
- Swathi Ravi
- Department of Surgery, Emory University, Atlanta, GA
- Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA
| | - Zheng Qu
- Department of Surgery, Emory University, Atlanta, GA
- Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA
| | - Elliot L. Chaikof
- Department of Surgery, Emory University, Atlanta, GA
- Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA
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Abstract
At present, strong requirements in orthopaedics are still to be met, both in bone and joint substitution and in the repair and regeneration of bone defects. In this framework, tremendous advances in the biomaterials field have been made in the last 50 years where materials intended for biomedical purposes have evolved through three different generations, namely first generation (bioinert materials), second generation (bioactive and biodegradable materials) and third generation (materials designed to stimulate specific responses at the molecular level). In this review, the evolution of different metals, ceramics and polymers most commonly used in orthopaedic applications is discussed, as well as the different approaches used to fulfil the challenges faced by this medical field.
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Affiliation(s)
- M Navarro
- Biomaterials, Implants and Tissue Engineering, Institute for Bioengineering of Catalonia (IBEC), CIBER-BBN, 08028 Barcelona, Spain.
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Kretlow JD, Mikos AG. 2007 AIChE Alpha Chi Sigma Award: From Material to Tissue: Biomaterial Development, Scaffold Fabrication, and Tissue Engineering. AIChE J 2008; 54:3048-3067. [PMID: 19756176 DOI: 10.1002/aic.11610] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The need for techniques to facilitate the regeneration of failing or destroyed tissues remains great with the aging of the worldwide population and the continued incidence of trauma and diseases such as cancer. A 16-year history in biomaterial scaffold development and tissue engineering is examined, beginning with the synthesis of novel materials and fabrication of 3D porous scaffolds. Exploring cell-scaffold interactions and subsequently cellular delivery using biomaterial carriers, we have developed a variety of techniques for bone and cartilage engineering. In addition to delivering cells, we have utilized growth factors, DNA, and peptides to improve the in vitro and in vivo regeneration of tissues. This review covers important developments and discoveries within our laboratory, and the increasing breadth in the scope of our work within the expanding field of tissue engineering is presented.
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Affiliation(s)
- James D Kretlow
- Department of Bioengineering, Rice University, P.O. Box 1892, MS 142, Houston, TX 77251-1892
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Stella JA, Liao J, Hong Y, David Merryman W, Wagner WR, Sacks MS. Tissue-to-cellular level deformation coupling in cell micro-integrated elastomeric scaffolds. Biomaterials 2008; 29:3228-36. [PMID: 18472154 DOI: 10.1016/j.biomaterials.2008.04.029] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2008] [Accepted: 04/08/2008] [Indexed: 10/22/2022]
Abstract
In engineered tissues we are challenged to reproduce extracellular matrix and cellular deformation coupling that occurs within native tissues, which is a meso-micro scale phenomenon that profoundly affects tissue growth and remodeling. With our ability to electrospin polymer fiber scaffolds while simultaneously electrospraying viable cells, we are provided with a unique platform to investigate cellular deformations within a three dimensional elastomeric fibrous scaffold. Scaffold specimens micro-integrated with vascular smooth muscle cells were subjected to controlled biaxial stretch with 3D cellular deformations and local fiber microarchitecture simultaneously quantified. We demonstrated that the local fiber geometry followed an affine behavior, so that it could be predicted by macro-scaffold deformations. However, local cellular deformations depended non-linearly on changes in fiber microarchitecture and ceased at large strains where the scaffold fibers completely straightened. Thus, local scaffold microstructural changes induced by macro-level applied strain dominated cellular deformations, so that monotonic increases in scaffold strain do not necessitate similar levels of cellular deformation. This result has fundamental implications when attempting to elucidate the events of de-novo tissue development and remodeling in engineered tissues, which are thought to depend substantially on cellular deformations.
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Affiliation(s)
- John A Stella
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15219, USA
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Zhang X, Baughman CB, Kaplan DL. In vitro evaluation of electrospun silk fibroin scaffolds for vascular cell growth. Biomaterials 2008; 29:2217-27. [PMID: 18279952 DOI: 10.1016/j.biomaterials.2008.01.022] [Citation(s) in RCA: 261] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Accepted: 01/28/2008] [Indexed: 01/02/2023]
Abstract
Human aortic endothelial (HAEC) and human coronary artery smooth muscle cell (HCASMC) responses on electrospun silk fibroin scaffolds were studied to evaluate potential for vascular tissue engineering. Cell proliferation studies supported the utility of this biomaterial matrix by both HAECs and HCASMCs. Alignment and elongation of HCASMCs on random non-woven nanofibrous silk scaffolds was observed within 5 days after seeding based on SEM and confocal microscopy. Short cord-like structures formed from HAECs on the scaffolds by day 4, and a complex interconnecting network of capillary tubes with identifiable lumens was demonstrated by day 7. The preservation of cell phenotype on the silk fibroin scaffolds was confirmed by the presence of cell-specific markers, including CD146, VE-cadherin, PECAM-1 and vWF for HAECs, and SM-MHC2 and SM-actin for HCASMCs at both protein and transcription levels using immunocytochemistry and real-time RT-PCR, respectively. Formation of ECM was also demonstrated for the HCASMCs, based on the quantification of collagen type I expression at protein and transcription levels. The results indicate a favorable interaction between vascular cells and electrospun silk fibroin scaffolds. When these results are factored into the useful mechanical properties and slow degradability of this protein biomaterial matrix, potential utility in tissue-engineered blood vessels can be envisioned.
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Affiliation(s)
- Xiaohui Zhang
- Department of Chemical and Biological Engineering and Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA
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Yao L, Liu J, Andreadis ST. Composite fibrin scaffolds increase mechanical strength and preserve contractility of tissue engineered blood vessels. Pharm Res 2007; 25:1212-21. [PMID: 18092140 DOI: 10.1007/s11095-007-9499-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Accepted: 11/08/2007] [Indexed: 10/22/2022]
Abstract
OBJECTIVES We recently demonstrated that fibrin-based tissue engineered blood vessels (TEV) exhibited vascular reactivity, matrix remodeling and sufficient strength for implantation into the veins of an ovine animal model, where they remained patent for 15 weeks. Here we present an approach to improve the mechanical properties of fibrin-based TEV and examine the relationship between mechanical strength and smooth muscle cell (SMC) function. MATERIALS AND METHODS To this end, we prepared TEV that were composed of two layers: a cellular layer containing SMC embedded in fibrin hydrogel to provide contractility and matrix remodeling; and a second cell-free fibrin layer composed of high concentration fibrinogen to provide mechanical strength. RESULTS The ultimate tensile force of double-layered TEV increased with FBG concentration in the cell-free layer in a dose-dependent manner. Double-layered TEV exhibited burst pressure that was ten-fold higher than single-layered tissues but vascular reactivity remained high even though the cells were constricting an additional tissue layer. CONCLUSION These results showed that mechanical strength results largely from the biomaterial but contractility requires active cellular machinery. Consequently, they may suggest novel approaches for engineering biomaterials that satisfy the requirement for high mechanical strength while preserving SMC function.
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Affiliation(s)
- Lan Yao
- Bioengineering Laboratory, Department of Chemical and Biological Engineering, State University of New York at Buffalo, Amherst, NY 14260, USA
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Shen H, Hu X, Yang F, Bei J, Wang S. Combining oxygen plasma treatment with anchorage of cationized gelatin for enhancing cell affinity of poly(lactide-co-glycolide). Biomaterials 2007; 28:4219-30. [PMID: 17618682 DOI: 10.1016/j.biomaterials.2007.06.004] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Accepted: 06/05/2007] [Indexed: 10/23/2022]
Abstract
Surface characteristics greatly influence attachment and growth of cells on biomaterials. Although polylactone-type biodegradable polymers have been widely used as scaffold materials for tissue engineering, lack of cell recognition sites, poor hydrophilicity and low surface energy lead to a bad cell affinity of the polymers, which limit the usage of polymers as scaffolds in tissue engineering. In the present study, surface of poly (L-lactide-co-glycolide) (PLGA) was modified by a method of combining oxygen plasma treatment with anchorage of cationized gelatin. Modification effect of the method was compared with other methods of oxygen plasma treatment, cationized gelatin or gelatin coating and combining oxygen plasma treatment with anchorage of gelatin. The change of surface property was compared by contact angles, surface energy, X-ray photoelectron spectra (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) measurement. The optimum oxygen pretreatment time determined by surface energy was 10 min when the power was 50 W and the oxygen pressure was 20 Pa. Analysis of the stability of gelatin and cationized gelatin anchored on PLGA by XPS, ATR-FTIR, contact angles and surface energy measurement indicated the cationized gelatin was more stable than gelatin. The result using mouse NIH 3T3 fibroblasts as model cells to evaluate cell affinity in vitro showed the cationized gelatin-anchored PLGA (OCG-PLGA) was more favorable for cell attachment and growth than oxygen plasma treated PLGA (O-PLGA) and gelatin-anchored PLGA (OG-PLGA). Moreover cell affinity of OCG-PLGA could match that of collagen-anchored PLGA (AC-PLGA). So the surface modification method combining oxygen plasma treatment with anchorage of cationized gelatin provides a universally effective way to enhance cell affinity of polylactone-type biodegradable polymers.
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Affiliation(s)
- Hong Shen
- BNLMS, State Key Laboratory of Polymer Physics & Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
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McMillan JR, Akiyama M, Tanaka M, Yamamoto S, Goto M, Abe R, Sawamura D, Shimomura M, Shimizu H. Small-diameter porous poly (epsilon-caprolactone) films enhance adhesion and growth of human cultured epidermal keratinocyte and dermal fibroblast cells. ACTA ACUST UNITED AC 2007; 13:789-98. [PMID: 17228993 DOI: 10.1089/ten.2006.0321] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Autologous keratinocyte grafts provide clinical benefit by rapidly covering wounded areas, but they are fragile. We therefore developed biocompatible hexagonal-packed porous films with uniform, circular pore sizes to support human keratinocytes and fibroblasts. Cells were cultured on these porous poly (epsilon-calprolactone) films with pore sizes ranging from novel ultra-small 3 microm to 20 microm. These were compared with flat (pore-less) films. Cell growth rates, adhesion, migration, and ultrastructural morphology were examined. Human keratinocytes and fibroblasts attached to all films. Furthermore, small-pore (3-5 microm) films showed the highest levels of cell adhesion and survival and prevented migration into the pores and opposing film surface. Keratinocyte migration over small-pore film surface was inhibited. Keratinocytes optimally attached to 3-microm-pore films due to a combination of greater pore numbers (porosity), a greater circumference of the pore edge per unit surface area, and greater frequency of flat surface areas for attachment, allowing better cell-substrate and cell-cell attachment and growth. The 3-microm pore size allowed cell-cell communication, together with diffusion of soluble nutrients and factors from the culture medium or wound substrate. These characteristics are considered important in developing grafts for use in the treatment of human skin wounds.
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Affiliation(s)
- James R McMillan
- Department of Dermatology, Hokkaido University, Graduate School of Medicine, Sapporo, Japan.
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Stylios G, Wan T, Giannoudis P. Present status and future potential of enhancing bone healing using nanotechnology. Injury 2007; 38 Suppl 1:S63-74. [PMID: 17383487 DOI: 10.1016/j.injury.2007.02.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
An overview of the current state of tissue engineering material systems used in bone healing is presented. A variety of fabrication processes have been developed that have resulted in porous implant substrates that can address unresolved clinical problems. The merits of these biomaterial systems are evaluated in the context of the mechanical properties and biomedical performances most suitable for bone healing. An optimal scaffold for bone tissue engineering applications should be biocompatible and act as a 3D template for in vitro and in vivo bone growth; in addition, its degradation products should be non-toxic and easily excreted by the body. To achieve these features, scaffolds must consist of an interconnected porous network of micro- and nanoscale to allow extensive body fluid transport through the pores, which will trigger bone ingrowth, cell migration, tissue ingrowth, and eventually vascularization.
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Jenkins M, Harrison K, Silva M, Whitaker M, Shakesheff K, Howdle S. Characterisation of microcellular foams produced from semi-crystalline PCL using supercritical carbon dioxide. Eur Polym J 2006. [DOI: 10.1016/j.eurpolymj.2006.07.022] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Rücker M, Laschke MW, Junker D, Carvalho C, Schramm A, Mülhaupt R, Gellrich NC, Menger MD. Angiogenic and inflammatory response to biodegradable scaffolds in dorsal skinfold chambers of mice. Biomaterials 2006; 27:5027-38. [PMID: 16769111 DOI: 10.1016/j.biomaterials.2006.05.033] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Accepted: 05/18/2006] [Indexed: 11/28/2022]
Abstract
For tissue engineering, scaffolds should be biocompatible and promote neovascularization. Because little is known on those specific properties, we herein studied in vivo the host angiogenic and inflammatory response after implantation of commonly used scaffold materials. Porous poly(L-lactide-co-glycolide) (PLGA) and collagen-chitosan-hydroxyapatite hydrogel scaffolds were implanted into dorsal skinfold chambers of balb/c mice. Additional animals received cortical bone as an isogeneic, biological implant, while chambers of animals without implants served as controls. Angiogenesis and neovascularization as well as leukocyte-endothelial cell interaction and microvascular permeability were analyzed over 14 day using intravital fluorescence microscopy. PLGA scaffolds showed a slight increase in leukocyte recruitment compared to controls. This was associated with an elevation of microvascular permeability, which was comparable to that observed in isogeneic bone tissue. Of interest, PLGA induced a marked angiogenic response, revealing a density of newly formed capillaries almost similar to that observed in bone implants. Histology showed infiltration of macrophages, probably indicating resorption of the biomaterial. In contrast, hydrogel scaffolds induced a severe inflammation, as indicated by an approximately 15-fold increase of leukocyte-endothelial cell interaction and a marked elevation of microvascular permeability. This was associated by induction of apoptotic cell death within the surrounding tissue and a complete lack of ingrowth of newly formed microvessels. Histology confirmed adequate engraftment of PLGA and isogeneic bone but not hydrogel within the host tissue. PLGA scaffolds show a better biocompatibility than hydrogel scaffolds and promote vascular ingrowth, guaranteeing adequate engraftment within the host tissue.
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Affiliation(s)
- Martin Rücker
- Department of Oral and Maxillofacial Surgery, Hannover Medical School, D-30625 Hannover, Germany.
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Ginty PJ, Howard D, Rose FRAJ, Whitaker MJ, Barry JJA, Tighe P, Mutch SR, Serhatkulu G, Oreffo ROC, Howdle SM, Shakesheff KM. Mammalian cell survival and processing in supercritical CO(2). Proc Natl Acad Sci U S A 2006; 103:7426-31. [PMID: 16651535 PMCID: PMC1464355 DOI: 10.1073/pnas.0508895103] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We demonstrate that mammalian cells can survive for 5 min within high-pressure CO(2)(.) Cell survival was investigated by exposing a range of mammalian cell types to supercritical CO(2) (scCO(2)) (35 degrees C, 74 bar; 1 bar = 100 kPa) for increasing exposure and depressurization times. The myoblastic C2C12 cell line, 3T3 fibroblasts, chondrocytes, and hepatocytes all displayed appreciable but varying metabolic activity with exposure times up to 1 min. With depressurization times of 4 min, cell population metabolic activity was >/=70% of the control population. Based on survival data, we developed a single-step scCO(2) technique for the rapid production of biodegradable poly(dl-lactic acid) scaffolds containing mammalian cells. By using optimum cell-survival conditions, scCO(2) was used to process poly(dl-lactic acid) containing a cell suspension, and, upon pressure release, a polymer sponge containing viable mammalian cells was formed. Cell functionality was demonstrated by retention of an osteogenic response to bone morphogenetic protein-2 in C2C12 cells. A gene microarray analysis showed no statistically significant changes in gene expression across 4,418 genes by a single-class t test. A significance analysis of microarrays revealed only eight genes that were down-regulated based on a delta value of 1.0125 and a false detection rate of 0.
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Affiliation(s)
- Patrick J. Ginty
- Schools of *Pharmacy and
- Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | | | | | - Martin J. Whitaker
- Schools of *Pharmacy and
- Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - John J. A. Barry
- Schools of *Pharmacy and
- Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - Patrick Tighe
- Division of Molecular Immunology, Queens Medical Centre, University Hospital, Nottingham NG7 2UH, United Kingdom; and
| | - Stacey R. Mutch
- Division of Molecular Immunology, Queens Medical Centre, University Hospital, Nottingham NG7 2UH, United Kingdom; and
| | - Gulay Serhatkulu
- Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - Richard O. C. Oreffo
- Bone and Joint Research Group, University of Southampton, Southampton SO16 6YD, United Kingdom
| | - Steven M. Howdle
- Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom
- To whom correspondence may be addressed. E-mail:
or
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Lv Q, Feng Q, Hu K, Cui F. Three-dimensional fibroin/collagen scaffolds derived from aqueous solution and the use for HepG2 culture. POLYMER 2005. [DOI: 10.1016/j.polymer.2005.10.137] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Duffy MT, Bloom JN, McNally-Heintzelman KM, Heintzelman DL, Soller EC, Hoffman GT. Sutureless ophthalmic surgery: a scaffold-enhanced bioadhesive technique. J AAPOS 2005; 9:315-20. [PMID: 16102479 DOI: 10.1016/j.jaapos.2005.04.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Revised: 04/04/2005] [Accepted: 04/04/2005] [Indexed: 11/26/2022]
Abstract
PURPOSE Bioadhesives have had limited use in ophthalmic surgery. Problems with these adhesives have included inadequate tensile strength and difficulty with their application to the tissue site. We evaluated a scaffold-enhanced cyanoacrylate bioadhesive composite as an alternative to sutures in ophthalmic surgery, including strabismus procedures. METHODS AND MATERIALS The bioadhesive composite consisted of 2-octyl-cyanoacrylate combined with either a poly(L-lactic-co-glycolic acid) (PLGA) scaffold or a rehydrated porcine small intestine submucosa (SIS) scaffold. Extraocular rectus muscle and sclera were obtained from rabbits (n = 40) and were used, with these bioadhesive composites, to produce rectus muscle-to-sclera, sclera-to-sclera, and rectus muscle-to-rectus muscle adhesions. Control adhesions were created with cyanoacrylate only. The breaking load of the tissue repair was measured with a material strength-testing machine. RESULTS In all cases, the scaffold-enhanced cyanoacrylate adhesions were significantly stronger (P < 0.001) than the cyanoacrylate alone. The rectus muscle-to-sclera adhesions were greater than the in vivo forces reported for the horizontal rectus muscles in humans in extreme gaze. CONCLUSION This scaffold-enhanced bioadhesive composite produced initial muscle-sclera adhesions with strength satisfactory for strabismus surgery. It also may be applicable to other categories of ophthalmic surgery as a substitute for sutures.
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Affiliation(s)
- Mark T Duffy
- Department of Ophthalmology and Visual Sciences, University of Illinois College of Medicine, Chicago, Illinois, USA
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Prabhakar RL, Brocchini S, Knowles JC. Effect of glass composition on the degradation properties and ion release characteristics of phosphate glass—polycaprolactone composites. Biomaterials 2005; 26:2209-18. [PMID: 15585222 DOI: 10.1016/j.biomaterials.2004.07.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2004] [Accepted: 07/07/2004] [Indexed: 11/24/2022]
Abstract
A series of polycaprolactone and ternary-based (Na(2)O)(0.55-x)(CaO)(x)(P(2)O(5))(0.45) glass composites were created, each containing 20% volume percentage of glass with various calcium compositions. A short-term degradation study was carried out to investigate the physical and ion release behaviour of these composites, utilising analytical techniques such as dynamical mechanical analysis, and ion chromatography. All the composites experienced significant loss of weight and stiffness throughout the study, with the 24 mol% calcium composites losing the greatest amount of weight and stiffness. The pH profile of the aqueous solutions in which the composites were placed were initially acidic, but began to neutralise mid-way through the study, with the 36 mol% solution achieving the most acidic conditions. The ion release behaviour mirrored the mass loss behaviour of the glass component of the composites. The cations (sodium and calcium ions) release was comparable with the initial stages of composite mass degradation, both of which exhibited almost immediate release when placed into solution. The 24 mol% composites underwent rapid rates of cation release, while the 36 mol% experienced the slowest rates of release. By contrast, anion (phosphates and polyphosphates) release showed a dissimilar trend, with rapid release of the P(2)O(7) and P(3)O(10) occurring during the first few hours in solution, whilst the P(3)O(9) structure released steadily during the first 48 h in solution. Finally, PO(4) release was at a constant rate over the duration of the study, releasing up to 300 ppm from the 32 and 36 mol% samples by the end of 200 h. To summarise, these results show that by combining phosphate glasses with biodegradable polymer, it is possible to create composites whose rate of degradation can be controlled to meet the needs of their end application.
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Affiliation(s)
- Roopa L Prabhakar
- Division of Biomaterials and Tissue Engineering, Eastman Dental Institute, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK
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Kakisis JD, Liapis CD, Breuer C, Sumpio BE. Artificial blood vessel: The Holy Grail of peripheral vascular surgery. J Vasc Surg 2005; 41:349-54. [PMID: 15768021 DOI: 10.1016/j.jvs.2004.12.026] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Artificial blood vessels composed of viable tissue represent the ideal vascular graft. Compliance, lack of thrombogenicity, and resistance to infections as well as the ability to heal, remodel, contract, and secrete normal blood vessel products are theoretical advantages of such grafts. Three basic elements are generally required for the construction of an artificial vessel: a structural scaffold, made either of collagen or a biodegradable polymer; vascular cells, and a nurturing environment. Mechanical properties of the artificial vessels are enhanced by bioreactors that mimic the in vivo environment of the vascular cells by producing pulsatile flow. Alternative approaches include the production of fibrocollagenous tubes within the recipient's own body (subcutaneous tissue or peritoneal cavity) and the construction of an artificial vessel from acellular native tissues, such as decellularized small intestine submucosa, ureter, and allogeneic or xenogeneic arteries. This review details the most recent developments on vascular tissue engineering, summarizes the results of initial experiments on animals and humans, and outlines the current status and the challenges for the future.
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Affiliation(s)
- John D Kakisis
- Department of Vascular Surgery, Yale University School of Medicine, New Haven, CT 06510, USA
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Boccaccini A, Blaker J, Maquet V, Day R, Jérôme R. Preparation and characterisation of poly(lactide-co-glycolide) (PLGA) and PLGA/Bioglass® composite tubular foam scaffolds for tissue engineering applications. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2005. [DOI: 10.1016/j.msec.2004.03.002] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Sarazin P, Roy X, Favis BD. Controlled preparation and properties of porous poly(l-lactide) obtained from a co-continuous blend of two biodegradable polymers. Biomaterials 2004; 25:5965-78. [PMID: 15183611 DOI: 10.1016/j.biomaterials.2004.01.065] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2003] [Accepted: 01/26/2004] [Indexed: 11/19/2022]
Abstract
This study prepares porous PLLA from a blend of two biodegradable polymers. This approach is based on a detailed and quantitative morphology control of the blends. Co-continuous blends comprised of poly(L-lactide)/poly(epsilon-caprolactone) PLLA/PCL, were prepared via melt processing. Through a judicious combination of concentration control and a subsequent annealing step it is possible to generate a wide range of sizes for the co-continuous phases. Subsequent extraction of the PCL porogen phase generates a fully interconnected porous PLLA material with a void volume between 50% and 60%. The volume average pore diameter is controlled from 1.5 to 88 microm as measured by mercury intrusion porosimetry. Through static annealing it is also possible to generate porous structures well beyond that upper limit of pore size. The upper limit of pore size reported above is in the range required for scaffolds for tissue engineering. Micrographs of porous polyglycolide and PCL derived from co-continuous blends of PLLA/polyglycolide and PCL/poly(ethylene oxide) are also shown and demonstrate the versatility and wide applicability of this preparation protocol. The porous structures produced from PLLA/PCL blends possess a high level of mechanical integrity and a degree of crystallinity between 25% and 38%. High values of both compressive modulus and strength at 10%-strain are obtained, greater than 190 and 11 MPa, respectively. The compressive modulus is found to be from 10% to 20% of that of the pure PLLA material. A series of loading studies were also carried out and it was shown that under a pressure of 40 atm applied for 1 h, the pores of a 1.5 microm porous PLLA structure were filled to approximately 80% by water. In addition, the loading of an aqueous solution of a model drug compound, bovine serum albumin (BSA), was carried out at 40 atm and the results indicate that large quantities of BSA (up to 25% of the weight of the original porous capsule) can be driven into the pores. These results indicate that the internal porous structure is accessible to aqueous solution and that this material also has potential as a substrate for controlled release applications.
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Affiliation(s)
- Pierre Sarazin
- Department of Chemical Engineering Ecole Polytechnique, Centre de Recherche Appliquée Sur les Polymères, P.O. Box 6079, Station Centre-Ville, Montréal, Que., Canada H3C 3A7
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Huang W, Carlsen B, Wulur I, Rudkin G, Ishida K, Wu B, Yamaguchi DT, Miller TA. BMP-2 exerts differential effects on differentiation of rabbit bone marrow stromal cells grown in two-dimensional and three-dimensional systems and is required for in vitro bone formation in a PLGA scaffold. Exp Cell Res 2004; 299:325-34. [PMID: 15350532 DOI: 10.1016/j.yexcr.2004.04.051] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2003] [Revised: 03/24/2004] [Indexed: 11/27/2022]
Abstract
Osteogenic differentiation of bone marrow stromal cells (BMSC) in a three-dimensional (3-D) scaffold has not been well studied. In this work, we studied expression of bone-related genes during differentiation of rabbit BMSCs in response to bone morphogenetic protein (BMP)-2 in both 2-D and 3-D culture systems. When BMSCs were cultured on films (2-D) of biodegradable poly(lactide-co-glycolide) (PLGA), increases in mRNA expression of type I collagen (Col I) and vascular endothelial growth factor (VEGF) became evident after 1 week. However, expression of both genes was only mildly stimulated by BMP-2. Expression of the osteopontin gene was highly stimulated by BMP-2 treatment. Expression of chordin, a BMP antagonist, increased significantly after 7 days. The increase was abrogated by BMP-2 treatment. BMP-2 was also able to stimulate mineralization of cultured BMSCs. After cells were switched to 3-D PLGA scaffolds for 24 h, expression of osteopontin and VEGF were markedly increased while expression of type I collagen and chordin remained unchanged. Expression of Col I did not increase with time in a 3-D culture as it did when cells were cultured on a 2-D film. We further explored the possibility of engineering bone tissue in vitro by seeding BMSCs into PLGA scaffolds. Cellular differentiation and bone formation in the scaffolds were analyzed histologically at 2 weeks and 2 months. Secretion of ECM by cells was evident at both 2-week and 2-month scaffolds, and was enhanced by rhBMP-2. Striking differences in 2-month scaffolds were observed between BMP-treated and untreated cells. A woven bone-like structure appeared in the scaffolds treated with BMP-2. The structure was verified to be bone-related by: (1) the presence of organized collagen fibrils; (2) the presence of mineral; and (3) morphological features of trabecular bone. Although collagen was abundant in the untreated 2-month scaffolds, it was disorganized. The untreated scaffolds also lacked mineral deposits, which were present in 2-D cultured cells even in the absence of BMP-2. Our results indicate that the requirement of osteo-inductive agents, such as BMP-2, is essential for bone tissue engineering.
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Affiliation(s)
- Weibiao Huang
- Plastic Surgery Section, VA Greater LA Healthcare System, Los Angeles, CA 90073, USA
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