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Gewert B, Plassmann MM, MacLeod M. Pathways for degradation of plastic polymers floating in the marine environment. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2015; 17:1513-1521. [PMID: 26216708 DOI: 10.1039/c5em00207a] [Citation(s) in RCA: 640] [Impact Index Per Article: 71.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Each year vast amounts of plastic are produced worldwide. When released to the environment, plastics accumulate, and plastic debris in the world's oceans is of particular environmental concern. More than 60% of all floating debris in the oceans is plastic and amounts are increasing each year. Plastic polymers in the marine environment are exposed to sunlight, oxidants and physical stress, and over time they weather and degrade. The degradation processes and products must be understood to detect and evaluate potential environmental hazards. Some attention has been drawn to additives and persistent organic pollutants that sorb to the plastic surface, but so far the chemicals generated by degradation of the plastic polymers themselves have not been well studied from an environmental perspective. In this paper we review available information about the degradation pathways and chemicals that are formed by degradation of the six plastic types that are most widely used in Europe. We extrapolate that information to likely pathways and possible degradation products under environmental conditions found on the oceans' surface. The potential degradation pathways and products depend on the polymer type. UV-radiation and oxygen are the most important factors that initiate degradation of polymers with a carbon-carbon backbone, leading to chain scission. Smaller polymer fragments formed by chain scission are more susceptible to biodegradation and therefore abiotic degradation is expected to precede biodegradation. When heteroatoms are present in the main chain of a polymer, degradation proceeds by photo-oxidation, hydrolysis, and biodegradation. Degradation of plastic polymers can lead to low molecular weight polymer fragments, like monomers and oligomers, and formation of new end groups, especially carboxylic acids.
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Affiliation(s)
- Berit Gewert
- Stockholm University, Department of Environmental Science & Analytical Chemistry (ACES), Stockholm, Sweden.
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Limbert G, Omar R, Krynauw H, Bezuidenhout D, Franz T. The anisotropic mechanical behaviour of electro-spun biodegradable polymer scaffolds: Experimental characterisation and constitutive formulation. J Mech Behav Biomed Mater 2015; 53:21-39. [PMID: 26301317 DOI: 10.1016/j.jmbbm.2015.07.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 07/07/2015] [Accepted: 07/16/2015] [Indexed: 01/17/2023]
Abstract
Electro-spun biodegradable polymer fibrous structures exhibit anisotropic mechanical properties dependent on the degree of fibre alignment. Degradation and mechanical anisotropy need to be captured in a constitutive formulation when computational modelling is used in the development and design optimisation of such scaffolds. Biodegradable polyester-urethane scaffolds were electro-spun and underwent uniaxial tensile testing in and transverse to the direction of predominant fibre alignment before and after in vitro degradation of up to 28 days. A microstructurally-based transversely isotropic hyperelastic continuum constitutive formulation was developed and its parameters were identified from the experimental stress-strain data of the scaffolds at various stages of degradation. During scaffold degradation, maximum stress and strain in circumferential direction decreased from 1.02 ± 0.23 MPa to 0.38 ± 0.004 MPa and from 46 ± 11 % to 12 ± 2 %, respectively. In longitudinal direction, maximum stress and strain decreased from 0.071 ± 0.016 MPa to 0.010 ± 0.007 MPa and from 69 ± 24 % to 8 ± 2 %, respectively. The constitutive parameters were identified for both directions of the non-degraded and degraded scaffold for strain range varying between 0% and 16% with coefficients of determination r(2)>0.871. The six-parameter constitutive formulation proved versatile enough to capture the varying non-linear transversely isotropic behaviour of the fibrous scaffold throughout various stages of degradation.
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Affiliation(s)
- Georges Limbert
- National Centre for Advanced Tribology at Southampton (nCATS), Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK; Bioengineering Science Research Group, Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK; Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa.
| | - Rodaina Omar
- Cardiovascular Research Unit, Chris Barnard Department of Cardiothoracic Surgery, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa
| | - Hugo Krynauw
- Cardiovascular Research Unit, Chris Barnard Department of Cardiothoracic Surgery, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa
| | - Deon Bezuidenhout
- Cardiovascular Research Unit, Chris Barnard Department of Cardiothoracic Surgery, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa
| | - Thomas Franz
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa; Centre for Research in Computational and Applied Mechanics, University of Cape Town, Rondebosch 7701, South Africa; Research Office, University of Cape Town, Mowbray 7701, South Africa
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53
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Pan G, Liu S, Zhao X, Zhao J, Fan C, Cui W. Full-course inhibition of biodegradation-induced inflammation in fibrous scaffold by loading enzyme-sensitive prodrug. Biomaterials 2015; 53:202-10. [DOI: 10.1016/j.biomaterials.2015.02.078] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 02/13/2015] [Accepted: 02/19/2015] [Indexed: 01/08/2023]
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Guo R, Ward CL, Davidson JM, Duvall CL, Wenke JC, Guelcher SA. A transient cell-shielding method for viable MSC delivery within hydrophobic scaffolds polymerized in situ. Biomaterials 2015; 54:21-33. [PMID: 25907036 PMCID: PMC4409667 DOI: 10.1016/j.biomaterials.2015.03.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 02/26/2015] [Accepted: 03/04/2015] [Indexed: 11/23/2022]
Abstract
Cell-based therapies have emerged as promising approaches for regenerative medicine. Hydrophobic poly(ester urethane)s offer the advantages of robust mechanical properties, cell attachment without the use of peptides, and controlled degradation by oxidative and hydrolytic mechanisms. However, the application of injectable hydrophobic polymers to cell delivery is limited by the challenges of protecting cells from reaction products and creating a macroporous architecture post-cure. We designed injectable carriers for cell delivery derived from reactive, hydrophobic polyisocyanate and polyester triol precursors. To overcome cell death caused by reaction products from in situ polymerization, we encapsulated bone marrow-derived stem cells (BMSCs) in fastdegrading, oxidized alginate beads prior to mixing with the hydrophobic precursors. Cells survived the polymerization at >70% viability, and rapid dissolution of oxidized alginate beads after the scaffold cured created interconnected macropores that facilitated cellular adhesion to the scaffold in vitro. Applying this injectable system to deliver BMSCs to rat excisional skin wounds showed that the scaffolds supported survival of transplanted cells and infiltration of host cells, which improved new tissue formation compared to both implanted, pre-formed scaffolds seeded with cells and acellular controls. Our design is the first to enable injectable delivery of settable, hydrophobic scaffolds where cell encapsulation provides a mechanism for both temporary cytoprotection during polymerization and rapid formation of macropores post-polymerization. This simple approach provides potential advantages for cell delivery relative to hydrogel technologies, which have weaker mechanical properties and require incorporation of peptides to achieve cell adhesion and degradability.
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Affiliation(s)
- Ruijing Guo
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA; Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Catherine L Ward
- US Army Institute of Surgical Research, Fort Sam Houston, TX, USA
| | - Jeffrey M Davidson
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, USA; Research Service, VA Tennessee Valley Healthcare System, Nashville, TN, USA
| | - Craig L Duvall
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Joseph C Wenke
- US Army Institute of Surgical Research, Fort Sam Houston, TX, USA
| | - Scott A Guelcher
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA; Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
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55
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Rottmar M, Richter M, Mäder X, Grieder K, Nuss K, Karol A, von Rechenberg B, Zimmermann E, Buser S, Dobmann A, Blume J, Bruinink A. In vitro investigations of a novel wound dressing concept based on biodegradable polyurethane. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2015; 16:034606. [PMID: 27877793 PMCID: PMC5099830 DOI: 10.1088/1468-6996/16/3/034606] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 03/15/2015] [Accepted: 03/15/2015] [Indexed: 06/06/2023]
Abstract
Non-healing and partially healing wounds are an important problem not only for the patient but also for the public health care system. Current treatment solutions are far from optimal regarding the chosen material properties as well as price and source. Biodegradable polyurethane (PUR) scaffolds have shown great promise for in vivo tissue engineering approaches, but accomplishment of the goal of scaffold degradation and new tissue formation developing in parallel has not been observed so far in skin wound repair. In this study, the mechanical properties and degradation behavior as well as the biocompatibility of a low-cost synthetic, pathogen-free, biocompatible and biodegradable extracellular matrix mimicking a PUR scaffold was evaluated in vitro. The novel PUR scaffolds were found to meet all the requirements for optimal scaffolds and wound dressings. These three-dimensional scaffolds are soft, highly porous, and form-stable and can be easily cut into any shape desired. All the material formulations investigated were found to be nontoxic. One formulation was able to be defined that supported both good fibroblast cell attachment and cell proliferation to colonize the scaffold. Tunable biodegradation velocity of the materials could be observed, and the results additionally indicated that calcium plays a crucial role in PUR degradation. Our results suggest that the PUR materials evaluated in this study are promising candidates for next-generation wound treatment systems and support the concept of using foam scaffolds for improved in vivo tissue engineering and regeneration.
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Affiliation(s)
- Markus Rottmar
- Laboratory for Biointerfaces, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstr. 5, CH-9014 St. Gallen, Switzerland
| | - Michael Richter
- Laboratory for Biointerfaces, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstr. 5, CH-9014 St. Gallen, Switzerland
| | - Xenia Mäder
- Laboratory for Biointerfaces, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstr. 5, CH-9014 St. Gallen, Switzerland
| | - Kathrin Grieder
- Laboratory for Biointerfaces, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstr. 5, CH-9014 St. Gallen, Switzerland
| | - Katja Nuss
- MSRU Vetsuisse Faculty ZH, University of Zurich, Winterthurerstr. 260, CH-8057 Zurich, Switzerland
| | - Agnieszka Karol
- MSRU Vetsuisse Faculty ZH, University of Zurich, Winterthurerstr. 260, CH-8057 Zurich, Switzerland
| | - Brigitte von Rechenberg
- MSRU Vetsuisse Faculty ZH, University of Zurich, Winterthurerstr. 260, CH-8057 Zurich, Switzerland
- CABMM, University of Zurich, Winterthurerstr. 260, CH-8057 Zurich, Switzerland
| | | | - Stephan Buser
- nolax AG, Eichenstr. 12, CH-6203 Sempach Station, Switzerland
| | - Andreas Dobmann
- nolax AG, Eichenstr. 12, CH-6203 Sempach Station, Switzerland
| | - Jessica Blume
- nolax AG, Eichenstr. 12, CH-6203 Sempach Station, Switzerland
| | - Arie Bruinink
- Laboratory for Biointerfaces, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstr. 5, CH-9014 St. Gallen, Switzerland
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Sgarioto M, Adhikari R, Gunatillake PA, Moore T, Patterson J, Nagel MD, Malherbe F. High Modulus Biodegradable Polyurethanes for Vascular Stents: Evaluation of Accelerated in vitro Degradation and Cell Viability of Degradation Products. Front Bioeng Biotechnol 2015; 3:52. [PMID: 26000274 PMCID: PMC4422008 DOI: 10.3389/fbioe.2015.00052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 03/27/2015] [Indexed: 01/13/2023] Open
Abstract
We have recently reported the mechanical properties and hydrolytic degradation behavior of a series of NovoSorb™ biodegradable polyurethanes (PUs) prepared by varying the hard segment (HS) weight percentage from 60 to 100. In this study, the in vitro degradation behavior of these PUs with and without extracellular matrix (ECM) coating was investigated under accelerated hydrolytic degradation (phosphate buffer saline; PBS/70°C) conditions. The mass loss at different time intervals and the effect of aqueous degradation products on the viability and growth of human umbilical vein endothelial cells (HUVEC) were examined. The results showed that PUs with HS 80% and below completely disintegrated leaving no visual polymer residue at 18 weeks and the degradation medium turned acidic due to the accumulation of products from the soft segment (SS) degradation. As expected the PU with the lowest HS was the fastest to degrade. The accumulated degradation products, when tested undiluted, showed viability of about 40% for HUVEC cells. However, the viability was over 80% when the solution was diluted to 50% and below. The growth of HUVEC cells is similar to but not identical to that observed with tissue culture polystyrene standard (TCPS). The results from this in vitro study suggested that the PUs in the series degraded primarily due to the SS degradation and the cell viability of the accumulated acidic degradation products showed poor viability to HUVEC cells when tested undiluted, however particles released to the degradation medium showed cell viability over 80%.
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Affiliation(s)
- Melissa Sgarioto
- Faculty of Life and Social Sciences, Swinburne University of Technology , Hawthorn, VIC , Australia ; UMR CNRS 7338 Biomécanique et Bioingénierie, Centre de Recherches de Royallieu, Université de Technologie de Compiègne , Compiègne , France
| | - Raju Adhikari
- CSIRO Manufacturing Flagship , Clayton, VIC , Australia
| | | | - Tim Moore
- PolyNovo Biomaterials Pty Ltd. , Port Melbourne, VIC , Australia
| | - John Patterson
- Faculty of Life and Social Sciences, Swinburne University of Technology , Hawthorn, VIC , Australia
| | - Marie-Danielle Nagel
- UMR CNRS 7338 Biomécanique et Bioingénierie, Centre de Recherches de Royallieu, Université de Technologie de Compiègne , Compiègne , France
| | - François Malherbe
- Faculty of Life and Social Sciences, Swinburne University of Technology , Hawthorn, VIC , Australia
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57
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Fang J, Ye SH, Wang J, Zhao T, Mo X, Wagner WR. Thiol click modification of cyclic disulfide containing biodegradable polyurethane urea elastomers. Biomacromolecules 2015; 16:1622-33. [PMID: 25891476 DOI: 10.1021/acs.biomac.5b00192] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Although the thiol click reaction is an attractive tool for postpolymerization modification of thiolmers, thiol groups are easily oxidized, limiting the potential for covalent immobilization of bioactive molecules. In this study, a series of biodegradable polyurethane elastomers incorporating stable cyclic disulfide groups was developed and characterized. These poly(ester urethane)urea (PEUU-SS) polymers were based on polycaprolactone diol (PCL), oxidized dl-dithiothreitol (O-DTT), lysine diisocyanate (LDI), or butyl diisocyanate (BDI), with chain extension by putrescine. The ratio of O-DTT:PCL was altered to investigate different levels of potential functionalization. PEG acrylate was employed to study the mechanism and availability of both bulk and surface click modification of PEUU-SS polymers. All synthesized PEUU-SS polymers were elastic with breaking strengths of 38-45 MPa, while the PEUU-SS(LDI) polymers were more amorphous, possessing lower moduli and relatively small permanent deformations versus PEUU-SS(BDI) polymers. Variable bulk click modification of PEUU-SS(LDI) polymers was achieved by controlling the amount of reduction reagent, and rapid reaction rates occurred using a one-pot, two-step process. Likewise, surface click reaction could be carried out quickly under mild, aqueous conditions. Furthermore, a maleimide-modified affinity peptide (TPS) was successfully clicked on the surface of an electrospun PEUU-SS(BDI) fibrous sheet, which improved endothelial progenitor cell adhesion versus corresponding unmodified films. The cyclic disulfide containing biodegradable polyurethanes described provide an option for cardiovascular and other soft tissue regenerative medicine applications where a temporary, elastic scaffold with designed biofunctionality from a relatively simple click chemistry approach is desired.
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Affiliation(s)
- Jun Fang
- †State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620, China.,‡McGowan Institute for Regenerative Medicine, University of Pittsburgh, 450 Technology Drive, Suite 300, Pittsburgh, Pennsylvania 15219, United States.,§Department of Surgery, University of Pittsburgh, 200 Lothrop Street F600, Pittsburgh, Pennsylvania 15219, United States.,∥College of Chemistry and Chemical Engineering and Biological Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620, China
| | - Sang-Ho Ye
- ‡McGowan Institute for Regenerative Medicine, University of Pittsburgh, 450 Technology Drive, Suite 300, Pittsburgh, Pennsylvania 15219, United States.,§Department of Surgery, University of Pittsburgh, 200 Lothrop Street F600, Pittsburgh, Pennsylvania 15219, United States
| | - Jing Wang
- †State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620, China.,∥College of Chemistry and Chemical Engineering and Biological Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620, China
| | - Ting Zhao
- ⊥Department of Pharmacology, School of Pharmacy, Second Military Medical University, 325 Guo He Road, Shanghai 200433, China
| | - Xiumei Mo
- †State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620, China.,∥College of Chemistry and Chemical Engineering and Biological Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620, China
| | - William R Wagner
- ‡McGowan Institute for Regenerative Medicine, University of Pittsburgh, 450 Technology Drive, Suite 300, Pittsburgh, Pennsylvania 15219, United States.,§Department of Surgery, University of Pittsburgh, 200 Lothrop Street F600, Pittsburgh, Pennsylvania 15219, United States.,#Department of Chemical Engineering, University of Pittsburgh, 1249 Benedum Hall, Pittsburgh, Pennsylvania 15261, United States.,▽Department of Bioengineering, University of Pittsburgh, 3700 O'Hara Street, Pittsburgh, Pennsylvania 15261, United States
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58
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Abstract
Frequent and frequently deliberate release of plastics leads to accumulation of plastic waste in the environment which is an ever increasing ecological threat.
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Affiliation(s)
- Neha Mahajan
- Department of Biotechnology
- Govt Degree College Kathua
- Higher Education Department
- India 184104
| | - Pankaj Gupta
- Department of Chemistry
- Govt Degree College Kathua
- Higher Education Department
- India 184104
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59
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Adolph EJ, Pollins AC, Cardwell NL, Davidson JM, Guelcher SA, Nanney LB. Biodegradable lysine-derived polyurethane scaffolds promote healing in a porcine full-thickness excisional wound model. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2014; 25:1973-85. [PMID: 25290884 DOI: 10.1080/09205063.2014.965997] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Lysine-derived polyurethane scaffolds (LTI-PUR) support cutaneous wound healing in loose-skinned small animal models. Due to the physiological and anatomical similarities of human and pig skin, we investigated the capacity of LTI-PUR scaffolds to support wound healing in a porcine excisional wound model. Modifications to scaffold design included the addition of carboxymethylcellulose (CMC) as a porogen to increase interconnectivity and an additional plasma treatment (Plasma) to decrease surface hydrophobicity. All LTI-PUR scaffold and formulations supported cellular infiltration and were biodegradable. At 15 days, CMC and plasma scaffolds simulated increased macrophages more so than LTI PUR or no treatment. This response was consistent with macrophage-mediated oxidative degradation of the lysine component of the scaffolds. Cell proliferation was similar in control and scaffold-treated wounds at 8 and 15 days. Neither apoptosis nor blood vessel area density showed significant differences in the presence of any of the scaffold variations compared with untreated wounds, providing further evidence that these synthetic biomaterials had no adverse effects on those pivotal wound healing processes. During the critical phase of granulation tissue formation in full thickness porcine excisional wounds, LTI-PUR scaffolds supported tissue infiltration, while undergoing biodegradation. Modifications to scaffold fabrication modify the reparative process. This study emphasizes the biocompatibility and favorable cellular responses of PUR scaffolding formulations in a clinically relevant animal model.
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Affiliation(s)
- Elizabeth J Adolph
- a Department of Chemical and Biomolecular Engineering , Vanderbilt University , Nashville , TN , USA
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60
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Su LC, Xie Z, Zhang Y, Nguyen KT, Yang J. Study on the Antimicrobial Properties of Citrate-Based Biodegradable Polymers. Front Bioeng Biotechnol 2014; 2:23. [PMID: 25023605 PMCID: PMC4090902 DOI: 10.3389/fbioe.2014.00023] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 06/17/2014] [Indexed: 02/05/2023] Open
Abstract
Citrate-based polymers possess unique advantages for various biomedical applications since citric acid is a natural metabolism product, which is biocompatible and antimicrobial. In polymer synthesis, citric acid also provides multiple functional groups to control the crosslinking of polymers and active binding sites for further conjugation of biomolecules. Our group recently developed a number of citrate-based polymers for various biomedical applications by taking advantage of their controllable chemical, mechanical, and biological characteristics. In this study, various citric acid derived biodegradable polymers were synthesized and investigated for their physicochemical and antimicrobial properties. Results indicate that citric acid derived polymers reduced bacterial proliferation to different degrees based on their chemical composition. Among the studied polymers, poly(octamethylene citrate) showed ~70-80% suppression to microbe proliferation, owing to its relatively higher ratio of citric acid contents. Crosslinked urethane-doped polyester elastomers and biodegradable photoluminescent polymers also exhibited significant bacteria reduction of ~20 and ~50% for Staphylococcus aureus and Escherichia coli, respectively. Thus, the intrinsic antibacterial properties in citrate-based polymers enable them to inhibit bacteria growth without incorporation of antibiotics, silver nanoparticles, and other traditional bacteria-killing agents suggesting that the citrate-based polymers are unique beneficial materials for wound dressing, tissue engineering, and other potential medical applications where antimicrobial property is desired.
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Affiliation(s)
- Lee-Chun Su
- Department of Bioengineering, University of Texas at Arlington, Arlington, TX, USA
| | - Zhiwei Xie
- Department of Biomedical Engineering, Materials Research Institute, The Huck Institutes of The Life Sciences, The Pennsylvania State University, University Park, PA, USA
| | - Yi Zhang
- Department of Bioengineering, University of Texas at Arlington, Arlington, TX, USA
| | - Kytai Truong Nguyen
- Department of Bioengineering, University of Texas at Arlington, Arlington, TX, USA
| | - Jian Yang
- Department of Biomedical Engineering, Materials Research Institute, The Huck Institutes of The Life Sciences, The Pennsylvania State University, University Park, PA, USA
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61
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Radiopaque iodinated poly(ester-urethane)s based on poly(butylene succinate): Retarded crystallization and dual recrystallization behaviour. POLYMER 2014. [DOI: 10.1016/j.polymer.2014.04.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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62
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Prieto EM, Page JM, Harmata AJ, Guelcher SA. Injectable foams for regenerative medicine. WILEY INTERDISCIPLINARY REVIEWS. NANOMEDICINE AND NANOBIOTECHNOLOGY 2014; 6:136-54. [PMID: 24127230 PMCID: PMC3945605 DOI: 10.1002/wnan.1248] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 08/13/2013] [Accepted: 09/17/2013] [Indexed: 12/21/2022]
Abstract
The design of injectable biomaterials has attracted considerable attention in recent years. Many injectable biomaterials, such as hydrogels and calcium phosphate cements (CPCs), have nanoscale pores that limit the rate of cellular migration and proliferation. While introduction of macroporosity has been suggested to increase cellular infiltration and tissue healing, many conventional methods for generating macropores often require harsh processing conditions that preclude their use in injectable foams. In recent years, processes such as porogen leaching, gas foaming, and emulsion-templating have been adapted to generate macroporosity in injectable CPCs, hydrogels, and hydrophobic polymers. While some of the more mature injectable foam technologies have been evaluated in clinical trials, there are challenges remaining to be addressed, such as the biocompatibility and ultimate fate of the sacrificial phase used to generate pores within the foam after it sets in situ. Furthermore, while implantable scaffolds can be washed extensively to remove undesirable impurities, all of the components required to synthesize injectable foams must be injected into the defect. Thus, every compound in the foam must be biocompatible and noncytotoxic at the concentrations utilized. As future research addresses these critical challenges, injectable macroporous foams are anticipated to have an increasingly significant impact on improving patient outcomes for a number of clinical procedures.
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Affiliation(s)
- Edna M Prieto
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA
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63
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Martin JR, Gupta MK, Page JM, Yu F, Davidson JM, Guelcher SA, Duvall CL. A porous tissue engineering scaffold selectively degraded by cell-generated reactive oxygen species. Biomaterials 2014; 35:3766-76. [PMID: 24491510 DOI: 10.1016/j.biomaterials.2014.01.026] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2013] [Accepted: 01/09/2014] [Indexed: 12/25/2022]
Abstract
Biodegradable tissue engineering scaffolds are commonly fabricated from poly(lactide-co-glycolide) (PLGA) or similar polyesters that degrade by hydrolysis. PLGA hydrolysis generates acidic breakdown products that trigger an accelerated, autocatalytic degradation mechanism that can create mismatched rates of biomaterial breakdown and tissue formation. Reactive oxygen species (ROS) are key mediators of cell function in both health and disease, especially at sites of inflammation and tissue healing, and induction of inflammation and ROS are natural components of the in vivo response to biomaterial implantation. Thus, polymeric biomaterials that are selectively degraded by cell-generated ROS may have potential for creating tissue engineering scaffolds with better matched rates of tissue in-growth and cell-mediated scaffold biodegradation. To explore this approach, a series of poly(thioketal) (PTK) urethane (PTK-UR) biomaterial scaffolds were synthesized that degrade specifically by an ROS-dependent mechanism. PTK-UR scaffolds had significantly higher compressive moduli than analogous poly(ester urethane) (PEUR) scaffolds formed from hydrolytically-degradable ester-based diols (p < 0.05). Unlike PEUR scaffolds, the PTK-UR scaffolds were stable under aqueous conditions out to 25 weeks but were selectively degraded by ROS, indicating that their biodegradation would be exclusively cell-mediated. The in vitro oxidative degradation rates of the PTK-URs followed first-order degradation kinetics, were significantly dependent on PTK composition (p < 0.05), and correlated to ROS concentration. In subcutaneous rat wounds, PTK-UR scaffolds supported cellular infiltration and granulation tissue formation, followed first-order degradation kinetics over 7 weeks, and produced significantly greater stenting of subcutaneous wounds compared to PEUR scaffolds. These combined results indicate that ROS-degradable PTK-UR tissue engineering scaffolds have significant advantages over analogous polyester-based biomaterials and provide a robust, cell-degradable substrate for guiding new tissue formation.
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Affiliation(s)
- John R Martin
- Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, PMB 351631, Nashville, TN 37235-1631, USA
| | - Mukesh K Gupta
- Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, PMB 351631, Nashville, TN 37235-1631, USA
| | - Jonathan M Page
- Chemical and Biomolecular Engineering, Vanderbilt University, 2301 Vanderbilt Place, VU Station B #351604, Nashville, TN 37235-1604, USA
| | - Fang Yu
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jeffrey M Davidson
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Medical Research Service, Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN 37212, USA
| | - Scott A Guelcher
- Chemical and Biomolecular Engineering, Vanderbilt University, 2301 Vanderbilt Place, VU Station B #351604, Nashville, TN 37235-1604, USA
| | - Craig L Duvall
- Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, PMB 351631, Nashville, TN 37235-1631, USA.
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Harmata AJ, Ward CL, Zienkiewicz KJ, Wenke JC, Guelcher SA. Investigating the Effects of Surface-Initiated Polymerization of ε-Caprolactone to Bioactive Glass Particles on the Mechanical Properties of Settable Polymer/Ceramic Composites. JOURNAL OF MATERIALS RESEARCH 2014; 29:2398-2407. [PMID: 25798027 PMCID: PMC4364443 DOI: 10.1557/jmr.2014.254] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Injectable bone grafts with strength exceeding that of trabecular bone could improve the management of a number of orthopaedic conditions. Ceramic/polymer composites have been investigated as weight-bearing bone grafts, but they are typically weaker than trabecular bone due to poor interfacial bonding. We hypothesized that entrapment of surface-initiated poly(ε-caprolactone) (PCL) chains on 45S5 bioactive glass (BG) particles within an in situ-formed polymer network would enhance the mechanical properties of reactive BG/polymer composites. When the surface-initiated PCL molecular weight exceeded the molecular weight between crosslinks of the network, the compressive strength of the composites increased 6- to 10-fold. The torsional strength of the composites exceeded that of human trabecular bone by a factor of two. When injected into femoral condyle defects in rats, the composites supported new bone formation at 8 weeks. The initial bone-like strength of BG/polymer composites and their ability to remodel in vivo highlight their potential for development as injectable grafts for repair of weight-bearing bone defects.
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Affiliation(s)
- Andrew J Harmata
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235 ; Center for Bone Biology, Vanderbilt Medical Center, Nashville, TN 37232
| | - Catherine L Ward
- Orthopaedic Task Area, U.S. Army Institute of Surgical Research, San Antonio, TX 78234
| | - Katarzyna J Zienkiewicz
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235
| | - Joseph C Wenke
- Orthopaedic Task Area, U.S. Army Institute of Surgical Research, San Antonio, TX 78234
| | - Scott A Guelcher
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235 ; Center for Bone Biology, Vanderbilt Medical Center, Nashville, TN 37232 ; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37235
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65
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Nelson CE, Kim AJ, Adolph EJ, Gupta MK, Yu F, Hocking KM, Davidson JM, Guelcher SA, Duvall CL. Tunable delivery of siRNA from a biodegradable scaffold to promote angiogenesis in vivo. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:607-14, 506. [PMID: 24338842 PMCID: PMC3951880 DOI: 10.1002/adma.201303520] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 10/14/2013] [Indexed: 05/17/2023]
Abstract
A system has been engineered for temporally controlled delivery of siRNA from biodegradable tissue regenerative scaffolds. Therapeutic application of this approach to silence prolyl hydroxylase domain 2 promoted expression of pro-angiogenic genes controlled by HIF1α and enhanced scaffold vascularization in vivo. This technology provides a new standard for efficient and controllable gene silencing to modulate host response within regenerative biomaterials.
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Affiliation(s)
- Christopher E. Nelson
- Biomedical Engineering – Vanderbilt University, VU Station B, Box 351631, Nashville TN 37235
| | - Arnold J. Kim
- Biomedical Engineering – Vanderbilt University, VU Station B, Box 351631, Nashville TN 37235
| | - Elizabeth J. Adolph
- Chemical and Biomolecular Engineering – Vanderbilt University, Nashville TN 37235
| | - Mukesh K. Gupta
- Biomedical Engineering – Vanderbilt University, VU Station B, Box 351631, Nashville TN 37235
| | - Fang Yu
- Department of Pathology – Vanderbilt University, Nashville TN 37235
| | - Kyle M. Hocking
- Biomedical Engineering – Vanderbilt University, VU Station B, Box 351631, Nashville TN 37235
| | | | - Scott A. Guelcher
- Chemical and Biomolecular Engineering – Vanderbilt University, Nashville TN 37235
| | - Craig L. Duvall
- Biomedical Engineering – Vanderbilt University, VU Station B, Box 351631, Nashville TN 37235
- Prof. C.L. Duvall, Vanderbilt University, VU Station B, Box 351631, Nashville, TN, 37235, USA,
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66
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Dumas JE, Prieto EM, Zienkiewicz KJ, Guda T, Wenke JC, Bible J, Holt GE, Guelcher SA. Balancing the rates of new bone formation and polymer degradation enhances healing of weight-bearing allograft/polyurethane composites in rabbit femoral defects. Tissue Eng Part A 2013; 20:115-29. [PMID: 23941405 DOI: 10.1089/ten.tea.2012.0762] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
There is a compelling clinical need for bone grafts with initial bone-like mechanical properties that actively remodel for repair of weight-bearing bone defects, such as fractures of the tibial plateau and vertebrae. However, there is a paucity of studies investigating remodeling of weight-bearing bone grafts in preclinical models, and consequently there is limited understanding of the mechanisms by which these grafts remodel in vivo. In this study, we investigated the effects of the rates of new bone formation, matrix resorption, and polymer degradation on healing of settable weight-bearing polyurethane/allograft composites in a rabbit femoral condyle defect model. The grafts induced progressive healing in vivo, as evidenced by an increase in new bone formation, as well as a decrease in residual allograft and polymer from 6 to 12 weeks. However, the mismatch between the rates of autocatalytic polymer degradation and zero-order (independent of time) new bone formation resulted in incomplete healing in the interior of the composite. Augmentation of the grafts with recombinant human bone morphogenetic protein-2 not only increased the rate of new bone formation, but also altered the degradation mechanism of the polymer to approximate a zero-order process. The consequent matching of the rates of new bone formation and polymer degradation resulted in more extensive healing at later time points in all regions of the graft. These observations underscore the importance of balancing the rates of new bone formation and degradation to promote healing of settable weight-bearing bone grafts that maintain bone-like strength, while actively remodeling.
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Affiliation(s)
- Jerald E Dumas
- 1 Department of Chemical and Biomolecular Engineering, Vanderbilt University , Nashville, Tennessee
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67
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Sanchez CJ, Prieto EM, Krueger CA, Zienkiewicz KJ, Romano DR, Ward CL, Akers KS, Guelcher SA, Wenke JC. Effects of local delivery of D-amino acids from biofilm-dispersive scaffolds on infection in contaminated rat segmental defects. Biomaterials 2013; 34:7533-43. [PMID: 23831189 DOI: 10.1016/j.biomaterials.2013.06.026] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 06/14/2013] [Indexed: 01/10/2023]
Abstract
Infectious complications of open fractures continue to be a significant factor contributing to non-osseous union and extremity amputation. The persistence of bacteria within biofilms despite meticulous debridement and antibiotic therapy is believed to be a major cause of chronic infection. Considering the difficulties in treating biofilm-associated infections, the use of biofilm dispersal agents as a therapeutic strategy for the prevention of biofilm-associated infections has gained considerable interest. In this study, we investigated whether local delivery of D-Amino Acids (D-AAs), a biofilm dispersal agent, protects scaffolds from contamination and reduces microbial burden within contaminated rat segmental defects in vivo. In vitro testing on biofilms of clinical isolates of Staphylococcus aureus demonstrated that D-Met, D-Phe, D-Pro, and D-Trp were highly effective at dispersing and preventing biofilm formation individually, and the effect was enhanced for an equimolar mixture of D-AAs. Incorporation of D-AAs into polyurethane scaffolds as a mixture (1:1:1 D-Met:D-Pro:D-Trp) significantly reduced bacterial contamination on the scaffold surface in vitro and within bone when implanted into contaminated femoral segmental defects. Our results underscore the potential of local delivery of d-AAs for reducing bacterial contamination by targeting bacteria within biofilms, which may represent a treatment strategy for improving healing outcomes associated with open fractures.
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Affiliation(s)
- Carlos J Sanchez
- United States Army Institute of Surgical Research, Extremity Trauma and Regenerative Medicine Task Area, Fort Sam Houston, San Antonio, TX, USA
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68
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Chan-Chan LH, Tkaczyk C, Vargas-Coronado RF, Cervantes-Uc JM, Tabrizian M, Cauich-Rodriguez JV. Characterization and biocompatibility studies of new degradable poly(urea)urethanes prepared with arginine, glycine or aspartic acid as chain extenders. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2013; 24:1733-1744. [PMID: 23615787 DOI: 10.1007/s10856-013-4931-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 04/13/2013] [Indexed: 06/02/2023]
Abstract
Polyurethanes are very often used in the cardiovascular field due to their tunable physicochemical properties and acceptable hemocompatibility although they suffer from poor endothelialization. With this in mind, we proposed the synthesis of a family of degradable segmented poly(urea)urethanes (SPUUs) using amino acids (L-arginine, glycine and L-aspartic acid) as chain extenders. These polymers degraded slowly in PBS (pH 7.4) after 24 weeks via a gradual decrease in molecular weight. In contrast, accelerated degradation showed higher mass loss under acidic, alkaline and oxidative media. MTT tests on polyurethanes with L-arginine as chain extenders showed no adverse effect on the metabolism of human umbilical vein endothelial cells (HUVECs) indicating the leachables did not provoke any toxic responses. In addition, SPUUs containing L-arginine promoted higher levels of HUVECs adhesion, spreading and viability after 7 days compared to the commonly used Tecoflex(®) polyurethane. The biodegradability and HUVEC proliferation on L-arginine-based SPUUs suggests that they can be used in the design of vascular grafts for tissue engineering.
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Affiliation(s)
- L H Chan-Chan
- Centro de Investigación Científica de Yucatán A. C., Calle 43 # 130 Col. Chuburná de Hidalgo, C.P.97200, Mérida, Yucatán, Mexico
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69
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Affiliation(s)
- Stéphanie Deshayes
- Department of Bioengineering; University of California; Los Angeles California 90095
| | - Andrea M. Kasko
- Department of Bioengineering; University of California; Los Angeles California 90095
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70
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Rodríguez-Évora M, Delgado A, Reyes R, Hernández-Daranas A, Soriano I, San Román J, Evora C. Osteogenic effect of local, long versus short term BMP-2 delivery from a novel SPU-PLGA-βTCP concentric system in a critical size defect in rats. Eur J Pharm Sci 2013; 49:873-84. [PMID: 23797057 DOI: 10.1016/j.ejps.2013.06.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 06/04/2013] [Accepted: 06/06/2013] [Indexed: 10/26/2022]
Abstract
A concentric delivery system, composed of the three biomaterials SPU, PLGA, and βTCP (segmented polyurethane, poly[lactic-co-glycolic acid], and β-tricalcium phosphate) was fabricated as an external, porous ring of βTCP with a pasty core of a new SPU, mixed with PLGA microspheres. The regenerative effects of two distinct doses of either immediately available or continuously released rhBMP-2 were evaluated in an 8mm, critical calvaria defect in rats. Protein dose and release kinetics affected material resorption rates and the progression of the regeneration process. Groups treated with the empty system alone or in conjunction with free rhBMP-2 did not respond. By contrast, after 12 weeks, approximately 20% and 60% of the defects implanted with systems loaded with 1.6 μg and 6.5 μg rhBMP-2, respectively were healed, with all the growth factor being released in the course of 6 weeks. The NMR, FTIR, GPC, DSC, and histological analyses showed that PLGA microsphere degradation occurred independently of the regenerative process. However, the resorption rate of the SPU and βTCP did depend on the regeneration process, which was governed by dose and release rate of rhBMP-2. Furthermore, the biocompatibility and high capacity of adaptation to the defect convert the herein proposed, new SPU polymer into a potential material for applications in tissue engineering and regenerative medicine.
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Affiliation(s)
- M Rodríguez-Évora
- Department of Chemical Engineering and Pharmaceutical Technology, University of La Laguna, 38200 La Laguna, Spain
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71
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Cherng JY, Hou TY, Shih MF, Talsma H, Hennink WE. Polyurethane-based drug delivery systems. Int J Pharm 2013; 450:145-62. [DOI: 10.1016/j.ijpharm.2013.04.063] [Citation(s) in RCA: 196] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 04/19/2013] [Accepted: 04/20/2013] [Indexed: 01/21/2023]
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72
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Page JM, Harmata AJ, Guelcher SA. Design and development of reactive injectable and settable polymeric biomaterials. J Biomed Mater Res A 2013; 101:3630-45. [DOI: 10.1002/jbm.a.34665] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 02/05/2013] [Accepted: 02/14/2013] [Indexed: 12/21/2022]
Affiliation(s)
- Jonathan M. Page
- Department of Chemical and Biomolecular Engineering; Vanderbilt University; Nashville Tennessee
- Center for Bone Biology; Department of Medicine; Vanderbilt University Medical Center; Nashville Tennessee
| | - Andrew J. Harmata
- Department of Chemical and Biomolecular Engineering; Vanderbilt University; Nashville Tennessee
- Center for Bone Biology; Department of Medicine; Vanderbilt University Medical Center; Nashville Tennessee
| | - Scott A. Guelcher
- Department of Chemical and Biomolecular Engineering; Vanderbilt University; Nashville Tennessee
- Center for Bone Biology; Department of Medicine; Vanderbilt University Medical Center; Nashville Tennessee
- Department of Biomedical Engineering; Vanderbilt University; Nashville Tennessee
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73
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Nelson CE, Gupta MK, Adolph EJ, Guelcher SA, Duvall CL. siRNA Delivery from an Injectable Scaffold for Wound Therapy. Adv Wound Care (New Rochelle) 2013; 2:93-99. [PMID: 24527332 DOI: 10.1089/wound.2011.0327] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Indexed: 12/24/2022] Open
Abstract
SIGNIFICANCE Aberrant overexpression of proinflammatory molecules is believed to be a key mediator in the formation of chronic skin wounds, and the inhibition of these signals may be an effective therapeutic strategy to promote healing. Small interfering RNA (siRNA) can provide gene-specific silencing and may present a safe and effective route for knockdown of inflammatory or other target proteins in chronic skin wounds. CRITICAL ISSUES siRNA suffers from delivery barriers in vivo such as susceptibility to degradation, membrane impermeability, and transient activity. Therefore, a delivery strategy that stabilizes siRNA, provides intracellular (cytoplasmic) delivery, and produces temporally sustained activity is needed. The novel approach described combines pH-responsive, siRNA-loaded nanoparticles into a biodegradable polyurethane (PUR) scaffold and presents a promising platform for effective, local silencing of deleterious genes in nonhealing skin wounds. RECENT ADVANCES The siRNA delivery barriers have been overcome using a nanoparticulate carrier that protects siRNA and responds to pH gradients in the endo-lysosomal pathway to mediate cytosolic delivery. Nanoparticle incorporation into a biodegradable PUR scaffold provides a means for controlling the delivery kinetics of siRNA-loaded carriers. Furthermore, the PUR is injectable, making it feasible for clinical use, and provides a porous tissue template for cell in-growth during tissue regeneration and remodeling. This local siRNA delivery platform can be tuned to optimize release kinetics for specific pathologies. FUTURE DIRECTIONS siRNA may provide a new class of biologic drugs that will outperform growth factor approaches, which have shown only moderate clinical success. The new platform presented here may provide clinicians with an improved option for wound care.
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Affiliation(s)
| | - Mukesh Kumar Gupta
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee
| | - Elizabeth J. Adolph
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee
| | - Scott A. Guelcher
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee
| | - Craig L. Duvall
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee
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74
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75
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Page JM, Prieto EM, Dumas JE, Zienkiewicz KJ, Wenke JC, Brown-Baer P, Guelcher SA. Biocompatibility and chemical reaction kinetics of injectable, settable polyurethane/allograft bone biocomposites. Acta Biomater 2012; 8:4405-16. [PMID: 22871639 DOI: 10.1016/j.actbio.2012.07.037] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 07/13/2012] [Accepted: 07/24/2012] [Indexed: 12/11/2022]
Abstract
Injectable and settable bone grafts offer significant advantages over pre-formed implants due to their ability to be administered using minimally invasive techniques and to conform to the shape of the defect. However, injectable biomaterials present biocompatibility challenges due to the potential toxicity and ultimate fate of reactive components that are not incorporated in the final cured product. In this study the effects of stoichiometry and triethylenediamine (TEDA) catalyst concentration on the reactivity, injectability, and biocompatibility of two component lysine-derived polyurethane (PUR) biocomposites were investigated. Rate constants were measured for the reactions of water (a blowing agent resulting in the generation of pores), polyester triol, dipropylene glycol (DPG), and allograft bone particles with the isocyanate-terminated prepolymer using an in situ attenuated total reflection Fourier transform infrared spectroscopy technique. Based on the measured rate constants, a kinetic model predicting the conversion of each component with time was developed. Despite the fact that TEDA is a well-known urethane gelling catalyst, it was found to preferentially catalyze the blowing reaction with water relative to the gelling reactions by a ratio >17:1. Thus the kinetic model predicted that the prepolymer and water proceeded to full conversion, while the conversions of polyester triol and DPG were <70% after 24h, which was consistent with leaching experiments showing that only non-cytotoxic polyester triol and DPG were released from the reactive PUR at early time points. The PUR biocomposite supported cellular infiltration and remodeling in femoral condyle defects in rabbits at 8weeks, and there was no evidence of an adverse inflammatory response induced by unreacted components from the biocomposite or degradation products from the cured polymer. Taken together, these data underscore the utility of the kinetic model in predicting the biocompatibility of reactive biomaterials.
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Affiliation(s)
- Jonathan M Page
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA
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76
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Morral-Ruíz G, Melgar-Lesmes P, García M, Solans C, García-Celma M. Design of biocompatible surface-modified polyurethane and polyurea nanoparticles. POLYMER 2012. [DOI: 10.1016/j.polymer.2012.10.039] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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77
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Yoshii T, Hafeman AE, Esparza JM, Okawa A, Gutierrez G, Guelcher SA. Local injection of lovastatin in biodegradable polyurethane scaffolds enhances bone regeneration in a critical-sized segmental defect in rat femora. J Tissue Eng Regen Med 2012; 8:589-95. [PMID: 22718577 DOI: 10.1002/term.1547] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 03/13/2012] [Accepted: 05/15/2012] [Indexed: 01/12/2023]
Abstract
Statins, a class of naturally-occurring compounds that inhibit HMG-CoA reductase, are known to increase endogenous bone morphogenetic protein-2 (BMP-2) expression. Local administration of statins has been shown to stimulate fracture repair in in vivo animal experiments. However, the ability of statins to heal more challenging critical-sized defects at the mid-diaphyseal region in long bones has not been investigated. In this study, we examined the potential of injectable lovastatin microparticles combined with biodegradable polyurethane (PUR) scaffolds in preclinical animal models: metaphyseal small plug defects and diaphyseal segmental bone defects in rat femora. Sustained release of lovastatin from the lovastatin microparticles was achieved over 14 days. The released lovastatin was bioactive, as evidenced by its ability to stimulate BMP-2 gene expression in osteoblastic cells. Micro-computed tomography (CT) and histological examinations showed that lovastatin microparticles, injected into PUR scaffolds implanted in femoral plug defects, enhanced new bone formation. Furthermore, bi-weekly multiple injections of lovastatin microparticles into PUR scaffolds implanted in critical-sized femoral segmental defects resulted in increased new bone formation compared to the vehicle control. In addition, bridging of the defect with newly formed bone was observed in four of nine defects in the lovastatin microparticle treatment group, whereas none of the defects in the vehicle group showed bridging. These observations suggest that local delivery of lovastatin combined with PUR scaffold can be an effective approach for treatment of orthopaedic bone defects and that multiple injections of lovastatin may be useful for large defects.
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Affiliation(s)
- Toshitaka Yoshii
- Department of Orthopaedic and Spinal Surgery, Tokyo Medical and Dental University, Tokyo, Japan; Orthopaedics and Rehabilitation, Vanderbilt University, Nashville, TN, USA; Center for Bone Biology, Vanderbilt Medical Center, TN Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA
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78
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Kavlock KD, Whang K, Guelcher SA, Goldstein AS. Degradable segmented polyurethane elastomers for bone tissue engineering: effect of polycaprolactone content. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2012; 24:77-93. [PMID: 22304961 DOI: 10.1163/156856212x624985] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Segmented polyurethanes (PURs), consisting of degradable poly(a-hydroxy ester) soft segments and aminoacid-derived chain extenders, are biocompatible elastomers with tunable mechanical and degradative properties suitable for a variety of tissue-engineering applications. In this study, a family of linear PURs synthesized from poly(ϵ-caprolactone) (PCL) diol, 1,4-diisocyanobutane and tyramine with theoretical PCL contents of 65-80 wt% were processed into porous foam scaffolds and evaluated for their ability to support osteoblastic differentiation in vitro. Differential scanning calorimetry and mechanical testing of the foams indicated increasing polymer crystallinity and compressive modulus with increasing PCL content. Next, bone marrow stromal cells (BMSCs) were seeded into PUR scaffolds, as well as poly(lactic-co-glycolic acid) (PLGA) scaffolds, and maintained under osteogenic conditions for 14 and 21 days. Analysis of cell number indicated a systematic decrease in cell density with increasing PUR stiffness at both 14 and 21 days in culture. However, at these same time points the relative mRNA expression for the bone-specific proteins osteocalcin and the growth factors bone morphogenetic protein-2 and vascular endothelial growth factor gene expression were similar among the PURs. Finally, prostaglandin E2 production, alkaline phosphatase activity and osteopontin mRNA expression were highly elevated on the most-crystalline PUR scaffold as compared to the PLGA and PUR scaffolds. These results suggest that both the modulus and crystallinity of the PUR scaffolds influence cell proliferation and the expression of osteoblastic proteins.
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Affiliation(s)
- Katherine D Kavlock
- School of Biomedical Engineering and Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0211, USA
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79
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Dumas JE, BrownBaer PB, Prieto EM, Guda T, Hale RG, Wenke JC, Guelcher SA. Injectable reactive biocomposites for bone healing in critical-size rabbit calvarial defects. Biomed Mater 2012; 7:024112. [DOI: 10.1088/1748-6041/7/2/024112] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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80
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Zhou L, Liang D, He X, Li J, Tan H, Li J, Fu Q, Gu Q. The degradation and biocompatibility of pH-sensitive biodegradable polyurethanes for intracellular multifunctional antitumor drug delivery. Biomaterials 2012; 33:2734-45. [DOI: 10.1016/j.biomaterials.2011.11.009] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 11/05/2011] [Indexed: 12/29/2022]
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81
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Adolph EJ, Hafeman AE, Davidson JM, Nanney LB, Guelcher SA. Injectable polyurethane composite scaffolds delay wound contraction and support cellular infiltration and remodeling in rat excisional wounds. J Biomed Mater Res A 2011; 100:450-61. [PMID: 22105887 DOI: 10.1002/jbm.a.33266] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2010] [Accepted: 09/07/2011] [Indexed: 11/06/2022]
Abstract
Injectable scaffolds present compelling opportunities for wound repair and regeneration because of their ability to fill irregularly shaped defects and deliver biologics such as growth factors. In this study, we investigated the properties of injectable polyurethane (PUR) biocomposite scaffolds and their application in cutaneous wound repair using a rat excisional model. The scaffolds have a minimal reaction exotherm and clinically relevant working and setting times. Moreover, the biocomposites have mechanical and thermal properties consistent with rubbery elastomers. In the rat excisional wound model, injection of settable biocomposite scaffolds stented the wounds at early time points, resulting in a regenerative rather than a scarring phenotype at later time points. Measurements of wound length and thickness revealed that the treated wounds were less contracted at day 7 compared to blank wounds. Analysis of cell proliferation and apoptosis showed that the scaffolds were biocompatible and supported tissue ingrowth. Myofibroblast formation and collagen fiber organization provided evidence that the scaffolds have a positive effect on extracellular matrix remodeling by disrupting the formation of an aligned matrix under elevated tension. In summary, we have developed an injectable biodegradable PUR biocomposite scaffold that enhances cutaneous wound healing in a rat model.
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Affiliation(s)
- Elizabeth J Adolph
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee
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82
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Nelson CE, Gupta MK, Adolph EJ, Shannon JM, Guelcher SA, Duvall CL. Sustained local delivery of siRNA from an injectable scaffold. Biomaterials 2011; 33:1154-61. [PMID: 22061489 DOI: 10.1016/j.biomaterials.2011.10.033] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 10/12/2011] [Indexed: 12/23/2022]
Abstract
Controlled gene silencing technologies have significant, unrealized potential for use in tissue regeneration applications. The design described herein provides a means to package and protect siRNA within pH-responsive, endosomolytic micellar nanoparticles (si-NPs) that can be incorporated into nontoxic, biodegradable, and injectable polyurethane (PUR) tissue scaffolds. The si-NPs were homogeneously incorporated throughout the porous PUR scaffolds, and they were shown to be released via a diffusion-based mechanism for over three weeks. The siRNA-loaded micelles were larger but retained nanoparticulate morphology of approximately 100 nm diameter following incorporation into and release from the scaffolds. PUR scaffold releasate collected in vitro in PBS at 37 °C for 1-4 days was able to achieve dose-dependent siRNA-mediated silencing with approximately 50% silencing achieved of the model gene GAPDH in NIH3T3 mouse fibroblasts. This promising platform technology provides both a research tool capable of probing the effects of local gene silencing and a potentially high-impact therapeutic approach for sustained, local silencing of deleterious genes within tissue defects.
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Affiliation(s)
- Christopher E Nelson
- Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, PMB 351631, 2301 Vanderbilt Place, Nashville, TN 37235-1631, USA
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83
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Abstract
OBJECTIVE To determine if a dual-purpose bone graft can regenerate bone and reduce infection in highly contaminated bone critical size defects in rats. METHODS Biodegradable polyurethane (PUR) scaffolds were loaded with recombinant human bone morphogenetic protein-2 (BMP-2) and vancomycin (Vanc). The release kinetics of the BMP-2 were tuned to take advantage of its mechanism of action (ie, an initial burst to recruit cells and sustained release to induce differentiation of the migrating cells). The Vanc release kinetics were designed to protect the graft from contamination until it is vascularized by having a burst for a week and remaining well over the minimum inhibitory concentration for Staphylococcus aureus for 2 months. The bone regeneration and infection reduction capability of these dual-purpose grafts (PUR+Vanc+BMP-2) were compared with collagen sponges loaded with BMP-2 (collagen+BMP-2) and PUR+BMP-2 in infected critical size rat femoral segmental defects. RESULTS The dual-delivery approach resulted in substantially more new bone formation and a modest improvement in infection than PUR+BMP-2 and collagen+BMP-2 treatments. CONCLUSIONS The PUR bone graft is injectable, provides a more sustained release of BMP-2 than the collagen sponge, and can release antibiotics for more than 8 weeks. Thus, the dual-delivery approach may improve patient outcomes of open fractures by protecting the osteoinductive graft from colonization until vascularization occurs. In addition, the more optimal release kinetics of BMP-2 may reduce nonunions and the amount of growth factor required.
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Brown KV, Li B, Guda T, Perrien DS, Guelcher SA, Wenke JC. Improving Bone Formation in a Rat Femur Segmental Defect by Controlling Bone Morphogenetic Protein-2 Release. Tissue Eng Part A 2011; 17:1735-46. [DOI: 10.1089/ten.tea.2010.0446] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Kate V. Brown
- Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, San Antonio, Texas
| | - Bing Li
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee
| | - Teja Guda
- Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, San Antonio, Texas
- Wake Forest Institute of Regenerative Medicine, Winston-Salem, North Carolina
| | - Daniel S. Perrien
- Department of Orthopaedics and Rehabilitation and Center for Bone Biology, Vanderbilt University, Nashville, Tennessee
| | - Scott A. Guelcher
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee
| | - Joseph C. Wenke
- Extremity Trauma and Regenerative Medicine Task Area, United States Army Institute of Surgical Research, San Antonio, Texas
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