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Shih H, Mirmira RG, Lin CC. Visible light-initiated interfacial thiol-norbornene photopolymerization for forming islet surface conformal coating. J Mater Chem B 2015; 3:170-175. [PMID: 26509035 DOI: 10.1039/c4tb01593b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A cytocompatible visible light-mediated interfacial thiol-norbornene photopolymerization scheme was developed for creating hydrogel conformal coating on pancreatic islets. The step-growth thiol-norbornene reaction affords high consistency and tunability in gel coating thickness. Furthermore, isolated islets coated with thiol-norbornene gel maintained their viability and function in vitro.
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Affiliation(s)
- Han Shih
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Raghavendra G Mirmira
- Departments of Pediatrics, Medicine, Cellular and Integrative Physiology, and Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Chien-Chi Lin
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA. ; Department of Biomedical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA
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Lee JI, Kim JY, Lee JG, Kim YS. Islet Encapsulation Using Chondrocyte. KOREAN JOURNAL OF TRANSPLANTATION 2014. [DOI: 10.4285/jkstn.2014.28.4.187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Affiliation(s)
- Jeong Ik Lee
- Department of Veterinary Medicine, College of Veterinary Medicine, Konkuk University, Seoul, Korea
- Department of Biomedical Science and Technology, Konkuk University, Seoul, Korea
- The Research Institute for Transplantation, Yonsei University College of Medicine, Seoul, Korea
| | - Joon Ye Kim
- The Research Institute for Transplantation, Yonsei University College of Medicine, Seoul, Korea
| | - Jae Geun Lee
- Department of Transplantation Surgery, Severance Hospital, Yonsei University Health System, Seoul, Korea
| | - Yu Seun Kim
- The Research Institute for Transplantation, Yonsei University College of Medicine, Seoul, Korea
- Department of Transplantation Surgery, Severance Hospital, Yonsei University Health System, Seoul, Korea
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Immunosuppressive therapy in allograft transplantation: from novel insights and strategies to tolerance and challenges. Cent Eur J Immunol 2014; 39:400-9. [PMID: 26155155 PMCID: PMC4440012 DOI: 10.5114/ceji.2014.45955] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 07/03/2014] [Indexed: 01/07/2023] Open
Abstract
Immunosuppression therapy is the key to successful post-transplantation outcomes. The need for ideal immunosuppression became durable maintenance of long-term graft survival. In spite of current immunosuppressive therapy regimens advances, surgical procedures, and preservation methods, organ transplantation is associated with a long-term poor survival and significant mortality. This has led to an increased interest to optimize outcomes while minimizing associated toxicity by using alternative methods for maintenance immunosuppression, organ rejection treatment, and monitoring of immunosuppression. T regulatory (Treg) cells, which have immunosuppressive functions and cytokine profiles, have been studied during the last decades. Treg cells are able to inhibit the development of allergen-specific cell responses and consequently play a key role in a healthy immune response to allergens. Mature dendritic cells (DCs) play a crucial role in the differentiation of Tregs, which are known to regulate allergic inflammatory responses. Advance in long-standing allograft outcomes may depend on new drugs with novel mechanisms of action with minimal toxicity. Newer treatment techniques have been developed, including using novel stem cell-based therapies such as mesenchymal stem cells, phagosomes and exosomes. Immunoisolation techniques and salvage therapies, including photopheresis and total lymphoid irradiation have emerged as alternative therapeutic choices. The present review evaluates the recent clinical advances in immunosuppressive therapies for organ transplantation.
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Onuki Y, Hasegawa N, Kida C, Obata Y, Takayama K. Study of the contribution of the state of water to the gel properties of a photocrosslinked polyacrylic acid hydrogel using magnetic resonance imaging. J Pharm Sci 2014; 103:3532-3541. [PMID: 25213087 DOI: 10.1002/jps.24140] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 06/20/2014] [Accepted: 08/06/2014] [Indexed: 11/11/2022]
Abstract
Photocrosslinked polyacrylic acid (PAA-HEMA) hydrogels are a promising candidate for use in dermatological patch adhesives. To gain further knowledge about the properties of this gel, we investigated the T1 relaxation time and the diffusion coefficient (D) of water in the hydrogels using magnetic resonance (MR) imaging. Hydrogels with different formulations and process factors were prepared and tested. The observed data were analyzed by ANOVA, which clarified the mode of action of the formulation and process factors based on these MR parameters. Various gel properties (i.e., gel fraction, swelling capacity, gel strength, and water-retention ability) were also measured, followed by a Bayesian network (BN) analysis. The BN allowed us to summarize well the relationships between the formulation and process factors, MR parameters, and gel properties. T1 was associated with the swelling and water-retention properties of the hydrogel, whereas D was associated with gel formation and gel strength. Furthermore, this study clarified that T1 and D mostly represented the hydration and water-compartmentalization effects of the hydrogel, respectively. In conclusion, the state of water seems to play an important role in the properties of the PAA-HEMA hydrogel.
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Affiliation(s)
- Yoshinori Onuki
- Department of Pharmaceutics, Hoshi University, Shinagawa, Tokyo 142-8501, Japan.
| | - Naoki Hasegawa
- Department of Pharmaceutics, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
| | - Chihiro Kida
- Department of Pharmaceutics, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
| | - Yasuko Obata
- Department of Pharmaceutics, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
| | - Kozo Takayama
- Department of Pharmaceutics, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
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Pal K, Banthia AK, Majumdar DK. Hydrogels for biomedical applications: a short review. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2014; 25:2215. [PMID: 17619971 DOI: 10.1007/s10856-007-3145-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Accepted: 07/31/2006] [Indexed: 05/16/2023]
Affiliation(s)
- Kunal Pal
- Materials Science Centre, Indian Institute of Technology, Kharagpur, 721302, India
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57
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Moon BU, Hakimi N, Hwang DK, Tsai SSH. Microfluidic conformal coating of non-spherical magnetic particles. BIOMICROFLUIDICS 2014; 8:052103. [PMID: 25332731 PMCID: PMC4189426 DOI: 10.1063/1.4892542] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 07/28/2014] [Indexed: 05/17/2023]
Abstract
We present the conformal coating of non-spherical magnetic particles in a co-laminar flow microfluidic system. Whereas in the previous reports spherical particles had been coated with thin films that formed spheres around the particles; in this article, we show the coating of non-spherical particles with coating layers that are approximately uniform in thickness. The novelty of our work is that while liquid-liquid interfacial tension tends to minimize the surface area of interfaces-for example, to form spherical droplets that encapsulate spherical particles-in our experiments, the thin film that coats non-spherical particles has a non-minimal interfacial area. We first make bullet-shaped magnetic microparticles using a stop-flow lithography method that was previously demonstrated. We then suspend the bullet-shaped microparticles in an aqueous solution and flow the particle suspension with a co-flow of a non-aqueous mixture. A magnetic field gradient from a permanent magnet pulls the microparticles in the transverse direction to the fluid flow, until the particles reach the interface between the immiscible fluids. We observe that upon crossing the oil-water interface, the microparticles become coated by a thin film of the aqueous fluid. When we increase the two-fluid interfacial tension by reducing surfactant concentration, we observe that the particles become trapped at the interface, and we use this observation to extract an approximate magnetic susceptibility of the manufactured non-spherical microparticles. Finally, using fluorescence imaging, we confirm the uniformity of the thin film coating along the entire curved surface of the bullet-shaped particles. To the best of our knowledge, this is the first demonstration of conformal coating of non-spherical particles using microfluidics.
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Affiliation(s)
- Byeong-Ui Moon
- Department of Mechanical and Industrial Engineering, Ryerson University , 350 Victoria St., Toronto, Ontario M5B 2K3, Canada
| | - Navid Hakimi
- Department of Chemical Engineering, Ryerson University , 350 Victoria St., Toronto, Ontario M5B 2K3, Canada
| | - Dae Kun Hwang
- Department of Chemical Engineering, Ryerson University , 350 Victoria St., Toronto, Ontario M5B 2K3, Canada
| | - Scott S H Tsai
- Department of Mechanical and Industrial Engineering, Ryerson University , 350 Victoria St., Toronto, Ontario M5B 2K3, Canada
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58
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Rengifo HR, Giraldo JA, Labrada I, Stabler CL. Long-term survival of allograft murine islets coated via covalently stabilized polymers. Adv Healthc Mater 2014; 3:1061-70. [PMID: 24497465 DOI: 10.1002/adhm.201300573] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/13/2013] [Indexed: 12/20/2022]
Abstract
Clinical islet transplantation (CIT) has emerged as a promising treatment option for type 1 diabetes mellitus (T1DM); however, the antirejection drug regimen necessary to mitigate allograft islet rejection is undesirable. The use of polymeric coatings to immunocamouflage the transplant from host immune attack has great potential. Alginate and poly(ethylene glycol) (PEG)-based polymers, functionalized with azide and phosphine, respectively, which form spontaneous and chemoselective crosslinks via the bioorthogonal Staudinger ligation scheme, were recently developed. Here, the utility of these polymers to form immunoprotective, ultrathin coatings on murine primary pancreatic islets is explored. Resulting coatings are nontoxic, with unimpaired glucose stimulated insulin secretion. Transplantation of coated BALB/c (H-2(d) ) islets into streptozotozin-induced diabetic C57BL/6 (H-2(b) ) results in prompt achievement of normoglycemia, at a rate comparable to controls. A significant subset of animals receiving coated islets (57%) exhibits long-term (>100 d) function, with robust islets observed upon explantation. Control islets rejected after 15 d (±9 d). Results illustrate the capacity of chemoselectively functionalized polymers to form coatings on islets, imparting no detrimental effect to the underlying cells, with resulting coatings exhibiting significant protective effects in an allograft murine model.
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Affiliation(s)
- Hernán R. Rengifo
- Diabetes Research Institute; Leonard M. Miller School of Medicine; University of Miami; 1450 NW 10 Ave Miami FL 33136 USA
| | - Jaime A. Giraldo
- Diabetes Research Institute; Leonard M. Miller School of Medicine; University of Miami; 1450 NW 10 Ave Miami FL 33136 USA
- Department of Biomedical Engineering; College of Engineering; University of Miami; 1450 NW 10 Ave Miami FL 33136 USA
| | - Irayme Labrada
- Diabetes Research Institute; Leonard M. Miller School of Medicine; University of Miami; 1450 NW 10 Ave Miami FL 33136 USA
| | - Cherie L. Stabler
- Diabetes Research Institute; Leonard M. Miller School of Medicine; University of Miami; 1450 NW 10 Ave Miami FL 33136 USA
- Department of Biomedical Engineering; College of Engineering; University of Miami; 1450 NW 10 Ave Miami FL 33136 USA
- Department of Surgery; Leonard M. Miller School of Medicine; University of Miami; 1450 NW 10 Ave Miami FL 33136 USA
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Amer LD, Mahoney MJ, Bryant SJ. Tissue engineering approaches to cell-based type 1 diabetes therapy. TISSUE ENGINEERING PART B-REVIEWS 2014; 20:455-67. [PMID: 24417705 DOI: 10.1089/ten.teb.2013.0462] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Type 1 diabetes mellitus is an autoimmune disease resulting from the destruction of insulin-producing pancreatic β-cells. Cell-based therapies, involving the transplantation of functional β-cells into diabetic patients, have been explored as a potential long-term treatment for this condition; however, success is limited. A tissue engineering approach of culturing insulin-producing cells with extracellular matrix (ECM) molecules in three-dimensional (3D) constructs has the potential to enhance the efficacy of cell-based therapies for diabetes. When cultured in 3D environments, insulin-producing cells are often more viable and secrete more insulin than those in two dimensions. The addition of ECM molecules to the culture environments, depending on the specific type of molecule, can further enhance the viability and insulin secretion. This review addresses the different cell sources that can be utilized as β-cell replacements, the essential ECM molecules for the survival of these cells, and the 3D culture techniques that have been used to benefit cell function.
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Affiliation(s)
- Luke D Amer
- 1 Department of Chemical and Biological Engineering, University of Colorado , Boulder, Colorado
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60
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Colton CK. Oxygen supply to encapsulated therapeutic cells. Adv Drug Deliv Rev 2014; 67-68:93-110. [PMID: 24582600 DOI: 10.1016/j.addr.2014.02.007] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 01/06/2014] [Accepted: 02/19/2014] [Indexed: 02/07/2023]
Abstract
Therapeutic cells encapsulated in immunobarrier devices have promise for treatment of a variety of human diseases without immunosuppression. The absence of sufficient oxygen supply to maintain viability and function of encapsulated tissue has been the most critical impediment to progress. Within the framework of oxygen supply limitations, we review the major issues related to development of these devices, primarily in the context of encapsulated islets of Langerhans for treating diabetes, including device designs and materials, supply of tissue, protection from immune rejection, and maintenance of cell viability and function. We describe various defensive measures investigated to enhance survival of transplanted tissue, and we review the diverse approaches to enhancement of oxygen transport to encapsulated tissue, including manipulation of diffusion distances and oxygen permeability of materials, induction of neovascularization with angiogenic factors and vascularizing membranes, and methods for increasing the oxygen concentration adjacent to encapsulated tissue so as to exceed that in the microvasculature. Recent developments, particularly in this latter area, suggest that the field is ready for clinical trials of encapsulated therapeutic cells to treat diabetes.
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61
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de Vos P, Lazarjani HA, Poncelet D, Faas MM. Polymers in cell encapsulation from an enveloped cell perspective. Adv Drug Deliv Rev 2014; 67-68:15-34. [PMID: 24270009 DOI: 10.1016/j.addr.2013.11.005] [Citation(s) in RCA: 186] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 08/26/2013] [Accepted: 11/13/2013] [Indexed: 02/07/2023]
Abstract
In the past two decades, many polymers have been proposed for producing immunoprotective capsules. Examples include the natural polymers alginate, agarose, chitosan, cellulose, collagen, and xanthan and synthetic polymers poly(ethylene glycol), polyvinyl alcohol, polyurethane, poly(ether-sulfone), polypropylene, sodium polystyrene sulfate, and polyacrylate poly(acrylonitrile-sodium methallylsulfonate). The biocompatibility of these polymers is discussed in terms of tissue responses in both the host and matrix to accommodate the functional survival of the cells. Cells should grow and function in the polymer network as adequately as in their natural environment. This is critical when therapeutic cells from scarce cadaveric donors are considered, such as pancreatic islets. Additionally, the cell mass in capsules is discussed from the perspective of emerging new insights into the release of so-called danger-associated molecular pattern molecules by clumps of necrotic therapeutic cells. We conclude that despite two decades of intensive research, drawing conclusions about which polymer is most adequate for clinical application is still difficult. This is because of the lack of documentation on critical information, such as the composition of the polymer, the presence or absence of confounding factors that induce immune responses, toxicity to enveloped cells, and the permeability of the polymer network. Only alginate has been studied extensively and currently qualifies for application. This review also discusses critical issues that are not directly related to polymers and are not discussed in the other reviews in this issue, such as the functional performance of encapsulated cells in vivo. Physiological endocrine responses may indeed not be expected because of the many barriers that the metabolites encounter when traveling from the blood stream to the enveloped cells and back to circulation. However, despite these diffusion barriers, many studies have shown optimal regulation, allowing us to conclude that encapsulated grafts do not always follow nature's course but are still a possible solution for many endocrine disorders for which the minute-to-minute regulation of metabolites is mandatory.
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62
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Scharp DW, Marchetti P. Encapsulated islets for diabetes therapy: history, current progress, and critical issues requiring solution. Adv Drug Deliv Rev 2014; 67-68:35-73. [PMID: 23916992 DOI: 10.1016/j.addr.2013.07.018] [Citation(s) in RCA: 214] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 07/10/2013] [Accepted: 07/22/2013] [Indexed: 02/07/2023]
Abstract
Insulin therapy became a reality in 1921 dramatically saving lives of people with diabetes, but not protecting them from long-term complications. Clinically successful free islet implants began in 1989 but require life long immunosuppression. Several encapsulated islet approaches have been ongoing for over 30 years without defining a clinically relevant product. Macro-devices encapsulating islet mass in a single device have shown long-term success in large animals but human trials have been limited by critical challenges. Micro-capsules using alginate or similar hydrogels encapsulate individual islets with many hundreds of promising rodent results published, but a low incidence of successful translation to large animal and human results. Reduction of encapsulated islet mass for clinical transplantation is in progress. This review covers the status of both early and current studies including the presentation of corporate efforts involved. It concludes by defining the critical items requiring solution to enable a successful clinical diabetes therapy.
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63
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Transplantation of Encapsulated Pancreatic Islets as a Treatment for Patients with Type 1 Diabetes Mellitus. Adv Med 2014; 2014:429710. [PMID: 26556410 PMCID: PMC4590955 DOI: 10.1155/2014/429710] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 11/30/2013] [Indexed: 12/19/2022] Open
Abstract
Encapsulation of pancreatic islets has been proposed and investigated for over three decades to improve islet transplantation outcomes and to eliminate the side effects of immunosuppressive medications. Of the numerous encapsulation systems developed in the past, microencapsulation have been studied most extensively so far. A wide variety of materials has been tested for microencapsulation in various animal models (including nonhuman primates or NHPs) and some materials were shown to induce immunoprotection to islet grafts without the need for chronic immunosuppression. Despite the initial success of microcapsules in NHP models, the combined use of islet transplantation (allograft) and microencapsulation has not yet been successful in clinical trials. This review consists of three sections: introduction to islet transplantation, transplantation of encapsulated pancreatic islets as a treatment for patients with type 1 diabetes mellitus (T1DM), and present challenges and future perspectives.
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64
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Hao Y, Lin CC. Degradable thiol-acrylate hydrogels as tunable matrices for three-dimensional hepatic culture. J Biomed Mater Res A 2013; 102:3813-27. [DOI: 10.1002/jbm.a.35044] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 11/08/2013] [Accepted: 11/26/2013] [Indexed: 11/12/2022]
Affiliation(s)
- Yiting Hao
- Department of Biomedical Engineering; Purdue School of Engineering and Technology; Indiana University-Purdue University Indianapolis; Indianapolis Indiana 46202
| | - Chien-Chi Lin
- Department of Biomedical Engineering; Purdue School of Engineering and Technology; Indiana University-Purdue University Indianapolis; Indianapolis Indiana 46202
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65
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El-Sherbiny IM, Yacoub MH. Hydrogel scaffolds for tissue engineering: Progress and challenges. Glob Cardiol Sci Pract 2013; 2013:316-42. [PMID: 24689032 PMCID: PMC3963751 DOI: 10.5339/gcsp.2013.38] [Citation(s) in RCA: 398] [Impact Index Per Article: 36.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 10/11/2013] [Indexed: 12/18/2022] Open
Abstract
Designing of biologically active scaffolds with optimal characteristics is one of the key factors for successful tissue engineering. Recently, hydrogels have received a considerable interest as leading candidates for engineered tissue scaffolds due to their unique compositional and structural similarities to the natural extracellular matrix, in addition to their desirable framework for cellular proliferation and survival. More recently, the ability to control the shape, porosity, surface morphology, and size of hydrogel scaffolds has created new opportunities to overcome various challenges in tissue engineering such as vascularization, tissue architecture and simultaneous seeding of multiple cells. This review provides an overview of the different types of hydrogels, the approaches that can be used to fabricate hydrogel matrices with specific features and the recent applications of hydrogels in tissue engineering. Special attention was given to the various design considerations for an efficient hydrogel scaffold in tissue engineering. Also, the challenges associated with the use of hydrogel scaffolds were described.
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Affiliation(s)
- Ibrahim M El-Sherbiny
- Center for Materials Science, University of Science and Technology, Zewail City of Science and Technology, 6th October City, 12588 Giza, Egypt
| | - Magdi H Yacoub
- Harefield Heart Science Centre, National Heart and Lung Institute, Imperial College, London, UK
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66
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Abstract
Although islet transplantation has demonstrated its potential use in treating type 1 diabetes, this remains limited by the need for daily immunosuppression. Islet encapsulation was then proposed with a view to avoiding any immunosuppressive regimen and related side effects. In order to obtain a standard clinical procedure in terms of safety and reproducibility, two important factors have to be taken into account: the encapsulation design (which determines the graft volume) and the implantation site. Indeed, the implantation site should meet certain requirements: (1) its space must be large enough for the volume of transplanted tissues; (2) there must be proximity to abundant vascularization with a good oxygen supply; (3) there must be real-time access to physiologically representative blood glucose levels; (4) there must be easy access for implantation and the reversibility of the procedure (for safety); and finally, (5) the site should have minimal early inflammatory reaction and promote long-term survival. The aim of this article is to review possible preclinical/clinical implantation sites (in comparison with free islets) for encapsulated islet transplantation as a function of the encapsulation design: macro/microcapsules and conformal coating.
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Sonnet C, Simpson CL, Olabisi RM, Sullivan K, Lazard Z, Gugala Z, Peroni JF, Weh JM, Davis AR, West JL, Olmsted-Davis EA. Rapid healing of femoral defects in rats with low dose sustained BMP2 expression from PEGDA hydrogel microspheres. J Orthop Res 2013; 31:1597-604. [PMID: 23832813 DOI: 10.1002/jor.22407] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 05/13/2013] [Indexed: 02/04/2023]
Abstract
Current strategies for bone regeneration after traumatic injury often fail to provide adequate healing and integration. Here, we combined the poly (ethylene glycol) diacrylate (PEGDA) hydrogel with allogeneic "carrier" cells transduced with an adenovirus expressing BMP2. The system is unique in that the biomaterial encapsulates the cells, shielding them and thus suppressing destructive inflammatory processes. Using this system, complete healing of a 5 mm-long femur defect in a rat model occurs in under 3 weeks, through secretion of 100-fold lower levels of protein as compared to doses of recombinant BMP2 protein used in studies which lead to healing in 2-3 months. New bone formation was evaluated radiographically, histologically, and biomechanically at 2, 3, 6, 9, and 12 weeks after surgery. Rapid bone formation bridged the defect area and reliably integrated into the adjacent skeletal bone as early as 2 weeks. At 3 weeks, biomechanical analysis showed the new bone to possess 79% of torsional strength of the intact contralateral femur. Histological evaluation showed normal bone healing, with no infiltration of inflammatory cells with the bone being stable approximately 1 year later. We propose that these osteoinductive microspheres offer a more efficacious and safer clinical option over the use of rhBMP2.
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Affiliation(s)
- Corinne Sonnet
- Center for Cell and Gene Therapy, Baylor College of Medicine, One Baylor Plaza, Alkek Building, Room N1010, Houston, Texas 77030, USA
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68
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Robles L, Storrs R, Lamb M, Alexander M, Lakey JRT. Current status of islet encapsulation. Cell Transplant 2013; 23:1321-48. [PMID: 23880554 DOI: 10.3727/096368913x670949] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Cell encapsulation is a method of encasing cells in a semipermeable matrix that provides a permeable gradient for the passage of oxygen and nutrients, but effectively blocks immune-regulating cells from reaching the graft, preventing rejection. This concept has been described as early as the 1930s, but it has exhibited substantial achievements over the last decade. Several advances in encapsulation engineering, chemical purification, applications, and cell viability promise to make this a revolutionary technology. Several obstacles still need to be overcome before this process becomes a reality, including developing a reliable source of islets or insulin-producing cells, determining the ideal biomaterial to promote graft function, reducing the host response to the encapsulation device, and ultimately a streamlined, scaled-up process for industry to be able to efficiently and safely produce encapsulated cells for clinical use. This article provides a comprehensive review of cell encapsulation of islets for the treatment of type 1 diabetes, including a historical perspective, current research findings, and future studies.
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Affiliation(s)
- Lourdes Robles
- Department of Surgery, University of California Irvine, Irvine, CA, USA
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69
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Ahn S, Lee H, Kim G. Functional cell-laden alginate scaffolds consisting of core/shell struts for tissue regeneration. Carbohydr Polym 2013; 98:936-42. [PMID: 23987431 DOI: 10.1016/j.carbpol.2013.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Revised: 06/04/2013] [Accepted: 07/03/2013] [Indexed: 10/26/2022]
Abstract
We report an innovative cell-dispensing process using a three-axis robot system coupled with a micro-core/shell nozzle and an aerosol cross-linking process to achieve controlled mechanical properties and high cell viability of porous cell-laden alginate scaffolds. The scaffolds were fabricated into layer-by-layer struts, which were used to design the pore structure. The struts consisted of a core/shell region; a low weight fraction of alginate and cells (MC3T3-E1) was injected in the shell region to efficiently exchange nutrients and metabolic wastes, while a high weight fraction of alginate without cells was deposited in the core region to improve the mechanical properties of the cell-laden scaffold. After 10 days of cell culture, the cell viability (95%) in the shell region improved significantly compared to 70% for the cells homogeneously distributed in the struts, and the mechanical properties were enhanced from 1.4 to 15.7 kPa. Stained nuclei and F-actin images showed that the laden cells proliferated well on the functional hydrogel scaffold after 20 days of cell culture, indicating that the cells concentrated in the shell region of the struts survived and increased their metabolic functions during several incubation periods compared to the standard cell-laden scaffold. This innovative cell-dispensing technique represents a promising fabrication tool for obtaining bottom-up scaffolds for various tissue regenerations.
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Affiliation(s)
- SeungHyun Ahn
- Department of Bio-Mechatronic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, South Korea
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70
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Abstract
It has been known for decades that encapsulation can protect transplanted islets from immune destruction in rodents, but it has proved difficult to extend this success to large animals and humans. A new study in this issue by Jacobs-Tulleneers-Thevissen et al (doi: 10.1007/s00125-013-2906-0 ) advances the field by showing that human islets contained in alginate capsules can function very well, not only in the peritoneal cavity of mice, but also in a human with type 1 diabetes. Many obstacles must still be overcome, but this technology has the potential to safely protect transplanted beta cells from autoimmunity and allorejection.
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Affiliation(s)
- G C Weir
- Section on Islet Cell Biology and Regenerative Medicine, Joslin Diabetes Center, One Joslin Place, Boston, MA 02215, USA.
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71
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Pareta R, Sanders B, Babbar P, Soker T, Booth C, McQuilling J, Sivanandane S, Stratta RJ, Orlando G, Opara EC. Immunoisolation: where regenerative medicine meets solid organ transplantation. Expert Rev Clin Immunol 2013; 8:685-92. [PMID: 23078065 DOI: 10.1586/eci.12.64] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Immunoisolation refers to an immunological strategy in which nonself antigens present on an allograft or xenograft are not allowed to come in contact with the host immune system, and it is implemented to prevent allorecognition and avoid immunosuppression. In this setting, the two most promising technologies, encapsulation of pancreatic islets (EPI) and immunocloaking (IC), are used. In the case of EPI, islets are inserted in capsules that, allow exchange of oxygen, nutrients and other molecules. In the case of IC, a natural nanofilm is injected prior to renal transplantation within the vasculature of the graft with the intent to pave the inner surface of the vascular lumen and camouflage the antigens located on the membrane of endothelia cells. Significant progress achieved in experimental models is leading EPI and IC to clinical translation.
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Affiliation(s)
- Rajesh Pareta
- Wake Forest Institute for Regenerative Medicine, Wake Forest University School of Medicine, Winston Salem, NC, USA
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Shih H, Fraser AK, Lin CC. Interfacial thiol-ene photoclick reactions for forming multilayer hydrogels. ACS APPLIED MATERIALS & INTERFACES 2013; 5:1673-80. [PMID: 23384151 PMCID: PMC4028632 DOI: 10.1021/am302690t] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Interfacial visible light-mediated thiol-ene photoclick reactions were developed for preparing step-growth hydrogels with multilayer structures. The effect of a noncleavage type photoinitiator eosin-Y on visible-light-mediated thiol-ene photopolymerization was first characterized using in situ photorheometry, gel fraction, and equilibrium swelling ratio. Next, spectrophotometric properties of eosin-Y in the presence of various relevant macromer species were evaluated using ultraviolet-visible light (UV-vis) spectrometry. It was determined that eosin-Y was able to reinitiate the thiol-ene photoclick reaction, even after light exposure. Because of its small molecular weight, most eosin-Y molecules readily leached out from the hydrogels. The diffusion of residual eosin-Y from preformed hydrogels was exploited for fabricating multilayer step-growth hydrogels. Interfacial hydrogel coating was formed via the same visible-light-mediated gelation mechanism without adding fresh initiator. The thickness of the thiol-ene gel coating could be easily controlled by adjusting visible light exposure time, eosin-Y concentration initially loaded in the core gel, or macromer concentration in the coating solution. The major benefits of this interfacial thiol-ene coating system include its simplicity and cytocompatibility. The formation of thiol-ene hydrogels and coatings neither requires nor generates any cytotoxic components. This new gelation chemistry may have great utilities in controlled release of multiple sensitive growth factors and encapsulation of multiple cell types for tissue regeneration.
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Affiliation(s)
| | | | - Chien-Chi Lin
- Corresponding author: Chien-Chi Lin, PhD., Assistant Professor, Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, 723 W. Michigan St. SL220K, Indianapolis, IN. 46202, USA, Phone: 317-274-0760,
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73
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Abdallat RG, Ahmad Tajuddin AS, Gould DH, Hughes MP, Fatoyinbo HO, Labeed FH. Process development for cell aggregate arrays encapsulated in a synthetic hydrogel using negative dielectrophoresis. Electrophoresis 2013; 34:1059-67. [PMID: 23436271 DOI: 10.1002/elps.201200459] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Revised: 12/27/2012] [Accepted: 01/02/2013] [Indexed: 12/19/2022]
Abstract
Spatial patterning of cells is of great importance in tissue engineering and biotechnology, enabling, for example the creation of bottom-up histoarchitectures of heterogeneous cells, or cell aggregates for in vitro high-throughput toxicological and therapeutic studies within 3D microenvironments. In this paper, a single-step process for creating peelable and resilient hydrogels, encapsulating arrays of biological cell aggregates formed by negative DEP has been devised. The dielectrophoretic trapping within low-energy regions of the DEP-dot array reduces cell exposure to high field stresses while creating distinguishable, evenly spaced arrays of aggregates. In addition to using an optimal combination of PEG diacrylate pre-polymer solution concentration and a novel UV exposure mechanism, total processing time was reduced. With a continuous phase medium of PEG diacrylate at 15% v/v concentration, effective dielectrophoretic cell patterned arrays and photo-polymerisation of the mixture was achieved within a 4 min period. This unique single-step process was achieved using a 30 s UV exposure time frame within a dedicated, wide exposure area DEP light box system. To demonstrate the developed process, aggregates of yeast, human leukemic (K562) and HeLa cells were immobilised in an array format within the hydrogel. Relative cell viability for both cells within the hydrogels, after maintaining them in appropriate iso-osmotic media, over a week period was greater than 90%.
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Affiliation(s)
- Rula G Abdallat
- Faculty of Engineering and Physical Sciences, Centre for Biomedical Engineering, University of Surrey, Guildford, Surrey, United Kingdom
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74
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Alge DL, Azagarsamy MA, Donohue DF, Anseth KS. Synthetically tractable click hydrogels for three-dimensional cell culture formed using tetrazine-norbornene chemistry. Biomacromolecules 2013; 14:949-53. [PMID: 23448682 PMCID: PMC3623454 DOI: 10.1021/bm4000508] [Citation(s) in RCA: 189] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
![]()
The implementation of bio-orthogonal
click chemistries is a topic
of growing importance in the field of biomaterials, as it is enabling
the development of increasingly complex hydrogel materials capable
of providing dynamic, cell-instructive microenvironments. Here, we
introduce the tetrazine–norbornene inverse electron demand
Diels–Alder reaction as a new cross-linking chemistry for the
formation of cell laden hydrogels. The fast reaction rate and irreversible
nature of this click reaction allowed for hydrogel formation within
minutes when a multifunctional PEG-tetrazine macromer was reacted
with a dinorbornene peptide. In addition, the cytocompatibility of
the polymerization led to high postencapsulation viability of human
mesenchymal stem cells, and the specificity of the tetrazine–norbornene
reaction was exploited for sequential modification of the network
via thiol–ene photochemistry. These advantages, combined with
the synthetic accessibility of the tetrazine molecule compared to
other bio-orthogonal click reagents, make this cross-linking chemistry
an interesting and powerful new tool for the development of cell-instructive
hydrogels for tissue engineering applications.
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Affiliation(s)
- Daniel L Alge
- Department of Chemical and Biological Engineering, the BioFrontiers Institute, and the Howard Hughes Medical Institute, University of Colorado at Boulder, Boulder, Colorado 80309, USA
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75
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Yamaji K, Kawasaki Y, Yoshitome K, Matsunaga H, Sendo T. Quantitation and human monocyte cytotoxicity of the polymerization agent 1-hydroxycyclohexyl phenyl ketone (Irgacure 184) from three brands of aqueous injection solution. Biol Pharm Bull 2013; 35:1821-5. [PMID: 23037171 DOI: 10.1248/bpb.b12-00210] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study, levels of the photoinitiator 1-hydroxycyclohexyl phenyl ketone (1-HCHPK) in aqueous injection solutions were analyzed by GC-MS. In our previous studies, photoinitiators such as 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMP) were detected in intravenous (i.v.) injection bag solution, and they were found to be cytotoxic to human monocytes. Therefore, we hypothesized that 1-HCHPK might display similarly cytotoxicity. The purpose of this study was to quantitate the amount of contaminants from plastic containers such as those used for peripheral parenteral nutrition and to determine the cytotoxicity of such extracts on human monocytes. The sample extraction procedure for GC-MS analysis involved a liquid-phase extraction. The solvent was evaporated under a stream of nitrogen at 50°C to yield a residue, which was dissolved in n-hexane and injected into a GC-MS. Normal human peripheral blood mononuclear cells (PBMC), isolated from the buffy coat by centrifugation, were suspended in RPMI 1640 medium supplemented with 10% (v/v) heat-inactivated fetal calf serum. In the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay, cells (1×10(4)) were treated with 1-HCHPK for 24 h or 48 h at 37°C. From the GC-MS analysis, 6.13-8.32 µg/mL of 1-HCHPK was found in 20 mL vials of water for injection solution. In the MTT assay, 1-HCHPK decreased cell viability for both the 24 h and 48 h incubation periods. In conclusion, our findings suggest that 1-HCHPK could promote adverse events in patients. Future studies will clarify the possible health risks of photoinitiator accumulation in human cells.
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Affiliation(s)
- Kazuhiko Yamaji
- Department of Pharmacy, Okayama University Hospital, 2–5–1 Shikata-cho, Kita-ku, Okayama 700–8558, Japan
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76
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Gurkan UA, Fan Y, Xu F, Erkmen B, Urkac ES, Parlakgul G, Bernstein J, Xing W, Boyden ES, Demirci U. Simple precision creation of digitally specified, spatially heterogeneous, engineered tissue architectures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:1192-8. [PMID: 23192949 PMCID: PMC3842103 DOI: 10.1002/adma.201203261] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 10/04/2012] [Indexed: 05/04/2023]
Affiliation(s)
- Umut Atakan Gurkan
- Harvard Medical School, Division of Biomedical Engineering at Brigham and Women's Hospital, Bio-Acoustic-MEMS in Medicine (BAMM) Laboratory, Harvard-MIT Health Sciences & Technology, 65 Landsdowne St. PRB 252, Cambridge, MA 02139, USA
| | - Yantao Fan
- Harvard Medical School, Division of Biomedical Engineering at Brigham and Women's Hospital, Bio-Acoustic-MEMS in Medicine (BAMM) Laboratory, Harvard-MIT Health Sciences & Technology, 65 Landsdowne St. PRB 252, Cambridge, MA 02139, USA
| | - Feng Xu
- Harvard Medical School, Division of Biomedical Engineering at Brigham and Women's Hospital, Bio-Acoustic-MEMS in Medicine (BAMM) Laboratory, Harvard-MIT Health Sciences & Technology, 65 Landsdowne St. PRB 252, Cambridge, MA 02139, USA
| | - Burcu Erkmen
- Harvard Medical School, Division of Biomedical Engineering at Brigham and Women's Hospital, Bio-Acoustic-MEMS in Medicine (BAMM) Laboratory, Harvard-MIT Health Sciences & Technology, 65 Landsdowne St. PRB 252, Cambridge, MA 02139, USA
| | - Emel Sokullu Urkac
- Harvard Medical School, Division of Biomedical Engineering at Brigham and Women's Hospital, Bio-Acoustic-MEMS in Medicine (BAMM) Laboratory, Harvard-MIT Health Sciences & Technology, 65 Landsdowne St. PRB 252, Cambridge, MA 02139, USA
| | - Gunes Parlakgul
- Harvard Medical School, Division of Biomedical Engineering at Brigham and Women's Hospital, Bio-Acoustic-MEMS in Medicine (BAMM) Laboratory, Harvard-MIT Health Sciences & Technology, 65 Landsdowne St. PRB 252, Cambridge, MA 02139, USA
| | - Jacob Bernstein
- Media Lab and McGovern Institute, Departments of Brain and Cognitive Sciences and Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Wangli Xing
- Medical Systems Biology Research Center, School of Medicine, Tsinghua University, Beijing 100084, PR China, National Engineering Research Center for Beijing Biochip Technology, 18 Life Science Parkway, Beijing, 102206, P. R. China
| | - Edward S. Boyden
- Media Lab and McGovern Institute, Departments of Brain and Cognitive Sciences and Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Utkan Demirci
- Harvard Medical School, Brigham and Women's Hospital, Harvard-MIT Health Sciences & Technology, 65 Landsdowne St. PRB 252, Cambridge, MA 02139, USA
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77
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Weir GC, Bonner-Weir S. Islet β cell mass in diabetes and how it relates to function, birth, and death. Ann N Y Acad Sci 2013; 1281:92-105. [PMID: 23363033 PMCID: PMC3618572 DOI: 10.1111/nyas.12031] [Citation(s) in RCA: 236] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In type 1 diabetes (T1D) β cell mass is markedly reduced by autoimmunity. Type 2 diabetes (T2D) results from inadequate β cell mass and function that can no longer compensate for insulin resistance. The reduction of β cell mass in T2D may result from increased cell death and/or inadequate birth through replication and neogenesis. Reduction in mass allows glucose levels to rise, which places β cells in an unfamiliar hyperglycemic environment, leading to marked changes in their phenotype and a dramatic loss of glucose-stimulated insulin secretion (GSIS), which worsens as glucose levels climb. Toxic effects of glucose on β cells (glucotoxicity) appear to be the culprit. This dysfunctional insulin secretion can be reversed when glucose levels are lowered by treatment, a finding with therapeutic significance. Restoration of β cell mass in both types of diabetes could be accomplished by either β cell regeneration or transplantation. Learning more about the relationships between β cell mass, turnover, and function and finding ways to restore β cell mass are among the most urgent priorities for diabetes research.
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Affiliation(s)
- Gordon C Weir
- Section on Islet Cell Biology and Regenerative Medicine, Research Division, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, MA 02215, USA.
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78
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Park JH, Pérez RA, Jin GZ, Choi SJ, Kim HW, Wall IB. Microcarriers designed for cell culture and tissue engineering of bone. TISSUE ENGINEERING PART B-REVIEWS 2013; 19:172-90. [PMID: 23126371 DOI: 10.1089/ten.teb.2012.0432] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Microspherical particulates have been an attractive form of biomaterials that find usefulness in cell delivery and tissue engineering. A variety of compositions, including bioactive ceramics, degradable polymers, and their composites, have been developed into a microsphere form and have demonstrated the potential to fill defective bone and to populate tissue cells on curved matrices. To enhance the capacity of cell delivery, the conventional solid form of spheres is engineered to have either a porous structure to hold cells or a thin shell to in-situ encapsulate cells within the structure. Microcarriers can also be a potential reservoir system of bioactive molecules that have therapeutic effects in regulating cell behaviors. Due to their specific form, advanced technologies to culture cell-loaded microcarriers are required, such as simple agitation or shaking, spinner flask, and rotating chamber system. Here, we review systematically, from material design to culture technology, the microspherical carriers used for the delivery of cells and tissue engineering, particularly of bone.
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Affiliation(s)
- Jeong-Hui Park
- Biomaterials and Tissue Engineering Lab, Department of Nanobiomedical Science & WCU Research Center, Dankook University, Cheonan, South Korea
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79
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80
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81
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Kim AR, Hwang JH, Kim HM, Kim HN, Song JE, Yang YI, Yoon KH, Lee D, Khang G. Reduction of inflammatory reaction in the use of purified alginate microcapsules. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2012; 24:1084-98. [PMID: 23683040 DOI: 10.1080/09205063.2012.735100] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Alginate, a polysaccharide extracted from brown seaweed, remains the most widely used biomaterial for immobilizing cells to be transplanted, because of the good viability of the encapsulated cells and the relatively ease of processing for cell encapsulation. However, the main drawback is the immune reaction in vivo. To overcome this problem, we have demonstrated a modified Korbutt method for alginate purification. After alginate microcapsules were manufactured, NIH/3T3 fibroblast cells were seeded in purified and non-purified alginate microcapsules, and the cell proliferation was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide assay. Reverse transcriptase-polymerase chain reaction was performed to assess the mRNA expression of RAW 264.7 macrophage cells for inflammation cytokines such as TNF-α. Purified and non-purified alginate microcapsules were implanted into Wister rats, and subsequently extracted after 1-2 weeks. Tissues surrounding the implants were harvested and underwent histological evaluation through H&E staining and immunohistochemical evaluation through ED-1 staining. In this result, contaminated materials in the purified alginate were eliminated by purification process. Thereby, density of inflammatory cell decreased about 30% more than non-purified alginate and thickness of fibrotic wall decreased about three times. In concluding, the purified alginate is anticipated to be highly potent for numerous biomaterial applications.
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Affiliation(s)
- A Ram Kim
- Department of BIN Fusion Technology, Polymer Nano Science & Technology and Polymer Fusion Research Center, Chonbuk National University, 567 Beackje-daero, Deokjin , Jeonju 561-756, Korea
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82
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Swartzlander MD, Lynn AD, Blakney AK, Kyriakides TR, Bryant SJ. Understanding the host response to cell-laden poly(ethylene glycol)-based hydrogels. Biomaterials 2012; 34:952-64. [PMID: 23149012 DOI: 10.1016/j.biomaterials.2012.10.037] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 10/11/2012] [Indexed: 01/07/2023]
Abstract
Poly(ethylene glycol) (PEG)-based hydrogels are promising in situ cell carriers for tissue engineering. However, their success in vivo will in part depend upon the foreign body reaction (FBR). This study tests the hypothesis that the FBR affects cells encapsulated within PEG hydrogels, and in turn influences the severity of the FBR. Fibroblasts were encapsulated within PEG hydrogels containing RGD to support cell attachment. Macrophages were seeded on top of cell-laden hydrogels to mimic in vivo macrophage interrogation and treated with lipopolysaccharide to induce an inflammatory phenotype. The presence of activated macrophages reduced fibroblast gene expression for extracellular matrix molecules and remodeling, but stimulated VEGF and IL-1β gene expression. Fibroblasts impacted macrophage phenotype leading to increased iNOS, IL-1β and TNF-α expressions. Syngeneic cell-laden and acellular hydrogels were also implanted subcutaneously into C57bl/6 mice for 2, 7 and 28 days. Encapsulated fibroblasts secreted collagen type I during the first week, but tissue deposition and cellularity decreased by 28 days. The presence of encapsulated fibroblasts led to greater acute inflammation, but did not influence the fibrotic response. In summary, this work emphasizes the importance of the host response in tissue engineering, and the potentially deleterious impact it may have on cell-laden synthetic scaffolds.
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Affiliation(s)
- Mark D Swartzlander
- Department of Chemical & Biological Engineering, University of Colorado, Boulder, CO 80303, USA.
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83
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Pishko M. Microfabricated Cell-based Biosensor Arrays. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2012; 2006:1058-64. [PMID: 17282370 DOI: 10.1109/iembs.2005.1616601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Here, we described the fabrication using photolithography of poly(ethylene glycol) (PEG)-based hydrogel microstructures encapsulating viable mammalian cells on glass and silicon substrates. Substrates were treated with 3-(trichlorosilyl) propyl methacrylate to form pendant acrylate group to covalent link the hydrogel microstructure. Cells were encapsulated in arrays of cylindrical hydrogel microstructures 600 and 50 μm in diameter and viability assays demonstrated that encapsulated cells remained viable after photoencapsulation. These microstructures had clearly defined, three-dimensional structure without any residual cells remaining surface and no delamination of hydrogel elements from functionalized substrate occurred in aqueous environment for over a week. By changing spin-coating rates and feature sizes of photomasks, we could create cell-containing microstructures with aspect ratios ranging from 0.12 to 1.4. In case of 50 μm hydrogel microstructure, number of cells could be limited to 1 or 2 cells per element and array consisting of 400 elements could be fabricated in a square of 2 mm<sup>2</sup>. These cell-containinghydrogel microstructures were also successfully fabricated in poly(dimethylsiloxane) microchannels to create optical biosensor arrays of individually addressable single or multiple cell- containing hydrogel microstructures with potential applications in drug screening or pathogen detection.
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Affiliation(s)
- Michael Pishko
- Department of Chemical Engineering, The Pennsylvania State, University, 204 Fenske Laboratory, University Park, PA 16802-4400
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84
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Ausländer S, Wieland M, Fussenegger M. Smart medication through combination of synthetic biology and cell microencapsulation. Metab Eng 2012; 14:252-60. [DOI: 10.1016/j.ymben.2011.06.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 05/11/2011] [Accepted: 06/09/2011] [Indexed: 01/05/2023]
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85
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Nazli C, Ergenc TI, Yar Y, Acar HY, Kizilel S. RGDS-functionalized polyethylene glycol hydrogel-coated magnetic iron oxide nanoparticles enhance specific intracellular uptake by HeLa cells. Int J Nanomedicine 2012; 7:1903-20. [PMID: 22619531 PMCID: PMC3356191 DOI: 10.2147/ijn.s29442] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The objective of this study was to develop thin, biocompatible, and biofunctional hydrogel-coated small-sized nanoparticles that exhibit favorable stability, viability, and specific cellular uptake. This article reports the coating of magnetic iron oxide nanoparticles (MIONPs) with covalently cross-linked biofunctional polyethylene glycol (PEG) hydrogel. Silanized MIONPs were derivatized with eosin Y, and the covalently cross-linked biofunctional PEG hydrogel coating was achieved via surface-initiated photopolymerization of PEG diacrylate in aqueous solution. The thickness of the PEG hydrogel coating, between 23 and 126 nm, was tuned with laser exposure time. PEG hydrogel-coated MIONPs were further functionalized with the fibronectin-derived arginine-glycine-aspartic acid-serine (RGDS) sequence, in order to achieve a biofunctional PEG hydrogel layer around the nanoparticles. RGDS-bound PEG hydrogel-coated MIONPs showed a 17-fold higher uptake by the human cervical cancer HeLa cell line than that of amine-coated MIONPs. This novel method allows for the coating of MIONPs with nano-thin biofunctional hydrogel layers that may prevent undesirable cell and protein adhesion and may allow for cellular uptake in target tissues in a specific manner. These findings indicate that the further biofunctional PEG hydrogel coating of MIONPs is a promising platform for enhanced specific cell targeting in biomedical imaging and cancer therapy.
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Affiliation(s)
- Caner Nazli
- Graduate School of Sciences and Engineering, Koç University, Istanbul, Turkey
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86
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Pal K, Banthia AK, Majumdar DK. Polymeric Hydrogels: Characterization and Biomedical Applications. Des Monomers Polym 2012. [DOI: 10.1163/156855509x436030] [Citation(s) in RCA: 227] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- K. Pal
- a Department of Biotechnology & Medical Engineering, National Institute of Technology, Rourkela-769008, India
| | - A. K. Banthia
- b Materials Science Center, Indian Institute of Technology, Kharagpur-721302, India
| | - D. K. Majumdar
- c Delhi Institute of Pharmaceutical Sciences and Research, Formerly College of Pharmacy, (University of Delhi), Pushp Vihar, Sector-III, New Delhi-110017, India
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87
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Tauro JR, Gemeinhart RA. Development of amine-containing polymeric particles. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2012; 16:1233-44. [PMID: 16268250 DOI: 10.1163/156856205774269539] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The objective of this study was to synthesize and characterize particles as a drug-delivery platform for gliomas, a highly advanced and invasive stage of brain tumor with poor prognosis. Poly(aminoethyl methacrylate-co-methyl methacrylate) particles were prepared by suspension polymerization and poly(aminoethyl methacrylate-co-poly(ethylene glycol) methacrylate) particles were prepared by emulsion (w/o) polymerization. Amine groups of the particles were complexed with tetrachloroplatinate to form a cisplatin-like molecule. Particles were characterized with respect to size, zeta-potential, amine content, loading efficiency and drug release. Poly(aminoethyl methacrylate-co-methyl methacrylate) particles had diameters of below 10 microm, whereas the poly(aminoethyl methacrylate-co-poly(ethylene glycol) methacrylate) particles had diameters of approx. 1 microm. Poly(aminoethyl methacrylate-co-poly(ethylene glycol) methacrylate) particles had a more positive zeta-potential as compared to poly(aminoethyl methacrylate-co-methyl methacrylate) particles, although the amino-group content of both particles was almost equivalent. The net positive charge on the particles decreased after complexation with tetrachloroplatinate for both types of particles. Both particles had very high platinum-loading efficiency (>85%) and showed slow release of platinum over time. Particles had relatively low cytotoxicity (LC50 > 100 microg/ml) and demonstrated a high degree of association with cells. Complexation with poly(aminoethyl methacrylate-co-methyl methacrylate) particles significantly reduced the toxicity of platinum. The poly(aminoethyl methacrylate-co-poly(ethylene glycol) methacrylate) particles have potential for being an effective drug-delivery platform and continued investigation is warranted.
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Affiliation(s)
- Jovita R Tauro
- Department of Biopharmaceutical Sciences, College of Pharmacy, University of Illinois, 833 South Wood Street (MC 865), Chicago, IL 60612-7231, USA
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Brunsen A, Ritz U, Mateescu A, Höfer I, Frank P, Menges B, Hofmann A, Rommens PM, Knoll W, Jonas U. Photocrosslinkable dextran hydrogel films as substrates for osteoblast and endothelial cell growth. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm34006b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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89
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Kawasaki Y, Yamaji K, Matsunaga H, Sendo T. Cytotoxicity of the Polymerization Agent, 2-Methyl-4'-(methylthio)-2-morpholinopropiophenone on Human Monocytes. Biol Pharm Bull 2012; 35:256-9. [DOI: 10.1248/bpb.35.256] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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90
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Aurand ER, Lampe KJ, Bjugstad KB. Defining and designing polymers and hydrogels for neural tissue engineering. Neurosci Res 2011; 72:199-213. [PMID: 22192467 DOI: 10.1016/j.neures.2011.12.005] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/07/2011] [Accepted: 12/07/2011] [Indexed: 12/16/2022]
Abstract
The use of biomaterials, such as hydrogels, as neural cell delivery devices is becoming more common in areas of research such as stroke, traumatic brain injury, and spinal cord injury. When reviewing the available research there is some ambiguity in the type of materials used and results are often at odds. This review aims to provide the neuroscience community who may not be familiar with fundamental concepts of hydrogel construction, with basic information that would pertain to neural tissue applications, and to describe the use of hydrogels as cell and drug delivery devices. We will illustrate some of the many tunable properties of hydrogels and the importance of these properties in obtaining reliable and consistent results. It is our hope that this review promotes creative ideas for ways that hydrogels could be adapted and employed for the treatment of a broad range of neurological disorders.
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Affiliation(s)
- Emily R Aurand
- Neuroscience Program, University of Colorado Denver - Anschutz Medical Campus, Aurora, CO 80045, USA.
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91
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Gauvin R, Parenteau-Bareil R, Dokmeci MR, Merryman WD, Khademhosseini A. Hydrogels and microtechnologies for engineering the cellular microenvironment. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2011; 4:235-46. [DOI: 10.1002/wnan.171] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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92
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Photocrosslinkable biodegradable responsive hydrogels as drug delivery systems. Int J Biol Macromol 2011; 49:948-54. [DOI: 10.1016/j.ijbiomac.2011.08.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 07/28/2011] [Accepted: 08/11/2011] [Indexed: 11/20/2022]
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93
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Lee BR, Hwang JW, Choi YY, Wong SF, Hwang YH, Lee DY, Lee SH. In situ formation and collagen-alginate composite encapsulation of pancreatic islet spheroids. Biomaterials 2011; 33:837-45. [PMID: 22054535 DOI: 10.1016/j.biomaterials.2011.10.014] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 10/10/2011] [Indexed: 11/19/2022]
Abstract
In this study, we suggest in situ islet spheroid formation and encapsulation on a single platform without replating as a method for producing mono-disperse spheroids and minimizing damage to spheroids during encapsulation. Using this approach, the size of spheroid can be controlled by modulating the size of the concave well. Here, we used 300 μm concave wells to reduce spheroid size and thereby eliminating the central necrosis caused by large volume. As the encapsulation material, we used alginate and collagen-alginate composite (CAC), and evaluated their suitability through diverse in vitro tests, including measurements of viability, oxygen consumption rate (OCR), hypoxic damage to encapsulated spheroids, and insulin secretion. For in situ encapsulation, alginate or CAC was spread over a concave microwell array containing spheroids, and CaCl(2) solution was diffused through a nano-porous dialysis membrane to achieve uniform polymerization, forming convex structures. By this process, the formation of uniform-size islet spheroids and their encapsulation without an intervening replating step was successfully performed. As a control, intact islets were evaluated concurrently. The in vitro test demonstrated excellent performance of CAC-encapsulated spheroids, and on the basis of these results, we transplanted the islet spheroids-encapsulated with CAC into the intraperitoneal cavity of mice with induced diabetes for 4 weeks, and evaluated subsequent glucose control. Intact islets were also transplanted as control to investigate the effect of encapsulation. Transplanted CAC-encapsulated islet spheroids maintained glucose levels below 200 mg/dL for 4 weeks, at which they were still active. At the end of the implantation experiment, we carried out intraperitoneal glucose tolerance test (IPGTT) in mice to investigate whether the implanted islets remained responsive to glucose. The glucose level in mice with CAC-encapsulated islet spheroids dropped below 200 mg/dL 60 min after glucose injection and was stably maintained. In conclusion, the proposed encapsulation method enhances the viability and function of islet spheroids, and protects these spheroids from immune attack.
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Affiliation(s)
- Bo Ram Lee
- Department of Biomedical Engineering, College of Health Science, Korea University, Seoul 136-703, Republic of Korea
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94
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Hume PS, Anseth KS. Polymerizable superoxide dismutase mimetic protects cells encapsulated in poly(ethylene glycol) hydrogels from reactive oxygen species-mediated damage. J Biomed Mater Res A 2011; 99:29-37. [PMID: 21793194 DOI: 10.1002/jbm.a.33160] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 05/01/2011] [Accepted: 05/06/2011] [Indexed: 01/18/2023]
Abstract
A polymerizable superoxide dismutase mimetic (SODm) was incorporated into poly(ethylene glycol) (PEG) hydrogels to protect encapsulated cells from superoxide-mediated damage. Superoxide and other small reactive oxygen species (ROS) can cause oxidative damage to donor tissue encapsulated within size exclusion barrier materials. To enzymatically breakdown ROS within biomaterial cell encapsulation systems, Mn(III) Tetrakis[1-(3-acryloxy-propyl)-4-pyridyl] porphyrin (MnTTPyP-acryl), a polymerizable manganese metalloporphyrin SOD mimetic, was photopolymerized with PEG diacrylate (PEGDA) to create functional gels. In unmodified PEG hydrogels, a significant reduction in metabolic activity was observed when encapsulated Min6 β-cells were challenged with chemically generated superoxide. Cells encapsulated within MnTPPyP-co-PEG hydrogels, however, demonstrated greatly improved metabolic activity following various superoxide challenges. Further, cells were encapsulated and cultured for 10 days within MnTPPyP-co-PEG hydrogels and challenged with superoxide on days 4, 6, and 8. At the conclusion of this study, cells in blank PEG hydrogels had no observable metabolic activity but when encapsulated in MnTPPyP-functionalized hydrogels, cells retained 60 ± 5% of the metabolic activity compared to untreated controls.
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Affiliation(s)
- Patrick S Hume
- Department of Chemical and Biological Engineering, University of Colorado, 424 UCB, Boulder, Colorado 80309, USA
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95
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Hume PS, Bowman CN, Anseth KS. Functionalized PEG hydrogels through reactive dip-coating for the formation of immunoactive barriers. Biomaterials 2011; 32:6204-12. [PMID: 21658759 DOI: 10.1016/j.biomaterials.2011.04.049] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 04/20/2011] [Indexed: 12/11/2022]
Abstract
Influencing the host immune system via implantable cell-delivery devices has the potential to reduce inflammation at the transplant site and increase the likelihood of tissue acceptance. Towards this goal, an enzymatically-initiated, dip-coating technique is adapted to fabricate conformal hydrogel layers and to create immunoactive polymer coatings on cell-laden poly(ethylene glycol) (PEG) hydrogels. Glucose oxidase (GOx)-initiated dip coatings enable the rapid formation of uniform, PEG-based coatings on the surfaces of PEG hydrogels, with thicknesses up to 500 μm where the thickness is proportional to the reaction time. Biofunctional coatings were fabricated by thiolating biomolecules that were subsequently covalently incorporated into the coating layer via thiol-acrylate copolymerization. The presence of these proteins was verified via fluorescent confocal microscopy and a modified ELISA, which indicated IgG concentrations as high as 13 ± 1 ng/coated cm² were achievable. Anti-Fas antibody, known to induce T cell apoptosis, was incorporated into coatings, with or without the addition of ICAM-1 to promote T cell interaction with the functionalized coating. Jurkat T cells were seeded atop functionalized coatings and the induction of apoptosis was measured as an indicator of coating bioactivity. After 48 h of interaction with the functionalized coatings, 61 ± 9% of all cells were either apoptotic or dead, compared to only 18 ± 5% of T cells on non-functionalized coatings. Finally, the cytocompatibility of the surface-initiated GOx coating process was confirmed by modifying gels with either encapsulated β-cells or 3T3 fibroblasts within a gel that contained a PEG methacrylate coating.
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Affiliation(s)
- Patrick S Hume
- Department of Chemical and Biological Engineering, University of Colorado, 424 UCB, Boulder, CO 80309, USA
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96
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Hsu CW, Olabisi RM, Olmsted-Davis EA, Davis AR, West JL. Cathepsin K-sensitive poly(ethylene glycol) hydrogels for degradation in response to bone resorption. J Biomed Mater Res A 2011; 98:53-62. [PMID: 21523904 DOI: 10.1002/jbm.a.33076] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 01/10/2011] [Accepted: 01/31/2011] [Indexed: 02/05/2023]
Abstract
We propose a new strategy of biomaterial design to achieve selective cellular degradation by the incorporation of cathepsin K-degradable peptide sequences into a scaffold structure so that scaffold biodegradation can be induced at the end of the bone formation process. Poly(ethylene glycol) diacrylate (PEGDA) hydrogels were used as a model biomaterial system in this study. A cathepsin K-sensitive peptide, GGGMGPSGPWGGK (GPSG), was synthesized and modified with acryloyl-PEG-succinimidyl carbonate to produce a cross-linkable cathepsin K-sensitive polymer that can be used to form a hydrogel. Specificity of degradation of the GPSG hydrogels was tested with cathepsin K and proteinase K as a positive control, with both resulting in significant degradation compared to incubation with nonspecific collagenases over a 24-h time period. No degradation was observed when the hydrogels were incubated with plasmin or control buffers. Cell-induced degradation was evaluated by seeding differentiated MC3T3-E1 osteoblasts and RAW264.7 osteoclasts on GPSG hydrogels that were also modified with the cell adhesion peptide RGDS. Resulting surface features and resorption pits were analyzed by differential interference contrast (DIC) and fluorescent images obtained with confocal microscopy. Results from both analyses demonstrated that GPSG hydrogels can be degraded specifically in response to osteoclast attachment but not in response to osteoblasts. In summary, we have demonstrated that by incorporating a cathepsin K-sensitive peptide into a synthetic polymer structure, we can generate biomaterials that specifically respond to cues from the natural process of bone remodeling.
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Affiliation(s)
- Chih-Wei Hsu
- Department of Bioengineering, Rice University, 6100 Main St., Houston, Texas 77005, USA
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97
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Wilson JT, Cui W, Kozlovskaya V, Kharlampieva E, Pan D, Qu Z, Krishnamurthy VR, Mets J, Kumar V, Wen J, Song Y, Tsukruk VV, Chaikof EL. Cell surface engineering with polyelectrolyte multilayer thin films. J Am Chem Soc 2011; 133:7054-64. [PMID: 21491937 DOI: 10.1021/ja110926s] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Layer-by-layer assembly of polyelectrolyte multilayer (PEM) films represents a bottom-up approach for re-engineering the molecular landscape of cell surfaces with spatially continuous and molecularly uniform ultrathin films. However, fabricating PEMs on viable cells has proven challenging owing to the high cytotoxicity of polycations. Here, we report the rational engineering of a new class of PEMs with modular biological functionality and tunable physicochemical properties which have been engineered to abrogate cytotoxicity. Specifically, we have discovered a subset of cationic copolymers that undergoes a conformational change, which mitigates membrane disruption and facilitates the deposition of PEMs on cell surfaces that are tailorable in composition, reactivity, thickness, and mechanical properties. Furthermore, we demonstrate the first successful in vivo application of PEM-engineered cells, which maintained viability and function upon transplantation and were used as carriers for in vivo delivery of PEMs containing biomolecular payloads. This new class of polymeric film and the design strategies developed herein establish an enabling technology for cell transplantation and other therapies based on engineered cells.
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Affiliation(s)
- John T Wilson
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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98
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Karajanagi SS, Yoganathan R, Mammucari R, Park H, Cox J, Zeitels SM, Langer R, Foster NR. Application of a dense gas technique for sterilizing soft biomaterials. Biotechnol Bioeng 2011; 108:1716-25. [PMID: 21337339 DOI: 10.1002/bit.23105] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 01/19/2011] [Accepted: 02/10/2011] [Indexed: 12/15/2022]
Abstract
Sterilization of soft biomaterials such as hydrogels is challenging because existing methods such as gamma irradiation, steam sterilization, or ethylene oxide sterilization, while effective at achieving high sterility assurance levels (SAL), may compromise their physicochemical properties and biocompatibility. New methods that effectively sterilize soft biomaterials without compromising their properties are therefore required. In this report, a dense-carbon dioxide (CO(2) )-based technique was used to sterilize soft polyethylene glycol (PEG)-based hydrogels while retaining their structure and physicochemical properties. Conventional sterilization methods such as gamma irradiation and steam sterilization severely compromised the structure of the hydrogels. PEG hydrogels with high water content and low elastic shear modulus (a measure of stiffness) were deliberately inoculated with bacteria and spores and then subjected to dense CO(2) . The dense CO(2) -based methods effectively sterilized the hydrogels achieving a SAL of 10(-7) without compromising the viscoelastic properties, pH, water-content, and structure of the gels. Furthermore, dense CO(2) -treated gels were biocompatible and non-toxic when implanted subcutaneously in ferrets. The application of novel dense CO(2) -based methods to sterilize soft biomaterials has implications in developing safe sterilization methods for soft biomedical implants such as dermal fillers and viscosupplements.
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Affiliation(s)
- Sandeep S Karajanagi
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
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99
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Hall KK, Gattás-Asfura KM, Stabler CL. Microencapsulation of islets within alginate/poly(ethylene glycol) gels cross-linked via Staudinger ligation. Acta Biomater 2011; 7:614-24. [PMID: 20654745 DOI: 10.1016/j.actbio.2010.07.016] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 07/09/2010] [Accepted: 07/14/2010] [Indexed: 11/18/2022]
Abstract
Functionalized alginate and poly(ethylene glycol) (PEG) polymers were used to generate covalently linked alginate-PEG (XAlgPEG) microbeads of high stability. The cell-compatible Staudinger ligation scheme was used to cross-link phosphine-terminated PEG chemoselectively to azide-functionalized alginate, resulting in XAlgPEG hydrogels. XAlgPEG microbeads were formed by co-incubation of the two polymers, followed by ionic cross-linking of the alginate using barium ions. The enhanced stability and gel properties of the resulting XAlgPEG microbeads, as well as the compatibility of these polymers for the encapsulation of islets and beta cells lines, were investigated. The data show that XAlgPEG microbeads exhibit superior resistance to osmotic swelling compared with traditional barium cross-linked alginate (Ba-Alg) beads, with a five-fold reduction in observed swelling, as well as resistance to dissolution via chelation solution. Diffusion and porosity studies found XAlgPEG beads to exhibit properties comparable with standard Ba-Alg. XAlgPEG microbeads were found to be highly cell compatible with insulinoma cell lines, as well as rat and human pancreatic islets, where the viability and functional assessment of cells within XAlgPEG are comparable with Ba-Alg controls. The remarkable improved stability, as well as demonstrated cellular compatibility, of XAlgPEG hydrogels makes them an appealing option for a wide variety of tissue engineering applications.
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Affiliation(s)
- K K Hall
- Department of Biomedical Engineering, College of Engineering, University of Miami, 1450 NW 10th Avenue, Miami, FL 33136, USA
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100
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Lynn AD, Blakney AK, Kyriakides TR, Bryant SJ. Temporal progression of the host response to implanted poly(ethylene glycol)-based hydrogels. J Biomed Mater Res A 2011; 96:621-31. [PMID: 21268236 DOI: 10.1002/jbm.a.33015] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 08/18/2010] [Accepted: 10/06/2010] [Indexed: 12/18/2022]
Abstract
Poly(ethylene glycol) (PEG) hydrogels hold great promise as in vivo cell carriers for tissue engineering. To ensure appropriate performance of these materials when implanted, the host response must be well understood. The objectives for this study were to characterize the temporal evolution of the foreign body reaction (FBR) to acellular PEG-based hydrogels prepared from PEG diacrylate precursors when implanted subcutaneously in immunocompentent c57bl/6 mice by (immuno)histochemical analysis and gene expression. Compared with a normal FBR elicited by silicone (SIL), PEG hydrogels without or with a cell adhesion ligand RGD elicited a strong early inflammatory response evidenced by a thick band of macrophages as early as day 2, persisting through two weeks, and by increased interleukin-1β expression. PEG-only hydrogels showed a slower, but more sustained progression of inflammation over PEG-RGD. Temporal changes in gene expression were observed in response to PEG-based materials and in general exhibited, elevated expression of inflammatory and wound healing genes in the tissues surrounding the implants, while the expression patterns were more stable in response to SIL. While a stabilized FBR was achieved with SIL and to a lesser degree with PEG-RGD, the PEG-only hydrogels had not yet stabilized after 4 weeks. In summary, PEG-only hydrogels elicit a strong early inflammatory reaction, which persists throughout the course of the implantation even as a collagenous capsule begins to form. However, the incorporation of RGD tethers partially attenuates this response within 2 weeks leading to an improved FBR to PEG-based hydrogels.
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Affiliation(s)
- Aaron D Lynn
- Department of Chemical and Biological Engineering, University of Colorado at Boulder, Boulder, Colorado 80309, USA
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