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Cell Journal، جلد ۱۷، شماره Suppl ۱، صفحات ۱۹-۲۰
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عنوان انگلیسی Os-2: Alginate Composition and Temperature Influence Microcapsule Permeability
چکیده انگلیسی مقاله Objective: Alginate encapsulated islets have the potential to cure Type I diabetes in humans and provide long-term protection from immune-mediated graft damage. Alginate pore size is a crucial parameter that aids in the protection of islets from host immune recognition, while allowing oxygen and insulin to diffuse into the capsules. The aim of this study is to determine the pore size of alginate microcapsules using dextrans of specific sizes to identify capsules with optimal diffusion parameters. Materials and Methods: Alginate microcapsules were made with 2.5% (w/v) ultra-pure low viscosity high mannuronate (UP LVM) and ultra-pure low viscosity high guluronate (UP LVG, NovaMatrix® PRONOVA™) using a microcapsule generator (Nisco Engineering AG) at standard settings (9 kV; voltage, 80rpm; stirrer speed, 3psi; air pressure, 30 mm; needle height, 25 G; needle gauge, 120 mM CaCl2; gelling solution). The microcapsules were then incubated at either 3oC or 37°C for a 24 hour period. Samples were taken post-incubation and plated on a slide flask to which a cocktail of three fluorescently-tagged dextrans were added: 3mg/mL of cascade blue conjugated 10kDa (Life Technologies, cat. D-1976), 15 mg/mL of fluorescein isothyocyanate (FITC) conjugated 150 kDa (Sigma-Aldridge, cat. FD150S-1G), and 15mg/mL of tetramethylrhodamine isothiocyanate conjugated 500 kDa (Sigma-Aldridge, cat. 52194-1G). Images were obtained using a two-photon confocal microscope (Zeiss LSM 520 Meta, LSM 4.2 SPI software by Carl Zeiss) at 0 and 30 minutes. The images were analyzed using the image analysis software, ImageJ, to determine the percentage change in fluorescence intensity inside the capsules. All data is reported as Mean ± SEM. Statistical analysis was performed using a one way ANOVA and P< 0.05 was considered statistically significant. Results: 10kDa dextrans were able to freely permeate both UP LVM and UP LVG alginate microcapsules with no significant change from 0 to 30 minutes at 3oC and 37oC. Thus, a small molecule like insulin (5-6 kDa) would be able to freely diffuse out of these microcapsules. 500kDa dextrans showed significantly higher diffusion in UP LVG (26.26 ± 0.9%; 3 oC, 16.25 ± 1.1%; 37oC) than UP LVM (0%; 3oC, 0%; 37oC), indicating that UP LVM alginate microcapsules are relatively impermeable to very large protein molecules. UP LVG microcapsules demonstrated significantly higher diffusion of 150 kDa dextrans (72.3 ± 0.7%; 37oC, 73.3 ± 0.5%; 37oC) when compared to UP LVM microcapsules (32.0 ± 1.1%, 3oC, -4.6 ± 0.5%; 37oC). This indicates that microcapsules show rapid diffusion of 150kDa dextrans independent of incubation temperature while high M alginate microcapsules do not (P< 0.001, ANOVA). Interestingly, a temperature-dependent reduction in dextran diffusion (and hence alginate pore size) is noted in UP LVM alginate microcapsules, a property that would enhance exclusion of IgG (~150 kDa) and other antibodies after transplantation.Conclusion: The results of this study suggest that alginate composition (specifically, guluronic acid content) and temperature greatly influence pore size and permeability. These results suggest that high mannuronate alginate microcapsules may confer significantly better protection from the humoral immune system (IgG antibodies); they are preferred candidates for further in vivo encapsulated islet transplant studies in small and large animal models.
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نویسندگان مقاله g kummerfeld | g kummerfeld


r krishnan | r krishnan


a najdahmadi | a najdahmadi


e botvinick | e botvinick


jrt lakey | jrt lakey


نشانی اینترنتی http://celljournal.org/journal/article/abstract/55
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