title: The Diffusive Properties of Hydrogel Microcapsules for Cell Encapsulation.
abstract: Hydrogel microcapsules have been used for decades to encapsulate cells and treat diseases ranging from neurodegenerative disorders to more systemic applications like Type I Diabetes. This cell encapsulation modality has been developed through more cumulative experiments than perhaps any other, owing to the relative ease of accessing the required materials, the commercial availability of droplet-generating instrumentation, and the mild microenvironment and unique permeability properties of hydrogels that are difficult to attain with alternative encapsulation systems employing thermoplastic materials. Because of their size and shape, microcapsules have an inherent advantage over macroencapsulation devices due to the more favorable surface area to volume ratio, which allows for greater efficiency in the amount of cellular cargo that is entrapped and enhanced nutrient exchange and efflux of secreted products. Unfortunately, with this significant positive benefit comes the caveat of difficult or impractical retrievability, highlighting the paradox that is particularly relevant as differentiated stem cell sources become more readily available. This chapter focuses on several techniques that can be used to evaluate the permeability and pore structure of hydrogel microcapsules, including a simplistic model for describing the diffusive behavior of alginate-polycation-alginate (APA) microcapsules with a liquid core, and an ancillary method to evaluate the ultrastructure of the APA membrane including morphometric analysis.
authors.affiliation: Cytosolv, Inc., 117 Chapman St., Suite 107, Providence, RI, USA.|Brown University, Providence, RI, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Lavin
authors.affiliation: Cytosolv, Inc., 117 Chapman St., Suite 107, Providence, RI, USA.|Brown University, Providence, RI, USA.
authors.forename: B E
authors.initials: BE
authors.lastname: Bintz
authors.affiliation: Cytosolv, Inc., 117 Chapman St., Suite 107, Providence, RI, USA. cgthanos@gmail.com.
authors.forename: C G
authors.initials: CG
authors.lastname: Thanos
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002214:Capsules / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D018914:Cells, Immobilized / Q000166:cytology / Q000637:transplantation; D003911:Dextrans / Q000008:administration & dosage / Q000737:chemistry; D004058:Diffusion; D004339:Drug Compounding / Q000379:methods; D016650:Fluorescein-5-isothiocyanate / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000737:chemistry; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D006801:Humans; D010539:Permeability; D016062:Porosity
chemical_list: D000464:Alginates; D002214:Capsules; D002412:Cations; D003911:Dextrans; D006603:Hexuronic Acids; C015219:fluorescein isothiocyanate dextran; D020723:Glucuronic Acid; D016650:Fluorescein-5-isothiocyanate
keywords: Alginate; Cell transplantation; Diffusion; Encapsulation; Microcapsule