title: Thermally induced gelable polymer networks for living cell encapsulation.
abstract: We report the encapsulation of MIN6 cells, a pancreatic beta-cell line, using thermally induced gelable materials. This strategy uses aqueous solvent and mild temperatures during encapsulation, thereby minimizing adverse effects on cell function and viability. Using a 2:1 mixture of PNIPAAm-PEG-PNIPAAm tri-block copolymer and PNIPAAm homopolymer that exhibit reversible sol-to-gel transition at approximately 30 degrees C, gels were formed that exhibit mechanical integrity, and are stable in H(2)O, PBS and complete DMEM with negligible mass loss at 37 degrees C for 60 days. MTT assays showed undetectable cytotoxicity of the polymers towards MIN6 cells. A simple microencapsulation process was developed using vertical co-extrusion and a 37 degrees C capsule collection bath containing a paraffin layer above DMEM. Spherical capsules with diameters ranging from 500 to 900 microm were formed. SEM images of freeze-dried capsules with PBS as the core solution showed homogenous gel capsule membranes. Confocal microscopy revealed that the encapsulated cells tended to form small aggregates over 5 days, and staining for live and dead cells showed high viability post-encapsulation. A static glucose challenge with day-5 cultured microencapsulated cells exhibited glucose-dependent insulin secretion comparable to controls of free MIN6 cells grown in monolayers. These results demonstrate the potential use of these thermo-responsive polymers as cell encapsulation membranes.
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, Canada.
authors.forename: Hong-Fang
authors.initials: HF
authors.lastname: Lu
authors.forename: Elisha D
authors.initials: ED
authors.lastname: Targonsky
authors.forename: Michael B
authors.initials: MB
authors.lastname: Wheeler
authors.forename: Yu-Ling
authors.initials: YL
authors.lastname: Cheng
mesh_terms: D000180:Acrylic Resins / Q000008:administration & dosage / Q000737:chemistry*; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D020099:Coated Materials, Biocompatible / Q000008:administration & dosage / Q000737:chemistry*; D006358:Hot Temperature; D007515:Islets of Langerhans / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D008422:Materials Testing; D051379:Mice; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D000180:Acrylic Resins; D020099:Coated Materials, Biocompatible; C052970:poly-N-isopropylacrylamide