Table 1 Synopsis of reports of pancreatic islet cells with biomaterial carriers 438 Biomaterial type Heparin Heparin + VEGF-A Heparin-PLA + VEGF-A + FGF Heparin-PLA + VEGF-A + FGF PLGA-matrigel PLGA Ethisorb® (PLGA + PDS) PHBHHx Oleyl-O-PEG PVA-alkyl + urokinase NIPA + laminin 5 In vitro outcome Attachment via biotin-avidin interaction Normal insulin secretion maintained. Attracted endothelial cells Attachment on islets. Increased islet viability and insulin secretion. Initiated islet endothelial cell sprouting – – – – Cell clustering and islet-like aggre- gates of NIT-1 cells within 72 h with an increase in insulin secre- tion and viability Crosslinked RIN cells into spheroids, insulin secretion was increased Attachment on islets with fibrinolytic activity and comparable insulin secretion Single rat islet cells cultured as a sheet remained viable and glucose responsive In vivo outcome Normalized blood glucose in diabetic mice. Decreased intraluminal clotting in pigs Normalized blood glucose levels in mice. Increase in blood vessel density Normalized blood glucose levels in diabetic mice with comparable insulin secretion to islets under the kidney capsule Normalized blood glucose levels in mice. Comparable results to islets under the kidney capsule Normalized pancreatectomized canine blood glucose for 2 (50%) and 5 (25%) months without exogenous insulin administration – – – – – Insulin and glucagon immunostaining were present 7 days post-transplantation Curr Diab Rep (2011) 11:434–444 Reference Cabric et al. [52] Cabric et al. [53••] Stendahl et al. [55] Chow et al. [56] Dufour et al. [59] Blomeier et al. [60] Kin et al. [61•] Yang et al. [62] Ito and Taguchi [64] Totani et al. [65] Shimizu et al. [66] Ethisorb® (Codman, Raynham, MA) FGF fibroblast growth factor; NIPA poly(N-isopropylacrylamide); PDS poly-p-dioxanone; PEG poly(ethylene glycol); PHBHHx 3-hydroxybutyrate and 3-hydroxyhexanoate; PLA poly(L-lactic acid/lactide); PLGA poly(lactic-co-glycolic acid); PVA poly(vinyl alcohol); VEGF-A vascular endothelial growth factor attracting maleimide and urokinase, which displays fibri- nolytic activity. Treated islets were able to secrete insulin comparable with untreated and PVA-alkyl islets in vitro and showed increased fibrinolysis, suggesting that they could potentially dampen IBMIRs [65]. Unlike the above hydrogels, poly(N-isopropylacryla- mide) (NIPA) polymer gels are thermo-responsive, under- going a volume change at about 34°C. A tissue engineering approach was performed by Shimizu et al. [66], in which isolated rat islets were trypsinized to form single cell suspensions and seeded onto NIPA hydrogels. Various extracellular matrix coatings were used to enhance attach- ment in vitro, with laminin 5 favoring viability and insulin secretion by single β cells. After 48 h of culture, the islet cell sheets were placed at 20°C to allow removal and were transferred to a support membrane for syngeneic transplan- tation. Weak insulin and glucagon staining were observed 7 days post-transplantation [66]. Although further function- al data were not shown, this report acts as a proof of concept that thermo-reactive NIPA polymers could poten- tially be used as an alternate delivery system for islet transplantation. Biopolymer Films To determine the best substrate for islet survival and function, a high-throughput approach was taken by Wil- liams et al. [67] and Mei et al. [68•]. In Williams et al.’s group [67], films from different materials were cast or coated as a monolayer on tissue culture plastic and seeded