Self-assembled ternary poly(vinyl alcohol)-alginate-gelatin hydrogel with controlled-release nanoparticles for pancreatic differentiation of iPS cells

A three-dimensional scaffold enables the formation of realistic tissue architecture and promotes physiological responses to activate the differentiation of induced pluripotent cells (iPSCs) into pancreatic islets. Poly(vinyl alcohol) (PVA), alginate (Alg) and gelatin (Gel) were conjugated with methacrylic anhydride (MA) and were photo-crosslinked to prepare PVAMA-AlgMA-GelMA hydrogel scaffolds using a water-in-oil self-assembly method. The swelling ratio, porosity and cell entrapment in the hydrogel were investigated with various molar percentages of polymer matrix. PVAMA and AlgMA assisted in improving the water content of the hydrogel, which created high porosity for the migration of iPSCs, and GelMA enhanced the cell entrapment efficiency. The self-assembled scaffolds with composition of PVAMA:AlgMA:GelMA = 1:1:2 were grafted with activin A and bone morphogenic protein 4 (BMP4) to induce iPSCs to definitive endoderm (DE) lineage, followed by treatment with retinoic acid-loaded solid lipid nanoparticles for controlled release and guided differentiation of DE cells into insulin-producing cells. Flow cytometry analysis and immunochemical staining evidenced that the scaffolds with crosslinked BMP4 boosted the role of surface activin A at activin A:BMP4 = 3:1 in endodermal differentiation of iPSCs to produce the highest level of insulin after pancreatic induction and glucose stimulation. The iPSC-laden PVAMA-AlgMA-GelMA hydrogel constructs composed of repeated units and modified with activin A and BMP4 can be promising in generating pancreas-mimetic structure and supporting the functions of pancreatic islets.