Regeneration of Pancreatic Cells Using Optimized Nanoparticles and l‑Glutamic Acid–Gelatin Scaffolds with Controlled Topography and Grafted Activin A/BMP4

Regeneration of insulin-producing cells (IPCs) from induced pluripotent stem cells (iPSCs) under controlled conditions has a lot of promise to emulate the pancreatic mechanism in vivo as a foundation of cell-based diabetic therapy. l-Glutamic acid–gelatin scaffolds with orderly pore sizes of 160 and 200 μm were grafted with activin A and bone morphogenic proteins 4 (BMP4) to differentiate iPSCs into definitive endoderm (DE) cells, which were then guided with fibroblast growth factor 7 (FGF7)-grafted retinoic acid (RA)-loaded solid lipid nanoparticles (FR-SLNs) to harvest IPCs. Response surface methodology was adopted to optimize the l-glutamic acid-to-gelatin ratio of scaffolds and to optimize surfactant concentration and lipid proportion in FR-SLNs. Experimental results of immunofluorescence, flow cytometry, and western blots revealed that activin A (100 ng/mL)–BMP4 (50 ng/mL)–l-glutamic acid (5%)–gelatin (95%) scaffolds provoked the largest number of SOX17-positive DE cells from iPSCs. Treatment with FGF7 (50 ng/mL)–RA (600 ng/mL)–SLNs elicited the highest number of PDX1-positive β-cells from differentiated DE cells. To imitate the natural pancreas, the scaffolds with controlled topography were appropriate for IPC production with sufficient insulin secretion. Hence, the current scheme using FR-SLNs and activin A–BMP4–l-glutamic acid–gelatin scaffolds in the two-stage differentiation of iPSCs can be promising for replacing impaired β-cells in diabetic management.