S13: Injectable polymeric scaffolds with degradable calcium alginate beads as a cell delivery system for tissue repair

While mammalian stem cells have shown therapeutic potential, introducing cells directly into the body results in large-scale death and migration of cells from the injection site. Thus, there is a compelling need for suitable injectable carriers that can provide a scaffold for attachment of transplanted cells and new tissue ingrowth. Due to their injectability and settability, lysine-derived polyurethane scaffolds are promising carriers for local delivery of cells using minimally invasive surgical techniques. In this study, synthesize injectable polyurethanes from a polyester triol, an iron catalyst, and a lysine triisocyanate-PEG prepolymer as carriers for cell delivery. Cells cannot be encapsulated directly in the polyurethane due to the chemical reaction with the cells. To protect cells during cure, we encapsulated bone marrow- and adiopose-derived stem cells in calcium alginate beads (300-800 μm) prior to adding to the polyurethane. To increase the degradation rate of the beads, which was designed to protect the cells from the reaction and subsequently degrade over 1-2 days, we investigated oxidized alginate. Cells were encapsulated in alginate beads with high viability (>90%). When 50 wt% alginate beads were embedded in the scaffolds, SEM images revealed both the beads and interconnected micro-pores (50-70 μm). However, cell viability decreased with decreasing bead diameter, suggesting that the chemical reaction may adversely affect the cells. Delaying addition of the alginate beads for 3 minutes restored cell viability to levels comparable to the bead control. These observations underscore the potential utility of injectable, settable polyurethane scaffolds as carriers for stem cells.