PDMSstar-PEG Hydrogels for Osteochondral Tissue Engineering

Tissue engineering may utilize a “materials-guided” approach to repair of osteochondral defects (OCDs) – damage extending from cartilage to subchondral bone. Based on the physical and chemical properties of the scaffold alone, cell behavior may be directed to regenerate tissues in a spatially controlled geometry. Conventional poly(ethylene glycol) diacrylate (PEG-DA) hydrogels, prepared via photocure of aqueous precursor solutions, have been extensively studied as instructive scaffolds. However, due to a somewhat narrow range of properties and a lack of bioactivity and osteoinductivity, PEG-DA hydrogels require modification in order to promote osteochondral regeneration. Towards this goal, three fabrication parameters were systematically studied. First, methacrylated star polydimethylsiloxane (PDMSstar-MA) was introduced with PEG-DA to induce the formation of hydroxyapatite (i.e. for bioactivity) and to promote mesenchymal stem cell (MSC) lineage progression towards osteoblast-like fates (i.e. for osteoinductivity). Second, solvent induced phase separation (SIPS), involving an organic fabrication solvent, was employed in lieu of a conventional aqueous fabrication solvent. Lastly, interconnected pores were introduced and tailored through a modified solvent-casting/particulate leaching (SCPL) technique in conjunction with SIPS. The influence of total macromer concentration, weight percent (wt%) ratio of PDMSstar-MA to PEG-DA and average salt particle size on bioactivity, morphology, hydration, degradation, and mechanical properties was evaluated