Physically crosslinked polyvinyl alcohol and gelatin interpenetrating polymer network theta-gels for cartilage regeneration

Theta-gels are hydrogels that form during the solidification and phase separation of two dislike polymers, in which a low molecular weight polymer behaves as a porogen and is removed through dialysis. For this study, interpenetrating polymer network (IPN) hydrogels were formed between polyvinyl alcohol (PVA) and gelatin using theta-gel fabrication techniques, i.e., in the presence of a porogen. The addition of gelatin to a PVA theta-gel, formed with a porogen, polyethylene glycol (PEG), created macro-porous hydrogels, and increased shear storage moduli and elastic moduli, compared to PVA-gelatin scaffold controls. A reduction in PVA crystallinity was verified by Fourier transform infrared (FTIR) spectroscopy in hydrogels fabricated using a porogen, i.e., PVA-PEG-gelatin, compared to PVA, PVA-PEG, or PVA-gelatin hydrogels alone. Van Geison staining confirmed the retention of gelatin after dialysis. A range of hydrogel moduli was achieved by optimizing PVA concentration, molecular weight, and gelatin concentration. PVA-gelatin hydrogels maintained primary human mesenchymal stem cell (MSC) viability. Soft (similar to 10 kPa) and stiff (similar to 100 kPa) PVA-gelatin hydrogels containing type II collagen significantly increased glycosaminoglycan (GAG) production compared to controls. PVA-gelatin hydrogels, formed using theta-gel techniques, warrant further investigation as articular cartilage tissue engineering scaffolds.