Photocrosslinked methacrylated poly(vinyl alcohol)/hydroxyapatite nanocomposite hydrogels with enhanced mechanical strength and cell adhesion

Poly(vinyl alcohol) (PVA) hydrogels with high water content, good load-bearing property, low frictional behavior as well as excellent biocompatibility have been considered as promising cartilage replacement materials. However, the lack of sufficient mechanical properties and cell adhesion are two critical barriers for their application as cartilage substitutes. To address these problems, herein, methacrylated PVA with low degree of substitution of methacryloyl group has been synthesized first. Then, methacrylated PVA-glycidyl methacrylate/hydroxyapatite (PVA-GMA/Hap) nanocomposite hydrogels have been developed by the photopolymerization approach subsequently. Markedly, both pure PVA-GMA hydrogel and PVA-GMA/Hap nanocomposite hydrogels exhibit excellent performance in compressive tests, and they are undamaged during compressive stress–strain tests. Moreover, compared to pure PVA-GMA hydrogels, 8.5-fold, 7.4-fold, and 14.2-fold increase in fracture stress, Young's modulus and toughness, respectively, can be obtained for PVA-GMA/Hap nanocomposite hydrogels with 10 wt % Hap nanoparticles. These enhancements can be ascribed to the intrinsic property of PVA-GMA and strong hydrogen bonding interactions between PVA-GMA chain and Hap nanoparticles. More interestingly, significant improvement in the cell adhesion can also be successfully achieved by incorporation of Hap nanoparticles. These biocompatible nanocomposite hydrogels have great potential to be used as cartilage substitutes.