Development of PVA Hydrogels with Superior Lubricity for Artificial Cartilage

Abstract

Physically cross-linked poly(vinyl alcohol) (PVA) gels are versatile biomaterials with their excellent biocompatibility and mechanical strength. Since the late 1970s, the semicrystalline PVA gels prepared by a freeze-thawing method (FT gel) have been extensively studied in characterizing the structural and functional properties for practical applications, such as artificial hydrogel cartilage. Recently, a simple preparation method for a physically cross-linked PVA gel by a cast-drying method (CD gel) was reported. Although the network nanostructures are similar, CD gels are transparent and elastic, while FT gels are opaque and less elastic. The crystallization conditions of these systems have been investigated; the gels become highly swollen and rigid by the selection of optimum preparation conditions. In this chapter, the mechanical properties of FT and CD gels, such as tearing energy, sliding friction, and abrasion loss, are reviewed in connection with the nano-and microstructures of physical PVA gels. The tribological properties of FT and CD gels are compared with that of natural cartilage. Based on experimental results, simple preparation methods to improve the mechanical and lubrication properties of physically cross-linked PVA gels are presented, and the mechanism of superior lubricity in newly developed PVA gels for artificial hydrogel cartilage is discussed.