Quantifying the lubricity of mechanically tough polyvinyl alcohol hydrogels for cartilage repair

Abstract

Polyvinyl alcohol hydrogels are biocompatible and can be used as synthetic articular cartilage. Their mechanical characteristics can be tailored by various techniques such as annealing or blending with other hydrophilic polymers. In this study, we quantified the coefficient of friction of various candidate polyvinyl alcohol hydrogels against cobalt-chrome alloy or swine cartilage using a new rheometer-based method. We investigated the coefficient of friction of polyvinyl alcohol-only hydrogels and blends with polyethylene glycol, polyacrylic acid, and polyacrylamide against swine cartilage and polished cobalt-chrome surfaces. The addition of the functional groups to polyvinyl alcohol, such as acrylamide (semi-interpenetrating network) and acrylic acid (blend), significantly reduced the coefficient of friction. The coefficient of friction of the polyvinyl alcohol-only hydrogel was measured as 0.4 ± 0.03 against cobalt-chrome alloy, and 0.09 ± 0.004 against cartilage, while those measurements for the polyvinyl alcohol-polyacrylic acid blends and polyvinyl alcohol-polyacrylamide semi-interpenetrating network were 0.07 ± 0.01 and 0.1 ± 0.003 against cobalt-chrome alloy, and 0.03 ± 0.001 and 0.02 ± 0.001 against cartilage, respectively. There was no significant or minimal difference in the coefficient of friction between samples from different regions of the knee, or animals, or when the cartilage samples were frozen for 1 day or 2 days before testing. However, changing lubricant from deionized water to ionic media, for example, saline or simulated body fluid, increased the coefficient of friction significantly.

High-Performance Photopolymerized Poly(vinyl alcohol)/Silica Nanocomposite Hydrogels with Enhanced Cell Adhesion

“…Furthermore, volume shrinkage of the hydrogels occurred in the freeze-drying process (Figure 4g). Generally, pure PVA hydrogels have a dense polymer crystalline network driven by hydrogen bonding 34 and this network is not very susceptible to creep and exhibits low creep strains. 35 However, the studied PVA−GMA hydrogels derived from low DS did not exhibit the strong crystalline network, probably attributed to low crosslinking density of the network (seen in section 3.5).…”

Wear Evaluation of Poly(vinyl alcohol) Hydrogel by UV Spectrometry and TOC Measurement of Lubricant

“…Moreover, among arti cial materials, it is the most similar to biological tissues. Therefore, hydrogels are applicable in biomaterials, and there are many studies on the application of hydrogels as arti cial joint cartilages [1][2][3][4][5]. Biocompatibility, mechanical properties, and durability are issues and evaluation points that must be considered in order to apply hydrogels as biomaterials [6,7].…”

“…In this study, we evaluated the wear of poly(vinyl alcohol) (PVA) gels. Because PVA gel is biocompatible and has superior mechanical properties, it has been widely studied as a candidate for arti cial cartilage [1,3,16]. PVA is fabricated industrially by saponi cation of poly(vinyl acetate); however, the saponi cation process is not perfect, and hence, un-saponi ed parts remain [17] (Scheme 1).…”

Fabrication and Characterization of a Multilayer Hydrogel as a Candidate for Artificial Cartilage

“…24,25 The annealing process can enhance the mechanical strength 26,27 and reduce the friction coefficient of hydrogels. 28 Although hydrogels have been extensively studied as cartilage substitutes, many high-strength hydrogels have been reported, their mechanical strength or tribological properties are somewhat different from those of cartilage. There are few research studies on gradient-layered structures.…”

“…HA as the main inorganic component of natural bone and can participate in the metabolism in the body so that it can improve the biological activity and cell adhesion of the hydrogel. − Besides, the elastic modulus increases and the viscous modulus reduces due to HA indicated by the nanoindentation test. , Furthermore, HA nanoparticles, as the dispersion enhancing phase to fill the uneven micro holes and defects, can improve the surface morphology for a better mechanical mechanism and lubricating properties. , Poly­(acrylic acid) (PAA), an ionic polymer with a large number of carboxyl hydrophilic groups that can react with other polymers such as hydrogen-bonding and ion–ion interactions, is wildly used in biomedical material. PAA added to the PVA hydrogel can form an interpenetrating network or a double network structure composite hydrogel to better improve the bonding strength, tensile strength, self-healing ability, and friction and wear resistance properties. , The annealing process can enhance the mechanical strength , and reduce the friction coefficient of hydrogels . Although hydrogels have been extensively studied as cartilage substitutes, many high-strength hydrogels have been reported, their mechanical strength or tribological properties are somewhat different from those of cartilage.…”