Tribological Characterization of Polyacrylamide-Alginate Hybrid Hydrogels as a Potential Candidate for Cartilage Replacement

Various hydrogels such as polyvinyl alcohol (PVA) and poly (2-hydroxyethyl methacrylate) were assessed as articular cartilage replacement in the past. In the current study, the biphasic, biocompatible, and mechanically tunable Polyacrylamide-Alginate (PAAm-Alg) hybrid hydrogel was evaluated with different parameters such as load, speed and lubrication to study friction and wear performance of the material. Dried mass loss of hydrogel with lubrication was in the range of 2-9 wt %. The average friction coefficient of hydrogel under bovine serum lubrication was measured as 0.03, which is fairly close to native cartilage tissue. SEM studies revealed adhesion as the dominant wear mechanism due to excessive plastic deformation, independent of load and speed condition while fatigue wear mechanism was more noticeable under 1.3MPa applied pressure. However, the lubrication has dramatically decreased the wear rate and as a result, it was difficult to distinguish the worn surface of hydrogel samples from the unworn surface and just a light depression was observed on the samples, which is promising for load-bearing applications such as cartilage replacement.