Investigation of tribological properties of HEMA-based cryogels as potential articular cartilage biomaterials

Tribology is one of the most important issues for the repair and regeneration of living tissues in the human body, as it deals with the wear, lubrication, and friction of interrelated surfaces. Hydrogels show potential as cartilage regeneration agents due to their biocompatibility and behave similarly to the lubricating mechanisms found in cartilage tissue. Cryogels, which are included in the class of hydrogels, are more stable than hydrogels in terms of mechanical strength, and references to the tribological properties of these polymers in the literature have been minimal so far. In this study, poly(HEMA-N-vinyl formamide) (poly(HEMA-NVF) and poly(HEMA-N-vinylpyrrolidone) (poly(HEMA-NVP) cryogels with improved hydrophilic properties were synthesized with pure poly(HEMA) cryogel. The swelling properties of HEMA-based cryogels were examined under the heading of various parameters, and their physicochemical characterizations were characterized via FTIR, SEM, mercury intrusion porosimetry, elemental analysis (EDX), and TGA methods. Before investigating tribological properties, a cytotoxicity test was performed for all cryogels. Then, in line with the study's primary purpose, the tribological properties of cryogels were examined. Abrasion tests were carried out on a pin-on-disc tester linked with ASTM G99-05 standard. According to the results, the friction coefficient of poly(HEMA-NVF) and poly(HEMA-NVP) cryogels is 21.62% and 10.51% higher than poly(HEMA) cryogel, respectively. In addition, the results of abrasion and 3D surface topography images prove that the poly(HEMA-NVP) cryogel wears less and its surface is less deformed than other cryogels.