Annealed Polyvinyl Alcohol Hydrogels for Cartilage Replacement: Effects of Synthesis Parameters on Mechanical Properties.

The objective of this paper was to determine the interactive effects of multiple synthesis parameters on annealed PVA hydrogel properties and assess these hydrogels for the application of cartilage replacement. PVA hydrogels were synthesized at two different molecular weight ranges (89-98 kDa and 146-186 kDa), two polymer concentrations (10% PVA and 20% PVA), and four different annealing temperatures (120 °C, 135 °C, 150 °C, and 165 °C). The compressive, tensile, and wear mechanical properties were measured, and the crystalline structure of these hydrogels was assessed via differential scanning calorimetry. Hydrogels showed increasing polymer weight percent, tensile modulus, and compressive modulus with increasing annealing temperature. Depending on synthesis parameters, the hydrogels matched or exceeded the previously published compressive and tensile properties of native cartilage. Higher molecular weight PVA hydrogels (146-186 kDa) exhibited less wear, but greater friction, compared to lower molecular weight PVA (89-98 kDa). The PVA hydrogels exhibited crystallinity in the range of 53-78%, but no consistent differences in crystallinity were detected between hydrogel variants. It was concluded that the (10% PVA, 146 kDa, 165 °C) annealed PVA hydrogel demonstrated the most appropriate balance of high tensile strength and compressive compliance comparable to cartilage.