Measurement of protein denaturation in human synovial fluid and its analogs using differential scanning calorimetry

Differential scanning calorimetry (DSC) was used to evaluate the thermal transitions associated with protein constituents of synovial fluid samples from three individuals with osteoarthritis. Analysis of the multi-component DSC curves revealed that major endothermic transitions of synovial fluid occur between 60 and 80 °C and can be resolved into three peaks, likely due to the unfolding of human serum albumin and immunoglobulins, and that the enthalpies of these transitions can be quantified in terms of their relative contribution to the total system enthalpy. DSC was also used to analyze a solution of bovine calf serum, a lubricant used in simulator wear testing of joint replacement implants, and the resulting endothermic transitions occurred in a temperature range relevant to that produced by frictional heat during such wear simulator testing. Results of this study indicate a new application for DSC as a direct method for studying thermal stabilities of both bovine calf serum and synovial fluid. The use of DSC is proposed as a diagnostic tool to detect altered thermal properties or protein concentrations indicative of a diseased or injured state, and as a development tool to test the efficacy of additives in controlling protein denaturation associated with increased wear in joint replacement implants.