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Experimental investigation of temperature-dependent denaturation behavior of type-I Collagen

Precise investigation of the temperature and the duration for collagen denaturation is critical for a number of applications, such as adjustment of temperature and duration during a laser-assisted tissue welding or collagen-based tissue repair products (films, implants, cross-linkers) preparation procedures. The result of such studies can serve as a guideline to mitigate potential side effects while maintaining the functionality of the collagen. Though a variety of collagen denaturation temperatures have been reported, there has not been a systematic study to report temperature-dependent denaturation rates. In this study, we perform a set of experiments on type-I collagen fiber bundles, extracted from the rat-tail tendon, and provide an Arrhenius model based on the acquired data. The tendons are introduced to buffer solutions having different temperatures, while monitoring the contrast in the crimp sights with a wide field microscope, where collagen fibers bend with respect to their original orientation. For all tested temperatures of 50°C–70 °C and tissues that were extracted from 5 rats, increasing the temperature reduced the contrast. On the average, we observed a decay of the contrast to half of its initial value at 37, 157, and 266 seconds when the collagen was introduced to 70 °C, 65 °C, and 60 °C buffer solutions, respectively. For the lower temperatures tested we only observed to be only about 20% and 2 % decay in the crimp contrast after > 2 hours at 55 °C and 50 °C, respectively. The observed denaturation behavior is also in line with Arrhenius Law, as expected. We are looking forward to expand this study to other types of collagen as a future work. Overall, with further development the data and model we present here could potentially serve as a guideline to determine limits for welding and manufacturing process of collagen-based tissue repair agents.