DYNAMIC HEAT-CAPACITY CHANGES OF LASER-IRRADIATED TYPE-I COLLAGEN FILMS

Background and Objective: A common assumption made in the thermal resp onse of biological materials due to laser irradiation is the constancy of the specific heat capacity at constant pressure, C-p. In this inve stigation, C-p of pure hydrated Type I collagen films is measured in t ime during laser irradiation. Study Design/Materials and Methods: A Nd :YAG laser scanning calorimeter is developed and used to test the cons tant heat capacity assumption by monitoring transient, laser-induced t hermal transitions in the collagen films. Results: Results of prelimin ary studies on the irreversible, laser induced thermal denaturation of collagen with heating rates of up to 110 K/sec show a broad C-p trans ition that can attain large values (20 J/g K). Conclusion: The magnitu de of the C-p change that occurs in response to laser irradiation show s that the assumption of a constant Cp when modeling heat transport in tissues is not always valid. (C) 1996 Wiley-Liss, Inc.