Optical characterization of heat dependent collagen denaturation via Mueller matrix polarimetry in combination with principal component analysis

Polarization properties of collagen in acidic and natural solutions were analyzed by a decoupling analytical technique based on Mueller matrix polarimetry (MMP). The proposed method was employed to derive five effective optical parameters of collagen solutions: (1) orientation angle of linear birefringence, (2) phase retardance of linear birefringence, (3) orientation angle of linear dichroism, (4) value of linear dichroism, and (5) optical rotation angle of circular birefringence. The temperature dependence of optical parameters was observed, and the denaturation (transition) temperature of collagen in two different solvents was deduced as 33.38 ± 2.78^◦C and 36.83 ± 2.43^◦C for acidic and natural solutions, respectively, based on a total of 100 measurements. Furthermore, using scatter plots generated by the first two components of principal component analysis (PCA), it was possible to distinguish all denaturized versus native and acid versus dialysis samples based on scatter plots. In comparison to higher cost and complex alternatives, such as circular dichroism spectroscopy, our results show the promise of using the combination of MMP and PCA as a low-cost method for identification and characterization of collagen denaturation.