Observation of Heat Propagation and Heat Induced Denaturation in Biological Tissues by Non-linear Optical Microscopy

• Main Authors: Chien-Sheng Liao, 廖建盛
• Other Authors: Shi-Wei Chu
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/72390982838688718909

碩士 === 國立臺灣大學 === 物理研究所 === 98 === Recently, thermal therapies have been applied to treatment of diseases increasingly. For examples, by heating cornea the induced shrinkage of collagen provides precise way to correct the hyperopia and astigmatism. Better understanding of molecular response to heat is not only of fundamental importance, but also necessary to optimize the heating strategies to reduce unwanted tissue damage. Moreover, it is helpful for surgical need to visualize distribution of temperature in the biological tissue by optical method. In our study, we observe heat induced denaturation of type 1 collagen which is the most abundant protein in human body by second harmonic generation microscopy (SHGM) and demonstrate a way to visualize distribution of temperature in the cell of plant by two photon excited microscopy. Considering that SHG is related to the molecular packing of the triple helix in collagen fibers, this nonlinear signal provides an insight of molecular dynamics during thermal denaturation. With the aid of SHG microscopy, we found a new step in collagen thermal denaturation process, de-crimp. During the de-crimp step, the characteristic crimp pattern of collagen fascicles disappeared due to the breakage of interconnecting bonds between collagen fibrils, while SHG intensity remained unchanged, suggesting the intactness of the triple helical molecules. At higher temperature, shrinkage is observed with strongly reduced SHG intensity, indicating denaturation at the molecular level. Referring to thermal imaging heat-induced change of chlorophyll fluorescence in intact leaves has been studied actively as a result fresh leaf is a suitable biological tissue for demonstration of thermal visualization by quantifying the intensity of fluorescence. Additionally, with the advantages of non-linear optical microscopy, this technique provides optical sectioning ability to visualize temperature distribution in three dimensions in sub-μm resolution, which is not achieved by any conventional method.