Theodossiou T, Rapti G S, Hovhannisyan V, Georgiou E, Politopoulos K, Yova D
Biomedical Optics and Applied Biophysics Laboratory, Department of Electrical and Computer Engineering, Division of Electromagnetics, Electrooptics and Electronic Materials, National Technical University of Athens, Zografou, Greece.
Lasers Med Sci. 2002;17(1):34-41. doi: 10.1007/s10103-002-8264-7.
Irreversible thermal conformational changes induced to collagen have been studied by optical methods. More specifically, second harmonic generation (SHG) from incident nanosecond Ng:YAG 1064 nm radiation and laser-induced fluorescence by 337 nm, pulsed nanosecond nitrogen laser excitation, at 405, 410 and 415 nm emission wavelengths were registered at eight temperatures (40 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees and 80 degrees C) and normalised with respect to the corresponding values at the ambient temperature of 30 degrees C. The heating protocol used in this work, was selected to monitor only permanent changes reflecting in the optical properties of the samples under investigation. In this context, the SHG, directly related to the collagen fibril population in triple helix conformation, indicated on irreversible phase transition around 64 degrees C. On the other hand fluorescence related to the destruction of cross-linked chromophores in collagen, some of which are related to the triple helix tertiary structure, also indicated a permanent phase transition around 63 degrees C. These results are in agreement with previous results from studies with differential scanning calorimetry. However SHG and fluorescence, being non-invasive optical methods are expected to have a significant impact in the fields of laser ablative surgery and laser tissue welding.
已通过光学方法研究了胶原蛋白诱导的不可逆热构象变化。更具体地说，在八个温度（40℃、50℃、55℃、60℃、65℃、70℃、75℃和80℃）下记录了入射纳秒Nd:YAG 1064nm辐射产生的二次谐波（SHG）以及337nm脉冲纳秒氮激光激发下在405nm、410nm和415nm发射波长处的激光诱导荧光，并相对于30℃环境温度下的相应值进行了归一化。本工作中使用的加热方案被选择用于仅监测反映所研究样品光学性质的永久性变化。在这种情况下，与三螺旋构象中的胶原纤维群体直接相关的SHG表明在64℃左右发生了不可逆相变。另一方面，与胶原蛋白中交联发色团破坏相关的荧光（其中一些与三螺旋三级结构有关）也表明在63℃左右发生了永久性相变。这些结果与先前差示扫描量热法研究的结果一致。然而，SHG和荧光作为非侵入性光学方法，有望在激光消融手术和激光组织焊接领域产生重大影响。
