Monitoring the thermally induced structural transitions of collagen by use of second-harmonic generation microscopy

The thermal disruption of collagen I in rat tail tendon is investigated with second-harmonic generation (SHG) microscopy. We investigate its effects on SHG images and intensity in the temperature range 25degrees-60degreesC. We find that the SHG signal decreases rapidly starting at 45degreesC. However, SHG imaging reveals that breakage of collagen fibers is not evident until 57degreesC and worsens with increasing temperature. At 57degreesC, structures of both molten and fibrous collagen exist, and the disruption of collagen appears to be complete at 60degreesC. Our results suggest that, in addition to intensity measurement, SHG imaging is necessary for monitoring details of thermally induced changes in collagen structures in biomedical applications. (C) 2005 Optical Society of America.