Abstract
The effects of photosensitizer concentration on singlet oxygen mediated photobleaching have been investigated in keratinocytes. Cells with different photosensitizer concentration were identified on the basis of the fluorescence signal amplitude and their fluorescence decay was then studied to see if there was a correlation with concentration. The experimental results show that the photobleaching was more rapid at higher concentration than at lower concentration, indicating that singlet oxygen plays a vital role in the rapid m-tetrahydroxyphenylchlorin (mTHPC) induced fluorescence photobleaching, causing the sensitizer to degrade.