PCR-based methodology for the determination of the photoprotection afforded by sunscreen application

We have applied a PCR-based methodology to study the DNA damage induced by UV-A, W-B and sunlight itself Our results, employing a cell-free system, in dicate that W-B (310 nm) is approximately 30-fold more potent at inhibiting DNA synthesis than UV-A (365 nm). We were also able to show that 20 min of sunlight exposure on a summer day induced DNA damage capable of inhibiting DNA synthesis. Hence, this methodology has a sensitivity suitable to detec t biologically relevant doses of UV light. In addition, we propose that thi s technique may be suitable to assess the relative photoprotection of comme rcially available sunscreens. We present here preliminary data on the photo protection afforded by the topical application. of sunscreen This photoprot ection was measured by a reduction in the subsequent UV-B- and W-A-induced DNA damage when sunscreen was applied. Our results demonstrate that the par ticular sunscreen rested was effective against both WE and UV-A. However th e estimated photoprotective factor of the sunscreen (against both W-A and U V-B) was approximately tenfold less than the stated Sun Protection Factor ( SPF) of 25. This methodology may also be useful in identifying new photopro tective agents by assessing their relative value as W-B and W-A absorbing a gents.