Photochemical and photophysical properties of sunscreens

Sunscreen enhancement of UV-induced reactive oxygen species in the skin

“…OMC and OC generate 1 O 2 as determined by fufuryl alcohol consumption in sodium phosphate buffer [9,13]. The same study did not find B3 to produce 1 O 2 ; however, it is known that the solvent affects the lifetime of the B3 triplet state needed for energy transfer to O 2 and it is possible that the highly lipophilic environment of the cell interior may enhance this lifetime [13,34]. The mechanism by which B3, OC, and OMC generate 1 O 2 is not fully understood.…”

“…To date the study of the effects of photoprotection molecules upon ROS production has been limited to a small number of solution-phase and in vitro experiments. Para-aminobenzoic acid (PABA) and 2-phenylbenzimidazle-5-sulfonic acid (PBSA) induce both 1 O 2 and thymine-dimer formation, although the two have not been definitely correlated [8][9][10][11][12][13][14]. Solution-phase studies found that octylmethoxycinnamate (OMC), octocrylene (OC), and PABA all produce 1 O 2 in phosphate-buffered saline (PBS) [8,13].…”

Mechanisms of Uv Stabilization

“…14 In addition, water on the surface may react with the hole to form hydroxyl radicals, which are highly reactive species, and the electron may react with oxygen to produce the superoxide radical and then go on to form hydrogen peroxide via disproportionation. 14 This scheme shows fewer safe energy conversions than described for organic UV absorbers. Manufacturers of titanium dioxide and other photochemically active screeners change their surface properties by coating and doping to reduce the catalytic effect of surface, which causes photodegradation of organic matrix in its vicinity, but all these modifications are not sufficient to prevent degradation (it can be only reduced).…”

“…14 When titanium dioxide is exposed to UV radiation, it absorbs energy and an electron is promoted from the valence band to the conduction band with concurrent formation of a hole, h + . 14 The separation of these two levels corresponds to the band gap energy, E bg (the band gap energy of anatase TiO 2 corresponds to a wavelength of 387 nm, in rutile to 405 nm, and in ZnO to 384 nm). 14 Migration of both the electron and the hole to the particle surface is then possible.…”

“…14 The separation of these two levels corresponds to the band gap energy, E bg (the band gap energy of anatase TiO 2 corresponds to a wavelength of 387 nm, in rutile to 405 nm, and in ZnO to 384 nm). 14 Migration of both the electron and the hole to the particle surface is then possible. From here, several processes may take place: hole-electron recombination, oxidation of an electron donor by the hole, or reduction of an electron acceptor by the electron.…”