Protection against solar UV radiation is a global public health need due to the increasing incidence of skin cancer over the last decades. Innovating in sunscreen is a challenging research and technology effort. Health authorities and consumers support the use of safe sunscreens that are highly protective, without causing adverse environmental effects. Organic UV filters, while providing cosmetic advantages, require frequent re-application, may penetrate the skin, and their release in the aquatic environment can have a significant impact on the marine ecosystem with special impact on coral. Based on breakthrough skin-bioadhesive technology, we have developed new organic UV filters that bind to the stratum corneum.
Skin-bioadhesive technology is based on the generation of innovative molecules with a core of known commercial UV filters with a bioadhesive group that binds to thiols at the surface of the skin. Among new UV filters with this technology, the UVA DHHB (diethylamino hydroxybenzoyl hexyl benzoate)-derived bioadhesive UV filter, M10, is the most advanced compound and was formulated for skin explants and human clinical tests. The efficacy and safety of M10 were evaluated in vitro and ex vivo using UV spectrum analysis, skin autofluorescence, UVA imaging, diffusion cell permeation and Raman confocal spectroscopy. The persistence of photoprotection over time was analyzed in vivo in a clinical study using UVA imaging facilities on human volunteers’ arms (N=15).
In vitro and ex vivo, comparison of M10 to DHHB formulated at the same molar concentration in the same chassis, demonstrated superiority of the bioadhesive M10 with respect to its efficacy, persistence and resistance to washes. Most importantly, the long-lasting photoprotection of M10 was observed in vivo in a clinical study as a human proof of concept of the technology. M10 showed a good tolerance, resistance to rubbing, reduced transversal skin diffusion and a persistence of photoprotection: M10 was significantly 47% more protective than DHHB, with 84% persistence 6 hours after application. The consequent reduction in the penetration of bioadhesive UV filters over the stratum corneum was confirmed by Raman confocal spectroscopy on human skin explants.
Studies with a novel UVA M10 UV filter demonstrated that skin bioadhesive technology can bind organic UV filters to the skin surface and the chemically modified UV filter persists in the stratum corneum with no accumulation in deeper skin layers, while preserving the active protective spectrum. We clinically observed a long-lasting photoprotective effect over 6 hours, substantially longer than the recommendation to reapply sunscreen every two hours. In addition to M10, other skin-bioadhesive UVA and UVB filters are being developed. The development of safe and long-lasting skin-bioadhesive UV filters could be a major advance in photoprotection research that the industry has been seeking over the past 20 years.