Galenic development of a new sunscreen product for skin cancer prevention

Abstract

[eng] Sunscreen application is one of the best methods to prevent erythema, keratogenic cancer, melanoma and premature skin ageing. UV filters are the active substances preventing the harmful effects. Commercial UV filters exert its maximal effectiveness once they are applied on skin. Instead, progressive UV filters develop into its active form, which absorb UV-light in presence of UVB light. Although new UV filters were developed, still one of the old generation UV filters, avobenzone, is one of the most marketed sunscreens for its high absorbance in the UVA range. On the other hand, avobenzone can degrade upon exposure towards UV radiation. The aim was to evaluate the implications of the new technology in real sun exposure conditions. The absorbance of the progressive UV filters: PRE-A, PRE-B and PRE-C were evaluated at different concentrations in Emollient-A. PRE-A demonstrated the highest activation and absorbance and was characterized physico-chemically. Different batches of PRE-A were irradiated with a solar simulator. The batch with the highest absorbance was compared to avobenzone for four hours in Emollient-A solution. While PRE-A increased the absorbance with increased irradiation, avobenzone degraded converging both absorbances at 4 h irradiation. Mixtures of avobenzone and PRE-A were irradiated in solution obtaining for the combination 2:1 (avobenzone:PRE-A) the highest aborbance after 4 h irradiation. In emulsion this combination delivered higher Solar protection factor (SPF) and Protection in the UVA range (UVA-PF) at 2,5 and 5 minimel erhitemal dose (MED) compared to the same amount of avobenzone. Therefore, it could be used as avobenzone booster. Experts recommend application of sunscreen products every 2 hours, as sweating and bathing contribute sunscreen film loss. This might be inconvenient to users and many of them admit not renewing sunscreen application, which decreases the effectiveness of the product. A bioadhesive sunscreen formulation with water resistant properties and SPF 30 was designed to ensure 100% stickiness of the UV filters after bathing. Moreover, the formulation should contain only photostable UV filters with no susception for being endocrine disruptors, bleaching of the coral reef or penetration potential. In addition, only non-comedogenic ingredients were used. The development process was made with a bioadhesive gel as starting point and small modifications were done each time. The objective was to achieve cosmetical elegance as this is the most determinant factor in the compliance of sunscreen application. Cosmetic elegance was evaluated according to a survey. The final formulation obtained the maximal score in 5/6 evaluation criteria. Finally, a stability test was performed including in use stability concluding stability at 12 months at room temperature.

[cat] L’objectiu fonamental de la tesi rau en l’estudi de tres nous filtres solars (un principal i dos secundaris), amb potencial protector de les radiacions UVA i UVB. S’ha caracteritzat galènicament, físicament i químicament el filtre solar principal, s’ha establert el comportament fotoquímic de diferents lots del nou filtre en condicions solars estàndard simulades de la vida real i la seva capacitat d’absorció en funció del dissolvent més adient per a la seva solubilització́. Per altra banda, s’ha estudiat la possibles sinergia d’aquest nou filtre quan es combina amb els dos filtres secundaris, així com la seva capacitat d’absorció́ de radiacions UV comparativament amb els filtres solars ja coneguts. Tot això porta a fer la recerca adient per a desenvolupar una crema per a l’administració del filtre principal, que mantingui les seves funcionalitats i presenti unes característiques que la facin assolir millores del que ja existeix comercialitzat. D’aquesta manera, s’arriba a una formulació d’una crema bioadhesiva, que permet la permanència perllongada del filtre fotoprotector en el lloc d’aplicació́, amb un factor de protecció solar elevat (SPF=30). Alhora, presenta una alta tolerabilitat. D’altra banda s’assoleixen unes bones propietats organolèptiques de la crema. La formulació final obté la puntuació màxima en 5/6 criteris d'avaluació de l’elegància estètica de la crema. També es demostra que la crema solar és resistent a l’aigua mantenint la completa efectivitat després del test d’immersió in vitro i es composa de filtres sostenibles al medi ambient i sense risc de penetració a la pell. Finalment, es va realitzar una prova d'estabilitat en la qual es van mesurar propietats organolèptiques, pH, viscositat, extensibilitat i reologia, concloent que la crema és estable després de 12 mesos.