Oxybenzone Entrapped in Mesoporous Silicate MCM-41

Oxybenzone is an organic ultraviolet absorbent commonly used as photoprotection agent in cosmetic formulations. Unfortunately, it shows safety problems because of its potential systemic absorption and skin photosensibilization. Thus, a new particulate carrier is proposed with the aim of solving these problems. Oxybenzone (OXY) was loaded into the mesopores of the silicate MCM-41 and the obtained particulate carrier (MCM-41-OXY) was mixed with melt tristearin or stearyl alcohol with the aim of plugging the MCM-41 mesopores and thus entrapped OXY inside the pores. These particles were characterized and incorporated in an emulgel. OXY release from these formulations was evaluated in vitro and was compared with those from emulgels containing free OXY and unplugged MCM-41-OXY. The photoprotection range of the hybrid materials was also investigated through spectrophotometric measurements. As concerns with UV absorption properties, it can be observed that the spectrum of the neat compound appears broader than those recorded for lipid/silicate particles and MCM-41-OXY, but MCM-41-OXY with tristearin presents a higher absorption intensity in UVA, UVB, and UVC regions, maintaining thus excellent photoprotection effects. Besides this aspect, the pore occlusion by means of the lipid ingredients offers a proper obstacle to sunscreen release, thus preventing the contact between the sunscreen and the skin and consequently both systemic absorption and cutaneous adverse reactions. The new lipid/MCM-41 particles appear to be promising candidates to formulate sunscreen preparations.