Microencapsulation of a cyclodextrin complex of the UV filter, butyl methoxydibenzoylmethane: in vivo skin permeation

Lipid microparticles loaded with the complex between hydroxypropyl--cyclodextrin (HP--CD) andthe sunscreen agent, butyl methoxydibenzoylmethane (BMDBM) were evaluated for their effect on theUV filter percutaneous penetration. The microparticles were prepared by the melt emulsification techniqueusing tristearin as lipidic material and hydrogenate phosphatidylcholine as the surfactant. Humanskin penetration was investigated in vivo by the tape stripping technique, a minimal invasive procedurebased on the progressive removal of the upper cutaneous layers (stratum corneum) with adhesivetape strips. The amount of sunscreen fixed to each strip was determined by HPLC after solvent extraction.The recovery of the UV filter from spiked adhesive tapes was >94.4% and the precision of themethod was better than 7.6% relative standard deviation. Non-encapsulated BMDBM, its complex withHP--CD, the lipid microparticles loaded with the sunscreen alone or the BMDBM/HP--CD complexwere introduced into oil-in-water emulsions and applied to human volunteers. Compared to the creamwith the non-encapsulated sunscreen agent (percentage of the applied dose penetrated, 9.7%±2.5), theamount of BMDBM diffusing into the stratum corneum was increased by the formulations containing theBMDBM/HP--CD complex (17.1%±3.2 of the applied dose) or the microparticles loaded with BMDBMonly (15.1%±2.7 of the applied dose). On the contrary, a significant decrease in the level of UV filterpenetrated into the stratum corneum was achieved by the cream containing the microencapsulatedBMDBM/HP--CD complex (percentage of the applied dose penetrated, 6.0%±1.5). The reduced BMDBMpercutaneous penetration attained by the latter system should enhance the UV filter efficacy and limitpotential toxicological risks.