Chitosan microparticles incorporating a hydrophilic sunscreen agent

A microparticulate delivery system incorporating the hydrophilic sunscreen agent, phenylbenzimidazole sulphonic acid (PBSA) was prepared for better in-use performance. Chitosan, not adequately considered for sunscreen delivery, was used a matrix material. Emulsion crosslinking with glutaraldehyde generated microparticles (MPs) with good features in terms of yield (≈76%), size (24–100 μm) and % incorporation efficiency (29–74%). PBSA release was sustained over 8 h according to a biphasic in-use relevant release pattern. The characteristics of PBSA-loaded chitosan MPs were determined by the interplay of the density of crosslinking of the chitosan matrix, particle size and chitosan–glutaraldehyde–PBSA interactions as evidenced by infrared and differential scanning calorimetric data. Incorporation of the sunscreen in chitosan MPs improved its in vitro UV screening effect using a model chitosan gel and Transpore™ tape. Accordingly, chitosan may be added to the platform of polymers suitable for the delivery of sunscreen actives, particularly hydrophilic agents.