Alginate microparticles as carriers for the UV filter 2-ethylhexyl 4-methoxycinnamate: Influence on photostability

Abstract

Objective: The organic ultraviolet UVB filter 2‐ethylhexyl 4‐methoxycinnamate (EHMC) was encapsulated in microparticles (MPs) of sodium alginate and co‐loaded with vitamin E (Vit.E) by an extrusion process using an aerodynamically assisted jetting (AAJ) methodology. The aim was to assess the effect of encapsulation concerning UVB filter release from the MPs and its photochemical stability. Methods: The EHMC photostability was analysed by exposing the samples (both MPs in aqueous dispersion and incorporated in a cream preparation) during 1 h to simulated solar light. For the MPs (empty‐MP, EHMC‐MP and EHMC + Vit.E‐MP), the morphology and size were characterized; while in the case of the encapsulated samples, the amount of EHMC‐loading was determined. The release of EHMC was evaluated by adding EHMC‐MP or EHMC + Vit.E‐MP to 65% ethanol in water under mechanical stirring at 32°C. Results: All MPs showed a homogeneous size distribution with a median of 90.5 ± 2.5 μm for EHMC‐MP and 70.4 ± 1.14 μm for EHMC + Vit.E‐MP. The encapsulation efficiency was 92.9% and 99.4% for EHMC‐MP and EHMC + Vit.E‐MP, respectively. The observed release from the MPs was lower than the dissolution of the pure UV filter. EHMC‐MP and EHMC + Vit.E‐MP were successfully incorporated into a cream formulation, with no evidence of phase separation or colour modification. Upon simulated light exposure, the photoisomerization/phototransformation of EHMC encapsulated in MPs and Vit.E‐MP decreased as compared to free EHMC, both in aqueous dispersion and as a cream. The conformational ratio of the isomers (Z‐/E‐EHMC) was found to be the lowest in the presence of Vit.E. Conclusion: This work demonstrates that use of these alginate microparticulate carriers could enhance the effectiveness of sunscreen preparations containing this UVB filter.