Incorporation of nanocapsules into gellan gum films: A strategy to improve the stability and prolong the cutaneous release of silibinin

Highlights: • SB nanocapsules were successfully incorporated into gellan gum films. • Transparent, flexible, thin and stable films were developed. • Nanocapsules improved SB homogeneity in the films. • Nano-based films controlled the SB release and its permeation through the skin. • The films showed no irritant potential according to the HET-CAM study. This study aimed to develop gellan gum films containing silibinin-loaded nanocapsules as a novel approach for cutaneous administration of this flavonoid. The nanocapsule suspensions were prepared and presented mean size around 140 nm with homogenous distribution, negative zeta potential and silibinin encapsulation efficiency close to 100%. Then, these suspensions were converted into gellan gum films by solvent casting method. The films were transparent, flexible and maintained the gellan gum hydrophilicity. Nanocapsules provided the silibinin homogenous distribution in the films and prolonged its release, as well as improved the gellan gum occlusion potential. Besides, the nanosuspensions conversion into films improved the silibinin stability. Additionally, the nano-based films presented a swelling index 1.5 times higher than films containing non-nanoencapsulated silibinin. Microscopic analysis evidenced the homogeneous surface of the nano-based films, while films containing non-nanoencapsulated silibinin presented small cracks. The in vitro skin permeation profile confirmed the silibinin gradual release from the nano-based films and its greater retention in the dermis when the skin is damaged. Finally, the formulations presented no irritant effect in the HET-CAM assay. Therefore, the conversion of silibinin-loaded nanocapsule suspensions into films might be considered a promising platform for skin delivery of this flavonoid.