Spontaneously Self-Assembled Microgel Film as Co-Delivery System for Skincare Applications

Abstract

Nowadays, the design of innovative delivery systems is driving new product developments in the field of skincare. In this regard, serving as potential candidates for on-demand drug delivery and fulfilling advanced mechanical and optical properties together with surface protection, spontaneously self-assembled microgel films can be proposed as ideal smart skincare systems. Currently, the high encapsulation of more than one drug simultaneously in a film is a very challenging task. Herein, different ratios (1:1, 3:1, 9:1) of different mixtures of hydrophilic/hydrophobic UVA/UVB-absorbers working together in synergy and used for skin protection were encapsulated efficiently into spontaneously self-assembled microgel films. In addition, in vitro release profiles show a controlled release of the different active molecules regulated by the pH and temperature of the medium. The analysis of the release mechanisms by the Peppas-Sahlin model indicated a superposition of diffusion-controlled and swelling-controlled releases. Finally, the distribution of active molecule mixtures into the film was studied by confocal Raman microscopy imaging corroborating the release profiles obtained.

Keywords: co-delivery; cosmetic active molecules; self-assembled microgel film.

Figure 1

Release kinetics as a function of pH for different mixtures at 25 °C. ■ DBBH at pH 6, □ DBBH at pH 4.4, ● Benzophenone-4 at pH 6, ○ Benzophenone at pH 4.4, ▲ Salicylic acid at pH 6, Δ Salicylic acid at pH 4.4.

Figure 2

Release kinetics as a function of temperature for different mixtures at pH 6. ■ DBBH at 25 °C, □ DBBH at 37 °C, ● Benzophenone-4 at 25 °C, ○ Benzophenone at 37 °C, ▲ Salicylic acid at 25 °C, Δ Salicylic acid at 37 °C.

Figure 3

Cross-sectional from the top (image top) to the bulk (image bottom) (50 × 50 µm²) (a) and 2D surface (75 × 75 µm²) (b) confocal images of different mixtures.