Tint-Adjustable Pickering Emulsion Sunscreen Based on Polydopamine-Coated Silica Nanoparticles

The application of mineral sunscreens is an effective and safe way to protect skin from damage by UV rays. However, many options on the market are not formulated with darker skin tones in mind, so they end up looking chalky. Tinted Pickering emulsions synthesized from polydopamine (PDA), a biologically friendly melanin-like particle, have the potential to resolve these issues and provide better protection for conditions such as hyperpigmentation and melisma. In this study, a series of amorphous SiO2-PDA nanoparticles with fumed silica as the nucleus scaffold and PDA coating as the adhesive layer were synthesized by a simple one-pot method. Compared to the pure spherical PDA nanoparticles without a scaffold, SiO2-PDA has a higher particle yield, lighter color, better dispersion performance, and superior emulsification ability. When further applied to the Pickering emulsion sunscreen, the chromaticity of the emulsions can be flexibly adjusted and effectively improved by the addition of titanium dioxide (TiO2) nanoparticles. Additionally, SiO2-PDA stabilized emulsion exhibits high UV absorption, photothermal effect, high free radical scavenging, and low skin penetration, which is a potential candidate by combining biocompatibility, long-term stability, and high safety in tinted sunscreens as well as other biomedical applications.