From biopolymers to Pickering emulsions: a green chemistry strategy to replace microplastics in next-generation cosmetics.

With the rising interest in eco-safe cosmetic products due to ongoing governmental restrictions and growing public concern regarding the effects of microplastics derived from synthetic products, research for biodegradable alternatives from renewable materials has been accelerated. Carbohydrate-based polymers can be considered suitable materials due to their excellent biodegradability, renewability, abundance, and versatility. In this study, microparticles based on starch, chitosan, and cellulose derivatives were produced using different methods to obtain micrometric particles with specific structural and rheological properties. In parallel, a formulation strategy was developed to establish a sustainable Pickering emulsion platform capable of incorporating and exploiting the functional properties of the produced biodegradable microparticles. Micrometric particles from native and chemically modified tapioca starch were found compatible with the optimized Pickering emulsion formulation. At the same time, the pseudoplastic flow behavior was maintained, and specific effects regarding droplet size distribution were achieved. The results provided evidence that the synthesized microparticles could serve effectively and safely as co-stabilizers and structuring-modifying agents for sustainable cosmetic emulsion formulation, confirming the appropriateness of the proposed biodegradable starch microparticles. In contrast, chitosan-based microparticles did not yield satisfactory texture or stabilization under the tested conditions, pointing toward additional optimization and investigation. This research confirms that chemically modified starch microparticles can be introduced effectively and safely as eco-safe, sustainable ingredients for next-generation, microplastic-free cosmetic formulations.