Dynamic biomass micro-nanofibre framework for entrapment and clearance of gastrointestinal microplastics

Microplastics (MPs) are infiltrating global food systems, where they disseminate systemically, posing unmet health risks as current strategies fail to prevent bioaccumulation. We have engineered an oral alginate-chitin micro-nanofibre framework (Alg-Ch) as a pH-responsive scavenger, which was formed via lyophilization-induced hydrogen bonding and physical entanglement between alginate microfibres and chitin nanofibrous sheets (1:10 ratio). Alg-Ch captured MPs predominantly through two mechanisms: electrostatic adsorption onto a protonated chitin nanonetwork in gastric acid, and physical entrapment by swollen alginate at intestinal pH. It captured 500-nm spherical MPs of varying surface chemistry (polystyrene (PS), PS-COOH, PS-NH₂) and composition (polyethylene terephthalate, polymethyl methacrylate), and irregular fragments including PS fibres, polypropylene, and polyethylene, achieving capacities of 816.6 mg g^-1 (stomach) and 1114.5 mg g^-1 (intestine), and retained >47% efficacy with food. In mice, Alg-Ch reduced colonic MP fluorescence by ∼50% within 2 h and accelerated faecal elimination. A 13-week Alg-Ch intervention restored tight-junction proteins ZO-1, occludin and claudin-5, decreased serum levels of interleukin-6, lipopolysaccharide, tumour necrosis factor and interleukin-1β, and promoted recovery of short-chain fatty acid-producing genera, with no evidence of body-weight loss, organ toxicity or histopathological lesions. This biocompatible platform unifies mechanical sequestration, barrier repair and microbiome rehabilitation, offering a scalable strategy to mitigate the risks of ingested MPs and the global health burden of plastic pollution.