Biological & Soft Matter Special Seminar: Hierarchically architected biopolymer nanostructures for active microplastics remediation and sustainable polymer substitutes

Abstract:

The replacement of synthetic nanomaterials with biodegradable alternatives made from abundant and sustainable natural biopolymers is a challenge of high societal importance. We will discuss how the process of antisolvent precipitation under shear enables the formation of diverse classes of biopolymer structures, including nanoparticles, rods, nanofibers, nanoribbons, sheets, and hierarchical nanomaterials. Specifically, we will focus on the unique capabilities enabled by a new class of soft dendritic colloids (SDCs) with hierarchical morphology (Nature Materials, 18:1315, 2019). The fractal branching and contact splitting phenomena enable a range of highly unusual properties of the SDCs – gelation at very low volume fractions, strong adhesion to surfaces, and ability to form new types of gels, nonwoven sheets and reinforced biocomposites. Alginate SDCs can be used in hierarchical hydrogel networks with synergistic combination of the colloidal and molecular networks (Nature Comm., 12:2834, 2021). One emerging application of the SDCs with high societal impact is as cleaners that capture microplastics for water remediation. Traditional water treatment methods such as filtration and centrifugation are not practical for large volumes of natural water. We use the unique properties of the SDCs in “active microcleaners,” which are made of chitosan and infused with a small amount of fatty acid, enabling them to self-propel and self-disperse in water by the Marangoni effect. The SDCs could enable the cleanup of microplastics in various types of aquifers, including saline seawater. Finally, we will discuss how agarose hydrogels reinforced with chitosan SDCs can find applications in high-performance bioplastic composites that have excellent mechanical performance, high optical transmittance, hydrostability, bactericidal activity and soil biodegradability (Cell Rep. Phys. Sci. 4:101732, 2023). The results suggest a universal strategy for making architected bioplastic composites that could serve as substitutes for present synthetic polymers.