Stimuli-responsive laccase/chitosan-g-PNIPAM complexes: A sustainable strategy for biodegradation of organic pollutants

Hybrid nanostructures from synthetic and biological macromolecules emerged as a significant research topic as they can find applications in biomedicine, catalysis, and environmental remediation. Herein, innovative nanostructures in the form of electrostatic complexes were prepared by the interaction of laccase with a hybrid graft copolymer, CHI-g-PNIPAM, obtained by grafting poly(N-isopropylacrylamide) containing carboxylate end-groups onto chitosan chains. The size, charge, morphology, and stability of the obtained nanostructures were investigated through light scattering measurements and scanning transmission electron microscopy, demonstrating the effect of the ratio between the components on the properties of the obtained co-assembled nanostructures. Also, molecular dynamics simulations were performed to determine the interaction mechanism between the copolymer and the enzyme. The use of the copolymer imparted the nanostructures with improved stability in various conditions and thermo-responsive behaviour, while the incorporation of laccase into such nanostructures enhanced the catalytic activity of the enzyme. The obtained hybrid nanostructures were successfully employed as catalysts for the degradation of indigo carmine and Congo red from aqueous solutions, demonstrating their potential as novel catalysts for cutting-edge applications.