Halloysite Nanotubes as Dynamic Interfaces for Functional Enzyme Biomaterials

Abstract

The development of robust and recyclable enzyme-based materials is essential for advancing sustainable biocatalysis and biotechnologies. Herein, we report the design of covalent enzyme-halloysite biohybrid materials obtained by the controlled functionalization of halloysite nanotubes (HNTs), a naturally abundant, low-cost, and biodegradable clay nanomaterial acting as a dynamic biological interface. Two structurally and functionally distinct enzymes, collagenase G (ColG) and laccase (Lac), were selected as model systems to investigate how the halloysite surface can modulate the enzyme organization and catalytic behavior. Through tailored interfacial functionalization of the HNT external surface, stable enzyme-clay biointerfaces were obtained while preserving enzymatic activity. Comprehensive spectroscopic, thermal, and microscopic analyses confirmed the successful formation of homogeneous hybrid biointerfaces and revealed distinct supramolecular organization, depending on the immobilized enzyme. Enzymatic assays demonstrate that both HNTs-ColG and HNTs-Lac retained their catalytic function after surface conjugation. Notably, the laccase-based biomaterial efficiently degrades methyl orange under mediator-free conditions, a behavior rarely observed in halloysite-supported laccase systems, while operating under both batch and continuous flow conditions and exhibiting high recyclability over multiple cycles. These findings suggest that halloysite nanotubes do not merely behave as a passive support but rather as adaptive inorganic-biological interfaces capable of dynamically influencing enzyme function through interfacial effects, in particular, via the covalent-induced conformational modulation of the enzyme after its grafting onto the external HNTs surface. The proposed strategy opens new perspectives for the development of functional enzyme materials for bioremediation and biomedical applications.