Multifunctional carbon nanotubes and their derived nano-constructs for enzyme immobilization - A paradigm shift in biocatalyst design

Carbon nanotubes (CNTs), both in pristine and chemically or structurally functionalized forms, have gained increasing research interests as an innovative type of nano-structured materials. Owing to unique structural and functional attributes of CNTs-based constructs such as tunable surface entities, nano-size structure, larger surface-volume area, and chemical, thermal, and mechanical stability, CNTs-based constructs have been extensively engineered and used for numerous applications, such as enzyme immobilization for robust bio-catalysis. Moreover, the unique catalytic chemistry of enzyme-linked CNTs along with a matching or compatible coordination with numerous materials offer potential applications, such as bio-catalysis, sensing, separation and purification, environmental remediation and other related biotechnological and biomedical applications. Simple coordination of CNTs with biocatalyst enables pronounced enzyme loading, elevated biocatalytic activity and notable stability. Immobilization of enzymes on CNTs-based nanocomposites is an emerging research arena for numerous applications. Both the noncovalent as well as covalent attachments are proposed for enzyme immobilization onto/into the CNTs. Surface functionalization of CNTs with polymeric, organic, and bio-molecules can furnish robust and biocompatible nanocomposites with particular functional moieties on their surface, and thus providing a basis for integrating a specific enzyme. A combination of the immobilization method used, and the nanotube interactions affect the catalytic performance, structural integrity and preservation of native enzyme functionalities. Considering the above points, the current review spotlights recent advances in the immobilization of various enzymes on multifunctional CNTs and their derived nano-constructs. Moreover, the potential applications of CNTs-immobilized biocatalyst in different fields such as electrochemical biosensing, biodiesel production, environmental remediation and protection, and lactose bioconversion are also thoroughly discussed. Finally, the work is summed-up with critical remarks and insightful opinions are directed in this important research area. (C) 2020 Elsevier B.V. All rights reserved.