Bioinspired Design of Alcohol [email protected] TiO2 Microreactors for Sustainable Cycling of NAD+/NADH Coenzyme
Key Laboratory of Solid Waste Treatment and Resource Recycle of Ministry of Education, Institute of Non-Metallic Minerals, Southwest University of Science and Technology, Mianyang 621010, China
Low-cost Wastewater Treatment Technology International Sci-Tech Cooperation Base of Sichuan Province, Mianyang 621010, China
Author to whom correspondence should be addressed.
Nanomaterials 2018, 8(2), 127; https://doi.org/10.3390/nano8020127
Received: 31 December 2017 / Revised: 1 February 2018 / Accepted: 19 February 2018 / Published: 24 February 2018
(This article belongs to the Special Issue Nanomaterials in Biocatalyst)
The bioinspired design and construction of [email protected] microreactors with specific cell-like functionality has generated tremendous interest in recent years. Inspired by their fascinating complexity, scientists have endeavored to understand the essential aspects of a natural cell and create biomimicking microreactors so as to immobilize enzymes within the hierarchical structure of a microcapsule. In this study, simultaneous encapsulation of alcohol dehydrogenase (ADH) was achieved during the preparation of microcapsules by the Pickering emulsion method using amphiphilic modified TiO2 nanoparticles (NPs) as building blocks for assembling the photocatalytic microcapsule membrane. The [email protected]2 NP microreactors exhibited dual catalytic functions, i.e., spatially confined enzymatic catalysis and the membrane-associated photocatalytic oxidation under visible light. The sustainable cycling of nicotinamide adenine dinucleotide (NAD) coenzyme between NADH and NAD+ was realized by enzymatic regeneration of NADH from NAD+ reduction, and was provided in a form that enabled further photocatalytic oxidation to NAD+ under visible light. This bioinspired [email protected]2 NP microreactor allowed the linking of a semiconductor mineral-based inorganic photosystem to enzymatic reactions. This is a first step toward the realization of sustainable biological cycling of NAD+/NADH coenzyme in synthetic functional microsystems operating under visible light irradiation.