Multi-functional Biomolecule-embedded Nanomaterial Interfaces via Layer-by-layer Assembly

Abstract

Preparation of functional interfaces on different substrates has drawn extensive research efforts for various purposes. Biointerfaces featuring an integration of a wide variety of biomaterials on electrode surfaces has been a hot topic since it is the most critical aspect in creation of biosensor, biofuel cell, and other bioelectronics devices. Recent research progress addresses the demand for hybrid bioelectrocatalytic systems, combining one or more biocatalysts and nanomaterials, like nanoparticles, carbon nanotubes (CNTs) in the biointerfaces. Here in the dissertation, we move forward towards the design of hybrid multienzyme-CNTs layered thin-film biointerfaces for advanced biosensor, biofuel cells development. Understanding of the interactions between biomolecules-nanomaterials interfaces, structural organization of layer-by-layer (LbL) self-assembled multilayers, electron transfer functions of the biointerfaces on the electrode as well as renewability of the biofunctionalized CNT interfaces were studied. In the first section, LbL biointerfaces consisted of alternating cushion layers of oppositely charged CNT-polyethyleneimine (CNT-PEI) and CNT-DNA, and a functional interface consisting of alternating layers of CNT-PEI and negatively charged CNT-acetylcholine esterase (CNT-AChE, pH 7.4) were fabricated under real-time monitoring. Comprehensive interfacial properties were investigated using different characterization tools. A partial desorption of the top enzymatic layer in the LbL structure was observed with a desorption strategy employing alkaline treatment, while further assembly of functional layers regained the functionality of biointerfaces. In the second section, a novel multienzyme-CNTs biosensing interfaces for biosensing application via LbL assembly of MWCNT-organophosphate Hydrolase (MWCNT-OPH) and MWCNT-AChE along with the same set of CNT-DNA and CNT-PEI cushioning bilayers on GCE were investigated. Design of the nanoarchitecture, including total number of layers, relative position of biocatalysts, and concentration of CNTs were explored. Successful discriminative detection of OP and non-OP pesticides was achieved with the biosensor. In the third section, we further employed the versatile LbL assembly technique to modify GCEs and screen printed electrodes (SPEs) utilizing MWCNTs/polyelectrolyte binary composites and an enzyme cascade (MWCNT-Invertase and MWCNT-GDH) to facilitate efficient electron transfer in sucrose/O2 biofuel cell. The LbL architecture showed advantages for sequential enzymatic reaction that favored the electron transfer and efficient penetration of substrate and products in a cascade system and therefore an enhancement of current density.