Layer-by-Layer Assembled Carbon Nanotube-Acetylcholinesterase/Biopolymer Renewable Interfaces: SPR and Electrochemical Characterization

Abstract

Developing simple, reliable, and cost-effective methods of renewing an inhibited biocatalyst (e.g., enzymatic interfaces) on biosensors is needed to advance multiuse, reusable sensor applications. We report a method for the renewal of layer-by-layer (LbL) self-assembled inhibition-based enzymatic interfaces in multiwalled carbon nanotube (MWCNT) armored acetylcholinesterase (AChE) biosensors. The self-assembly process of MWCNT dispersed enzymes/biopolymers was investigated using surface plasmon resonance (SPR). The LbL fabrication consisted of alternating cushion layers of positively charged CNT-polyethylenimine (CNT-PEI) and negatively charged CNT-deoxyribonucleic acid (CNT-DNA) and a functional interface consisting of alternating layers of CNT-PEI and negatively charged CNT-acetylcholine esterase (CNT-AChE, pH 7.4). The observed SPR response signal increased while assembling the different layers, indicating the buildup of multiple layers on the Au surface. A partial desorption of the top enzymatic layer in the LbL structure was observed with a desorption strategy employing alkaline treatment. This indicates that the strong interaction of CNT-biopolymer conjugates with the Au surface was a result of both electrostatic interactions between biopolymers and the surface binding energy from CNTs: the closer the layers are to the Au surface, the stronger the interactions. In contrast, a similar LbL assembly of soluble enzyme/polyelectrolytes resulted in stronger desorption on the surface after the alkaline treatment; this led to the investigation of AChE layer removal, permanently inhibited after pesticide exposure on glassy carbon (GC) electrodes, while keeping the cushion layers intact. The desorption strategy permitted the SPR and electrochemical electrode surfaces to be regenerated multiple times by the subsequent self-assembly of fresh PEI/AChE layers. Flow-mode electrochemical amperometric analysis demonstrated good stability toward the determination of acetylcholine with 97.1 ± 2.7% renewability. Our simple, inexpensive approach shows the potential of renewable LbL self-assembled functional interfaces for multiple uses in a wide field of applications such as biosensing, various biotechnological processes, and the food and health industries.

Layer-by-Layer Assembly of Carbon Nanotubes Modified with Invertase/Glucose Dehydrogenase Cascade for Sucrose/O2Biofuel Cell

“…13 INV was immobilized onto carboxylated MWCNTs via the NHS/EDC crosslinking process and the protocol was used as previously described with minor modifications. 22,25 For enzyme immobilization, 2.5 mg of INV was dissolved in phosphate/nitrate buffer (100 mM, pH 7.0) dispersed with EDC/NHS activated MWCNTs and was allowed to incubate overnight at 4…”

“…24,25 To the best of our knowledge, no study on the fabrication of bioanode utilizing an enzyme cascade by layer by layer assembly method and investigation corresponding to its biofuel cell performance has been explored.…”

Effects of Measurements Conditions on an Extended-Gate FET used as pH sensor

“…The isoelectric point, or point of zero charge (PZC), is the point where the electrical charge density on a surface is zero. Depending on the electrolyte pH, the SnO 2 :F surface can be neutral, positively or negatively charged [35][36][37] .…”

Frontiers in electrochemical sensors for neurotransmitter detection: towards measuring neurotransmitters as chemical diagnostics for brain disorders

“…Zhang et al used the layer-by-layer self-assembly technique to create a renewable ACh biosensor. 92 The enzyme interfaces were renewed by treatment with NaOH and fresh layers of multiwalled carbon nanotubes with polyethylenediamine and acetylcholinesterase. Researchers are also increasingly interested in the use of safe materials.…”