Insect Odorant-Binding Protein Modified Biosensor for Sensitive and Specific Electrochemical Detection of Alcohols

Abstract

Olfaction biosensors are playing crucial roles in detecting volatile organic compounds (VOCs) in various domains, while the response pattern of biosensor to different alcohols and the underlying reasons for the differences in response remain unclear. Herein, this study presents a sensitive electrochemical olfactory biosensor utilizing Drosophila odorant-binding protein (LUSH) as a sensing material for the detection of 11 alcohols with different molecular structures (alkyl chain lengths, hydroxyl group numbers and cyclic alcohols) and phenol. The electrodes covalently immobilized with the LUSH proteins were characterized by atomic force microscopy (AFM), and their ability to detect alcohols was investigated through electrochemical impedance spectroscopy (EIS). Results showed the LUSH-modified biosensor exhibited ultrasensitive detection of alcohols (detection limits: 10~100 fM), with linear ranges of 10–14–10−7 M and coefficient of determination (R2) of 0.948–0.992. In addition, the biosensor demonstrated high selectivity toward interference compounds (selectivity coefficients: < 0.22), excellent reproducibility (relative standard deviation, RSD: 1.2%, n = 4 for parallel sensors), and good stability (the response decreased by 10.2% on the 10th day). Notably, the sensitivity of the biosensor to alcohols showed the alkyl chain-length dependence of the n-alcohols and was influenced by the number of hydroxyl groups and the cyclic structure. More importantly, molecular docking revealed the binding modes, binding energies, and key amino acids involved in the interaction between the LUSH protein and alcohols, and explained the discrepancies in response.

Keywords: Biosensor, electrochemical impedance spectroscopy, Insect odorant-binding protein, VOCs, Alcohols detection, molecular docking