Insect odorant-binding protein modified biosensor for sensitive and specific electrochemical detection of alcohols

Olfaction biosensors are playing crucial roles in detecting volatile organic compounds (VOCs) in various domains, while the response pattern of biosensors 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), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), and their ability to detect alcohols was investigated through EIS. Results showed that the LUSH modified biosensor exhibited ultrasensitive detection of multiple alcohols (detection limits: 10-100 fM), with linear ranges from 10^-14 to 10^-7 M and coefficients of determination (R²) of 0.948-0.992. In addition, the biosensor demonstrated high selectivity toward interfering compounds (selectivity coefficients <0.22), excellent reproducibility (relative standard deviation, RSD: 1.2%, n = 4 for parallel sensors), and good stability (response decreased by 10.2% on the 10^th day). Notably, the sensitivity of the biosensor to alcohols showed alkyl chain-length dependence of 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 LUSH-alcohol interaction and explained the response discrepancies.