A Highly Sensitive and Rapid Enzyme Biosensor Based on AuNPs/CS@cMWCNTS for Detecting Fusarium Acid

Fusarium acid (FSA) serves as a highly sensitive biomarker for the early warning of bulb rot in Lanzhou lily caused by Fusarium oxysporum infection. Realizing its highly sensitive, accurate, and rapid detection is crucial for the early warning and control of lily bulb rot. Herein, an enzyme biosensor based on the enzyme inhibition principle was developed for the rapid detection of FSA. Firstly, chitosan-functionalized carboxylated multi-walled carbon nanotubes (CS@cMWCNTS) and gold nanoparticles (AuNPs) were modified on a bare electrode by drop coating and electrochemical deposition methods, respectively. Subsequently, dopamine β-hydroxylase (DBH) was firmly immobilized on the electrode surface through the gold-sulfur bond. Because the activity of DBH can be inhibited by FSA, which leads to a noticeable change in the signal response during the conversion of dopamine (DA) to norepinephrine (NA). Under optimized experimental conditions, the sensor exhibits an excellent linear relationship in the concentration range of 1.00 × 10⁻⁵ μg ml⁻¹ ∼ 1.00 × 10³ μg ml⁻¹ with the correlation coefficient of 0.9856 and the detection limit is 4.60pg ml⁻¹. Additionally, the sensor showed good stability, repeatability (RSD 1.85%), and selectivity. The method was applied to analyze FSA in the extraction from Lanzhou lily with a recovery higher than 97.59% and RSD less than 1.383%. This method enables the highly sensitive and rapid detection of FSA in real samples, and provides scientific basis and technical support for early warning of diseases and accurate implementation of prevention and control strategies in crop planting and production.