Salicylic Acid (SA) detection using bi-enzyme microfluidic electrochemical sensor

摘要

Salicylic Acid (SA) is a phyto-hormone involved in the regulation of induced plant defense mechanisms, primarily against biotic stresses. Various methods have been reported for detecting SA. The electrochemical methods offer economical, portable, and accurate concentration measurement of bio-chemicals like SA. Electrochemical biosensors often require modification of the working electrode (WE) with specific materials to fiinctionalize it with bio-molecules, needed for target analyte recognition. The proposed biosensor provides a unique methodology of selectively coating the inter-digital electrodes (IDE) and further applying the method to develop a biosensor to detect SA. The electrodes are fabricated using a novel deposition process termed as, Capillary action assisted deposition (CAAD) which consists of IDEs fabricated in the form of small finger-like channels connected to a wider main channel. The drop-casted sample automatically flows from the main channel into the fine fingers under the effect of capillary action. The sensor includes a 3-electrode system arranged in a 3-D geometry, forming an integrated microfluidic channel for analyte solution flow. The WE is selectively coated with, first, Graphene oxide (GO) and next, the bi-enzyme Salicylate Hydroxylase (SH) and Tyrosinase (TYR) recipe using the proposed CAAD process. The bi-enzyme exhibits selectivity towards SA and the proposed sensor shows the detection range of 0.5 μM to 64 μM. The electrochemical reactions are characterized by Chrono-amperometry (CA) and shows the sensitivity of 34.4 μA cm~(-2) per decade change in SA concentration (in μM). To the best of our knowledge, the proposed bi-enzyme system in a microfluidic device for SA sensing is the first of its kind.