Development of a paper-based enzymatic microfluidic biosensor to detect organophosphate pesticides

Food safety is a critical issue, and the detection of food pollutants is of paramount importance. The development of rapid, reliable, and effective tools for the identification of food contamination (i.e., pesticides) is crucial to meet the growing demand for safe high-quality food. This thesis presents the development of a colorimetric paper-based microfluidic biosensor for the detection of organophosphate pesticides (OPs) by measuring the quantity of the enzyme acetylcholine esterase (AChE). The biosensor uses a colorimetric assay to detect the presence of OPs in sample solutions based on the principle of enzyme inhibition. The AChE substrate chromogen indoxyl acetate (IDA) is used to identify these toxic substances. The activity of the enzyme is hindered when OPs are present in the sample being tested, resulting in a less intense color change. The biosensor assay uses simple sensitive visual screening carts in which the enzyme is immobilized by physical absorption directly on the paper support. Different concentrations of the organophosphate pesticides (chlorpyrifos, dichlorvos, and malathion) were used to validate the biosensor, and the inhibition color change and IC50 value were compared with those obtained using colorimetric biosensors for OPs in the literature. A proof-of-concept biosensor was developed in the current thesis using these paper tests, combining seven microfluidic channels with paper-based sensing platforms. The biosensor showed medium-low sensitivity and selectivity for the detection of organophosphate pesticides. However, optimization of the biosensor has the potential to offer an accurate and affordable method for field-based monitoring and detection. This biosensor could have various applications, including agricultural, food safety, and environmental monitoring, offering a promising platform for numerous applications. Improved performance and reliability of the optimized biosensor could make it a valuable tool for the detection of organophosphate pesticides in various environments.