A paper-based lateral flow strip assay based on enzyme-mediated pectin viscosity change for the determination of polygalacturonase activity

Abstract

In this study, a simple, convenient, and cost-effective paper-based lateral flow strip sensor combined with a smartphone was developed for the determination of polygalacturonase (PG) activity based on the modulation of viscosity of pectin solution, which can be visualized by the difference in the average diffusion distance on the pH indicator strips. Effects of the pectin concentration, enzymatic reaction time, the volume of diffusion liquid, and the diffusion time on the average diffusion distance were systematically investigated. For quantitative analysis of PG activity, the images of the pH indicator strips after lateral flow diffusion were collected by a smartphone and processed through Adobe Photoshop CS 5.1 software. Under the optimal conditions, the average lateral flow diffusion distance shows a good linear relationship with PG activity in the range of 0.025–0.80 U/mL, and the limit of quantification is 0.025 U/mL. Finally, the applicability of the proposed strategy was successfully verified by measuring PG activity in cucumber sample. The recoveries are in the range of 87.4%–96.7%. In short, the present study developed a convenient, low-cost, and accurate approach for on-site detecting of PG activity, especially in remote or resource-limited regions.