Polyvinyl alcohol/starch modified cotton thread for glucose distance-based colorimetric detection

Abstract

In this thesis, polyvinyl alcohol (PVA) and starch modified cotton thread was developed as a cotton thread-based device for distance-based colorimetric detection of hydrogen peroxide (H2O2) and glucose. PVA and starch, the biocompatible polymers, were modified on a cotton thread to enhance the enzymatic stability and reagent immobilization efficiency. The colorimetric glucose detection of the device was based on a bienzymatic reaction involving glucose oxidase (GOx) and horseradish peroxidase (HRP), incorporated with potassium iodide (KI) as an indicator, which was oxidized by H2O2 to provide blue-black color band of an iodine–starch complex. The length of color band on the cotton thread is proportional to H2O2 and glucose concentrations, allowing for a simple and rapid quantitative detection observed by the naked eyes without any signal readout instrument. For the best performance of the proposed device, various parameters were studied, such as the ratio of PVA/starch, KI volume, HRP volume and sample volume. Under the optimal conditions, the cotton thread-based device was used to detect H2O2 and glucose providing linear ranges of 1.0-6.0 mM and 0.1-5.0 mM with detection limits of 0.25 mM and 0.1 mM, respectively. Furthermore, the interference effect of glucose detection was also investigated and the obtained results showed no interfering from common compounds in human tear (i.e. potassium chloride, sodium chloride, urea, ascorbic acid, uric acid, cholesterol and bovine serum albumin). Eventually, the developed device could be successfully applied for the quantitative determination of glucose in artificial human tear.