Detection of HO and catalase on a paper-based flow sensor constructed with borate cross-linked PVA hydrogel.

The detections of HO and catalase play an important role in daily life. This study introduces a paper-based flow sensor that is specifically designed to detect HO and catalase. The sensor utilizes a hydrogel composed of cross-linked 4-carboxyphenylboronic acid and polyvinyl alcohol. When HO is in contact with the hydrogel, the B-C bonds of the hydrogel undergo a reactive process, causing decomposition of the hydrogel. The pH indicator strip enables the visual monitoring of the viscosity change that occurs during the gel-sol transition. The quantification of HO is accomplished by assessing the proportion of water coverage on the pH indicator strip. The sensor shows a detection limit of 0.077 wt% and is applicable for the quantitative measurement of HO in routinely used disinfectants. Furthermore, the presence of catalase is effectively identified and the detection of catalase in milk is successfully fulfilled. In summary, this work proposes a simple, user-friendly, label-free, and cost-effective method for constructing a paper-based flow sensor using borate cross-linked polyvinyl alcohol hydrogel, showing great potential for detecting HO and catalase in various practical scenarios.