Detection of H₂O₂ and catalase on a paper-based flow sensor constructed with borate cross-linked PVA hydrogel

The detections of H₂O₂ and catalase play an important role in daily life. This study introduces a paper-based flow sensor that is specifically designed to detect H₂O₂ and catalase. The sensor utilizes a hydrogel composed of cross-linked 4-carboxyphenylboronic acid and polyvinyl alcohol. When H₂O₂ 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 H₂O₂ 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 H₂O₂ 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 H₂O₂ and catalase in various practical scenarios.