Urease-modified LAPS: Two-dimensional dynamic detection of enzymatic reactions

Abstract

• Urea-sensitive LAPS fabricated by a layer-by-layer self-assembly technique. • The enzymatic reactions are monitored dynamically in spatially resolved manner. • A method for the selection of monitoring windows based on threshold intersections. • The 2D images are more uniform and reduce demand for the number of pixel points. Light addressable potentiometric sensor (LAPS) is a semiconductor-based electrochemical sensor with flat surface structure and superior light addressability, making it an ideal platform for visualizing enzymatic reactions. However, it is hardly to observe the true process of reactions because a large amount of information unrelated to the enzymatic reaction, such as buffer diffusion caused by pH gradient, is contained in photocurrent images. In this study, urea-sensitive LAPS were obtained by immobilizing urease on the surface of LAPS with Si/SiO 2 /Si 3 N 4 structured using a layer-by-layer self-assembly technique and a method for the selection of enzymatic reaction monitoring windows based on threshold intersections is proposed to reduce the influence of non-enzymatic reaction factors. The overall performance of the urea-sensitive LAPS was excellent, with a sensitivity of 92.04 ± 4.04 mV/pC urea and a linearity of 99.16 % in the range of 1–20 mM. The mean square error of photocurrent images using this method is reduced by an order of magnitude compared to original images, which are more uniform and reduce the pixel demand. Our work provides a more complete assessment of urea-sensitive LAPS, and the proposed window selection method based on threshold intersections provides a viable method for dynamic monitoring of chemical images with high uniformity and high refresh rates.