Visual electrophoresis titration model for portable enzyme inhibition assays by moving reaction boundary chip

The concept of visual enzyme inhibition-electrophoresis titration (EI-ET) was proposed for design of moving reaction boundary based portable EI-ET chip device without use of traditional optical detector and power supply. Theoretical results revealed that a series of enzyme inhibition and kinetic parameters could be obtained via an EI-ET run. As a proof of concept, horseradish peroxidase and Cu(I) were respectively chosen as model enzyme and inhibitor for the experiments of EI-ET. The experiments demonstrated the successful screening of enzyme inhibitor and validated the EI-ET theory. Particularly, EI-ET method had many merits, e.g., real direct visual detection, phone-like portability, extreme simplicity and low-cost in contrast to traditional ELISA. In addition, the EI-ET method had high specificity, sensitivity (0.3 ng/mL), recovery (>85 %) and stability (<7.6 %). The EI-ET concept opens multi-windows for development of portable electrophoresis, titration and enzyme assay devices, and shows potentials to visual drug screening, enzyme inhibition kinetics sensing and portable clinical diagnosis as well as inhibitor/activator analysis.