Multienzyme detection and in-situ monitoring of enzyme activity by bending CE using quantum dots-based polypeptide substrate.

Multienzyme detection and monitoring enzyme activity in situ are significant for the disease to diagnose. This study aims to develop a quantum dots (QDs)-based nanoprobe Cyanine5-DDDLEVLFQFPGLVPRGSGGHHHHHH-QDs (Cy5-LEVLVP-QD), which is able to detect two enzymes inside a bent capillary using CE. Cy5-LEVLVP and QDs were allowed to bind with each other through metal affinity interaction and then injected the Cy5-LEVLVP-QD complex into a capillary with different bends, followed by related enzyme that can cleave the Cy5-LEVLVP peptide. The fluorescence of Cy5 was excited by QDs due to Förster resonance energy transfer. By monitoring the peaks produced by the original Cy5-LEVLVP-QD complex and a significant fluorescence change, sensitive analysis of two different enzymes was conducted. Therefore, the novel approach of using capillaries with semicircular bends could prove particularly useful for enzyme investigating in disease.