An evanescent waves sensor based on polydopamine-gold coated chalcogenide tapered fiber for enzyme activity profiling

Abstract

In this research, we demonstrate a high-sensitivity tapered fiber (TF) sensor made of As2S3 chalcogenide glass coated with polydopamine (PDA) and gold nanoparticles (AuNPs). The presence of in-situ grown AuNPs on the PDA-coated TF surface via the reduction of Au ions by catechol groups in PDA, facilitated efficient light coupling with evanescent waves, thereby improving the IR absorption of molecules. The sensor was utilized to measure the activity of the glucose oxidase enzyme as a point-of-concept analyte. This process of enzyme catalyzing the conversion of glucose to hydrogen peroxide and Gluconic acid can be recorded by the sensor. In investigating the enzyme activity and D-glucose oxidation kinetics, we monitored the intensity of the Gluconic acid band at 5.764 μm, which arises from the C=O stretching vibration, as a function of time. The estimated enzyme activity using the PDA/AuNPs-coated TF sensor was 103.66 ± 2.87 Umg−1 when the enzyme activity of the sample was 100 Umg−1 which is consistent with standard value. The Lineweaver–Burk plot yielded the following kinetic constants: Km = 16.10 ± 1.63 mM and Vmax = 93.72 ± 12.71 μmol/min. Results suggest that this sensor has great application potential in various enzyme activity applications.