Fluorescent ZnO Quantum Dot Probe to Study Glucose–Glucose Oxidase Interaction via Fluorescence Resonance Energy Transfer

Abstract

In this work, emphasis is to utilize FRET method to analyze GOx and glucose interaction using fluorescent ZnO QDs as the probes. Fluorescent ZnO and ZnOext QDs were synthesized using sol– gel technique and green synthesis method as donor and acceptor nanoprobes. Structural, optical and morphological characterization of QDS were carried out using UV-visible absorption, fluorescence, FTIR, XRD and field emission scanning electron microscopy. Band gap estimated from Tauc plot is 3.49 and 3.35 eV for ZnO and ZnOext QDs and XRD reveal Wurtzite structure of grown crystals. Systematic absorption study for ZnO–GOx and ZnOext–GOx reveal association constant of –8.3361 M–1 and –2.57646 M –1 for ZnO and ZnOext using Benesi-Hildebrand plot. The binding constant obtained from Stern-Volmer equation is 1.0466 μM –1 and 1.97 μM –1 for ZnO/ZnOext–GOx conjugate and suggest static quenching in the system. CD spectroscopy reveal native state of protein in conjugate sytem. Constant Förster radius (Ro) in ZnOext–GOx system suggest the average 〈κ2〉 as 2/3 and is independent of donor–acceptor distance as normally assumed in FRET system varies from ∼4.5% in ZnO–GOx and ∼5% in ZnOext–GOx system. It indicate better energy transferrin earlier system than formal. The physiological range of glucose from 60 mg–440 mg/dl using this technique in which ZnOext–GOx as donor probe exhibit better response towards glucose than ZnO–GOx system and correlated to the presence of phyotochemicals on the QD surface.