A novel dual-color glucose detection method based on G-quadruplex DNAzyme catalytic properties: Utilizing ABTS2− and acid violet 7 for high sensitivity and visual semi-quantitative analysis

A novel dual-color method for glucose detection has been devised, leveraging the combination of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium (ABTS²⁻) and acid violet 7, based on the catalytic properties of G-quadruplex DNAzymes. In the presence of K⁺, the oligonucleotide 5′-GTGGGTAGGGCGGGTTGG-3′ (PS2.M) forms a G-quadruplex structure. When bound to hemin, this structure mimics horseradish peroxidase (HRP) and catalyzes the oxidation of colorless ABTS²⁻ to green ABTS^•− by H₂O₂. The H₂O₂ is produced through the reaction between glucose and oxygen, catalyzed by glucose oxidase. By linking these two reactions, the oxidation of glucose can be translated into a color change in ABTS²⁻. Under optimal conditions, the absorbance at 420 nm (A_{420 nm}) is directly proportional to the glucose concentration within a range of 1.0 μM to 40.0 μM. The linear regression equation is A = 0.175 + 0.0334C (C: μM, R = 0.998), with a detection limit of 0.1 μM (3σ/slope). Furthermore, the introduction of acid violet 7 as a reference molecule enables the green color intensity change to be transduced into a color transition from red to gray and then to green, facilitating high-resolution semi-quantitative analysis of glucose by visual inspection. Importantly, our proposed method has been validated through its application to the detection of glucose concentrations in human serum, yielding promising results that underscore its potential for clinical diagnostics and research applications. Our findings represent a substantial advancement in the field of glucose detection and offer a promising alternative to existing methods.