Selective, colorimetric assay of glucose in urine using G-quadruplex-based DNAzymes and 10-acetyl-3,7-dihydroxy phenoxazine.

A selective, colorimetric assay for detection of glucose in urine was developed by transducing oxidation of glucose into the color change of 10-acetyl-3,7-dihydroxy phenoxazine (ADHP) using hemin-G quadruplex DNAzyme. Oligonucleotide 5'-ATTGGGAGGGATTGGGTGGGCAC-3' was used to form a stable G-quadruplex structure. After binding with hemin, the complex of G-quadruplex and hemin acted as a horseradish peroxidase mimicking DNAzyme and catalyzed the oxidation of colorless ADHP to red resorufin by H2O2 produced by the reaction of glucose and oxygen catalyzed by glucose oxidase. Therefore, the oxidation of glucose could be transduced into the color change of ADHP by combining these two reactions. Under the optimum conditions, the absorbance of resorufin at 570 nm was proportional to the concentration of glucose over the range of 3.0-100 μM, with a linear regression equation of A=0.017+0.0035 C (C: μM, R=0.988) and a detection limit of 1.0 μM (signal/noise 3). Some interfering compounds, such as acetaminophen, uric acid, and ascorbic acid exhibited no response under the same conditions. Therefore, the assay can be used in the selective detection of glucose in human serum and urine samples.