Colorimetric analysis of sulfate-reducing bacterial DNA based on catalytic hemin/G-quadruplex loaded rigid DNA triangle

Here a colorimetric sensing platform for sulfate-reducing bacterial DNA analysis was described by using a catalytic hemin/G-quadruplex loaded rigid DNA triangle assembly. This two-dimensional rigid DNA triangle structure was assembled by target bacterial DNA and three hairpin beacon probes. As three tips of hairpin probes carry specific recognition sites for G-quadruplex formation, target bacterial DNA trigger the opening of hairpin probes, not only forming a steady rigid DNA triangle but also activating the hemin/G-quadruplex horseradish peroxidase mimicking DNAzyme. The resultant hemin/G-quadruplex loaded rigid DNA triangle assembly catalyzes a colorimetric reaction with the signal intensity correlated to target concentrations, achieving target bacterial DNA detection with a detection limit as low as 23.99 fM. We further analyzed actual bacteria with this system, by acquiring bacterial DNA including bacteria-specific sequences with polymerase chain reaction (PCR), with the detection limit down to 1 cfu/mL. The system shows good selectivity for the target and resistance to interference, highly stable performance for serum samples application, showing great potential for application in the fields of genetic analysis, environmental monitoring, and medical testing.