Label-free fluorescent aptasensor for sensitive detection of oxytetracycline based on CRISPR/Cas12a and G-quadruplex DNAzyme with rhodamine B reporting

The assay achieved a detection limit of 0.3 nM for oxytetracycline (OTC).

• Oxytetracycline is commonly found in food and the environment due to overuse, raising concerns about resistance and toxicity.
• Current detection methods are accurate but costly and technically complex, necessitating simpler alternatives.
• The developed fluorescent aptasensor uses CRISPR/Cas12a and G-quadruplex DNAzyme catalysis to detect OTC.
• In the presence of OTC, the aptamer releases the activator strand, preventing the formation of the G4 DNAzyme and preserving fluorescence.
• The assay effectively quantified OTC in real samples, including river water and milk, demonstrating its practicality for monitoring antibiotic residues.

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