A simple self-assembly aptasensor for ultrasensitive detection of kanamycin based on carbon dots and Ti₃C₂ MXene nanocomposite

Antibiotics play an excellent role in preventing and treating animal diseases, but their improper use poses a potential threat to public health. Designing a sensing platform to detect trace amounts of antibiotic residues in actual samples is a significant challenge. To achieve this objective, a self-assembly aptasensor based on a two-round signal amplification strategy for kanamycin (KANA) trace detection was demonstrated by employing carbon dot (CD) decorated Ti₃C₂ MXene as electrode modification material and the complex of double-stranded DNA (dsDNA) and methylene blue (MB) as probes, where dsDNA was composed of complementary DNA (cDNA) and aptamers. The CDs can effectively suppress the self-stacking of Ti₃C₂ MXene to promote electron transfer and provide plenty of exposed active sites for the aptamer to capture KANA precisely. The MB inserted into dsDNA would be liberated upon interaction with KANA due to a competitive process that occurs among cDNA and KANA, reducing electrical signal. Under the optimal conditions, the constructed aptasensor exhibited a good linear relationship between the output signal and the logarithm of KANA concentration in the range of 1 fM-1 mM, and the limit of detection is 0.892 fM. The satisfactory selectivity, stability, and reproducibility suggested that the prepared aptasensor can be a universal platform to detect other antibiotic residues by anchoring corresponding aptamers. Furthermore, it has been successfully applied to determine KANA in milk samples (recovery rates ranged from 101.01% to 107.21%, and the RSD was below 5%), demonstrating potential application prospects in the food-safety analysis field.