A dual-mode electrochemical and fluorescence aptasensor based on CDs@Cu/Al-MOF and TiC for the detection of kanamycin in milk.

A dual-mode electrochemical and fluorescent sensing platform for the highly sensitive detection of kanamycin (KANA) in milk was constructed, which leveraged the synergistic effects of carbon dots (CDs)-loaded metal-organic frameworks (CDs@Cu/Al-MOF) and TiC, along with the competitive binding of complementary DNA (cDNA) strands to KANA-specific aptamers. Loading CDs onto Cu/Al-MOF effectively prevented the aggregation of CDs and shielded the fluorescent signals from environmental interference, significantly enhancing signal stability. When a glassy carbon electrode (GCE) functionalized with TiC and aptamers was immersed in a solution of cDNA-functionalized CDs@Cu/Al-MOF, the aptamers hybridized with the cDNA, anchoring the CDs@Cu/Al-MOF onto the GCE surface. This resulted in enhanced electrochemical signals and weakened fluorescence intensity in the solution. Upon introduction of KANA, the aptamer preferentially bound to KANA and the cDNA/CDs@Cu/Al-MOF detached from the electrode, leading to a decrease in the electrochemical signal and an increase in the fluorescence signal. The developed dual-mode aptasensor enabled highly sensitive detection of KANA within a range of 100 fM-1 μM, with the limit of detection (LOD) as low as 0.5254 fM (electrochemical mode) and 0.4398 fM (fluorescence mode). The dual-mode aptasensor exhibited excellent selectivity, reproducibility, and promising performance in real milk sample analysis.