A new strategy for the development of efficient impedimetric tobramycin aptasensors with metallo-covalent organic frameworks (MCOFs)

Two bimetallic CoNi-based metallo-covalent organic frameworks (MCOFs) were prepared and explored as the sensitive platforms of impedimetric aptasensors for efficient detection of tobramycin (TOB). The two CoNi-MCOFs were constructed using metallophthalocyanine tetra-amine (MPc-TA, M = Co²⁺ or Ni²⁺) and 4,4'-(1,10-phen-anthroline-2,9-diyl) dibenzaldehyde (PTD) as building units and further coordinating to the secondary metal ions (Ni²⁺ or Co²⁺) by phenanthroline. Interestingly, the immobilization ability of CoPc-TA-PTD(Ni) to TOB-targeted aptamer is higher than that of NiPc-TA-PTD(Co) due to its stronger binding interactions to aptamer. As a result, the CoPc-TA-PTD(Ni)-based aptasensor shows the superior TOB detection ability, giving a low detection limit of 0.07 fg mL^-1 and satisfied sensing performances, such as high selectivity, good reproducibility, and excellent stability. Also, the aptasensor shows the acceptable applicability for detecting TOB in milk or chicken egg. This MCOFs-based sensing strategy could be extensively applied to detect other analytes by anchoring the corresponding probes.