Covalent and non-covalent synergy in molecularly imprinted polymer-coated hollow nanocages for selective electrochemical recognition of azithromycin.

An azithromycin-imprinted electrochemical sensor was developed using hollow nanocages derived from metal-organic frameworks, combined with multi-walled carbon nanotubes. The modification of the molecularly imprinted layer enhanced selective recognition for azithromycin by enabling dual binding modes through covalent (boronate ester bonds) and non-covalent (hydrogen bonding) interactions. The hollow porous structure of the Co3O4/CNFs (carbon-nitrogen frameworks) nanocages reduced the diffusion distance of electrolytes across the electrode surface, accelerated the redox reaction, enhanced sensing signals, and enhanced sensitivity. Moreover, the combination of Co3O4/CNFs nanocages and multi-walled carbon nanotubes significantly enhanced the conductivity of the modified electrodes, thus further improving sensitivity. It also provided a larger support area for constructing the imprinted layer, which increased recognition sites. After optimization, the sensor exhibited excellent azithromycin recognition, with a broad linear range (0.2-500 μM) and a low limit of detection (0.12 μM). The sensor showed satisfactory recoveries in real sample analysis (milk = 94.67%-100.99%, urine = 96.89%-107.33%), highlighting its significant potential for monitoring trace levels of azithromycin.