Preparation of CHS-Fe3O4@@ZIF-8 peroxidase-mimic with an ultra-thin hollow layer for ultrasensitive electrochemical detection of kanamycin.

A highly sensitive and selective electrochemical biosensor was developed for the detection of kanamycin using a core-hollow-shell structured peroxidase-mimic nanozyme, CHS-Fe₃O₄@@ZIF-8. The synthesized CHS-Fe3O4@@ZIF-8 was characterized with scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was found that the CHS-Fe3O4@@ZIF-8 exhibits excellent peroxidase-like activity due to  its ultra-thin hollow layer. Besides, CHS-Fe3O4@@ZIF-8 functionalized with complementary chains of kanamycin aptamer was anchored to the electrode surface via complementary base pairing with the kanamycin aptamer. Upon the presence of kanamycin, a strand displacement reaction was triggered leading to a reduction in the number of the CHS-Fe3O4@@ZIF-8, which slowed down the catalytic reaction of the substrate 3,3',5,5' -tetramethylbenzidine (TMB) facilitated by CHS-Fe3O4@@ZIF 8. Differential pulse voltammetry (DPV) was employed to measure and record changes in peak current resulting from catalytic oxidation product formation (oxidation product of TMB). The electrochemical signal exhibited a linear relationship with logarithmic variations in kanamycin concentration within a range spanning from 10 to 8000 pM and achieved an impressive detection limit as low as 7.52 pM. Furthermore, successful detection of kanamycin content in serum samples using this sensor demonstrated its good specificity and reproducibility. These findings indicate that the constructed electrochemical kanamycin sensor holds significant potential for practical applications. The biosensor demonstrated high selectivity, distinguishing kanamycin from other antibiotics, and exhibited good reproducibility, making it reliable for practical applications. The successful detection of kanamycin in serum samples further underscores the sensor's potential for real-world applications, particularly in monitoring antibiotic residues in food products and clinical diagnostics.