Fabrication of polydopamine nanoparticles-based electrochemical sensor for geometry-sensitive detection of chloramphenicol

Abstract

Chloramphenicol (CAP), a broad-spectrum antibiotic, and the residues in food have profound effect on human’s health, making the detection of antibiotic residues a pressing need. Herein, we synthesized and compared two different geometries of polydopamine polymer, amorphous polydopamine (pDA) and polydopamine nanoparticles (pDA-NPs), for the establishment of a metal-free, green electrochemical sensor for the sensing of CAP. The intrinsic reducing ability of polydopamine was exploited because the catechol group can act on the nitro group of CAP. However, only the geometry of pDA-NPs enabled the sensitive detection of CAP, while the amorphous pDA was no match for the performance. The detection discrepancy may be ascribed to the geometry differences, where pDA-NPs were more likely in a curvature structure while amorphous pDA polymer in a linear structure. Computational method also justified that the curvature structure let to a favorable arrangement toward the sensing of CAP, where more electrons are easier to transfer from the dopamine to the closest oxygen atom of CAP as compared to linear form. The pDA-NPs-based electrochemical sensor presented high sensitivity with a detection limit of 2.57 nM, as well as excellent selectivity in discriminating CAP against the co-existence of other antibiotic and interfering species. Reproducibility was also validated by showing the sensing consistency with which the sensor for three measurements and up to 14-day storage, with CV of 3.4 % and 5.5 %, respectively. A recovery rate from 87 % to 104 % was obtained from a real milk sample spiked with CAP, showing great promise of the developed electrochemical sensor as a facile monitoring tool for CAP in reality.