Sensitive electrochemical detection of Salmonella with chitosan–gold nanoparticles composite film

•A novel immunosensor using dispersed gold nanoparticles in chitosan film.•GNPs played an important role to amplify the electrochemical signals.•The resulting immunosensor shows high selectivity towards Salmonella.•Ultrasensitive detection of Salmonella with a low detection limit of 5 CFU/mL.

An ultrasensitive electrochemical immunosensor for detection of Salmonella has been developed based on using high density gold nanoparticles (GNPs) well dispersed in chitosan hydrogel and modified glassy carbon electrode. The composite film has been oxidized in NaCl solution and used as a platform for the immobilization of capture antibody (Ab1) for biorecognition. After incubation in Salmonella suspension and horseradish peroxidase (HRP) conjugated secondary antibody (Ab2) solution, a sandwich electrochemical immunosensor has been constructed. The electrochemical signal was obtained and improved by comparing the composite film with chitosan film. The result has shown that the constructed sensor provides a wide linear range from 10 to 105 CFU/mL with a low detection limit of 5 CFU/mL (at the ratio of signal to noise, S/N=3:1). Furthermore, the proposed immunosensor has demonstrated good selectivity and reproducibility, which indicates its potential in the clinical diagnosis of Salmonella contaminations.

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