Cationic Polymer-Coated Magnetic Nanoparticles for the Separation and Detection of Bacterial Contamination in food samples

Abstract

Rapid and high-efficiency measurement of bacteria can help prevent foodborne diseases. In this research, a simple method was devised for detecting the total bacteria count in food samples, employing an integrated approach with chitosan-coated magnetic nanoparticles for bacteria capture and a portable glucose meter (PGM) for detection readout. Magnetic nanoparticles (MNPs) were first synthesized using the co-precipitation of Fe2+ and Fe3+ in the presence of NH4OH. To increase nanoparticles stability, citric acid was added after MNPs formation. The MNPs are subsequently coated with chitosan polymer using two approaches: 1) electrostatic adsorption, resulting in MNPs-CH, and 2) chemical bonding, resulting in MNPs-PDA-CH. Both MNPs-CH and MNPs-PDA-CH were characterized using various techniques such as ATR-FTIR, TEM, Zeta-potential, and EDX. After being coated with chitosan, the surface charge of MNPs changed from negative to positive, making them suitable for bacteria capture. Both MNPs-CH and MNPs-PDA-CH demonstrated strong capture capabilities for Escherichia coli and Staphylococcus aureus through electrostatic adsorption between the positively charged nanoparticles and the negatively charged bacteria. Subsequently, the captured bacteria could be detected using PGMs. The decrease in glucose consumption by bacteria was proportional to the concentration of bacteria, with a good linear range. This method demonstrates good detection performance for both gram-negative Escherichia coli and gram-positive Staphylococcus aureus in dried seafood samples. The detection accuracy in real samples is 95%. By measuring the glucose consumption by bacteria, this method offers a simple and cost-effective means of detecting the total bacteria count in food and environmental samples.

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