Tailor-made magnetic nanocomposite with pH and thermo-dual responsive copolymer brush for bacterial separation

Abstract

Rapid detection of pathogenic bacteria particularly in food samples demands efficient separation and enrichment strategies. Here, hydrophilic temperature-responsive boronate affinity magnetic nanocomposites were established for selective enrichment of bacteria. The thermo-responsive polymer brushes were developed by surface-initiated atom transfer radical polymerization of N-isopropylacrylamide (NIPAm) and allyl glycidyl ether (AGE), followed by a reaction of epoxy groups, and incorporation of fluorophenylboronic acid. The physical and chemical characteristics of the magnetic nanocomposites were analyzed systematically. After optimization, S. aureus and Salmonella spp. showed high binding capacities of 32.14 × 10⁶ CFU/mg and 50.98 × 10⁶ CFU/mg in 0.01 M PBS (pH 7.4) without bacteria death. Bacterial bindings can be controlled by altering temperature and the application of competing monosaccharides. The nanocomposite was then utilized to enrich S. aureus and Salmonella spp. from the spiked tap water, 25% milk, and turbot extraction samples followed by multiplex polymerase chain reaction (mPCR), which resulted in high bacteria enrichment, and demonstrated great potential in separation of bacteria from food samples.

Keywords: Bacteria; Bio-separation; Boronate affinity; Composite magnetic nanocomposite; Polymer; Surface-initiated atom transfer radical polymerization.