First Observation of Physically Capturing and Maneuvering Bacteria using Magnetic Clays

A new class of nanohybrids composed of structurally exfoliated silicate platelets and magnetic iron oxide nanoparticles was synthesized and shown to be capable of capturing microbes in liquid microbiological media. Nanoscale silicate platelets with an approximate thickness of 1.0 nm were prepared from the naturally occurring mineral clays montmorillonite and mica; these clays yielded platelets with lateral dimensions on the order of 80–100 nm and 300–1000 nm, respectively. The magnetic Fe3O4 nanoparticles, approximately 8.3 nm in diameter, were coated in situ onto the silicates during the synthesis process, which involved the coprecipitation of aqueous Fe2+/Fe3+ salts. Owing to the high surface area-to-volume ratios and the presence of ionically charged groups (i.e., ≡SiO–Na+), the silicate nanoplatelets exhibited intense noncovalent bonding forces between Fe3O4 nanoparticles and the surrounding microorganisms. The Fe3O4-on-nanoplatelet nanohybrids enabled the entrapment of bacterial cells in liquid micro...