2 research outputs found
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 Fe<sub>3</sub>O<sub>4</sub> nanoparticles,
approximately 8.3 nm in diameter, were coated in situ onto the silicates
during the synthesis process, which involved the coprecipitation of
aqueous Fe<sup>2+</sup>/Fe<sup>3+</sup> salts. Owing to the high surface
area-to-volume ratios and the presence of ionically charged groups
(i.e., SiO<sup>–</sup>Na<sup>+</sup>), the silicate
nanoplatelets exhibited intense noncovalent bonding forces between
Fe<sub>3</sub>O<sub>4</sub> nanoparticles and the surrounding microorganisms.
The Fe<sub>3</sub>O<sub>4</sub>-on-nanoplatelet nanohybrids enabled
the entrapment of bacterial cells in liquid microbiological media.
These captured bacteria formed bacterial aggregates on the order of
micrometers that became physically maneuverable under a magnetic field.
This phenomenon was demonstrated with <i>Staphylococcus aureus</i> in liquid microbiological media by physically removing them using
a magnetic bar; in two experimental examples, bacterial concentrations
were reduced from 10<sup>6</sup> to 10<sup>2</sup> and from 10<sup>4</sup> to 10<sup>0</sup> CFU/mL (colony formation unit/mL con).
Under a scanning electron microscope, these bacteria appeared to have
rough and wrinkled surfaces due to the accumulated silicate platelets.
Furthermore, the external application of a high-frequency magnetic
field completely destroyed these aggregated microbes by the magnetically
induced heat. Hence, the newly developed nanohybrids were shown to
be viable for physically capturing microbes and also for potential
hyperthermia treatment applications
Additional file 1: of Core-shell of FePt@SiO2-Au magnetic nanoparticles for rapid SERS detection
TEM images of core-shell nanoparticles. Figure S1. TEM images of (A) FePt@SiO2-N and (B) gold nanoparticles (scale bar: 50 nm). Figure S2. TEM images of Au-FePt@SiO2-N with various EDS concentration: (A) 0 mM, (B) 0.1 M, (C) 0.2 M, (D) 0.3 M, (E) 0.4 M and (F) 0.5 M (scale bar: 50 nm). Figure S3. TEM images of Au-FePt@SiO2-N (0.3 M) with various gold concentration: (A) 0 μM, (B) 47.6 μM, (C) 95.2 μM, (D)142.8 μM, (E)190.4 μM, and (F) 238 μM (scale bar, 100 nm