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Coupling of radiofrequency with magnetic nanoparticles treatment as an alternative physical antibacterial strategy against multiple drug resistant bacteria

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ABSTRACT

Antibiotic resistant bacteria not only affect human health and but also threatens the safety in hospitals and among communities. However, the emergence of drug resistant bacteria is inevitable due to evolutionary selection as a consequence of indiscriminate antibiotic usage. Therefore, it is necessary to develop a novel strategy by which pathogenic bacteria can be eliminated without triggering resistance. We propose a novel magnetic nanoparticle-based physical treatment against pathogenic bacteria, which blocks biofilm formation and kills bacteria. In this approach, multiple drug resistant Staphylococcus aureus USA300 and uropathogenic Escherichia coli CFT073 are trapped to the positively charged magnetic core-shell nanoparticles (MCSNPs) by electrostatic interaction. All the trapped bacteria can be completely killed within 30 min owing to the loss of membrane potential and dysfunction of membrane-associated complexes when exposed to the radiofrequency current. These results indicate that MCSNP-based physical treatment can be an alternative antibacterial strategy without leading to antibiotic resistance, and can be used for many purposes including environmental and therapeutic applications.

No MeSH data available.


Synthesis of Fe3O4@SiO2-NH2 magnetic core-shell nanoparticles (MCSNPs) and characterization of their physicochemical properties.(a) Schematic diagram showing the steps for synthesizing the Fe3O4 magnetic core, surface coating with SiO2 shell, and functionalization with amine group (-NH2). (b) TEM image of a bare Fe3O4 nanoparticle core showing a diameter close to 10 nm. (c) Evaluation of particle size and distribution by dynamic light scattering. The average size of the bare Fe3O4 magnetic core is 10 nm in diameter while the average size of the final amine functionalized Fe3O4@SiO2 particle is increased up to 53 nm. (d) Magnetization properties of the Fe3O4 core alone, Fe3O4 core with silica coating (Fe3O4@SiO2), and amine functionalized Fe3O4@SiO2 -NH2 (MCSNP) particles were 55.0, 40.9, and 38.8 emu/g, respectively.
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f1: Synthesis of Fe3O4@SiO2-NH2 magnetic core-shell nanoparticles (MCSNPs) and characterization of their physicochemical properties.(a) Schematic diagram showing the steps for synthesizing the Fe3O4 magnetic core, surface coating with SiO2 shell, and functionalization with amine group (-NH2). (b) TEM image of a bare Fe3O4 nanoparticle core showing a diameter close to 10 nm. (c) Evaluation of particle size and distribution by dynamic light scattering. The average size of the bare Fe3O4 magnetic core is 10 nm in diameter while the average size of the final amine functionalized Fe3O4@SiO2 particle is increased up to 53 nm. (d) Magnetization properties of the Fe3O4 core alone, Fe3O4 core with silica coating (Fe3O4@SiO2), and amine functionalized Fe3O4@SiO2 -NH2 (MCSNP) particles were 55.0, 40.9, and 38.8 emu/g, respectively.

Mentions: The iron oxide core (Fe3O4) coated with silica shell was synthesized, and subsequently the silicon shell was functionalized by conjugating amine groups as described as a schematic diagram in Fig. 1a, corresponding method and supporting information. The synthesis of the Fe3O4 core was verified by detection of peaks at 723 and 710 eV using X-ray photoelectron spectroscopy (XPS) analysis, which corresponds to the energy at 2p3/2 and 2p1/2 of pure Fe3O4 (Supplementary Figure S1A). Upon silica coating, the intensity of Fe electronic configuration peaks was decreased and the characteristic peak of Si2p (Si-O) was seen at 103 eV (Supplementary Figure S1B). Finally, functionalized amine (-NH2) on the surface of Fe3O4–SiO2 core-shell was confirmed by a peak at 399 eV (Supplementary Figure S1B). Exact intensities of each peak corresponding to Si, O, Fe and amine groups were confirmed by X-Ray photoelectron spectroscopy (Supplementary Figure S1C-F). The TEM imaging showed that the size of Fe3O4 cores range between 10 to 15 nm (Fig. 1b). Dynamic light scattering (DLS) measurements showed that the average size distribution of Fe3O4 core NP was increased from 10 nm to 53 nm in diameter upon silica coating (Fig. 1c). The magnetization of bare Fe3O4 core was 55 emu/g and was decreased up to 40.90 emu/g and 37.81 emu/g after SiO2 and NH2 coating, respectively (Fig. 1d), suggesting the net magnetization of core Fe3O4 was affected by the coating of non-magnetic molecules. Zeta potential of NPs was examined at each synthesis stages, and Fe3O4@SiO2-NH2 in PBS buffer (pH 7.4) was confirmed to be 7.2 (Supplementary Figure S2A,B), suggesting that MCSNPs maintain a positive charge at physiological pH (pH 7.4), which is important for trapping bacteria with negative surface charge27.


Coupling of radiofrequency with magnetic nanoparticles treatment as an alternative physical antibacterial strategy against multiple drug resistant bacteria
Synthesis of Fe3O4@SiO2-NH2 magnetic core-shell nanoparticles (MCSNPs) and characterization of their physicochemical properties.(a) Schematic diagram showing the steps for synthesizing the Fe3O4 magnetic core, surface coating with SiO2 shell, and functionalization with amine group (-NH2). (b) TEM image of a bare Fe3O4 nanoparticle core showing a diameter close to 10 nm. (c) Evaluation of particle size and distribution by dynamic light scattering. The average size of the bare Fe3O4 magnetic core is 10 nm in diameter while the average size of the final amine functionalized Fe3O4@SiO2 particle is increased up to 53 nm. (d) Magnetization properties of the Fe3O4 core alone, Fe3O4 core with silica coating (Fe3O4@SiO2), and amine functionalized Fe3O4@SiO2 -NH2 (MCSNP) particles were 55.0, 40.9, and 38.8 emu/g, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037373&req=5

f1: Synthesis of Fe3O4@SiO2-NH2 magnetic core-shell nanoparticles (MCSNPs) and characterization of their physicochemical properties.(a) Schematic diagram showing the steps for synthesizing the Fe3O4 magnetic core, surface coating with SiO2 shell, and functionalization with amine group (-NH2). (b) TEM image of a bare Fe3O4 nanoparticle core showing a diameter close to 10 nm. (c) Evaluation of particle size and distribution by dynamic light scattering. The average size of the bare Fe3O4 magnetic core is 10 nm in diameter while the average size of the final amine functionalized Fe3O4@SiO2 particle is increased up to 53 nm. (d) Magnetization properties of the Fe3O4 core alone, Fe3O4 core with silica coating (Fe3O4@SiO2), and amine functionalized Fe3O4@SiO2 -NH2 (MCSNP) particles were 55.0, 40.9, and 38.8 emu/g, respectively.
Mentions: The iron oxide core (Fe3O4) coated with silica shell was synthesized, and subsequently the silicon shell was functionalized by conjugating amine groups as described as a schematic diagram in Fig. 1a, corresponding method and supporting information. The synthesis of the Fe3O4 core was verified by detection of peaks at 723 and 710 eV using X-ray photoelectron spectroscopy (XPS) analysis, which corresponds to the energy at 2p3/2 and 2p1/2 of pure Fe3O4 (Supplementary Figure S1A). Upon silica coating, the intensity of Fe electronic configuration peaks was decreased and the characteristic peak of Si2p (Si-O) was seen at 103 eV (Supplementary Figure S1B). Finally, functionalized amine (-NH2) on the surface of Fe3O4–SiO2 core-shell was confirmed by a peak at 399 eV (Supplementary Figure S1B). Exact intensities of each peak corresponding to Si, O, Fe and amine groups were confirmed by X-Ray photoelectron spectroscopy (Supplementary Figure S1C-F). The TEM imaging showed that the size of Fe3O4 cores range between 10 to 15 nm (Fig. 1b). Dynamic light scattering (DLS) measurements showed that the average size distribution of Fe3O4 core NP was increased from 10 nm to 53 nm in diameter upon silica coating (Fig. 1c). The magnetization of bare Fe3O4 core was 55 emu/g and was decreased up to 40.90 emu/g and 37.81 emu/g after SiO2 and NH2 coating, respectively (Fig. 1d), suggesting the net magnetization of core Fe3O4 was affected by the coating of non-magnetic molecules. Zeta potential of NPs was examined at each synthesis stages, and Fe3O4@SiO2-NH2 in PBS buffer (pH 7.4) was confirmed to be 7.2 (Supplementary Figure S2A,B), suggesting that MCSNPs maintain a positive charge at physiological pH (pH 7.4), which is important for trapping bacteria with negative surface charge27.

View Article: PubMed Central - PubMed

ABSTRACT

Antibiotic resistant bacteria not only affect human health and but also threatens the safety in hospitals and among communities. However, the emergence of drug resistant bacteria is inevitable due to evolutionary selection as a consequence of indiscriminate antibiotic usage. Therefore, it is necessary to develop a novel strategy by which pathogenic bacteria can be eliminated without triggering resistance. We propose a novel magnetic nanoparticle-based physical treatment against pathogenic bacteria, which blocks biofilm formation and kills bacteria. In this approach, multiple drug resistant Staphylococcus aureus USA300 and uropathogenic Escherichia coli CFT073 are trapped to the positively charged magnetic core-shell nanoparticles (MCSNPs) by electrostatic interaction. All the trapped bacteria can be completely killed within 30 min owing to the loss of membrane potential and dysfunction of membrane-associated complexes when exposed to the radiofrequency current. These results indicate that MCSNP-based physical treatment can be an alternative antibacterial strategy without leading to antibiotic resistance, and can be used for many purposes including environmental and therapeutic applications.

No MeSH data available.