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

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.


Related in: MedlinePlus

Magnetic trapping of bacteria using MCSNPs, and AFM images of UPEC.(a) Magnetic trapping efficiency of UPEC MDRB treated at different concentrations of MCSNPs was assessed by measuring the optical density (OD600) and bioluminescence of free bacteria after magnetic field separation. (b) SEM images of MCSNP-trapped UPEC when 6 mg/mL of MCSNP was incubated with 1 × 108 bacteria. The inset shows the SEM image when bacteria were treated with 1 mg/mL MCSNP. (c–e) AFM amplitude images of UPEC for the assessment of phenotype of wild type UPEC (c), ∆fimA deletion-insertion mutant (d), and complementation strains (e). AFM images of UPEC strains show the presence of numerous fimbriae in the wild type UPEC, absence of fimbriae in the ∆fimA deletion-insertion mutant (∆fimAΩkmr), and the restoration of fimbriae in the complemented strain of ∆fimA knockout (∆fimAΩkmr::pQE30fimA). (c’–e’) AFM images of the same samples in (c–e) in height mode. The diameter of fimbriae in black box is displayed in figure (c”–e”). Note that ∆fimA knockout strain shows no distinct fibril due to the absence of fimbriae (d”). (f) AFM images of 10 × 10 μm2 scan shows MCSNPs bound to fimbriae of UPEC, inset shows enlarged scan (5 × 5 μm2). (g) MCSNP-mediated trapping and capture efficiencies of WT, ∆fimA knockout, and complemented UPEC strains show that the capturing efficiency of the knockout strain is 55% lower than the wild type and complemented strains.
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f2: Magnetic trapping of bacteria using MCSNPs, and AFM images of UPEC.(a) Magnetic trapping efficiency of UPEC MDRB treated at different concentrations of MCSNPs was assessed by measuring the optical density (OD600) and bioluminescence of free bacteria after magnetic field separation. (b) SEM images of MCSNP-trapped UPEC when 6 mg/mL of MCSNP was incubated with 1 × 108 bacteria. The inset shows the SEM image when bacteria were treated with 1 mg/mL MCSNP. (c–e) AFM amplitude images of UPEC for the assessment of phenotype of wild type UPEC (c), ∆fimA deletion-insertion mutant (d), and complementation strains (e). AFM images of UPEC strains show the presence of numerous fimbriae in the wild type UPEC, absence of fimbriae in the ∆fimA deletion-insertion mutant (∆fimAΩkmr), and the restoration of fimbriae in the complemented strain of ∆fimA knockout (∆fimAΩkmr::pQE30fimA). (c’–e’) AFM images of the same samples in (c–e) in height mode. The diameter of fimbriae in black box is displayed in figure (c”–e”). Note that ∆fimA knockout strain shows no distinct fibril due to the absence of fimbriae (d”). (f) AFM images of 10 × 10 μm2 scan shows MCSNPs bound to fimbriae of UPEC, inset shows enlarged scan (5 × 5 μm2). (g) MCSNP-mediated trapping and capture efficiencies of WT, ∆fimA knockout, and complemented UPEC strains show that the capturing efficiency of the knockout strain is 55% lower than the wild type and complemented strains.

Mentions: The trapping efficiency of MCSNP for MDRB was evaluated using multidrug resistant uropathogenic Escherichia coliCFT073 bacteria (hereafter referred as UPEC). For visualization of MCSNP-mediated bacterial trapping, genes responsible for bioluminescence, luxCDABE, were inserted in the UPEC strains (Supplementary Figure S3, Tables S1 and S2). Wild type (WT) or genetically engineered bioluminescent bacteria were mixed with varying concentrations of MCSNPs for 10 minutes, and then the MCSNP-trapped bacteria were captured using an external magnetic field. The amount of remaining free bacteria in solution was quantified by measuring the OD600 or bioluminescence. The capture efficiency for UPEC reached 90.1% when 6 mg/mL MCSNPs were mixed with 108 bacteria (60 pg per cell equivalent) in 1 mL PBS buffer (pH 7.4) (Fig. 2a). The trapping efficiency was further evaluated using bioluminescent UPEC bacteria and was found to be consistent with the optical density measurement (Fig. 2a). To further investigate binding of MCSNPs to the bacterial cell surface, the MCSNP treated cells were examined using scanning electron microscopy (SEM) (Fig. 2b). The SEM images of UPEC clearly showed the binding of MCSNPs on the bacterial surface, presumably due to electrostatic interaction of the positively charged MCSNPs with negatively charged UPEC cell surface (Fig. 2b). SEM image analysis of MCSNPs bound to bacteria showed that MCSNPs are closely packed on the outer membrane of UPEC (Fig. 2b and inset). The electrostatic attachment of numerous MCSNPs at the bacterial surface makes them responsive towards an external magnetic field, which enables the separation of the MCSNP-bound bacteria from free bacteria. In addition, it is also expected that most MCSNPs in the current study, with the size of 53 nm, remained on the surface instead of entering into the cells, because it is known that NPs bigger than 40 nm cannot penetrate the cell membrane passively18. These physicochemical properties of MCSNPs can be applied to reduce contaminating MDRB pathogens in water to negligible levels by MCSNP-mediated bacterial-trapping and facile magnetic capture, which is useful to avoid any contamination with bacterial toxins and other harmful bacterial components.


Coupling of radiofrequency with magnetic nanoparticles treatment as an alternative physical antibacterial strategy against multiple drug resistant bacteria
Magnetic trapping of bacteria using MCSNPs, and AFM images of UPEC.(a) Magnetic trapping efficiency of UPEC MDRB treated at different concentrations of MCSNPs was assessed by measuring the optical density (OD600) and bioluminescence of free bacteria after magnetic field separation. (b) SEM images of MCSNP-trapped UPEC when 6 mg/mL of MCSNP was incubated with 1 × 108 bacteria. The inset shows the SEM image when bacteria were treated with 1 mg/mL MCSNP. (c–e) AFM amplitude images of UPEC for the assessment of phenotype of wild type UPEC (c), ∆fimA deletion-insertion mutant (d), and complementation strains (e). AFM images of UPEC strains show the presence of numerous fimbriae in the wild type UPEC, absence of fimbriae in the ∆fimA deletion-insertion mutant (∆fimAΩkmr), and the restoration of fimbriae in the complemented strain of ∆fimA knockout (∆fimAΩkmr::pQE30fimA). (c’–e’) AFM images of the same samples in (c–e) in height mode. The diameter of fimbriae in black box is displayed in figure (c”–e”). Note that ∆fimA knockout strain shows no distinct fibril due to the absence of fimbriae (d”). (f) AFM images of 10 × 10 μm2 scan shows MCSNPs bound to fimbriae of UPEC, inset shows enlarged scan (5 × 5 μm2). (g) MCSNP-mediated trapping and capture efficiencies of WT, ∆fimA knockout, and complemented UPEC strains show that the capturing efficiency of the knockout strain is 55% lower than the wild type and complemented strains.
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f2: Magnetic trapping of bacteria using MCSNPs, and AFM images of UPEC.(a) Magnetic trapping efficiency of UPEC MDRB treated at different concentrations of MCSNPs was assessed by measuring the optical density (OD600) and bioluminescence of free bacteria after magnetic field separation. (b) SEM images of MCSNP-trapped UPEC when 6 mg/mL of MCSNP was incubated with 1 × 108 bacteria. The inset shows the SEM image when bacteria were treated with 1 mg/mL MCSNP. (c–e) AFM amplitude images of UPEC for the assessment of phenotype of wild type UPEC (c), ∆fimA deletion-insertion mutant (d), and complementation strains (e). AFM images of UPEC strains show the presence of numerous fimbriae in the wild type UPEC, absence of fimbriae in the ∆fimA deletion-insertion mutant (∆fimAΩkmr), and the restoration of fimbriae in the complemented strain of ∆fimA knockout (∆fimAΩkmr::pQE30fimA). (c’–e’) AFM images of the same samples in (c–e) in height mode. The diameter of fimbriae in black box is displayed in figure (c”–e”). Note that ∆fimA knockout strain shows no distinct fibril due to the absence of fimbriae (d”). (f) AFM images of 10 × 10 μm2 scan shows MCSNPs bound to fimbriae of UPEC, inset shows enlarged scan (5 × 5 μm2). (g) MCSNP-mediated trapping and capture efficiencies of WT, ∆fimA knockout, and complemented UPEC strains show that the capturing efficiency of the knockout strain is 55% lower than the wild type and complemented strains.
Mentions: The trapping efficiency of MCSNP for MDRB was evaluated using multidrug resistant uropathogenic Escherichia coliCFT073 bacteria (hereafter referred as UPEC). For visualization of MCSNP-mediated bacterial trapping, genes responsible for bioluminescence, luxCDABE, were inserted in the UPEC strains (Supplementary Figure S3, Tables S1 and S2). Wild type (WT) or genetically engineered bioluminescent bacteria were mixed with varying concentrations of MCSNPs for 10 minutes, and then the MCSNP-trapped bacteria were captured using an external magnetic field. The amount of remaining free bacteria in solution was quantified by measuring the OD600 or bioluminescence. The capture efficiency for UPEC reached 90.1% when 6 mg/mL MCSNPs were mixed with 108 bacteria (60 pg per cell equivalent) in 1 mL PBS buffer (pH 7.4) (Fig. 2a). The trapping efficiency was further evaluated using bioluminescent UPEC bacteria and was found to be consistent with the optical density measurement (Fig. 2a). To further investigate binding of MCSNPs to the bacterial cell surface, the MCSNP treated cells were examined using scanning electron microscopy (SEM) (Fig. 2b). The SEM images of UPEC clearly showed the binding of MCSNPs on the bacterial surface, presumably due to electrostatic interaction of the positively charged MCSNPs with negatively charged UPEC cell surface (Fig. 2b). SEM image analysis of MCSNPs bound to bacteria showed that MCSNPs are closely packed on the outer membrane of UPEC (Fig. 2b and inset). The electrostatic attachment of numerous MCSNPs at the bacterial surface makes them responsive towards an external magnetic field, which enables the separation of the MCSNP-bound bacteria from free bacteria. In addition, it is also expected that most MCSNPs in the current study, with the size of 53 nm, remained on the surface instead of entering into the cells, because it is known that NPs bigger than 40 nm cannot penetrate the cell membrane passively18. These physicochemical properties of MCSNPs can be applied to reduce contaminating MDRB pathogens in water to negligible levels by MCSNP-mediated bacterial-trapping and facile magnetic capture, which is useful to avoid any contamination with bacterial toxins and other harmful bacterial components.

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.


Related in: MedlinePlus