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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.


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Membrane perturbation of UPEC by RMT.(a) Outer cell membrane permeability of UPEC by RF and RMT treatments. (b–e’) AFM amplitude mode images of UPEC cell surfaces after treatment at various conditions: (b–e) cell morphology and (b’–e’) outer membrane topography analyses of UPEC incubated at 46 °C without MSCNPs (b,b’), and with MCSNPs (c,c’), UPEC treated with RF at 46 °C without MCSNPs (d,d’), and with MCSNPs at 46 °C (RMT, e,e’). Note that carter-type pits with 10–17 nm depths towards the inner membranes were observed after RMT treatment (e’). (f) Inner membrane (IM) potential of UPEC after RF or RMT treatment at 46 °C. (g) Schematic diagrams showing the UPEC membrane and membrane associated electron transport chain in control cells (left) and cells after RMT treatment (right). Outer membranes were damaged and crater-like pits were formed by ROS, heat, and mechanical vibration from NPs after RF application. Consequently, loss of inner membrane potential and dysfunction of membrane associated complexes followed. Eventually, these factors induce bacterial cell death.
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f5: Membrane perturbation of UPEC by RMT.(a) Outer cell membrane permeability of UPEC by RF and RMT treatments. (b–e’) AFM amplitude mode images of UPEC cell surfaces after treatment at various conditions: (b–e) cell morphology and (b’–e’) outer membrane topography analyses of UPEC incubated at 46 °C without MSCNPs (b,b’), and with MCSNPs (c,c’), UPEC treated with RF at 46 °C without MCSNPs (d,d’), and with MCSNPs at 46 °C (RMT, e,e’). Note that carter-type pits with 10–17 nm depths towards the inner membranes were observed after RMT treatment (e’). (f) Inner membrane (IM) potential of UPEC after RF or RMT treatment at 46 °C. (g) Schematic diagrams showing the UPEC membrane and membrane associated electron transport chain in control cells (left) and cells after RMT treatment (right). Outer membranes were damaged and crater-like pits were formed by ROS, heat, and mechanical vibration from NPs after RF application. Consequently, loss of inner membrane potential and dysfunction of membrane associated complexes followed. Eventually, these factors induce bacterial cell death.

Mentions: Recently, it was reported that upon RF exposure, iron oxide magnetic nanoparticles attached to the liposome can deflect and perturb the membrane, acting as mechanical transducers to transfer the energy of radiofrequency to the liposome42. Since MCSNP can closely pack on the bacterial surface (Fig. 2b), it is tempting to hypothesize that the MNP can mechanically perturb the cell membrane under a RF field. This possibility was further investigated by measuring the outer membrane (OM) permeability of bacteria bound to MCSNPs using hydrophobic 1-N-phenylnaphthylamine (NPN) that shows fluorescence when it attaches to the phospholipid layer after passing through the outer membrane. The NPN fluorescence from the RMT samples was 5 fold higher than control (UPEC incubated at 46 °C for 30 min), while the fluorescence from the RF-treated samples was just 3 fold higher than control (Fig. 5a), suggesting a greater loss of the permeability barrier during RMT. To further examine the membrane permeability in detail, bacterial cell surfaces were visualized by AFM after removal of MCSNP using PBS buffer (Fig. 5b–e’). Control UPEC cells incubated at 46 °C without MCSNP, or exposed to RF at 46 °C, showed no noticeable alteration in their surface (XY plane at Fig. 5b–d and Z-axis at Fig. 5b’–d’) and were found to be comparable to the cell surface treated at 25 °C without or with MCSNP (Supplementary Figure S8A,B). However, UPEC strains showed crater type pits in their OM with increased roughness (~10–17 nm deep) under RMT (Fig. 5e–e’). To get an in-depth insight into the bioenergetics of the cells upon perturbation of the OM barrier, the inner membrane (IM) potential (∆ψ) was measured using lipophilic DiSC3(5), a potentiometric fluorescent probe representing the membrane potential by emitting fluorescence when it is released from the membrane upon collapse of the transmembrane potential due to membrane depolarization43. As expected, RF combined with MCSNP drastically lost IM potential compared to RF treatment alone at 46 °C (Fig. 5f). Taken together, these results suggest that membrane-bound MCSNP can damage OM and the IM potential under RF, which causes bacterial death.


Coupling of radiofrequency with magnetic nanoparticles treatment as an alternative physical antibacterial strategy against multiple drug resistant bacteria
Membrane perturbation of UPEC by RMT.(a) Outer cell membrane permeability of UPEC by RF and RMT treatments. (b–e’) AFM amplitude mode images of UPEC cell surfaces after treatment at various conditions: (b–e) cell morphology and (b’–e’) outer membrane topography analyses of UPEC incubated at 46 °C without MSCNPs (b,b’), and with MCSNPs (c,c’), UPEC treated with RF at 46 °C without MCSNPs (d,d’), and with MCSNPs at 46 °C (RMT, e,e’). Note that carter-type pits with 10–17 nm depths towards the inner membranes were observed after RMT treatment (e’). (f) Inner membrane (IM) potential of UPEC after RF or RMT treatment at 46 °C. (g) Schematic diagrams showing the UPEC membrane and membrane associated electron transport chain in control cells (left) and cells after RMT treatment (right). Outer membranes were damaged and crater-like pits were formed by ROS, heat, and mechanical vibration from NPs after RF application. Consequently, loss of inner membrane potential and dysfunction of membrane associated complexes followed. Eventually, these factors induce bacterial cell death.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f5: Membrane perturbation of UPEC by RMT.(a) Outer cell membrane permeability of UPEC by RF and RMT treatments. (b–e’) AFM amplitude mode images of UPEC cell surfaces after treatment at various conditions: (b–e) cell morphology and (b’–e’) outer membrane topography analyses of UPEC incubated at 46 °C without MSCNPs (b,b’), and with MCSNPs (c,c’), UPEC treated with RF at 46 °C without MCSNPs (d,d’), and with MCSNPs at 46 °C (RMT, e,e’). Note that carter-type pits with 10–17 nm depths towards the inner membranes were observed after RMT treatment (e’). (f) Inner membrane (IM) potential of UPEC after RF or RMT treatment at 46 °C. (g) Schematic diagrams showing the UPEC membrane and membrane associated electron transport chain in control cells (left) and cells after RMT treatment (right). Outer membranes were damaged and crater-like pits were formed by ROS, heat, and mechanical vibration from NPs after RF application. Consequently, loss of inner membrane potential and dysfunction of membrane associated complexes followed. Eventually, these factors induce bacterial cell death.
Mentions: Recently, it was reported that upon RF exposure, iron oxide magnetic nanoparticles attached to the liposome can deflect and perturb the membrane, acting as mechanical transducers to transfer the energy of radiofrequency to the liposome42. Since MCSNP can closely pack on the bacterial surface (Fig. 2b), it is tempting to hypothesize that the MNP can mechanically perturb the cell membrane under a RF field. This possibility was further investigated by measuring the outer membrane (OM) permeability of bacteria bound to MCSNPs using hydrophobic 1-N-phenylnaphthylamine (NPN) that shows fluorescence when it attaches to the phospholipid layer after passing through the outer membrane. The NPN fluorescence from the RMT samples was 5 fold higher than control (UPEC incubated at 46 °C for 30 min), while the fluorescence from the RF-treated samples was just 3 fold higher than control (Fig. 5a), suggesting a greater loss of the permeability barrier during RMT. To further examine the membrane permeability in detail, bacterial cell surfaces were visualized by AFM after removal of MCSNP using PBS buffer (Fig. 5b–e’). Control UPEC cells incubated at 46 °C without MCSNP, or exposed to RF at 46 °C, showed no noticeable alteration in their surface (XY plane at Fig. 5b–d and Z-axis at Fig. 5b’–d’) and were found to be comparable to the cell surface treated at 25 °C without or with MCSNP (Supplementary Figure S8A,B). However, UPEC strains showed crater type pits in their OM with increased roughness (~10–17 nm deep) under RMT (Fig. 5e–e’). To get an in-depth insight into the bioenergetics of the cells upon perturbation of the OM barrier, the inner membrane (IM) potential (∆ψ) was measured using lipophilic DiSC3(5), a potentiometric fluorescent probe representing the membrane potential by emitting fluorescence when it is released from the membrane upon collapse of the transmembrane potential due to membrane depolarization43. As expected, RF combined with MCSNP drastically lost IM potential compared to RF treatment alone at 46 °C (Fig. 5f). Taken together, these results suggest that membrane-bound MCSNP can damage OM and the IM potential under RF, which causes bacterial death.

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