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Published on: November 15, 2012
Lethal puncturing of planktonic Gram-positive and Gram-negative bacteria by magnetically-rotated silica hexapods
Kecheng Quan1, Yu Qin2, Kai Chen2
1College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, PR China; School of Materials Science and Engineering, Peking University, Beijing 100871, PR China.
Abstract:
Planktonic bacterial presence in many industrial and environmental applications and personal health-care products is generally countered using antimicrobials. However, antimicrobial chemicals present an environmental threat, while emerging resistance reduces their efficacy. Suspended bacteria have no defense against mechanical attack. Therefore, we synthesized silica hexapods on an α-Fe2O3 core that can be magnetically-rotated to inflict lethal cell-wall-damage to planktonic Gram-negative and Gram-positive bacteria. Hexapods possessed 600 nm long nano-spikes, composed of SiO2, as shown by FTIR and XPS. Fluorescence staining revealed cell wall damage caused by rotating hexapods. This damage was accompanied by DNA/protein release and bacterial death that increased with increasing rotational frequency up to 500 rpm. Lethal puncturing was more extensive on Gram-negative bacteria than on Gram-positive bacteria, which have a thicker peptidoglycan layer with a higher Young's modulus. Simulations confirmed that cell-wall-puncturing occurs at lower nano-spike penetration levels in the cell walls of Gram-negative bacteria. This approach offers a new way to kill bacteria in suspension, not based on antimicrobial chemicals.
Insights
Researchers developed magnetic silica hexapods to mechanically destroy planktonic bacteria, offering a novel chemical-free antimicrobial strategy. This physical method effectively damages bacterial cell walls, leading to cell death in both Gram-negative and Gram-positive bacteria.
Area of Science:
- Materials Science
- Microbiology
- Nanotechnology
Background:
- Antimicrobial agents face environmental concerns and developing resistance.
- Planktonic bacteria in various applications require effective control methods.
- Current methods often rely on chemical agents with limitations.
Purpose of the Study:
- To develop a novel, non-chemical method for controlling planktonic bacteria.
- To investigate the efficacy of magnetically-actuated silica hexapods for bacterial cell disruption.
- To compare the mechanical damage inflicted on Gram-negative versus Gram-positive bacteria.
Main Methods:
- Synthesis of silica hexapods on an alpha-iron oxide (α-Fe2O3) core.
- Magnetic rotation of hexapods to induce mechanical stress on bacterial cell walls.
- Fluorescence staining to visualize cell wall damage and assess bacterial viability.
- Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) for material characterization.
- Computational simulations to understand cell wall penetration mechanics.
Main Results:
- Silica hexapods with 600 nm nano-spikes were successfully synthesized.
- Rotating hexapods caused significant cell wall damage, DNA/protein release, and bacterial death.
- Bacterial death increased with rotational frequency up to 500 rpm.
- Gram-negative bacteria showed more extensive damage than Gram-positive bacteria due to cell wall structure.
- Simulations confirmed easier cell wall puncturing in Gram-negative bacteria.
Conclusions:
- Magnetically-rotated silica hexapods provide an effective mechanical method for killing planktonic bacteria.
- This approach offers a promising alternative to traditional chemical antimicrobials.
- The differential efficacy against Gram-negative and Gram-positive bacteria is linked to cell wall properties.
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