Silver nanoparticles (AgNPs) are known to have excellent antibacterial properties and are considered by many to be a strong contender in the critical search for an answer to antibiotic-resistant bacteria. They block enzymes and can cause bacteria to have irregularly shaped membranes, producing results ranging from inhibited growth to cell death. However, a collaboration of researchers from Kumamoto University, Keio University, and Dai Nippon Toryo Co., Ltd. in Japan found that AgNPs have a propensity to conglomerate, which results in a reduction of antibacterial attributes. They solved the conglomeration problem by coating the nanoparticles with gold. Unfortunately, this also caused a reduction of the antibacterial effects since the silver was no longer exposed. This prompted the researchers to search for a method to keep the shape of the nanoparticles as well as the antibacterial properties.
Pulsed laser irradiation on the gold-coated silver nanoparticles (Ag@Au NPs) provided a solution to the problem. When Ag@Au NPs are irradiated with a pulse laser, the morphology of the NPs changes from a triangular plate to a spherical shape. This is due to the metals melting from the heat of the laser pulse.
The researchers showed that Ag@Au NPs were about half triangular and half spherical before irradiation but jumped to 94% spherical after irradiation. Furthermore, the silver-to-gold ratio of the pre-irradiation Ag@Au NPs was around 22:1, but the post-irradiation ratio was near 4.5:1.
This was interpreted by the researchers as the generation of defects in the gold-coating which allowed for some of the silver to escape as ions. This is an important aspect of the pulsed laser irradiation process since the release of silver produces the bactericidal effect.
"We have developed a method to activate the antibacterial properties of silver nanoparticles at will," said Professor Takuro Niidome, leader of the research group. "Our experiments have shown that, while non-irradiated gold-coated silver nanoparticles have only minor antibacterial properties, the effects are significantly increased after pulsed laser irradiation.
We hope to develop this technology further as a method of managing bacteria that have developed antibacterial resistance."
The irradiated Ag@Au NPs were highly effective against Escherichia coli, resulting in a 0% colony survival rate. Silver NPs alone were similarly effective, but the Ag@Au NPs had the advantages of being activated as needed and did not tend to clump together like the silver NPs.
This research was posted online in the Royal Society of Chemistry journal Nanoscale on 11 October 2017.
Kyaw, K., Ichimaru, H., Kawagoe, T., Terakawa, M., Miyazawa, Y., Mizoguchi, D., Tsushida, M, Niidome, T. (2017). Effects of pulsed laser irradiation on gold-coated silver nanoplates and their antibacterial activity. Nanoscale. doi:10.1039/c7nr06513b
J. Sanderson | EurekAlert!
Magnetic nano-imaging on a table top
20.04.2018 | Georg-August-Universität Göttingen
New record on squeezing light to one atom: Atomic Lego guides light below one nanometer
20.04.2018 | ICFO-The Institute of Photonic Sciences
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
20.04.2018 | Physics and Astronomy
20.04.2018 | Interdisciplinary Research
20.04.2018 | Physics and Astronomy