Nanoparticles with pulse laser controlled antibacterial properties

October 26, 2017, Kumamoto University
When gold-coated silver nanoplates are irradiated with a pulsed laser, they change shape into a sphere and release silver ions which produces a strong antibacterial effect. Credit: Dr. Takuro Niidome

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 on the gold-coated (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 -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 have only minor , the effects are significantly increased after pulsed 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.

Explore further: Painting fingernails with silver and gold

More information: Kaung Kyaw et al, Effects of pulsed laser irradiation on gold-coated silver nanoplates and their antibacterial activity, Nanoscale (2017). DOI: 10.1039/c7nr06513b

Related Stories

Painting fingernails with silver and gold

March 29, 2017

Since ancient times, people have used lustrous silver, platinum and gold to make jewelry and other adornments. Researchers have now developed a new way to add the metals to nail polish with minimal additives, resulting in ...

Wiping out bacteria with nanoparticle-cotton fibers

July 4, 2017

Silver has been used as an antimicrobial agent for more than 100 years. Today, silver in the form of nanoparticles is incorporated in such products as plastic food containers, medical materials, and clothing. In textiles, ...

Nanosilver and the future of antibiotics

May 27, 2015

Precious metals like silver and gold have biomedical properties that have been used for centuries, but how do these materials effectively combat the likes of cancer and bacteria without contaminating the patient and the environment?

Antibacterial silver nanoparticles are a blast

May 24, 2010

Writing in the International Journal of Nanoparticles, Rani Pattabi and colleagues at Mangalore University, explain how blasting silver nitrate solution with an electron beam can generate nanoparticles that are more effective ...

Nanoparticles take a bite out of infections

July 11, 2017

Antibiotic-resistant bacteria that colonize surfaces and medical equipment are causing alarming annual rises in the number of patients becoming infected in hospitals and clinics. A KAUST team is working to reduce these numbers ...

Recommended for you

Single-celled architects inspire new nanotechnology

July 16, 2018

Diatoms are tiny, unicellular creatures, inhabiting oceans, lakes, rivers, and soils. Through their respiration, they produce close to a quarter of the oxygen on earth, nearly as much as the world's tropical forests. In addition ...

X-ray triggered nano-bubbles to target cancer

July 16, 2018

Innovative drug filled nano-bubbles, able to be successfully triggered in the body by X-rays, have been developed by researchers, paving the way for a new range of cancer treatments for patients.

Smart window controls light and heat, kills microorganisms

July 13, 2018

A new smart window offers more than just a nice view—it also controls the transmittance of sunlight, heats the interiors of buildings by converting solar radiation into heat, and virtually eliminates E. coli bacteria living ...

Quantum dot white LEDs achieve record efficiency

July 12, 2018

Researchers have demonstrated nanomaterial-based white-light-emitting diodes (LEDs) that exhibit a record luminous efficiency of 105 lumens per watt. Luminous efficiency is a measure of how well a light source uses power ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.