Tag Archives: biofilm

Eradicating bacteria biofilm with nanocrystals

A January 8, 2021 news item on ScienceDaily announces new work from South Korea’s Pohang University of Science & Technology (POSTECH),

The COVID-19 pandemic is raising fears of new pathogens such as new viruses or drug-resistant bacteria. To this, a Korean research team has recently drawn attention for developing the technology for removing antibiotic-resistant bacteria by controlling the surface texture of nanomaterials.

A joint research team from POSTECH and UNIST [Ulsan National Institute of Science and Technology] has introduced mixed-FeCo-oxide-based surface-textured nanostructures (MTex) as highly efficient magneto-catalytic platform in the international journal Nano Letters. The team consisted of professors In Su Lee and Amit Kumar with Dr. Nitee Kumari of POSTECH’s Department of Chemistry and Professor Yoon-Kyung Cho and Dr. Sumit Kumar of UNIST’s Department of Biomedical Engineering.

Caption: Schematic diagram showing removal of bacterial biofilm via Mtex Credit: POSTECH

A January 8, 2021 POSTECH press release (also on EurkeAlert), which originated the news item, delves further,

First, the researchers synthesized smooth surface nanocrystals in which various metal ions were wrapped in an organic polymer shell and heated them at a very high temperature. While annealing the polymer shell, a high-temperature solid-state chemical reaction induced mixing of other metal ions on the nanocrystal surface, creating a number of few-nm-sized branches and holes on it. This unique surface texture was found to catalyze a chemical reaction that produced reactive oxygen species (ROS) that kills the bacteria. It was also confirmed to be highly magnetic and easily attracted toward the external magnetic field. The team had discovered a synthetic strategy for converting normal nanocrystals without surface features into highly functional mixed-metal-oxide nanocrystals.

The research team named this surface topography – with branches and holes that resembles that of a ploughed field – “MTex.” This unique surface texture has been verified to increase the mobility of nanoparticles to allow efficient penetration into biofilm matrix while showing high activity in generating reactive oxygen species (ROS) that are lethal to bacteria.

This system produces ROS over a broad pH range and can effectively diffuse into the biofilm and kill the embedded bacteria resistant to antibiotics. And since the nanostructures are magnetic, biofilm debris can be scraped out even from the hard-to-reach microchannels.

“This newly developed MTex shows high catalytic activity, distinct from the stable smooth-surface of the conventional spinel forms,” explained Dr. Amit Kumar, one of the corresponding authors of the paper. “This characteristic is very useful in infiltrating biofilms even in small spaces and is effective in killing the bacteria and removing biofilms.”

“This research allows to regulate the surface nanotexturization, which opens up possibilities to augment and control the exposure of active sites,” remarked Professor In Su Lee who led the research. “We anticipate the nanoscale-textured surfaces to contribute significantly in developing a broad array of new enzyme-like properties at the nano-bio interface.”

Here’s a link to and a citation for the paper,

Surface-Textured Mixed-Metal-Oxide Nanocrystals as Efficient Catalysts for ROS Production and Biofilm Eradication by Nitee Kumari, Sumit Kumar, Mamata Karmacharya, Sateesh Dubbu, Taewan Kwon, Varsha Singh, Keun Hwa Chae, Amit Kumar, Yoon-Kyoung Cho, and In Su Lee. Nano Lett. 2021, 21, 1, 279–287 DOI: https://doi.org/10.1021/acs.nanolett.0c03639 Publication Date: December 11, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.

Killer graphene spikes to kill bacteria on medical implants

Implants of all kinds (hip replacements, knee replacements, etc.) seem to be on the rise and along with that an increasing number of infections. A Swedish research team announces a technology that could make implants safer in an April 16, 2018 news item on Nanowerk,

A tiny layer of graphene flakes becomes a deadly weapon and kills bacteria, stopping infections during procedures such as implant surgery. This is the findings of new research from Chalmers University of Technology, Sweden, recently published in the scientific journal Advanced Materials Interfaces (“Vertically Aligned Graphene Coating is Bactericidal and Prevents the Formation of Bacterial Biofilms”).

An April 16, 2018 Chalmers University of Technology press release (also on EurekAlert), which originated the news item, provides more detail about the scope of the problem and the proposed solution (Note: A link has been removed),

Operations for surgical implants, such as hip and knee replacements or dental implants, have increased in recent years. However, in such procedures, there is always a risk of bacterial infection. In the worst case scenario, this can cause the implant to not attach to the skeleton, meaning it must be removed.

Bacteria travel around in fluids, such as blood, looking for a surface to cling on to. Once in place, they start to grow and propagate, forming a protective layer, known as a biofilm.

A research team at Chalmers has now shown that a layer of vertical graphene flakes forms a protective surface that makes it impossible for bacteria to attach. Instead, bacteria are sliced apart by the sharp graphene flakes and killed. Coating implants with a layer of graphene flakes can therefore help protect the patient against infection, eliminate the need for antibiotic treatment, and reduce the risk of implant rejection. The osseointegration – the process by which the bone structure grow to attach the implant – is not disturbed. In fact, the graphene has been shown to benefit the bone cells.

Chalmers University is a leader in the area of graphene research, but the biological applications did not begin to materialise until a few years ago. The researchers saw conflicting results in earlier studies. Some showed that graphene damaged the bacteria, others that they were not affected.

“We discovered that the key parameter is to orient the graphene vertically. If it is horizontal, the bacteria are not harmed” says Ivan Mijakovic, Professor at the Department of Biology and Biological Engineering.

The sharp flakes do not damage human cells. The reason is simple: one bacterium is one micrometer – one thousandth of a millimeter – in diameter, while a human cell is 25 micrometers. So, what constitutes a deadly knife attack for a bacterium, is therefore only a tiny scratch for a human cell.

“Graphene has high potential for health applications. But more research is needed before we can claim it is entirely safe. Among other things, we know that graphene does not degrade easily” says Jie Sun, Associate Professor at the Department of Micro Technology and Nanoscience.

Good bacteria are also killed by the graphene. But that’s not a problem, as the effect is localised and the balance of microflora in the body remains undisturbed.

“We want to prevent bacteria from creating an infection. Otherwise, you may need antibiotics, which could disrupt the balance of normal bacteria and also enhance the risk of antimicrobial resistance by pathogens” says Santosh Pandit, postdoc at Biology and Biological Engineering.

Vertical flakes of graphene are not a new invention, having existed for a few years. But the Chalmers research teams are the first to use the vertical graphene in this way. The next step for the research team will be to test the graphene flakes further, by coating implant surfaces and studying the effect on animal cells.

Chalmers cooperated with Wellspect Healthcare, a company which makes catheters and other medical instruments, in this research. They will now continue with a second study.

Here’s a link to and a citation for the paper,

Vertically Aligned Graphene Coating is Bactericidal and Prevents the Formation of Bacterial Biofilms by Santosh Pandit, Zhejian Cao, Venkata R. S. S. Mokkapati, Emanuele Celauro, Avgust Yurgens, Martin Lovmar, Fredrik Westerlund, Jie Sun, Ivan Mijakovic. Advanced Materials Interfaces Volume5, Issue7 April 9, 2018 Pages 1701331 [sic] https://doi.org/10.1002/admi.201701331 First published [online]: 2 February 2018

This paper is behind a paywall.

Finally, here’s a ‘killer spikes’ video made available by Chalmers University of Technology,

Bacteria is shocked, I tell you, shocked

Casablanca (1942, black and white, Hollywood movie) lovers may recognize the paraphrase of just one of the many famous lines in the movie. However, this ‘shocking’ news has more to do with preventing bacteria from congregating on surfaces according to a Jan. 12, 2014 news item by Alexander Chilton on Azonano (Note: Links have been removed),

Researchers at Rensselaer Polytechnic Institute and Cornell University have devised a new nanoscale surface which uses an electrochemical anodization process in order to prevent the surface attachment of bacteria.

The research published in the Biofouling journal focuses on the formation of nanoscale pores which alter the surface energy and electrical charge of a metal surface. A repulsive force is exerted on the bacterial cells, which prevents the attachment of bacteria and the formation of a biofilm. The size of the nanoscale pores formed can be as small as 15 nanometers.

The application of the anodization process to aluminum created a nanoporous surface, known as alumina. This surface proved effective in preventing the attachment of two popular bacterial species: Listeria monocytogenes and Escherichia coli O157:H7.

Krishna Ramanujan’s Jan. 9, 2015 article for Cornell University’s Chronicle explains why the scientists are excited about the anodization technique,

“It’s probably one of the lowest-cost possibilities to manufacture a nanostructure on a metallic surface,” said Carmen Moraru, associate professor of food science and the paper’s senior author. …

Finding low-cost solutions to limiting bacterial attachments is key, especially in biomedical and food processing applications.  …

Anodized metals could be used to prevent buildups of biofilms – slick communities of bacteria that adhere to surfaces and are tricky to remove – in biomedical clean rooms and in equipment parts that are hard to reach or clean, Moraru said.

There are other strategies for limiting bacterial attachment to surfaces, including chemicals and bactericides, but these have limited applications, especially when it comes to food processing, Moraru said. With food processing, surfaces must meet food safety guidelines and be inert to food that they may contact.

Here’s a link to and a citation for the paper,

Alumina surfaces with nanoscale topography reduce attachment and biofilm formation by Escherichia coli and Listeria spp. by Guoping Feng, Yifan Cheng, Shu-Yi Wang, Lillian C. Hsu, Yazmin Feliz, Diana A. Borca-Tasciuc, Randy W. Worobo, & Carmen I. Moraru. Biofouling: The Journal of Bioadhesion and Biofilm Research Volume 30, Issue 10, 2014 pages 1253-1268 DOI: 10.1080/08927014.2014.976561 Published online: 27 Nov 2014

This article is open access.

Physics and coral skeletons at the nanoscale

Given that today, Oct. 31, 2013, is Hallowe’en, it seems thematically appropriate to be talking about skeletons, in this case, coral skieleton. An Oct. 29, 2013, news item on Nanowerk profiles the research (Note: A link has been removed),

An international team of scientists, led by physicists from the University of York, has shed important new light on coral skeleton formation.

Their investigations (“Microstructural evolution and nanoscale crystallography in scleractinian coral spherulites”), carried out at the nanoscale, provide valuable new information for scientists and environmentalists working to protect and conserve coral from the threats of acidification and rising water temperatures.

The Oct. 29, 2013 University of York (UK) news release, which originated the news item, describes coral and what the scientists were looking for,

As corals grow, they produce limestone – calcium carbonate – skeletons which build up over time into vast reefs. The skeleton’s role is to help the coral’s upper living biofilm to move towards the light and nutrients.

Understanding the calcification mechanism by which these skeletons are formed is becoming increasingly important due to the potential impact of climate change on this process.

The scientists looked at the smallest building blocks that can be identified – a microstructure called spherulites – by making a thin cross-section less than 100 nanometres in thickness of a skeleton crystal. They then used Transmission Electron Microscopy (TEM) to analyse the crystals in minute detail.

The TEM micrographs revealed three distinct regions: randomly orientated granular, porous nanocrystals; partly oriented nanocrystals which were also granular and porous; and densely packed aligned large needle-like crystals.

These different regions could be directly correlated to times of the day – at sunset, granular and porous crystals are formed, but as night falls, the calcification process slows down and there is a switch to long aligned needles.

“It has been suspected for some time that the contrast bands seen in crystals in optical images were daily bands. Through our research we have been able to show what the crystals actually contain and the differences between day and night crystals.” [said corresponding author Renée van de Locht,]

I know coral is important but I didn’t know why (from the news release),

Corresponding author Renée van de Locht, a final-year PhD student with the Department of Physics at the University of York, says, “Coral plays a vital role in a variety of eco-systems and supports around 25 per cent of all marine species. In addition, it protects coastlines from wave erosion and plays a key role in the fisheries and tourism industries. However, the fundamental principles of coral’s skeleton formation are still not fully understood.

While the researchers are concerned about climate change and ocean acidification, there are other agendas being pursued as well (from the news release),

The York researchers are now turning their attention to looking directly at the effects of acidification. Their latest research is looking at five-day old coral larvae and compares a population from a normal seawater environment with another in an acidic environment.

The aim is to investigate the nanoscale impacts of the different environments at an early growth stage to assess how these could affect the whole colony and the bigger reef.

The coral research at York is also part of a much larger project looking at the hard and soft matter interface called the MIB – Interface between Materials and Biology – project. Nature has created materials that combine mineral (hard) and organic (soft) components in a way that provides properties that are extremely well suited to function – for example in bone, egg or mollusc shells. The collaborative project aims to develop a working understanding of how this control is worked out in natural systems, so that the same techniques can be used to develop new materials with specially tailored properties.

Here’s a citation for and a link to the published research paper,

Microstructural evolution and nanoscale crystallography in scleractinian coral spherulites by Renée van de Locht, Andreas Verch, Martin Saunders, Delphine Dissard, Tim Rixen, Aurélie Moya, and Roland Kröger. Journal of Structural Biology, Volume 183, Issue 1, July 2013, Pages 57–65 DOI:10.1016/j.jsb.2013.05.005

The paper is behind a paywall which includes a rental option, as well as, the option of paying for the paper outright. You can also try accessing the paper here at ResearchGate which requires that you register for a free account.