New types of polymers are able to seek out and destroy antibiotic-resistant bacteria, including MRSA (Methicillin-resistant Staphylococcus aureus) in what scientists from IBM and the Institute of Bioengineering and Nanotechnology describe as a "nanomedicine breakthrough". They published their report in Nature Chemistry
Nanomedicine is the medical application of nanotechnology. Nanotechnology, also known as nanotech, is the study of manipulating matter on a molecular or atomic scale. A polymer is any of many natural and synthetic compounds of abnormally high molecular weight - they consist of up to millions of repeated linked units, each a fairly light and simple molecule.
The scientists explain that these nanostructures are attracted to infected cells like a magnet. They home-in on resistant bacteria and destroy them without harming healthy cells - they are selective. The nanostructures break through the cell wall and membrane of the bacterium, something most traditional antibiotics do not do. This breakthrough was achieved by applying principles utilized in semiconductor manufacturing.
The term MRSA (Methicillin-resistant Staphylococcus aureus) is used to describe some strains of the bacteria, Staphylococcus aureus, that are resistant to several antibiotics, including methicillin. Staphylococcus aureus lives on the surface of human skin and inside the nose. Usually, it is harmless, and most carriers have no idea that they have it. It spreads easily from person-to-person with contact.
Staphylococcus aureus becomes a problem if it enters the body through a cut or wound. Most healthy individual's immune systems fight off a Staphylococcus aureus infection and at the most have mild symptoms. However, those with weakened immune systems can develop more serious complications - they can develop boils, abscesses, impetigo, septic-wounds, heart-valve problems and toxic shock syndrome. For those with weakened immune systems, such infections can be life-threatening. The problem with MRSA is that it is resistant to most antibiotics that are normally used effectively to treat Staphylococcus aureus infections.
According to the National Institutes of Health (NIH), USA, MRSA caused nearly 95,000 infections in the USA in 2005 - it was linked to nearly 19,000 hospital stay-related deaths.
MRSA poses two challenges:
- Drug resistance - the microorganism can evolve to resist antibiotics effectively; current treatments do not damage the cell wall and membrane of the bacterium.
- Dosage - in order to kill such infections with traditional antibiotics, the dose has to be so high that healthy red blood cells are also destroyed.
"The number of bacteria in the palm of a hand outnumbers the entire human population. With this discovery we've been able to leverage decades of materials development traditionally used for semiconductor technologies to create an entirely new drug delivery mechanism that could make them more specific and effective."
These biodegradable nanostructures could be administered either by injection or topically (onto the skin). They could be applied to consumer products that touch the skin, such as soaps, hand sanitizers, and deodorants. They could be used to heal wounds, treat TB (tuberculosis) and other lung infections, the authors explain.
Dr. Yiyan Yang, Group Leader, Institute of Bioengineering and Nanotechnology, Singapore, said:
"Using our novel nanostructures, we can offer a viable therapeutic solution for the treatment of MRSA and other infectious diseases. This exciting discovery effectively integrates our capabilities in biomedical sciences and materials research to address key issues in conventional drug delivery."
How do these polymers work?Our immune system is designed to fight off harmful substances. However, for a number of reasons, several conventional antibiotics currently available are either rejected by the body or have poor results against drug-resistant bacteria.
IBM Research and the Institute of Bioengineering and Nanotechnology developed antimicrobial agents that are designed to specifically target an infected area, this allows for the drug to be delivered straight into the bloodstream (systemically).
As soon as the polymers touch water or the human body, they self-assemble into a new polymer structure designed to specifically target the membranes of bacteria based on electrostatic interaction - they break through the cell membrane and walls, making it impossible for the bacteria to develop resistant to these nanoparticles.
The new polymer structures only destroy infected areas, leaving healthy ones, especially red blood cells, alone. Red blood cells transport vital oxygen around the body.
These substances are biodegradable, they do not build up in body organs, rather they are eliminated from the body.
"Biodegradable nanostructures with selective lysis of microbial membranes"
Fredrik Nederberg, Ying Zhang, Jeremy P. K. Tan, Kaijin Xu, Huaying Wang, Chuan Yang, Shujun Gao, Xin Dong Guo, Kazuki Fukushima, Lanjuan Li, James L. Hedrick & Yi-Yan Yang
Nature Chemistry 2011. DOI: 10.1038/nchem.1012
Written by Christian Nordqvist