A visualization of the nanosponges embedded in hydrogel - (Image by Weiwei Gao, Jacobs School of Engineering, UCSD)

MRSA, or Methicillin-Resistant Staphylococcus Aureus, is the latest antibiotic-resistant bacterial strain to strike fear into the hearts of epidemiologists. The staph infections caused by MRSA are no more virulent than other strains of staph, but the evolved resistance to almost all known antibiotics makes those infections extremely difficult to treat successfully. MRSA has become an unwanted and dangerous complication in hospitals and nursing homes and is increasingly migrating out into more open communities.

Now, researchers at the University of California, San Diego (UCSD) have come up with a new way to fight the bacteria, one that doesn’t rely on antibiotic drugs at all, but on a far older method of fighting disease that has been given a boost by modern science: a cleaning agent that absorbs the toxic cells via a hydrogel populated by nanosponges.

The nanosponges are artificially-engineered nanoparticles made up of lipids, coated with a membrane making them appear as a red blood cell. Red blood cells are the targets that the MRSA bacteria seek; presented with the opportunity, they will be absorbed into the nanosponges and hopefully be drawn away from the actual biological systems of the infected patient.

The nanosponge concept was developed at the University of Bern, in Switzerland, last year. The opportunity to develop a treatment which would not potentially increase the antibiotic resistance of the staph strain was obvious immediately. Other efforts to fight MRSA have only served to strengthen its power, as it evolves to resist ever more powerful antibiotics. But the nanosponges did not directly target the bacteria and so would not give rise to further resistance. Instead, the sponges absorb the toxins emitted by the bacteria, weakening them and allowing the body’s natural immune defenses to attack them without the use of antibiotics.

But there was a problem — the nanosponges, by themselves, would tend to disperse away from infection sites almost as soon as they were applied. They were not staying in the area of the infection long enough to absorb the bacterial toxins in any significant numbers.

The UCSD team found a way to embed the sponges within a hydrogel matrix — a sticky gel made of water and non-toxic polymers. The substance was specially designed to trap the nanosponges while remaining porous enough to allow the toxins to penetrate. The gel could be applied topically to open wound sites infected by the MRSA bacteria, and would cling there until washed away. The gel would hold the concentration of nanosponges directly where they were needed to absorb the MRSA toxins.

Because the mechanism of action doesn’t involve antibiotics, the resistance of the bacteria does not affect the treatment. Instead, it is more akin to cleaning up the infection … one of the oldest ways to fight staph, and one that doesn’t rely on traits which might develop a resistance effect.

Early tests on MRSA-infected mice have proven promising. Researchers say that within 48 hours of hydrogel being injected at the wound sites, 80 percent of the nanospores remained in place and active, absorbing toxins and reducing the size of the skin lesions compared to control subjects.

There's no indication yet of when the nanosponge-infused hydrogel might make it into mainstream medical treatment, but for beleaguered hospitals awash in MRSA, it can't come soon enough.

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