Gel filled with toxin-absorbing nanosponges cleans up MRSA

SAN DIEGO, May 18 (UPI) -- When it comes to countering MRSA -- the bacteria lurking in hospitals and on the skin of healthcare workers around the world -- smaller is better.

Researchers at the University of California, San Diego have designed tiny sponges that absorb and neutralize the pore-forming toxins that make MRSA so dangerous. But countertops aren't the target for these toxin-absorbing nanosponges, infected flesh is.

In gel form, the tiny sponges were able shrink skin lesions on MRSA-infected mice. Scientists used a hydrogel, a gel made of water and polymers, to hold the nanosponges in place while they got to work disinfecting.

"We combined the strengths of two different materials -- nanosponges and hydrogels -- to create a powerful formulation to treat local bacterial infections," research leader Liangfang Zhang, nanoengineering professor in the Jacobs School of Engineering at UCSD, said in a press release. "Nanosponges alone are difficult to use on local tissues because they diffuse away to other parts of the body very quickly. By integrating the nanosponges into a hydrogel, we can retain them at the site of infection."

In the research, detailed in the latest issue of the journal Advanced Materials, builds on a 2013 study, Zhang and his team demonstrated the ability of the nanosponge to remove MRSA toxins from the bloodstream.

The nanosponge works by disguising itself as a red blood cell, using a red blood cell membrane coating as a mask. Red blood cells are the intended targets of malicious bacteria like methicillin-resistant Staphylococcus aureus (MRSA). The sponges attract and counteract the red blood cell-seeking toxins. The technology can potentially work on all sorts of harmful invaders, including snake venom, E. coli and other antibiotic-resistant bacteria.

"One way to treat these infections is to remove the toxins, which act as a weapon and a defense shield for the bacteria that produce them," said Zhang. "We hypothesize that without the toxins, the bacteria become significantly weakened and exposed, allowing the body's immune system to kill them more easily without the use of drugs."

A sponge-filled gel and injectable sponges could be used in concert to help disinfect both a surface wound and the bloodstream.

"After injecting the nanosponge-hydrogel at the infected spot, we observed that it absorbed the toxins secreted by the bacteria and prevented further damage to the local blood, skin and muscle tissues," said Zhang.