Nanoengineers at the University of California, San Diego have developed a gel filled with toxin-absorbing nanosponges that could lead to an effective treatment for skin and wound infections caused by MRSA (methicillin-resistant Staphylococcus aureus), an antibiotic-resistant bacteria. Data findings showed that the novel ‘nanosponge-hydrogel’ minimized the growth of skin lesions on mice infected with MRSA, without the use of antibiotics. The researchers recently published their findings in the journal Advanced Materials.
To make the nanosponge-hydrogel, the team mixed nanosponges into a hydrogel, which is a gel made of water and polymers. The hydrogel holds the nanosponges in place so that they can remove toxins at the infected spot. The team explain that nanosponges are nanoparticles that absorb dangerous toxins produced by MRSA, E. coli and other antibiotic-resistant bacteria.
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 the researchers were able to retain them at the site of infection. Since the nanosponge-hydrogel treatment does not involve antibiotics, the team state that it will not be affected by existing bacterial antibiotic resistance or cause the bacteria to develop new resistance.
In previous studies the team saw the nanosponges absorbing harmful bacterial toxins in the bloodstream and drawing them away from their real targets, red blood cells. In the current study the team report that removing bacterial toxins could potentially lead to clearing up antibiotic-resistant bacterial infections. The researchers hypothesize that without the toxins, the bacteria should become significantly weakened and exposed, allowing the body’s immune system to kill them more easily without the use of drugs.
In the current study each nanosponge is coated in a red blood cell membrane. This coating disguises the nanosponges as red blood cells, which are the real targets of the harmful toxins produced by MRSA. By masquerading as red blood cells, the nanosponges attract harmful toxins and remove them from the bloodstream. In order for the nanosponges to remove toxins from a specific spot, such as an infected skin wound. This is where the hydrogel plays a role; it can hold billions of nanosponges per milliliter in one spot. The hydrogel’s pores are also small enough to keep most of the nanosponges from escaping, but big enough so that toxins can easily get inside and attach to the nanosponges.
The data findings showed that the hydrogel was effective at holding the nanosponges in place within the body. Two days after the nanosponge-hydrogel was injected underneath the skin of a mouse, nearly 80 percent of the nanosponges were still found at the injection site. When nanosponges were injected without the hydrogel, only 20 percent of them remained at the injection site after two hours. Most of them diffused to the surrounding tissues.
The researchers surmise that the nanosponge-hydrogel treatment kept down the size of skin lesions caused by MRSA infections. In mice, the skin lesions that were treated with the nanosponge-hydrogel were significantly smaller than those that were left untreated. After injecting the nanosponge-hydrogel at the infected spot, the team observed that it absorbed the toxins secreted by the bacteria and prevented further damage to the local blood, skin and muscle tissues.
The researchers state that the next step after this validation is to pursue clinical trials.