Faced with apocalyptic warnings over antibiotic resistance, scientists have come up with a new way to tackle MRSA (methicillin-resistant Staphylococcus aureus). They have produced a gel that soaks up toxins released by MRSA bacteria, the most common cause of antimicrobial resistant infections. It could in future be placed on a patient’s skin or wounds to treat infections, or even be left behind during surgery to counter possible infections.
Researchers at the University of California, San Diego, US, created the new biodegradable gel using tiny ‘nanosponges’ (Liangfang Zhang et al, Adv. Mater., doi: 10.1002/adma.201501071).The nanosponge particles are embedded in a biodegradable hydrogel and act as a decoy for a variety of tissue-damaging MRSA toxins that target blood cells; each particle comprises a polymer core coated in red blood cell membranes.
‘The nanosponges just sit there and soak up all the toxins secreted by the bacteria. Uniquely these hydrogels are porous structures and we engineered their pore size so that they allow toxins in but do not allow the nanosponges out,’ explains lead author and nanoengineer Liangfang Zhang. In tests on MRSA-infected mice in the laboratory, the gel was found to reduce the lesion size by over 60% with a single dose of the gel.
When alpha-toxin was added to the nanosponge plus gel, its concentration decreased gradually within the first hour until it was almost halved.
Removing the toxins should allow the immune cells to better fight the bacteria. ‘The nanosponge doesn’t need to know what the toxin looks like. As long as the toxin is attacking red blood cell membranes, it will neutralise them,’ says Zhang. He plans to test the gel out on human patients in the next year or two.
‘This effort to come up with an alternative strategy against MRSA is really important and this way of going about it is pretty unique,’ says material scientist Eric Appel at Massachusetts Institute of Technology. ‘People have been using hydrogels to deliver specific factors that improve tissue regeneration. This new hydrogel-type material [could be] applied during surgery to prevent infection and speed recovery.’
However, ‘to use nanogel as a treatment, future experiments will require the nanogel to be injected or administered after symptoms of infection are already established,’ comments Jodi Lindsay, a bacteriologist at St George’s University of London. ‘This is a more rigorous test of the effectiveness of the treatment. The preliminary data suggest there is still some development of the nanogel approach required in order to increase its effectiveness, or it will need to be co-administered with other treatments.’