Microbes evolved drug resistance almost as soon as we started to attack them with pharmaceuticals. However, the ability of bacteria to defeat almost all of our antibiotics is becoming a bigger problem as the resistance spreads. Fungal infection and emergent viruses, aside drug-resistant bacteria could be the biggest pathogenic threat to global health. Even a mere scratch could kill especially the elderly, the ill, and immuno-compromised patients. Materials science could help address this problem through the development, not of antibiotics, but of antimicrobial substances that can mitigate the problem by improving the way we keep pathogens at bay in the hospital and at the patient's bedside, for instance.

A US team has now developed charged multiblock polymers - thermoplastic elastomers - in which the mid-block has been selectively sulfonated and so is hydrophilic and can swell in water. This and its other properties, the team suggests, endows the polymer with a self-sterilizing capacity that could be used to kill almost all bacteria on a surface within five minutes. The material works against Gram-positive and Gram-negative bacteria. The researchers confess that this is a "surprising response". Fortunately, they can now explain the mode of action as being due to the "dramatic reduction in surface pH level that is remarkably effective against microbes with a typically anionic outer membrane".

The team suggests that their novel antibacterial polymers would have applications in the medical and healthcare environment but might also be useful in biomedical research applications, other areas such as smart textiles, separation membranes, and perhaps even for food packaging. Moreover, the very same materials are just as effective against pathogenic viruses. They point out that eventually the polymers lose their self-sterilizing capacity but this can be recovered through a quick dunk in an acidic solution.

"These polymers constitute a facile, inexpensive, comprehensive, and environmentally benign preventative route by which to combat the worldwide proliferation of drug-resistant microbes," the team reports [Peddinkti, B.S.T. et al., Mater. Horizons (2019); DOI: 10.1039/C9MH00726A]

"Functional block polymers like this are highly versatile - usable as water-treatment media, soft actuators, solar cells and gas-separation membranes - and environmentally benign since they can be readily recycled and re-used," team leader Richard Spontak of North Carolina State University, Raleigh, USA explains. "These features make them particularly attractive for widespread use." He adds that "This work focused on only one polymer series manufactured by Kraton Polymers. We are very eager to see how we can further modify this and other polymers to retain such effective and fast-acting antimicrobial properties while improving other attributes that would be attractive for other applications."