The nanoparticles are made out of a polymer capped with polyethylene glycol, an often used material which is nontoxic and helps in evading the immune system as long as the nanoparticles have not reached their target. The ingenious part is how the particles target bacteria: at first they have a slight negative charge, another mechanism to avoid being cleared by the immune system. At the site of infection, the environment is a bit more acidic than elsewhere, and this acidity causes the nanoparticles to switch their charge from negative to positive. Bacteria have negatively charged cell walls and thus the nanoparticles form a strong connection with the bacteria’s cell wall.
Next the nanoparticles start releasing their payload, in this study vancomycin, but other antibiotics or combinations of drugs will also be possible. Besides the ability to deliver high dose antibiotics directly to the target site, this approach also has the advantage that it partly mitigates the negative effect of the acidic environment on the effectivity of antibiotics.The drug payload is released over a period of one to two days in order to completely eradicate the bacteria. The research is still in an early stage with the first animal studies being conducted right now, but the mechanisms and early results sound promising. The current study was published last month in ACS Nano.
MIT press release: Target: Drug-resistant bacteria