May 7, 2012
New Research Uses Nanoparticles to Deliver Antibiotics to Beneficial Bacteria
Connie K. Ho for RedOrbit.com
Researchers at the Massachusetts Institute of Technology (MIT) and Brigham and Women´s Hospital, a teaching affiliate of Harvard Medical School, recently released information that they have studied a nanoparticle to help the immune system. The nanoparticle can focus on particular infection sites with specific antibiotics. The study is published in the journal American Chemical Society´s journal ACS Nano. According to Aleks Radovic-Moreno, a MIT graduate student and lead author of the paper, this new method would help maintain the beneficial bacteria found in humans and lessen the side effects of other antibiotics.
The research team first designed the nanoparticle from a polymer capped with polyethylene glycol (PEG), which is normally found in drug delivery. PEG is particularly important as it is nontoxic and can help nanoparticles move through the bloodstream without being noticed by the immune system. The group then designed the nanoparticles to be able to switch their charge depending on their environment. The switch in the nanoparticle was activated by the acidic environment around the bacteria. This was to solve previous problems that researchers have encountered; they would attempt to activate the bacteria with a positive charge, hoping that the bacteria´s negatively charged walls would cling to the, but found that the particles were released from the body by the immune system prior to reaching the bacteria.
Apart from the PEG layer, the nanoparticles also had a pH-sensitive layer of amino acid histidine. When the pH drops from seven to six and increases in acidity, the polyhistidine molecule will gain protons, making the molecules have a positive charge. The nanoparticles will then bind to the bacteria, causing a release of the drug that´s embedded in the core of the particle. The study by the researchers delivered the antibiotic vancomycin, but it could deliver other antibiotics or mix of drugs. The antibiotics that were carried by the nanoparticles were still found to be potent, more so than traditional antibiotics that are used in acidic environments.
Researchers state that the current version of the nanoparticle releases the drugs over a one to two-day period.
“You don´t want just a short burst of drug, because bacteria can recover once the drug is gone. You want an extended release of drug so that bacteria are constantly being hit with high quantities of drug until they´ve been eradicated,” commented Radovic-Moreno in a prepared statement.
The group also hopes that, through further research, these nanoparticles that have high antibiotics will also be able to overcome bacterial resistance.
“When bacteria are drug resistant, it doesn´t mean they stop responding, it means they respond but only at higher concentrations. And the reason you can´t achieve these clinically is because antibiotics are sometimes toxic, or they don´t stay at that site of infection long enough,” remarked Radovic-Moreno in the statement.
In continuing with their research, the team is examining how negatively charged tissue cells and proteins at infection sites will affect the nanoparticles delivery of the antibiotics. They are also studying if the nanoparticles will stay in the pH-sensitive body and, if so, how long it´ll take the particles to reach the target sites.