Saturday, May 5, 2012

Nanoparticles can overcome antibiotic resistance

Antibiotic resistance is one of the biggest threats to mankind in our ongoing fight against bacteria. While we have developed many drugs that are able to kill microbes, they have come up with ways of resistance. Our current arsenal of antibiotics is rapidly being degraded because of bacterial adaptation. Some multi-resistant microbes have become very hard to treat, which makes it necessary to develop new drugs. Scientists from MIT and a subsidiary of Harvard Medical School have found a way to kill bacteria effectively using nanoparticles. Previous studies already showed other molecules we may be able to use.

One of the key aspects of drug therapy is targeting: getting your substance to act where it is required reduces side-effects and increases efficacy. Getting antibiotics to the site of infection will result in more dead bacteria and less harm done to otherwise healthy tissue because of toxicity. This is exactly what the nanostructures developed by MIT and Harvard need to achieve. Their tiny particles can be loaded with antibiotics, whereafter they are led to the infection site. The structures are not hindered by the immune system due to a special coating: normally, the body's protective systems try to destroy everything that is 'foreign', be it bacteria or molecules that are beneficial for our health.
The loaded nanoparticles travel through the bloodstream, and are able to detect a site of infection by assessing acid levels. When bacteria infect tissues, the surroundings become increasingly acidic, which is exactly the trigger needed by the tiny structures to unleash their deadly load. Scientists have built in a 'detector' that switches the molecular charge from positive to negative when the nanoparticle is present in an acidic environment. The change in electrical charge results in decoupling of the antibiotics from the nanostructure, after which it can assert its destructive effect. That means the antibiotics are only unleashed at a site of infection, thereby making its toxic effects much more efficiently distributed.

In their experiments, scientists loaded their nanodevices with vancomycin, a powerful antibiotic frequently used to treat bacteria that are resistant to other forms of antibiotics. They found that the nano-coupled drugs were able to retain their potency, while ordinary antibiotics became less efficacious when dropped into an acidic environment. Another beneficial effect is the fact that the nanodevice slowly releases its drug content over the course of two days, meaning bacteria that survive the initial 'attack' can be killed over time. Higher potency and the ability to deliver higher loads due to targeting means the nanosystem can possibly overcome infections with resistant bacteria. Naturally, it is still necessary to prove that it works in human patients suffering from these kinds of infections.

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