Sponges for Toxins

Sept. 6, 2013

By Medical Discovery News

People reach to sponges for soaking up messes, washing the dishes, and cleaning appliances. But sponges can also clean up toxins – inside the body, no less.

For years, scientists have worked to develop methods to remove toxins that destroy cells and tissues. This has been a challenge due the variety of infectious agents and poisons that produce toxins. Recently, a significant advance using nanosponges could lead to the removal of many life-threatening toxins from the bloodstream. 

Nanosponges, developed by bioengineers at the University of California-San Diego, work much like their name implies – they are designed to absorb specific substances. These nanoparticles can remove toxins produced by bacteria such as the common skin infection Staphylococcus aureus, even the antibiotic-resistant MRSA strain. These bacteria produce something called pore-forming toxins. These toxins attack cells by inserting themselves in the cell membranes, creating holes in the surface of the cell, and allowing cell contents to leak out or large amounts of external water to rush in.

In either case, this causes the cell to die. Significant or rapid loss of cells results in the damage seen during disease processes. Nanosponges work by absorbing dangerous toxins, thereby preventing them from destroying cells. To work at this level, nanosponges must be super small – 85 nanometers in diameter, about 90 times smaller than a red blood cell.  

A major issue with all drugs delivered by the bloodstream is how to prevent the immune system from removing them. Since the immune system’s job is to remove foreign agents, it is a challenge to thwart its attacks long enough for a drug to do its job. Nanosponges can overcome this with a clever technique called cloaking. Just like the enchanted invisibility cloak Harry Potter uses, nanosponges become “invisible” to the immune system by blending in with their surroundings. The nanosponge is coated with pieces of the membranes of red blood cells. This makes them look like smaller versions of red blood cells and not foreign invaders to the immune system. Cloaking is so effective that the nanosponges can still be detected in the blood 72 hours after injection, long enough to remove pore-forming toxins in the blood before the nanosponge is removed by the liver. And since they are much smaller than human cells, it’s safe to use a large dose where nanosponges outnumber red blood cells. 

The pore-forming toxins usually attack red blood cells, but when they attach to a nanosponge in disguise, they are trapped by the nanosponge’s core, which is made of a polymer called poly lactic co-glycolic acid. Each nanosponge can trap about 30 – 900 toxin molecules, depending on the type of toxin. A remarkable 90 percent of animals survived a lethal dose of MRSA toxin when they received nanosponge injections. 

MRSA is just the beginning. With this platform technology, scientists can jump into using nanosponges with other toxins as well, even bee venom. If the clinical trials in humans have similar results, nanosponges could revolutionize the way doctors treat these diseases. 

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