S. Shrivastava et al., ACS Nano

Unstickers. Nano-sized grains of silver (black dots) can keep blood platelet cells from bonding together.

So Long Aspirin, Hello Silver

Millions of people around the world are prone to dangerous blood clots. Now researchers have had early success with a new way to prevent them--and the strokes, heart attacks, and pulmonary embolisms they cause. Nano-sized particles of silver can stop sticky blood cells called platelets from clinging together in laboratory strains of mice, the team reports.

Platelets help the body stop bleeding. But if they clump together too much, they can also form clots within the bloodstream. A deep-vein thrombosis, for example, can form in the lower leg and block blood flow. If the clot is not broken up quickly using injections of powerful anticoagulants, it can break loose and cut blood supply to the heart or brain, with fatal consequences. As a result, the nearly 500 million sufferers worldwide of clotting-related disorders--including this reporter--must take daily doses of anticoagulants, which carry dangers of their own, such as spontaneous and uncontrollable internal bleeding.

The key, then, is to find an agent that prevents platelets from sticking together too much without impeding their ability to shunt a bleed. Recent research on silver nanoparticles--tiny grains of the metal less than 1/50,000th the width of a human hair--indicated that they might do the trick. So a biomedical team from Banaras Hindu University in Varanasi, India, began exploring their potential, in cooperation with materials science colleagues at the university and at the International Advanced Research Centre for Powder Metallurgy and New Materials in Balapur, India.

The researchers injected mice with blood genetically engineered to be prone to clotting and then administered the nano-silver. As the team reports online in ACS Nano, the nano-silver particles inhibit the ability of the sticky platelet surface proteins to bind these cells together into aggregates, much like adding sand to adhesive tape reduces its ability to stick. "This helps the nano-silver to keep platelets in an inactive state," says biochemist and co-author Debabrata Dash of Banaras. The nanoparticles were "far more effective" than current therapies, he adds. At the same time, the nanoparticles don't interfere with the other proteins in the blood that help form clots, as do conventional anticoagulants, so the danger of uncontrolled bleeding is reduced.

Dash notes that the nanoparticles appear "to be fairly safe to human beings," but like any other new medical technique, they will have to be studied for potential toxic effects.

Cellular biologist Jonathan Gibbins of the University of Reading in the United Kingdom agrees that caution is warranted. "The work is at a relatively early stage, with key questions such as potential toxicity and mechanisms of action remaining to be addressed," he says. "But this certainly is a new and unexpected dimension to platelet research." Likewise, biochemist Stan Heptinstall of the University of Nottingham in the United Kingdom cautions that the research is "at the very beginning." The key issue, he says, is whether the nano-silver will compromise the body's important blood-clotting functions in humans.

Posted in Plants & Animals, Health