Putting the brakes on blood clots

Whether you get a paper cut or have a bad accident, our bodies respond  with a near-universal command: when bleeding, clot. Within seconds of skin being broken, a cascade of cells and proteins align at precise positions to hold the breach. They form a fine mesh to stop blood flow, identify offensive invaders (splinter or microbe?) and recruit cells to clean up the mess. The operation is swift, precise, and for minor injuries, leaves no trace.

For major wounds and during surgeries though, doctors must use anti-coagulant drugs to stop the clotting process and ensure a free flow of blood. However, once an anti-coagulant is used, the only way to reinitiate the process of clotting is to wait for the drug to run out.

Now, a laser-controlled gold switch could change that wait, as researchers have developed a way to switch blood clotting on and off with the flick of a nanoparticle switch. The switch relies on the ability of paired particles to release two different DNA molecules from their surface depending on the wavelength of laser light used to turn the switch on. When released, one piece of DNA binds to thrombin, a key protein in the clotting cascade, and blocks its activity, preventing coagulation. When the complementary DNA piece is released from the nanoparticle, it acts as an antidote, releasing thrombin to restore clotting.

Prior to this advance, there was no way to restore clotting after an anticoagulant was administered. As Kimberly Hamad-Schifferli, senior author on the study, explained in an MIT news release, “It’s like you have a light bulb, and you can turn it on with the switch just fine, but you can’t turn it off. You have to wait for it to burn out.”

The new method developed in this study could provide doctors and researchers with a more precise way to control where and when blood coagulates during surgery and healing. In the MIT news release, Luke Lee, a professor of bioengineering at the University of California at Berkeley (not an author on the study), elaborates, “It’s really a fascinating idea that you can control blood clotting not just one way but by having two different optical antennae to create two-way control. It’s an innovative and creative way to interface with biological systems.”

Citation: de Puig H, Cifuentes Rius A, Flemister D, Baxamusa SH, Hamad-Schifferli K (2013) Selective Light-Triggered Release of DNA from Gold Nanorods Switches Blood Clotting On and Off. PLoS ONE 8(7): e68511. doi:10.1371/journal.pone.0068511

Image: Red blood cells with gold nanorods (yellow dots) on their surfaces. The blue represents a fixing polymer. credit: Helena de Puig