Teams of researchers at opposite ends of the country have recently developed an improved system to deliver chemotherapy drugs to attack malignant cells. Scientists at both the Massachusetts Institute of Technology and the University of California at Sand Diego have devised a method involving microscopic machines known as nanoparticles. Although cancer researchers have used nanoparticles for several years to deliver chemotherapy treatments, this new method employs an added layer of accuracy.
While some cancer-fighting efforts with nanoparticles involve a single nanoparticle, the cooperative effort at MIT and UCSD involves a two-stage delivery system. The first stage acts as a “scout”, locating the cancerous cells by tracking their protein emissions, which differ from those of health cells. Once the scout particle locates an area of malignant activity, it sends a signal to the second-stage nanoparticles. The second-stage particles deliver the chemotherapy drug and shrink the tumor.
Most methods that use nanoparticles to administer chemotherapy drugs are highly inefficient, with only one percent of the injected medication reaching the target. In tests on laboratory mice, the scientists found that the two-stage system delivered the drugs at 40 times the rate found in most single-stage methods. Geoffrey von Maltzahn, the lead author of the paper on this method, said that the dual-stage method “can improve the efficiency with which (nanoparticles) find and treat diseases like cancer.”
One of the keys to the success of the dual-stage system is that the “scout” particles are actually rod-shaped, microscopic gold particles. In addition to its connotations of wealth, gold is also highly conductive to both heat and electricity. When researchers shone a bright light on areas affected by the gold nanoparticles, the gold heated up and damaged the blood vessels around the tumor.
As the tumor began to bleed, the body sent a signal to its blood-clotting agents to create a protein known as fibrin. The second-stage nanoparticles also picked up on that signal and sent the drug to the bleeding tumor. The particles followed the signal deployed the drug to the tumor site. The blood clot closed around the malignant cells and sealed in the drug. This method improved both the accuracy and efficacy of the drug delivery system.
The method has shown great promise in the laboratory, as it improves the concentration of drugs delivered to the tumor site while greatly reducing the side effects associated with conventional chemotherapy treatments. However, much more research and effort will need to be done to see if it can be applied to human patients. One problem could be that the system could create blood clots in other areas of the body away from the tumor. Blood clots in the brain are often the source of strokes, and clots in the heart can cause pulmonary embolism and death.
“If you’re going to trigger coagulation, you want to be very selective, so that you don’t cause damage in other parts of the body,” said Dr. Anil Sood, an oncology specialist at the MD Anderson Cancer Center in Houston.