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Nanotechnologies for Cardiac Diagnosis and Treatment

Weighing in at a little less than three-quarters of a pound, the heart has the formidable task of pumping oxygen- and nutrient-rich blood through the 60,000-mile highway of blood vessels to all the tissues of the body. Unfortunately, more than 15 million Americans suffer from coronary artery disease, which occurs when the arteries that carry blood to the heart muscle become narrowed by the buildup of plaque deposits along the arterial walls. This process, known as atherosclerosis, impairs the heart’s ability to pump enough blood through the coronary arteries to provide adequate oxygen and nutrients to the body. As a result, a blood clot can form on top of a plaque, leading to a fatal heart attack.

Although current drugs, devices, and lifestyle changes have significantly reduced the number of deaths from atherosclerosis-related disease, there is still no cure. It is critical, therefore, that more effective heart therapies be developed.

Over next decade, nanotechnology—the science of engineering and controlling matter at the molecular scale to create devices with novel chemical, physical and/or biological properties—has the potential to change how atherosclerosis and other heart diseases are treated.

It is difficult to picture a nanoparticle, as a single nanoparticle is 100 times smaller than a red blood cell. To give an idea of how small that is, it would take eight hundred 100-nanometer particles lined up side by side to match the width of a single human hair. Many of the nanomedicines presently in development for heart disease are composed of nanoparticles smaller than 50 nanometers in size.

Researchers are discovering that there is much to be learned from these minuscule nanoparticles. Recently, a group of Boston researchers used targeted nanoparticle technology to reduce atherosclerosis in an animal model in the first study of its kind. By using biodegradable, nano “drones” to deliver a drug specifically designed to promote healing, they were able to successfully restructure atherosclerotic plaques in a mouse, making the plaques more stable. Bearing in mind that mice don’t get heart attacks, the scientists hypothesize that by remodeling the original plaque environment for humans, they could block plaque rupture and thrombosis, thereby preventing heart attacks and strokes.

The researchers were able to make the nanoparticles in the study latch onto the arterial plaque, releasing a drug that quells inflammation damage. After five weeks of nanomedicine, the atherosclerosis was significantly repaired, and plaques were stabilized, making it less likely for the plaques to block the blood vessels.

The targeted nanomedicines used were nanoengineered to carry an inflammation-resolving drug payload derived from one of the body’s own natural inflammation-resolving proteins, called Annexin A1. About 70 percent of the nanoparticles implanted themselves on the plaques and slowly released their drugs. One thousand times smaller than the tip of a single strand of human hair, the nanomedicines’ size was key in facilitating the accumulation and retention within the plaques.

In another recent study, researchers in Ann Arbor, Michigan used nanoparticles on the hearts of sheep to target and destroy cells that cause cardiac arrhythmias. These erratic heartbeats are caused by malfunctions in the myocyte cells of heart muscle, which normally helps regulate heartbeat. The two treatment options for cardiac arrhythmia are drug therapy and cardiac ablation, a procedure which burns away the malfunctioning cells. Ablation, however, can damage the arteries, which is why scientists are trying to develop a safer and efficacious procedure.

The Michigan group used nanomedicine to target and ablate the sheep’s malfunctioning cardiac myocyte cells. Since the scientists needed nanoparticles small enough to penetrate the tiny pores inside the heart capillaries, yet large enough to carry the light-sensitivity chemical that causes it to be absorbed by the cardiac myocytes, they created a tiny particle barely six nanometers in size.

Low-level, red light was then delivered to the area, destroying only the cells that had absorbed the nanoparticles, while leaving other heart cells unharmed. By using this red light illumination instead of a high-power laser, they were able to develop a far more precise technique that didn’t damage the arteries. The procedure looks much like today’s cardiac ablation, and human trials are scheduled.

The multidisciplinary scientific field of nanotechnology has the potential to revolutionize medicine and the treatment of cardiovascular ailments over the next decade, with doctors deploying armies of tiny robots to deliver drugs precisely where needed for the treatment of atherosclerosis and other lethal heart ailments. Challenges remain, but companies are already creating nanotechnologies that are in various stages of development to help treat, repair—and possibly even prevent—heart attacks and other heart-related ailments.

For more information about Dr. Artzi’s research, please contact Partners HealthCare Innovation by clicking here.