Scientists studying the applications of nanotechnology in medical care have found that boron nanoparticles show promise in the fight against cancer.

Boron, in its bulk form, is an element that is used to control the rate of reactions in nuclear reactors by absorbing neutrons. Neutrons are uncharged particles that, along with protons (positively charged particles), make up the nucleus of atoms.

When neutrons collide with the nucleus of atoms such as uranium, they cause the uranium atom to fission (split into two other, smaller atoms) and generate energy. Because it can absorb neutrons, boron can be used to stop that reaction.

Two types of boron atoms (called isotopes) occur naturally. The type of boron atom that occurs most frequently, about 80 percent of the time, has 5 protons and 6 neutrons in its nucleus. Because that adds up to 11 neutrons, it is called boron-11.

The boron that naturally occurs the other 20 percent of the time has 5 protons and 5 neutrons and is called boron-10. It’s this isotope that is good at absorbing neutrons. Nuclear theoreticians say that boron-11 is more stable than boron-10 because the neutrons are paired in boron-11 but the fifth neutron in boron-10 is unpaired. Therefore, if a neutron wanders by the unpaired neutron, it grabs hold of it.

Researchers are delivering boron nanoparticles to cancer tumors using targeted drug delivery methods and then irradiating the tumor with neutrons. When boron absorbs a neutron, it splits up and sends out charged particles, called alpha particles, that destroy the cancer cells.

You can’t directly irradiate the tumor with alpha particles because they are short-range particles that wouldn’t be able to penetrate through the body to the tumor. Instead, researchers use the longer range particle, the neutron, which is transformed into the short-range, very destructive alpha particle.

When boron absorbs neutrons it produces destructive alpha particles in a tumor, effectively concentrating the effect of the neutrons and allowing a low dose of neutron to kill the tumor. Although neutrons just pass through most materials, some other atoms in the body absorb neutrons that cause damage to healthy tissue. By keeping the dose of neutrons as low as possible, the damage to healthy tissue is minimized.