Nanotechnology covers a huge range of disciplines, ranging from developing enhanced night vision contact lenses to building “thirsty” water filtration devices. Drug delivery systems also employ nanotechnology, such as using genetically modified algae to imprison chemotherapy drugs and send them to different parts of the body. Now, scientists have managed to use an electric field to quickly isolate these nanoparticles, allowing them to be removed from laboratory samples of human blood with ease, as reported in the journal Small.

Nanoparticles used for medical purposes, regardless of what they’re made of, are roughly one thousand times smaller than the width of the average human hair. They sometimes serve as medical “backpacks,” tough transportation units for drugs – including chemotherapy treatments – that travel through the blood after being injected into the host. Some are coated in specific antibodies, allowing them to target specific areas; others can be heated up, causing them to incinerate tumorous tissue.

Although some nanoparticles are capable of dissolving in the blood after they’ve reached their target area, many are made of materials that cannot, meaning that eventually they have to be removed. They’re found in the plasma component of the blood, the yellowy-hued substance that holds the red blood cells together in suspension.

Medical nanoparticles are often removed from a diluted blood plasma sample by using a centrifuge to spin them out of it; a targeting chemical is often added to the surface of the nanoparticles to make them more readily identifiable. This method clearly cannot be employed in a medical situation involving a person: The nanoparticles would in this case have to be isolated in a specific part of the person’s circulatory system before being removed along with a large amount of their blood plasma, something that is currently not viable.

Although this new method still requires the removal of blood plasma, it requires no chemical alteration or dilution, and quickly and efficiently removes the nanoparticles with no change to the plasma itself.

^{Image credit: Centrifuges are often used to remove nanoparticles from blood samples. Minerva Studio/Shutterstock}

The plasma is placed into contact with platinum electrodes covered in a hydrogel layer. An alternating electrical current is generated, which temporarily causes the positive and negative changes within the nanoparticles to become imbalanced. This means that the nanoparticles are now attracted towards the electrodes; they travel towards them, while leaving the blood plasma components behind. The plasma is then washed out of the environment.

This attractive force effect – called dielectrophoresis – is not quite the same as electromagnetism. It is only possible because the nanoparticles in this case are made of non-magnetic materials that respond to this type of alternating electrical current, meaning that some types of nanoparticles won’t be able to be retrieved in this way. However, the device used to generate the current is in itself a breakthrough: It is roughly the size of a dime, and can withstand the extremely high salt concentrations present in blood plasma. Most significantly, its actions leaves the plasma completely intact.

“This is the first example of isolating a wide range of nanoparticles out of plasma with a minimum amount of manipulation,” said Stuart Ibsen, a postdoctoral fellow in the Department of NanoEngineering at UC San Diego and first author of the study, in a statement. “We've designed a very versatile technique that can be used to recover nanoparticles in a lot of different processes.”