An intravascular magnetic wire for the high-throughput retrieval of circulating tumour cells in vivo

Technical principle

If approved for use in humans, the magnetic wire (depicted in gray) would be inserted into a vein in the arm (in light pink) and attract floating cancer cells labeled with magnetic nanoparticles (light green and gray) that have come from the tumor (neon green).Credit: Courtesy of Sam Gambhir

The wires that pass through the vein attract special magnetic nanoparticles that are designed to be tumor cells, and if there is a tumor somewhere in the body, the tumor cells may roam in the blood. Since these tumor cells are essentially magnetized, the magnetic wires can draw cells from free-flowing  blood  using the same force that is attached to the refrigerator.

To date, this technology has only been used in pigs. The study found that the technology attracted 10-80 times more tumor cells than existing blood-based cancer detection methods, making  it an  effective  tool for early  detection of disease. The technology can even help doctors assess a patient's  response to a particular cancer treatment: if the treatment is effective, the level of tumor cells in the blood should leave the tumor as the cell dies and then decline as the tumor shrinks.

Currently, the author of the communication, Dr. Sam Gambhir, is focusing on magnetic wire as a method of cancer detection, but its impact may be broader. Gambhir said, "It may also be useful for other diseases, as long as there are target cells or molecules in the blood. For example, if you are examining a bacterial infection, then in any case circulating tumor DNA or rare cells that cause inflammation, magnetic wires and nanoparticles will Helps to enrich the signal and detect disease or infection."

Break with tradition

Cells that shed from the tumor and freely swim in the bloodstream, also known as circulating tumor cells, serve as biomarkers of cancer, indicating the presence of disease.

So why do you need a new way to capture cells in your blood? Isn't a simple blood sample unable to extract the same floating tumor cells?

This is due to the small number of circulating tumor cells. If only regular blood samples are taken, there may be no circulating tumor cells in the test tube. Gambhir said, "It's like looking for a grain of sand in the bathtub, but only a few glasses of water. So the doctor finally said, okay, nothing."

Gambhir said that this is where he sees the magnetic wires producing different effects. The nanoparticles contain antibodies that are locked to circulating tumor cells. Once the suspended tumor cells and nanoparticles are combined, the cells will pinch tiny magnets. When the cell-magnet complex  flows  through  the wires, the magnetic force forces it to deviate from the normal path in the  bloodstream  and adhere to the wires. Then, the lead was taken out of the vein, and the cells were peeled off for analysis.

Currently, Gambhir and his team have not tested the lead in the human body, they need to apply for approval from the FDA, but they have successfully tested the pig in the veins near the pig's ear. This vein is very similar to the vein in the human arm. Compared to the 5 ml blood sample, the magnetic wire extracted cancer cells were 10-80 times more; compared with the commercially available  magnet  wire based  detection method, the line drew 500 to 5000 or more tumor cells.

Gambhir said: "It is estimated that 80 tubes of blood are needed to match the sampling of the wire within 20 minutes. It is impractical to extract 80 tubes of blood from a person. Therefore, I hope this method can enrich the detection ability and let us better understand The extent to which these circulating tumor cells are rare, and the time they exist after the onset of cancer."

Future

Gambhir noted that the technology can also be used to collect genetic information about tumors that are difficult to biopsy, or to provide information about the effectiveness of cancer treatment. Magnetic wires can even develop into a treatment by themselves.

Currently, Gambhir is working on preparing this technology for humans, including the approval of nanoparticles. His laboratory is conducting toxicity studies on mice, paying close attention to what happens with the remaining nanoparticles that are not bound. Experiments have shown that there are no signs of toxicity so far. Gambhir is also working on nanoparticles that have been approved by the FDA and are working to adjust them for use in wires. Once the technology is approved for use in humans, its goal is to develop it into a multi-pronged tool to facilitate the detection,  diagnosis, treatment  and  evaluation  of cancer treatments.