Detecting Cancer By Levitating Cells

Scientists use magnetic levitation as a means of sorting cells and are able to differentiate between white blood cells, red blood cells and various types of cancers. The method, which is relatively straightforward and scalable, could offer incredible value to researchers and clinicians. Led by Utkan Demirci, a bioengineer at Stanford University, the results were reported this week in the Proceedings of the National Academy of Sciences.

Human blood cells: this electron microscope image shows disc-shaped red blood cells and spiky white blood cells. From the National Cancer Institute.Human blood cells: this electron microscope image shows disc-shaped red blood cells and spiky white blood cells. From the National Cancer Institute.

Magnetic levitation as a means of characterizing materials is not a new technology. Food scientists have used it to study the density of liquids in evaluating the sugar content of a soft drink of the alcohol percentage of a cocktail, for example. It works because everything has a magnetic susceptibility – that is, everything has some response to a magnetic field. However, the degree of this response scales with the size of the item in question to the point where it is too small to be useful for analyzing individual cells. For many small materials, this problem is circumvented by adding magnetic iron oxide particles to artificially increase the magnetic susceptibility; however, this procedure would be toxic to living cells.

To evade the problem, the team instead concerned themselves with the magnetic properties of the liquid around the cells. Aside from making the small magnetic response of the cells a non-issue, this strategy makes the whole technique more viable and cost-effective by removing the need to manipulate the cells themselves. The researchers passed the cells through a fluid-filled channel located between two magnets and laced the fluid with gadolinium particles. Gadiolinium (Gd) is a magnetic rare-earth metal best known for its use as a contrast agent in MRI scanning. By applying a magnetic field in such a way as to pull the Gd particles downward, a buoyant force is created that pushes the cells upward. Different types of cells then “levitate” in the fluid chamber at different heights depending upon their density relative to the surrounding medium.

There are a number of reasons this cellular accounting process is a true medical breakthrough. For one, the resolution of this method of cell detection is unprecedented due to each type of cell having a unique levitation profile. White blood cells are distinguishable from red blood cells, an important diagnostic test as low white blood cell counts are a sign of proneness to infection. Cancer cells are also easily spotted amongst typical blood cells, but more than that, different types of cancer cells levitate at specific heights. The scientists were able to determine unique density blueprints for breast, esophageal, colorectal, and nonsmall cell lung cancer cell lines. This methodology will also allow for the early detection of cancerous cells as it can pick out individual cancerous cells even at extremely low concentrations (0.0001 g/mL). Finally, this technology is more reliable than many traditional diagnostic tests for cancers. These standard tests rely on binding to particular features on the exterior of a cancerous cell, but often yield false negatives and positives due to the diversity of the cellular surface. Detection by density should be far more reliable.

While cancer remains an ongoing threat for which scientists and clinicians are constantly seeking new treatments and cures, it is equally important that tests enabling early detection be developed. This newly reported research provides the route to a rapid and reliable method of testing for not only cancers, but any number of cellular anomalies, and will almost certainly save lives when it comes to fruition.

Via Science News and PNAS.