I remember playing with a toy called Wooly Willy. (You can look it up on Wikipedia, which says it was still in production in 2010.) You use a magnetic wand to capture tiny black iron shavings, and deposit them on the picture of a bald man. You can make hair, eyebrows, sideburns, moustache, beard—or just make him look weird and funny which is greatly amusing to a 5-year old boy! Today’s kids are computer-savvy and can pretty much do the same on a computer screen using a mouse and a simple art program. Still, it was very cool to move those iron shavings around as you controlled the magnet to create images.
Imagine if the metal shavings were reduced to very, very small fragments (nanoparticles) that could be used as an imaging contrast agent to help detect and even treat disease. Magnetic resonance imaging is obviously sensitive to magnetized substances, and a particular form of iron, an iron oxide called magnetite, is now being used to produce such particles. When they are coated with special polymers, the result is a fine powder that can be blended with liquid and injected into the body. Certain types of healthy cells take up the particles (which “light up” on imaging) whereas cancer cells do not. On MRI scans, the presence and absence of image enhancement distinguishes the cancer cells from healthy cells. See my article at https://sperlingprostatecenter.com/nanoparticle-enhanced-mri-detects-lymph-node-metastasis-of-prostate-cancer/ for more details.
Such nanoparticles derived from iron and other metals are already being used or tested in the lab or clinical trials for imaging prostate cancer that has spread to lymph nodes, tumors of the brain and other organs, and for diagnosing infection and inflammation. Also, studies on killing cancer by infusing neighbor cells with such nanoparticles and then exposing the area to near-infrared laser (which heats the nanoparticles to lethal temperatures, called photothermal therapy) are under way. I foresee many practical applications of iron and other metal nanoparticles in medicine.
The history of medicine is full of evolutionary examples from an early precursor to a safe and effective technology. While I’m not suggesting that Wooly Willy was such a precursor, it shows how far we’ve come from a simply children’s toy to the movement of magnetized nanoparticles for creating images in the human body that can only add to our diagnostic and treatment resources.