Now, a Massachusetts-based research team has developed an implantable diagnostic device that can do just that. The device, which could be inserted at the time of biopsy, is a cylindrical, 5-mm implant containing magnetic nanoparticles coated with target-specific antibodies. It's made of polyethylene, a material that's commonly used in orthopaedic implants.
A semi-permeable polycarbonate membrane allows target molecules to enter the implant, while keeping the magnetic nanoparticles trapped. Once inside the device, the target molecules bind to the nanoparticles and cause them to clump together. That clumping can then be detected using MRI (Biosens.Bioelectron. doi: 10.1016/j.bios.2009.04.010).
The researchers - from Massachusetts Institute of Technology and Harvard-MIT Health Sciences & Technology in Cambridge; and Massachusetts General Hospital and Tufts Medical Center in Boston - successfully used the device to track a tumour marker in mice for one month. They transplanted human tumours into the mice, and then monitored the levels of human chorionic gonadotropin, a hormone produced by the tumour cells.
"What this does is basically take the lab and put it in the patient," said Michael Cima, professor of materials science and engineering at MIT. "This is one of the tools we're going to need if we're going to turn cancer from a death sentence to a manageable disease."
Ultimately, such implants could provide real-time information about whether a tumour is growing or shrinking, and whether it has metastasized or is about to do so. The devices could also be tailored to monitor chemotherapy agents, or measure pH or oxygen levels, which reveal tumour metabolism and therapeutic response.
Cima believes that an implant to test for pH levels could be commercially available within a few years, followed by devices to test for complex chemicals such as hormones and drugs.
• This article first appeared on our sister website, medicalphysicsweb.org.