An implantable diagnostic device that senses the local in vivo environment. This device, which could be left behind during biopsy, uses a semi-permeable membrane to contain nanoparticle magnetic relaxation switches. A cell line secreting a model cancer biomarker produced ectopic tumors in mice. Short term applications for this device are numerous, including verification of successful tumor resection. This may represent the first continuous monitoring device for soluble cancer biomarkers in vivo.
The cylindrical, 5-millimeter implant contains magnetic nanoparticles coated with antibodies specific to the target molecules. Target molecules enter the implant through a semipermeable membrane, bind to the particles and cause them to clump together. That clumping can be detected by MRI (magnetic resonance imaging).
The device is made of a polymer called polyethylene, which is commonly used in orthopedic implants. The semipermeable membrane, which allows target molecules to enter but keeps the magnetic nanoparticles trapped inside, is made of polycarbonate, a compound used in many plastics.
Cima said he believes an implant to test for pH levels could be commercially available in a few years, followed by devices to test for complex chemicals such as hormones and drugs.
Photograph of in vivo device (a) and schematic of MRSw aggregation (b). Two populations of MRSw, each functionalized with a different monoclonal antibody for the β-subunit of hCG. Both particle populations must be present for aggregation of the MRSw to occur.