By combining the sensing capabilities of nanoscale magnetic relaxation switches (MRS) within multi-reservoir structures, a potentially powerful implantable multiplexed sensor has been developed. MRS are magnetic nanoparticles that decrease the transverse relaxation time (T2) of water in the presence of an analyte.

The switches encased in polydimethylsiloxane (PDMS) devices with polycarbonate membranes (10 nm pores) have demonstrated in vitro sensing of the beta subunit of human chorionic gonadotrophin (hCG-), which is elevated in testicular and ovarian cancer. Devices showed transverse relaxation time (T2) shortening by magnetic resonance imaging (MRI) when incubated in analyte solutions of 0.5 to 5 µg hCG- mL–1.

The decrease in T2 was between 9% and 27% (compared to control devices) after approximately 28 h. This prototype device is an important first step in developing an implantable sensor for detecting soluble cancer biomarkers in vivo. Source : Karen D. Daniel, Grace Y. Kim, Christophoros C. Vassiliou, Farzad Jalali-Yazdi, Robert Langer and Michael J. Cima - RS.C Publishing