An oligonucleotide-based biosensor offers the tantalizing potential of continuous, real-time monitoring of drug dosages in patients.

The lowdown: Personalized medicine promises the right drug, at the right dose, for the right patient, at the right time. Progress is being made on all four fronts, but in terms of dosage most available biosensors can currently only measure drug concentrations at a single time point. Continuous, real-time monitoring offers the possibility of more effectively tailoring dosages to each patient, maximizing efficacy and minimizing toxicity. Brian Scott Ferguson, of the University of California in Santa Barbara, USA, and his colleagues therefore set out to develop a biosensor that can “continuously measure in vivo concentrations of a wide range of circulating biomolecules”. They describe the resulting microfluidic electrochemical detector for in vivo continuous monitoring (MEDIC) in Science Translational Medicine .

The MEDIC device is built around drug-specific aptamer probes tethered to gold electrodes. As blood is drawn through the device, the probes reversibly bind to their target drug and the resulting electrochemical signal provides a drug dosing readout. As a proof of concept, they used probes specific for the anticancer drug doxorubicin and the antibiotic kanamycin to measure drug concentrations in blood drawn continuously from live rats. “The modular architecture of MEDIC means that it can be adapted to a wide range of target molecules simply by exchanging the aptamer probes,” the authors report.

The authors note that by integrating multiple probes into one device, they will be able to simultaneously measure concentrations of the drug and the biomarkers that are indicative of response, facilitating optimal dosing in real time. “Such adaptive dosing technology could also enable the expanded use of drugs with narrow therapeutic indices,” they write.