Summary. Our overarching research goal is the development of a minimally invasive, receptor-based
technology able to monitor the concentration of effectively any specific molecule (irrespective of its chemical
reactivity) in the living body. To this end, we have already demonstrated the ability of electrochemical,
aptamer-based (E-AB) sensors to monitor a range of drugs and metabolites in situ in the blood vessels and
brain of awake, freely moving rats with seconds resolution and measurement durations of hours. A potentially
significant limitation of the platform, however, is its reliance on nucleic acid aptamers, the limited chemical
complexity of which will no doubt ultimately restrict the number of targets amenable to detection using the
approach. In response, we propose here to develop the first sensors in this class that instead employ proteins
as their recognition elements. Specifically, we propose two aims that will significantly de-risk the development
of protein-folding-based electrochemical sensors, setting the stage for their development as a powerful new
approach to molecular monitoring. First, we will expand beyond the single, proof-of-principle example (a sensor
fabricated using the FynSH3 domain as our receptor) we have realized to date to sensors against three
additional, clinically important targets (the sepsis-diagnostic cytokine IL-6, the chemotherapeutic and immune
modulator methotrexate, and the immunosuppressant cyclosporine) as evidence that our design strategy is
general. Second, we will adapt these sensors, which we have already shown are capable of multi-hour
performance in undiluted whole blood in vitro, to the more challenging measurement conditions found in vivo. If
successful, the R21-scale project described here will lay the foundation for an R01-level research program that
couples this technology with in vitro and in vivo protein selection to create sensors supporting the continuous,
real time measurement of many clinically important molecules, including narrow-therapeutic-index drugs and
protein biomarkers indicative of the status of many grievous, rapidly progressive diseases.