Kevin W. Plaxco

Electrochemical aptamer‐based sensors support the high‐frequency, real‐time monitoring of molecules‐of‐interest in vivo. Achieving this requires methods for correcting the sensor drift seen during in vivo placements. While this correction ensures EAB sensor measurements remain accurate, as drift progresses it reduces the signal‐to‐noise ratio and precision. Here, we show that enzymatic cleavage of the sensor's target‐recognizing DNA aptamer is a major source of this signal loss. To demonstrate this, we deployed a tobramycin‐detecting EAB sensor analog fabricated with the DNase‐resistant “xenonucleic acid” 2’O‐methyl‐RNA in a live rat. In contrast to the sensor employing the equivalent DNA aptamer, the 2’O‐methyl‐RNA aptamer sensor lost very little signal and had improved signal‐to‐noise. We further characterized the EAB sensor drift using unstructured DNA or 2’O‐methyl‐RNA oligonucleotides. While the two devices drift similarly in vitro in whole blood, the in vivo drift of the 2’O‐methyl‐RNA‐employing device is less compared to the DNA‐employing device. Studies of the electron transfer kinetics suggested that the greater drift of the latter sensor arises due to enzymatic DNA degradation. These findings, coupled with advances in the selection of aptamers employing XNA, suggest a means of improving EAB sensor stability when they are used to perform molecular monitoring in the living body.