Near-Infrared Optical Detection of Dopamine Using Xeno Nucleic Acid (XNA) Sensors

Single-walled carbon nanotubes (SWCNTs) emit near-infrared fluorescence that is beneficial for in vitro and in vivo optical sensing. State-of-the-art SWCNT sensors are functionalised with single-stranded DNA (ssDNA) sequences that control the dispersivity, brightness, biocompatibility, and selectivity of the sensor. However, the fluorescence of the ssDNA-functionalized nanotube sensors is sensitive to changes in the local ion concentration. This sensitivity is problematic not only for measurements in complex biofluids, but also for sensing neurotransmitters, whose concentrations are strongly coupled to spatial and temporal ion fluctuations. The fluctuating ion concentrations can therefore interfere with the accurate optical detection of neurotransmitters, thereby limiting the use of ssDNA-SWCNT sensors for detecting and treating neurological diseases.

We present an optical SWCNT dopamine sensor with improved stability towards cation-induced fluorescence changes. The synthetic biology approach presented in this work serves as a complementary means for enhancing nanotube optoelectronic behaviour, unlocking previously unexplored possibilities for developing nano-bioengineered sensors with augmented capabilities.