Optical Fibers Functionalized with Single-Walled Carbon Nanotubes for Flexible Fluorescent Catecholamine Detection

Despite the blockbuster popularity of drugs that act on catecholamine receptors, catecholamine dynamics in human health and disease remain an incomplete picture. Recent advances in fluorescent sensors have enabled unprecedented access to catecholamine dynamics in preclinical animal models, but the requirements of these technologies limit translational value for clinical diagnostics. Here, we present a flexible and convenient tool for fluorescent catecholamine detection by functionalizing optical fibers with single-walled carbon nanotube (SWNT)-based near-infrared catecholamine sensors (nIRCats), a form factor that has potential for more convenient and less invasive clinical translation. We show that these near-infrared functionalized (nIRF) fibers respond to dopamine in a biologically-relevant concentration range (10nM through 1 μM) with a mean ΔF/F0 of 0.022 through 0.411, with no statistically significant effect on signal magnitude after 16-hour exposure to human blood plasma. We further demonstrate the utility of these fibers in as little as 10 μL volumes of clinically relevant biofluids up to 24 weeks after preparation, with a ΔF/F0 of up to 0.059 through 1.127 for 10 nM through 1 μM dopamine. We also introduce a compact, mobile dual-near-infrared fiber photometry rig and demonstrate its success detecting dopamine with 0.005 ΔF/F0 in acute brain slices with nIRF fibers. Together, this fiber-based tool and photometry rig expand the toolbox of catecholamine detection technologies to a broader range of applications.