Imaging Striatal Dopamine Release Using a Non-Genetically Encoded Near-Infrared Fluorescent Catecholamine Nanosensor

Abraham G. Beyene; Kristen Delevich; Jackson Travis Del Bonis-O’Donnell; David J. Piekarski; Wan Chen Lin; A. Wren Thomas; Sarah J. Yang; Polina Kosillo; Darwin Yang; Linda Wilbrecht; Markita P. Landry

For neurotransmitter response screens, we collected the near-infrared fluorescence spectrum from 198 µL aliquots of nanosensor (5 mg/L SWNT concentration) before and after addition of 2 µL of 10 mM solutions of each analyte neurotransmitter (for a 100 µM final analyte concentration in each well of a 96-well plate). All neurotransmitter analytes were purchased from Sigma-Aldrich. Neurotransmitter analytes were incubated for 5 minutes before taking post-analyte fluorescence measurements. Responses were calculated for the integrated fluorescence count as ∆F/F0 = (F-F0)/F0, where F0 is total fluorescence before analyte addition and F is total fluorescence after analyte addition or for peak fluorescence change corresponding to the (9,4) SWNT chirality (~1128 nm center wavelength). All measurements were made in triplicate. Reported results are mean and standard deviations of the triplicate measurements. All nIRCat nanosensor batches were tested for catecholamine responses prior to use for tissue catecholamine imaging. Dopamine receptor drugs were purchased from Tocris (quinpirole and sulpiride), abcam (SCH 23390) and Sigma-Aldrich (haloperidol). nIRCat fluorescence modulation to dopamine receptor drugs were measured after addition of 1 µM drug quantities (final concentration in well) in each well. Post-drug fluorescence spectra were taken after 5minute drug incubation. To measure nIRCat response to dopamine in the presence of drugs, dopamine aliquots were added to each drug-incubated well to obtain 100 µM dopamine, and post-dopamine fluorescence spectra were taken after an additional 5-minute incubation period.