NEAR-INFRARED SURFACE-ENHANCED RAMAN-SCATTERING (NIR-SERS) OF NEUROTRANSMITTERS IN COLLOIDAL SILVER SOLUTIONS

NIR-SERS spectra are measured for the neurotransmitters dopamine and norepinephrine at concentrations as low as 5 x 10(-9) M in colloidal silver solutions with accumulation times as short as 25 ms. The detection range and acquisition time are on the order of physiologically relevant concentrations and the time scale of neuronal processes, respectively. The spectra are obtained using a CCD detection system, dye laser at 830 nm for excitation, fiber optic probe and high throughput spectrograph. Mixtures containing the two neurotransmitters are used to demonstrate the capability of extracting quantitative information from SERS spectra. Albumin added to the sample up to 0.5% concentration does not show any influence on the SERS spectra of the neurotransmitters in the silver colloidal solutions. The results demonstrate the potential of NIR-SERS in probing dopamine and norepinephrine with high sensitivity and specificity. They also suggest that NIR-SERS from colloidal silver solution can be a powerful tool for the study of neurotransmitters in brain extracts and dialysates.