Time-resolved fluorescence spectroscopy of dopamine in the single cells

Dopamine hydrochloric acid salt in aqueous solution was excited at 266 nm Al₂O₃:Ti laser and the sufficient fluorescence emission peaking at 330 nm was detected with a streak camera. The fluorescence decay curve was fitted by 1-exponentional functions, with the lifetime of approximately 0.80 ns. The influence of deep-UV laser excitation on cells is also discussed for the direct observation of dopamine in the living cells. In addition, it is needed to detect the dopamine fluorescence in the living cell sensitively, and separately from emission of other fluorescent species. When instrumental arrangement and time-resolved spectral analysis can make it possible to solve such problems, direct visualization of the secretion process of individual cells will be achieved by the laser-induced native fluorescence imaging microscopy, without using any additional fluorescent probes. This quantitative imaging technique will provide a useful noninvasive approach for the study of dynamic cellular changes and the understanding of the molecular mechanisms of information transporting processes.