Dopamine Imaging in Living Cells and Retina by Surface-Enhanced Raman Scattering Based on Functionalized Gold Nanoparticles.

Retinal dopamine is believed to be involved in the development of myopia, which is projected to affect almost half of the world population's visual health by 2050. Direct visualization of dopamine in the retina with high spatial precision is essential for understanding the biochemical mechanism during the development of myopia. However, there are very few approaches for the direct detection of dopamine in the visual system, particularly in the retina. Here, we report surface-enhanced Raman scattering (SERS)-based dopamine imaging in cells and retinal tissues with high spatial precision. The surface of gold nanoparticles is modified with N-butylboronic acid-2-mercaptoethylamine and 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester), which shows excellent specific reaction with dopamine. The existence of dopamine triggers the aggregation of gold nanoparticles that subsequently form plasmonic hot spots to dramatically increase the Raman signal of dopamine. The as-synthesized SERS nanoprobes have been evaluated and applied for dopamine imaging in living cells and retinal tissues in form-deprivation (FD) myopia guinea pigs, followed by further investigation on localized dopamine levels in the FD-treated mice. The results suggest a declined dopamine level in mice retina after 2-week FD treatment, which is associated with the development of myopia. Our approach will greatly contribute to better understanding the localized dopamine level associated with myopia and its possible treatments. Furthermore, the imaging platform can be utilized to sensing other important small molecules within the biological samples.