Ratiometric near infrared fluorescence imaging of dopamine with 1D and 2D nanomaterials

Neurotransmitters are released by neuronal cells to exchange information. Resolving their spatiotemporal patterns is crucial to understand chemical neurotransmission. Here, we present a ratiometric sensor for the neurotransmitter dopamine that combines Egyptian blue (CaCuSi₄O₁₀) nanosheets (EB-NS) and single-walled carbon nanotubes (SWCNTs). They both fluoresce in the near infrared (NIR) region, which is beneficial due to their ultra-low background and phototoxicity. (GT)₁₀-DNA-functionalized monochiral (6,5)-SWCNTs increase their fluorescence (1000 nm) in response to dopamine, while EB-NS serve as a stable reference (936 nm). A robust ratiometric imaging scheme is implemented by directing these signals on two different NIR sensitive cameras. Additionally, we demonstrate stability against mechanical perturbations and image dopamine release from differentiated dopaminergic Neuro 2a cells. Therefore, this technique enables robust ratiometric and non-invasive imaging of cellular responses.