Imaging of Monoamine Neurotransmitters with Fluorescent Nanoscale Sensors

Cells use biomolecules to convey information. For instance, neurons communicate by releasing chemicals called neurotransmitters, including several monoamines. The information transmitted by neurons is, in part, coded in the type and amount of neurotransmitter released, the spatial distribution of release sites, the frequency of release events, and the diffusion range of the neurotransmitter. Therefore, quantitative information about neurotransmitters at the (sub)cellular level with high spatiotemporal resolution is needed to understand how complex cellular networks function. So far, various analytical methods have been developed and used to detect neurotransmitter secretion from cells. However, each method has limitations with respect to chemical, temporal and spatial resolution. In this review, we focus on emerging methods for optical detection of neurotransmitter release and discuss fluorescent sensors/probes for monoamine neurotransmitters such as dopamine and serotonin. We focus on the latest advances in near infrared fluorescent carbon nanotube-based sensors and engineered fluorescent proteins for monoamine imaging, which provide high spatial and temporal resolution suitable for examining the release of monoamines from cells in cellular networks.