Nanomaterial-enhanced fluorescence sensors for dopamine neurotransmitters: a photophysical perspective

Neurotransmitters are critical in regulating mood, motivation, reward, and various bodily functions. These are necessary elements for cognitive and physical processes. In addition, neurotransmitters play a crucial role in the electrochemical signaling molecules that are crucial for regulating the proper functioning of the brain. Dysfunction of neurotransmitters is associated with several mental disorders. Consequently, detecting and monitoring neurotransmitters are of utmost importance for neurological diagnosis and treatment. Biosensors play a crucial role in detecting and monitoring neurotransmitters like dopamine (DA). This review examines the fundamental nanomaterials and mechanisms utilized in fluorescent-based DA biosensors, with an emphasis on fluorescence resonance energy transfer (FRET) and photo-induced electron transfer (PET) mechanisms. Carbon dots, gold nanoparticles, quantum dots, graphene, and carbon nanotubes have been widely utilized for FRET- and PET-based DA sensing fluorescent probes, demonstrating high sensitivity and specificity. Beyond these conventional mechanisms, innovative fluorescence strategies such as aggregation-induced emission (AIE), turn-on fluorescent probes, and ratiometric fluorescence approaches have further enhanced dopamine detection. Additionally, advanced fluorescent-based nanomaterials like gold nanoclusters, metal-organic frameworks (MOFs), polymer nanocomposites, and liposome-based sensors have expanded the capabilities of fluorescence biosensing. Various fluorescence spectroscopy and microscopy techniques are discussed. Additionally, this review explores emerging technologies and future advancements in fluorescence-based dopamine sensing, highlighting the role of nanomaterial functionalization in enhancing diagnostic accuracy and real-world applicability.