Over recent decades, the discovery of fluorescent sensors has been considered to be of high importance in biomedical research, especially in the detection of neurotransmitter agents. Neurotransmitters are chemicals that directly mediate activities in the nervous system, often related to mood or behavior. The need to objectively and simultaneously quantify neurotransmitters online is vital to determining Alzheimer’s, Parkinson’s, depression, and schizophrenia. In conventional techniques of monitoring neurotransmitters, e.g., electrochemical, the methods are often invasive and require extensive analysis, and the results are not real-time. However, recent developments in fluorescent sensors have enabled other methods for the determination of neurotransmitters in different biological samples, such as biofluids and tissue, that are more sensitive, selective, and non-destructive. This article is a review focused on recent advances in fluorescent sensors for neurotransmitter detection and the field application of these sensors in the biomedical sciences.
The Need for Advanced Neurotransmitter Detection Techniques
The human nervous system possesses a certain complex of substances, of which neurotransmitters are the focus of attention. Imbalances in neurotransmitter concentrations cause distinct neurological conditions; therefore, there should be precise measurements of these molecules. The classical techniques for the determination of neurotransmitters, like HPLC and mass spectrometry, though precise, are often slow, expensive, and require a fair amount of sample preparation. In addition, they are not time-dependent, and this is very important, especially since the neurotransmitter release and uptake processes in the brain are time-dependent.
The application of fluorescent sensors can be considered rather prospective for neurotransmitter detection due to their high sensitivity and selectivity, as well as the possibility of working in real time. These sensors are based on the principle of fluorescence: a molecule captures light at one wavelength and radiates it at another wavelength. When designed with specific recognition elements, fluorescent sensors can selectively capture target neurotransmitters, and thereby, the change in fluorescence serves as the basis for the concentration of the neurotransmitter. This makes it possible to monitor the levels of neurotransmitters in living tissues and biofluids in real-time, and this affords an understanding of the pathogenesis of neurological disorders.