Clinical implications and electrochemical biosensing of monoamine neurotransmitters in body fluids, in vitro, in vivo, and ex vivo models.

Monoamine neurotransmitters (MNTs) belong to one of the most important groups of neurotransmitters in the central nervous system. They play crucial role in functioning of cardiovascular, renal, and hormonal systems along with establishing human brain-body integration. Abnormal level of MNT is associated with numerous psychotic (schizophrenia, depression, dementia, etc.) and neurodegenerative diseases (Alzheimer's, Parkinson's, Huntington's disease, etc.), therefore their sensitive and robust detection is of great clinical significance. Electrochemical detection (ECD) techniques have been paving the path in this direction, for more than four decades now. Keeping the immense importance of MNTs in mind, this review has been formulated to describe fundamentals of MNTs followed by their clinical significance in neuroscience. Herein, we have emphasized on the ECD of MNTs, in various matrices reported till date. In order to provide information on ECD of MNTs in clinically comparable systems, we have included a comprehensive discussion on sensor design and its analytical performance towards analyzing MNTs in the in vitro, in vivo, and ex vivo models. An extensive table is also incorporated to provide better understanding of the role of MNTs in various clinical conditions. Furthermore, this review briefly discusses the challenges faced with EC sensing techniques and loopholes present in current research works. Apart from this, three extended tables are also included in this review, to provide an insight into the amount of work done in ECD of MNTs in last ten years (2008-2018). These tables comprehensively discuss sensor fabrication strategies for determining MNTs in various matrices and models along with their mode of detection and analytical performance.