Electrochemical Investigation of Neurotransmitters for Environmental Toxins and Drug Development

Abstract

Neurotransmitters are signaling molecules released by neurons, essential for neurological and psychological functions. They serve as biomarkers for predicting neurodegenerative disease progression and assessing drug efficacy and toxicity. Comprehensive electrochemical neurotransmitter detection can reveal insights into neuronal transmission and metabolic disruptions from toxicants. However, simultaneous detection and monitoring of multiple neurotransmitters remain challenging for electrochemical biosensors. This dissertation describes the development of electrochemical sensors utilizing enzymatic conversion to study neurochemical dysregulation from environmental toxins and their potential therapies. We characterized 8-channel and 3-channel screen-printed electrode arrays via an in-house developed microclinical analyzer (µCA). These multichannel designs allow simultaneous neurotransmitter detection without crosstalk interference. Enzyme immobilization and polymer deposition on the electrodes ensured sensitive and stable measurements along detection limits appropriate for neurochemical investigation. Additionally, m-phenylenediamine electrodeposition interference was demonstrated to effectively reduce electrochemical interference from the ascorbic acid and dopamine typically found in neuronal systems. Environmental toxins, particularly organophosphate pesticides such as chlorpyrifos (CPF) and its metabolite chlorpyrifos-oxon (CPO), disrupt neurotransmission and cause significant brain damage, raising public health concerns. CPF and CPO impair glutamate neurotransmission and inhibit acetylcholinesterase (AChE). Human iPSC-derived astrocytes were utilized to assess changes in glutamate uptake in response to CPF/CPO exposure. Acute exposure to high toxin concentrations caused marked dysregulation of glutamate uptake. AChE inhibition was confirmed using acetylcholine sensors. Beta-lactam antibiotics, such as ceftriaxone (CEF), showed potential in reducing CPF toxicity and mitigating glutamate uptake inhibition after 100 µM CPF exposure. However, CEF did not facilitate the restoration of AChE activity after acute exposure to CPO. This study highlights the effectiveness of electrochemical biosensing techniques in exploring the neurotoxic effects of environmental toxins on specific cell types and neurochemical pathways.