Self-Assembly of SiO<SUB>2</SUB> Nanoparticles for the Potentiometric Detection of Neurotransmitter Acetylcholine and Its Inhibitor

Abstract

The detection and quantification of neurotransmitter acetylcholine (ACh) are relevant because modifications in the ACh levels constitute a threat to human health. The biological regulator of this neurotransmitter is acetylcholinesterase (AChE), an enzyme that catalyzes the hydrolysis of ACh to choline and acetic acid. However, its activity is inhibited in the presence of organophosphate and carbamate pesticides, compromising the degradation of the neurotransmitter. There has been a growing interest in faster and more sensitive detection systems that include new methods and materials for the determination of the ACh concentration. This paper proposes a potentiometric biosensor for the detection of neurotransmitter ACh and its inhibitors, specifically organophosphate pesticide methamidophos. The biosensor is based on a self-assembled platform formed by poly(allylamine) hydrochloride (PAH) and silicon dioxide nanoparticles (SiO 2 -Np) that contains the immobilized enzyme AChE. First, the responses of the biosensor were investigated for different concentrations of ACh in buffer solutions. After quantifying ACh, the inhibition of AChE in the presence of methamidophos was determined, enabling the quantification of methamidophos expressed as the percentage of enzyme inhibition. The potential advantages of this biosensor include simplicity in building the electrode, possible production on an industrial scale, limited need for qualified personnel to operate the device and low processing cost.

Analyzing Electrochemical Sensing Fundamentals for Health Applications

“…[215] Imbalanced ACh regulation in the brain can cause neuropsychiatric disorders such as schizophrenia, Alzheimer's, Parkinson's, and myasthenia gravis. [215,217] Potentiometric enzymebased detection of ACh has been presented in several literature sources [215,[217][218][219] but the electrode represented in [218] is a better fit with the physiological range but has a high LOD, making it less suitable. The potentiometric ACh sensors listed in Table 5 do not meet the requirements.…”

“…For the enzymatic determination of ACh, various materials have been investigated using potentiometric techniques, such as oxatub [4] arenes (a naphthalene-based macrocycle), a biomimetic-imprinted material (BIM) of MWCNTs and ANI, a self-assembled platform formed by PAH and SiO 2 -Np, and carboxylated SWCNT-TF as a pH electrode. [215,[217][218][219] In addition, a polymeric structure of PANI was employed as a physical support for the composite of MWCNTs and ANI. [215,217] SiO 2 -Np, an insulator, was used to contain the immobilized enzyme AChE.…”

“…[215,217] SiO 2 -Np, an insulator, was used to contain the immobilized enzyme AChE. [218] Meanwhile, carboxylated SWCNT-TFserved as an effective pH sensor. [219] A composite of AChE and ChO was used as a sensing surface with a good electronic conducting intermediary layer of molecularly bonded GO and IL of 1-allyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide (AMIM TFSI) on a GCE for detecting Ch and ACh, respectively, using DPV.…”

Targeted Nanoparticles for Selective Marking of Neuromuscular Junctions and ex Vivo Monitoring of Endogenous Acetylcholine Hydrolysis

“…Thus, ex vivo monitoring of endogenous acetylcholine (ACh), which is the neurotransmitter that triggers contraction of skeletal muscle cells, is a very challenging task. The majority of techniques available from the literature is based on electrochemical or fluorescent enzyme-based assays paired with microdialysis of ACh. − The main limitation of microdialysis is an off-line sample analysis, which results in long sampling interval from 5 to 20 min. ,,− This precludes simultaneous monitoring of dynamic changes in the concentration of endogenous ACh.…”