Acetylcholinesterase biosensor for carbamate drugs based on tetrathiafulvalene-tetracyanoquinodimethane/ionic liquid conductive gels

TCNQ and Its Derivatives as Electrode Materials in Electrochemical Investigations-Achievement and Prospects: A Review

7,7',8,8'-tetracyanoquinodimethane (TCNQ) is one of the most widely used effective surface electron acceptors in organic electronics and sensors, which opens up a very interesting field in electrochemical applications. In this review article, we outline the historical context of electrochemically stable selective electrode materials based on TCNQ and its derivatives and their development, their electrochemical characteristics, and the experimental aspects of their electrochemical applications. TCNQ-modified electrodes are characterized by long-term stability, reproducibility, and a low detection limit compared to other sensors; thus, their use can increase determination speed and flexibility and reduce investigation costs. TCNQ and its derivatives can also be successfully combined with other detector materials for cancer-related clinical diagnostic testing. Examples of simple, rapid, and sensitive detection procedures for various analytes are provided. Applications of new electrochemically stable TCNQ-based metal/covalent-organic hybrid frameworks, with exceptionally large surface areas, tunable pore sizes, diverse functionality, and high electrical conductivity, are also presented. As a result, they also offer enormous potential as revolutionary catalysts, drug carrier systems, and smart materials, as well as for use in gas storage. The use of TCNQ compounds as promising active electrode materials in high-power organic batteries/energy storage devices is discussed. We hope that the information featured in this review will provide readers with a good understanding of the chemistry of TCNQ and, more importantly, help to find good ways to prepare new micro-/nanoelectrode materials for rational sensor design.

Electrochemical Acetylcholinesterase Sensors for Anti-Alzheimer's Disease Drug Determination

Neurodegenerative diseases and Alzheimer's disease (AD), as one of the most common causes of dementia, result in progressive losses of cholinergic neurons and a reduction in the presynaptic markers of the cholinergic system. These consequences can be compensated by the inhibition of acetylcholinesterase (AChE) followed by a decrease in the rate of acetylcholine hydrolysis. For this reason, anticholinesterase drugs with reversible inhibition effects are applied for the administration of neurodegenerative diseases. Their overdosage, variation in efficiency and recommendation of an individual daily dose require simple and reliable measurement devices capable of the assessment of the drug concentration in biological fluids and medications. In this review, the performance of electrochemical biosensors utilizing immobilized cholinesterases is considered to show their advantages and drawbacks in the determination of anticholinesterase drugs. In addition, common drugs applied in treating neurodegenerative diseases are briefly characterized. The immobilization of enzymes, nature of the signal recorded and its dependence on the transducer modification are considered and the analytical characteristics of appropriate biosensors are summarized for donepezil, huperzine A, rivastigmine, eserine and galantamine as common anti-dementia drugs. Finally, the prospects for the application of AChE-based biosensors in clinical practice are discussed.

Recent Advantages of Mediator Based Chemically Modified Electrodes; Powerful Approach in Electroanalytical Chemistry

Background:

Modified electrodes have advanced from the initial studies aimed at understanding electron transfer in films to applications in areas such as energy production and analytical chemistry. This review emphasizes the major classes of modified electrodes with mediators that are being explored for improving analytical methodology. Chemically modified electrodes (CMEs) have been widely used to counter the problems of poor sensitivity and selectivity faced in bare electrodes. We have briefly reviewed the organometallic and organic mediators that have been extensively employed to engineer adapted electrode surfaces for the detection of different compounds. Also, the characteristics of the materials that improve the electrocatalytic activity of the modified surfaces are discussed.

Objective:

Improvement and promotion of pragmatic CMEs have generated a diversity of novel and probable strong detection prospects for electroanalysis. While the capability of handling the chemical nature of the electrode/solution interface accurately and creatively increases , it is predictable that different mediators-based CMEs could be developed with electrocatalytic activity and completely new applications be advanced.

Development of MIF/IL-1β biosensors for discovery of critical quality attributes and potential allergic rhinitis targets from clinical real-world data by intelligent algorithm coupled with in vitro and vivo mechanism validation

There are still huge challenges from clinical real-world data to accurate targets and critical quality attributes (CQAs) for effective treatment of allergic rhinitis (AR). Here, we present a novel integrated strategy that biosensors and intelligent algorithms were used to angle AR targets and CQAs from clinical real world. Firstly, bagging and boosting partial least squares discrimination analysis (PLS-DA) and Monte-Carlo sampling were proposed to screen accurate AR targets. Macrophage migration inhibitory factor (MIF) and Interleukin-1beta (IL-1β) potential targets were obtained based on large-scale analysis of one thousand proteins and in-depth precise screening of seventy proteins. Furthermore, high electron mobility transistor (HEMT) biosensors were fabricated and successfully modified by MIF and IL-1β potential targets with a low detection concentration as 1 pM and quantitative range from 1 pM to 10 nM. Surprisingly, through MIF/IL-1β biosensors, we angled 5-O-methylvisammioside, amygdalin, and cimicifugoside three CQAs. The strong interaction was discovered among three CQAs and MIF/IL-1β biosensors with almost all K_D up to 10^-11 M. Finally, interaction among three CQAs and MIF/IL-1β biosensors were evaluated by in vitro and vivo experiments. In this paper, two critical potential targets and three effective CQAs for AR treatment were discovered and validated by biosensor and advanced algorithms. It provides a superior integrated idea for angling critical targets and CQAs from clinical real-world data by biosensors and informatics.

A sensitive fluorescence assay of organophosphorus pesticides using acetylcholinesterase and copper-catalyzed click chemistry

Organophosphorus pesticides (OPs) are widely used in agricultural fields, but exhibit high toxicity to human beings. A sensitive fluorescence assay for organophosphorus pesticides was developed using the inhibition of acetylcholinesterase (AChE) activity and the copper-catalyzed click chemical reaction. In the click reaction, two hybridized DNA probes can be ligated with copper ions, inducing a fluorescence quenching during the strand displacement reaction. AChE can hydrolyze acetylthiocholine (ATCh) to form thiocholine (TCh) which contains a thiol group. TCh will react with copper ions, blocking the click reaction and a high fluorescence signal is observed. But in the presence of OPs, the activity of AChE is inhibited, releasing a high concentration of copper ions that catalyze the click chemical reaction and resulting in decreased fluorescence signals. Taking advantage of the copper-mediated signal amplification effect, the sensitivity was improved. This assay has also been applied to detect OPs in river water samples with satisfactory results, which demonstrates that the method has great potential for practical applications in environmental protection and food safety fields.

Biosensors in Drug Discovery and Drug Analysis

Background:

The determination of drugs in pharmaceutical formulations and human biologic fluids is important for pharmaceutical and medical sciences. Successful analysis requires low sensitivity, high selectivity and minimum interference effects. Current analytical methods can detect drugs at very low levels but these methods require long sample preparation steps, extraction prior to analysis, highly trained technical staff and high-cost instruments. Biosensors offer several advantages such as short analysis time, high sensitivity, real-time analysis, low-cost instruments, and short pretreatment steps over traditional techniques. Biosensors allow quantification not only of the active component in pharmaceutical formulations, but also the degradation products and metabolites in biological fluids. The present review gives comprehensive information on the application of biosensors for drug discovery and analysis. Moreover, this review focuses on the fabrication of these biosensors.

Methods:

Biosensors can be classified as the utilized bioreceptor and the signal transduction mechanism. The classification based on signal transductions includes electrochemical optical, thermal or acoustic. Electrochemical and optic transducers are mostly utilized transducers used for drug analysis. There are many biological recognition elements, such as enzymes, antibodies, cells that have been used in fabricating of biosensors. Aptamers and antibodies are the most widely used recognition elements for the screening of the drugs. Electrochemical sensors and biosensors have several advantages such as low detection limits, a wide linear response range, good stability and reproducibility. Optical biosensors have several advantages such as direct, real-time and label-free detection of many biological and chemical substances, high specificity, sensitivity, small size and low cost. Modified electrodes enhance sensitivity of the electrodes to develop a new biosensor with desired features. Chemically modified electrodes have gained attention in drug analysis owing to low background current, wide potential window range, simple surface renewal, low detection limit and low cost. Modified electrodes produced by modifying of a solid surface electrode via different materials (carbonaceous materials, metal nanoparticles, polymer, biomolecules) immobilization. Recent advances in nanotechnology offer opportunities to design and construct biosensors. Unique features of nanomaterials provide many advantages in the fabrication of biosensors. Nanomaterials have controllable chemical structures, large surface to volume ratios, functional groups on their surface. To develop proteininorganic hybrid nanomaterials, four preparation methods have been used. These methods are immobilization, conjugation, crosslinking and self-assembly. In the present manuscript, applications of different biosensors, fabricated by using several materials, for drug analysis are reviewed. The biosensing strategies are investigated and discussed in detail.

Results:

Several analytical techniques such as chromatography, spectroscopy, radiometry, immunoassays and electrochemistry have been used for drug analysis and quantification. Methods based on chromatography require timeconsuming procedure, long sample-preparation steps, expensive instruments and trained staff. Compared to chromatographic methods, immunoassays have simple protocols and lower cost. Electrochemical measurements have many advantages over traditional chemical analyses and give information about drug quantity, metabolic fate of drugs, and pharmacological activity. Moreover, the electroanalytical methods are useful to determine drugs sensitively and selectivity. Additionally, these methods decrease analysis cost and require low-cost instruments and simple sample pretreatment steps.

Conclusion:

In recent years, drug analyses are performed using traditional techniques. These techniques have a good detection limit, but they have some limitations such as long analysis time, expensive device and experienced personnel requirement. Increased demand for practical and low-cost analytical techniques biosensor has gained interest for drug determinations in medical sciences. Biosensors are unique and successful devices when compared to traditional techniques. For drug determination, different electrode modification materials and different biorecognition elements are used for biosensor construction. Several biosensor construction strategies have been developed to enhance the biosensor performance. With the considerable progress in electrode surface modification, promotes the selectivity of the biosensor, decreases the production cost and provides miniaturization. In the next years, advances in technology will provide low cost, sensitive, selective biosensors for drug analysis in drug formulations and biological samples.

A highly sensitive and low-background fluorescence assay for pesticides residues based on hybridization chain reaction amplification assisted by magnetic separation

Due to the concern over food safety, it is important to detect the pesticides residues in agricultural products. Here, a highly sensitive and low background fluorescent strategy for the detection of pesticides residues has been developed. The fluorescence intensity of N-methyl mesoporphyrin IX (NMM) binding G-quadruplex could be turn off because of inhibiting effect of the pesticides on the acetylcholinesterase (AChE) activity. For that, four single-stranded DNAs (named linker, trigger, H1 and H2, respectively) are rational designed and T-Hg-T mismatches duplex DNAs as a recognizer combined with the separation of magnetic beads. The design of hybridization chain reaction (HCR) amplification strategy assisted by magnetic separation has been adopted to improve the detection sensitivity. In the presence of pesticides, the amount of the thiol group generated by hydrolysis reaction of acetylcholine (ACh) is reduced, lead to release of less trigger DNA. Therefor subsequent HCR process is retarded with decreased fluorescence intensity. The reduced fluorescence intensity has a quantitative relationship with the pesticide concentration. The limit of detection of chlorpyrifos was estimated to be 2.0 ng ml-1. It has been applied to detect the pesticides residues in real samples.

Recent Advances in Electrochemical Biosensors Based on Enzyme Inhibition for Clinical and Pharmaceutical Applications

A large number of enzyme inhibitors are used as drugs to treat several diseases such as gout, diabetes, AIDS, depression, Parkinson's and Alzheimer's diseases. Electrochemical biosensors based on enzyme inhibition are useful devices for an easy, fast and environment friendly monitoring of inhibitors like drugs. In the last decades, electrochemical biosensors have shown great potentials in the detection of different drugs like neostigmine, ketoconazole, donepezil, allopurinol and many others. They attracted increasing attention due to the advantage of being high sensitive and accurate analytical tools, able to reach low detection limits and the possibility to be performed on real samples. This review will spotlight the research conducted in the past 10 years (2007-2017) on inhibition based enzymatic electrochemical biosensors for the analysis of different drugs. New assays based on novel bio-devices will be debated. Moreover, the exploration of the recent graphical approach in diagnosis of reversible and irreversible inhibition mechanism will be discussed. The accurate and the fast diagnosis of inhibition type will help researchers in further drug design improvements and the identification of new molecules that will serve as new enzyme targets.

Glassy carbon electrode modified with 7,7,8,8-tetracyanoquinodimethane and graphene oxide triggered a synergistic effect: Low-potential amperometric detection of reduced glutathione

A sensitive electrochemical sensor based on the synergistic effect of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and graphene oxide (GO) for low-potential amperometric detection of reduced glutathione (GSH) in pH 7.2 phosphate buffer solution (PBS) has been reported. This is the first time that the combination of GO and TCNQ have been successfully employed to construct an electrochemical sensor for the detection of glutathione. The surface of the glassy carbon electrode (GCE) was modified by a drop casting using TCNQ and GO. Cyclic voltammetric measurements showed that TCNQ and GO triggered a synergistic effect and exhibited an unexpected electrocatalytic activity towards GSH oxidation, compared to GCE modified with only GO, TCNQ or TCNQ/electrochemically reduced GO. Three oxidation waves for GSH were found at -0.05, 0.1 and 0.5V, respectively. Amperometric techniques were employed to detect GSH sensitively using a GCE modified with TCNQ/GO at -0.05V. The electrochemical sensor showed a wide linear range from 0.25 to 124.3μM and 124.3μM to 1.67mM with a limit of detection of 0.15μM. The electroanalytical sensor was successfully applied towards the detection of GSH in an eye drop solution.

Acetylcholinesterase biosensor based on the mesoporous carbon/ferroferric oxide modified electrode for detecting organophosphorus pesticides

In this paper a biosensor modified by ordered mesoporous carbon–chitosan (OMC–CS)/ferroferric oxide–chitosan (Fe₃O₄–CS) was developed on the surface of screen-printed carbon electrodes (SPCEs).

Electrochemical pesticide sensor based on Langmuir–Blodgett film of cobalt phthalocyanine-anthraquinone hybrid

A cathode active and selective pesticide electrochemical sensor based on Langmuir–Blodgett (LB) film of cobalt phthalocyanine-anthraquinone hybrid (CoPc-AQ) was constructed for the first time in this study. Cobalt-based, Pc ring-based, and anthraquinone-based reduction processes of CoPc-AQ indicated suitability of the complex as a possible electrochemical catalyst and sensor for detection of target species. LB film of CoPc-AQ on ITO (ITO/CoPc-AQ electrode) was titrated with eserine and carbofuran pesticides and interaction of the electrode with these pesticides was tested with square wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS), and double potential step chronocoulometry (DPSCC) techniques. ITO/CoPc-AQ electrode selectively sensed carbofuran and eserine pesticides. While ITO/CoPc-AQ electrode senses carbofuran with the voltammetric responses recorded at anodic potentials (1.20 V), eserine sensing affected antraquinone based reduction peaks recorded at cathodic potentials (-0.80 V). Modification of ITO/CoPc-AQ electrode with nano-platinum and nano-gold particles (ITO/CoPc-AQ-n Pt and ITO/CoPc-AQ-n Au ) increased the sensitivity of the electrode. All basic sensor parameters of modified electrodes were derived with different measurement techniques and compared with each other. The lowest detection limit (2.30 × 10-9 M) was recorded with EIS techniques on ITO/CoPc-AQ-n Pt electrode for sensing of eserine.

Implantable (Bio)sensors as new tools for wireless monitoring of brain neurochemistry in real time

Implantable electrochemical microsensors are characterized by high sensitivity, while amperometric biosensors are very selective in virtue of the biological detecting element. Each sensor, specific for every neurochemical species, is a miniaturized high-technology device resulting from the combination of several factors: electrode material, shielding polymers, applied electrochemical technique, and in the case of biosensors, biological sensing material, stabilizers, and entrapping chemical nets. In this paper, we summarize the available technology for the in vivo electrochemical monitoring of neurotransmitters (dopamine, norepinephrine, serotonin, acetylcholine, and glutamate), bioenergetic substrates (glucose, lactate, and oxygen), neuromodulators (ascorbic acid and nitric oxide), and exogenous molecules such as ethanol. We also describe the most represented biotelemetric technologies in order to wirelessly transmit the signals of the above-listed neurochemicals. Implantable (Bio)sensors, integrated into miniaturized telemetry systems, represent a new generation of analytical tools that could be used for studying the brain’s physiology and pathophysiology and the effects of different drugs (or toxic chemicals such as ethanol) on neurochemical systems.