Imprinted electrochemical sensor for dopamine recognition and determination based on a carbon nanotube/polypyrrole film

Electric wiring of bacteria using redox polymers and selective measurement of metabolic activity in the presence of surrounding planktonic bacteria

Non-electroactive bacteria (n-EAB), constituting the majority of known bacteria to date, have been underutilized in electrochemical conversion technologies due to their lack of direct electron transfer to electrodes. In this study, we established an electric wiring between n-EAB (gram-positive Bacillus subtilis and gram-negative Escherichia coli) and an extracellular electrode via a ferrocene-polyethyleneimine-based redox polymer (Fc-PEI). Chronoamperometry recordings indicated that Fc-PEI can transfer intracellular electrons to the extracellular electrode regardless of the molecular organization of PEI (linear or branched) and the membrane structure of bacteria (gram-positive or -negative). As fluorescence staining suggested, Fc-PEI improves the permeability of the bacterial cell membrane, enabling electron carriers in the cell to react with Fc. In addition, experiments with Fc-immobilized electrodes without PEI suggested the existence of an alternative electron transfer pathway from B. subtilis to the extracellular Fc adsorbed onto the cell membrane. Furthermore, we proposed for the first time that the bacteria/Fc-linear PEI modified structure enables selective measurement of immobilized bacterial activity by physically blocking contact between the electrode surface and planktonic cells co-existing in the surrounding media. Such electrodes can be a powerful analytical tool for elucidating the metabolic activities of specific bacteria wired to the electrode even within complex bacterial communities.

Molecularly Imprinted Polypyrrole-Modified Screen-Printed Electrode for Dopamine Determination

This paper introduces a quantitative method for dopamine determination. The method is based on a molecularly imprinted polypyrrole (e-MIP)-modified screen-printed electrode, with differential pulse voltammetry (DPV) as the chosen measurement technique. The dopamine molecules are efficiently entrapped in the polymeric film, creating recognition cavities. A comparison with bare and non-imprinted polypyrrole-modified electrodes clearly demonstrates the superior sensitivity, selectivity, and reproducibility of the e-MIP-based one; indeed, a sensitivity of 0.078 µA µM-1, a detection limit (LOD) of 0.8 µM, a linear range between 0.8 and 45 µM and a dynamic range of up to 350 µM are achieved. The method was successfully tested on fortified synthetic and human urine samples to underline its applicability as a screening method for biomedical tests.

Molecularly Imprinted Polymer-based voltammetric sensor for amino acids/indazole derivatives synthetic cannabinoids detection

BACKGROUND

Synthetic cannabinoids (SCs) are a broad class of illicit drugs that are classified according to the chemical structure of the aromatic core that they present (i.e., indole, imidazole, pyrrole) and their detection is still a challenge, despite their widespread diffusion. The identification of a specific class of SC in complex matrices, such as real samples with a rapid, economic analytical device useable directly in the field, is highly desirable, as it can provide immediate and reliable information that eventually addresses more targeted analyses.

RESULTS

The present paper proposes a Molecularly Imprinted Polymer (MIP)-based voltammetric sensor for the rapid and selective detection of indazole-type SCs. In this context, a polyacrylate-based MIP was used to functionalize a Pt electrode. The MIP composition was optimized through a Design of Experiments approach, and for the sake of safety, a non-psychotropic compound structurally related to the selected SCs was employed as the template in the MIP formulation. A complete characterization of the electrochemical behavior of the selected SCs was performed, and differential pulse voltammetry (DPV) in acetonitrile/lithium perchlorate 0.1 M was the technique applied for their quantification. LOD around 0.01 mM and linearity up to 0.8 mM were found. Comparison with the non-imprinted (NIP) modified and bare electrodes showed better selectivity and reproducibility of the MIP-based sensor. Recovery tests (in the 70-115 % range) were performed on simulated pills and smoking mixtures to test the reliability of the proposed method.

SIGNIFICANCE

The method proposed allows the identification and quantification of indazole-based SCs as a class in complex matrices. Due to the selectivity of the obtained device, no clean-up of the sample before analyses is needed. For the same reason, the interference of cutting substances and natural cannabinoids was negligible.

Electrochemically Synthesized MIP Sensors: Applications in Healthcare Diagnostics

Early-stage detection and diagnosis of diseases is essential to the prompt commencement of treatment regimens, curbing the spread of the disease, and improving human health. Thus, the accurate detection of disease biomarkers through the development of robust, sensitive, and selective diagnostic tools has remained cutting-edge scientific research for decades. Due to their merits of being selective, stable, simple, and having a low preparation cost, molecularly imprinted polymers (MIPs) are increasingly becoming artificial substitutes for natural receptors in the design of state-of-the-art sensing devices. While there are different MIP preparation approaches, electrochemical synthesis presents a unique and outstanding method for chemical sensing applications, allowing the direct formation of the polymer on the transducer as well as simplicity in tuning the film properties, thus accelerating the trend in the design of commercial MIP-based sensors. This review evaluates recent achievements in the applications of electrosynthesized MIP sensors for clinical analysis of disease biomarkers, identifying major trends and highlighting interesting perspectives on the realization of commercial MIP-endowed testing devices for rapid determination of prevailing diseases.

A Review on CNTs-Based Electrochemical Sensors and Biosensors: Unique Properties and Potential Applications

Carbon nanotubes (CNTs), are safe, biocompatible, bioactive, and biodegradable materials, and have sparked a lot of attention due to their unique characteristics in a variety of applications, including medical and dye industries, paper manufacturing and water purification. CNTs also have a strong film-forming potential, permitting them to be widely employed in constructing sensors and biosensors. This review concentrates on the application of CNT-based nanocomposites in the production of electrochemical sensors and biosensors. It emphasizes the synthesis and optimization of CNT-based sensors for a range of applications and outlines the benefits of using CNTs for biomolecule immobilization. In addition, the use of molecularly imprinted polymer (MIP)-CNTs in the production of electrochemical sensors is also discussed. The challenges faced by the current CNTs-based sensors, along with some the future perspectives and their future opportunities, are also briefly explained in this paper.

A review on carbon-based molecularly-imprinted polymers (CBMIP) for detection of hazardous pollutants in aqueous solutions

This article discusses the unique properties and performance of carbon-based molecularly-imprinted polymers (MIPs) for detecting hazardous pollutants in aqueous solutions. Although MIPs have several advantages such as specific recognition sites, selectivity, and stability, they suffer from a series of drawbacks, including loss of conductivity, electrocatalytic activity, and cost, which limit their use in various fields. Carbon-based MIPs, which utilize carbon electrodes, carbon nanoparticles, carbon dots, carbon nanotubes, and graphene substrates, have been the focus of research in recent years to enhance their properties and remove their weaknesses as much as possible. These carbon-based nanomaterials have excellent sensitivity and specificity for molecular identification. As a result, they have been widely used in various applications, such as assessing the environmental, biological, and food samples. This article examines the growth of carbon-based MIPs and their environmental applications.

Tailoring Diffusional Fields in Zwitterion/Dopamine Copolymer Electropolymerized at Carbon Nanowalls for Sensitive Recognition of Neurotransmitters

The importance of neurotransmitter sensing in the diagnosis and treatment of many psychological illnesses and neurodegenerative diseases is non-negotiable. For electrochemical sensors to become widespread and accurate, a long journey must be undertaken for each device, from understanding the materials at the molecular level to real applications in biological fluids. We report a modification of diamondized boron-doped carbon nanowalls (BCNWs) with an electropolymerized polydopamine/polyzwitterion (PDA|PZ) coating revealing tunable mechanical and electrochemical properties. Zwitterions are codeposited with PDA and noncovalently incorporated into a structure. This approach causes a specific separation of the diffusion fields generated by each nanowall during electrochemical reactions, thus increasing the contribution of the steady-state currents in the amperometric response. This phenomenon has a profound effect on the sensing properties, leading to a 4-fold enhancement of the sensitivity (3.1 to 14.3 μA cm^-2 μM^-1) and a 5-fold decrease of the limit of detection (505 to 89 nM) in comparison to the pristine BCNWs. Moreover, as a result of the antifouling capabilities of the incorporated zwitterions, this enhancement is preserved in bovine serum albumin (BSA) with a high protein concentration. The presence of zwitterion facilitates the transport of dopamine in the direction of the electrode by intermolecular interactions such as cation-π and hydrogen bonds. On the other hand, polydopamine units attached to the surface form molecular pockets driven by hydrogen bonds and π-π interactions. As a result, the intermediate state of dopamine-analyte oxidation is stabilized, leading to the enhancement of the sensing properties.

Technology for Rapid Detection of Cyromazine Residues in Fruits and Vegetables: Molecularly Imprinted Electrochemical Sensors

Cyromazine is an insect growth regulator insecticide with high selectivity and is widely used in the production and cultivation of fruits and vegetables. In recent years, incidents of excessive cyromazine residues in food have occurred frequently, and it is urgent to establish an accurate, fast, and convenient method for the detection of cyromazine residues to ensure the safety of edible agricultural products. To achieve rapid detection of cyromazine residues, we prepared a molecularly imprinted electrochemical sensor for the detection of cyromazine residues in agricultural products. Samples of tomato (Lycopersicon esculentum Miller), cowpea (Vigna unguiculata), and water were tested for the recovery rate of cyromazine. The results showed that the concentration of cyromazine showed a good linear relationship with the peak response current of the sensor developed in this study. The lower limit of detection for cyromazine was 0.5 µmol/L, and the sensor also had good reproducibility and interference resistance. This paper can be used as a basis for the study of methods for the detection of cyromazine residues in edible agricultural products.

Development of an Electrochemical Sensor Using a Modified Carbon Paste Electrode with Silver Nanoparticles Capped with Saffron for Monitoring Mephedrone

Mephedrone, also known as 4-methylmethcathinone, is growing into a prominent recreational drug for young people. When it came to detecting mephedrone, limited efforts were made using electrochemical sensors. As a result, this application depicts the fabrication of a new, sensitive, selective, and economical electrochemical sensor capable of detecting mephedrone by using silver nanoparticles capped with saffron produced through electropolymerization to modify carbon paste electrodes (CPEs). Silver nanoparticles (AgNPs) were capped with saffron (AgNPs@Sa) using a green method. AgNPs@Sa were studied using electron scanning microscopy (SEM) and UV-vis spectroscopy. The sensor was evaluated under the optimum condition to determine its analytical features. The results showed that this procedure had a wide linear range, low detection limit and sufficient reproducibility. Furthermore, the sensor posed sufficient stability. Moreover, it was applied in the determination of mephedrone in urine samples, showing the potential applicability of this electrochemical sensor in real sample analysis.

Electrochemically Deposited Molecularly Imprinted Polymer-Based Sensors

This review is dedicated to the development of molecularly imprinted polymers (MIPs) and the application of MIPs in sensor design. MIP-based biological recognition parts can replace receptors or antibodies, which are rather expensive. Conducting polymers show unique properties that are applicable in sensor design. Therefore, MIP-based conducting polymers, including polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene), polyaniline and ortho-phenylenediamine are frequently applied in sensor design. Some other materials that can be molecularly imprinted are also overviewed in this review. Among many imprintable materials conducting polymer, polypyrrole is one of the most suitable for molecular imprinting of various targets ranging from small organics up to rather large proteins. Some attention in this review is dedicated to overview methods applied to design MIP-based sensing structures. Some attention is dedicated to the physicochemical methods applied for the transduction of analytical signals. Expected new trends and horizons in the application of MIP-based structures are also discussed.

Synthesis of POMOFs with 8-fold helix and its composite with carboxyl functionalized SWCNTs for the voltammetric determination of dopamine

Although many satisfactory studies have been developed for biomolecule detection, the complexity of biofluids still poses a major challenge to improve the performance of nanomaterials as electrochemical sensors. Herein, unprecedented polyoxometalate-based metal-organic frameworks (POMOFs) with 8-fold meso-helical feature, [Ag₅(trz)₄]₂[PMo₁₂O₄₀] (PAZ), were synthesized and explored as electrochemical sensors to detect dopamine (DA). To improve the conductivity of PAZ and the binding ability with single-walled carbon nanotubes (SWCNTs), the nanocomposite of carboxyl functionalized SWCNTs (SWCNTs-COOH) with nano-PAZ (NPAZ), NPAZ@SWCNTs-COOH, was fabricated, and transmission electron microscopy (TEM) shows that NPAZ can interact stably and uniformly with SWCNTs-COOH, owing to more defect sites on the surface of SWCNTs-COOH. The electrochemical result of NPAZ@SWCNTs-COOH/GCE towards detecting DA shows that the linear range was from 0.05 to 100 μM with a detection limit (LOD) of 8.6 nM (S/N = 3). A new electrochemical biosensing platform by combining 8-fold helical POMOFs with SWCNTs-COOH was developed for enhancing detection of dopamine for the first time, exhibiting the lowest detection limit to date.

Carbon-Based Quantum Dots for Electrochemical Detection of Monoamine Neurotransmitters-Review

Imbalance in the levels of monoamine neurotransmitters have manifested in severe health issues. Electrochemical sensors have been designed for their determination, with good sensitivity recorded. Carbon-based quantum dots have proven to be an important component of electrochemical sensors due to their high conductivity, low cytotoxicity and opto-electronic properties. The quest for more sensitive electrodes with cheaper materials led to the development of electrochemical sensors based on carbon-based quantum dots for the detection of neurotransmitters. The importance of monoamine neurotransmitters (NTs) and the good electrocatalytic activity of carbon and graphene quantum dots (CQDs and GQDs) make the review of the efforts made in the design of such sensors for monoamine NTs of huge necessity. The differences and the similarities between these two quantum dots are highlighted prior to a discussion of their application in electrochemical sensors over the last ten years. Compared to other monoamine NTs, dopamine (DA) was the most studied with GQDs and CQD-based electrochemical sensors.

Molecularly imprinted sol-gel electrochemical sensor for sildenafil based on a pencil graphite electrode modified by Preyssler heteropolyacid/gold nanoparticles/MWCNT nanocomposite

An electrochemical sensor based on the imprinted sol-gel on pencil graphite electrode (PGE) modified with functionalized multiwalled carbon nanotube (MWCNT), gold nanoparticles (AuNPs), and Preyssler heteropolyacid (PHPA) nanohybrid was fabricated for the determination of trace amounts of sildenafil. The pencil graphite electrode was first deposited by the AuNPs@PHPA-MWCNT nanohybrids, and then, the modified electrode of MIP-sol-gel/AuNPs@PHPA-MWCNTs was prepared by the electrochemical method. The synthesized nanohybrids and prepared modified electrodes were characterized with FE-SEM, FTIR, EDX, XRD, and UV/Vis. Cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry techniques were applied for the electrochemical analysis using the modified electrodes. By measuring the oxidation and reduction currents of the potassium ferricyanide probe, the efficiency of this sensor was evaluated for the detection of sildenafil. The anodic peak current was measured at 0.2 V vs. Ag/AgCl by differential pulse voltammetry in the potential range - 0.1 to 0.5 V (vs. Ag/AgCl). Under the optimum conditions, the current response for the detection of sildenafil was linear in two concentration ranges of 0.1-2 and 2-30 nM and the obtained limit of detection was 0.033 nM. The constructed sensor was used for the measurement of sildenafil in real samples.

A feasible sonochemical approach to synthesize CuO@CeO2 nanomaterial and their enhanced non-enzymatic sensor performance towards neurotransmitter

A nanostructured and high conductive cupric oxide (CuO NPs) with hierarchical CeO₂ sheets-like structure was synthesized by a facile sonochemical approach. Furthermore, CuO/CeO₂ nanostructure is synthesized by high-intensity ultrasonic probe (Ti-horn, 50 kHz and 100 W) at ambient air. Moreover, the synthesized CuO/CeO₂ material was characterized by various analytical techniques including FESEM, EDX, XRD and electrochemical methods. Then, the synthesized CuO/CeO₂ composite was applied for the electrocatalytic detection of dopamine using CV and DPV techniques. In addition, the CuO/CeO₂ modified electrode has good electrocatalytic performance with high linear range from 0.025 to 98.5 µM towards the determination of dopamine drug and high sensitivity of the CuO/CeO₂ modified drug sensor was calculated as 16.34 nM and 4.823 μA·µM^-1·cm^-2, respectively. Moreover, a repeatability, reproducibility and stability of the CuO@CeO₂ mixture modified electrode were analyzed towards the determination of dopamine biomolecule. Interestingly, the real time application of CuO@CeO₂ modified electrode was established in different serum and drug samples.

Molecularly imprinted polymer-based bioelectrical interfaces with intrinsic molecular charges

For enzyme-/antibody-free and label-free biosensing, a molecularly imprinted polymer (MIP)-based membrane with phenylboronic acid (PBA) molecules, which induces the change in the density of molecular charges based on the small biomolecule–PBA diol binding, has been demonstrated to be suitable for the bioelectrical interface of biologically coupled gate field-effect transistor (bio-FET) sensors. MIP-coated gate FET sensors selectively detect various small biomolecules such as glucose, dopamine, sialic acid, and oligosaccharides without using labeled materials. In particular, the well-controlled MIP film by surface-initiated atom transfer radical polymerization (SI-ATRP) contributes to the quantitative analysis of small biomolecule sensing, resulting in potentiometric Langmuir isotherm adsorption analysis by which the parameters such as the binding affinity between small biomolecules and MIP cavities are evaluated. Also, the output electrical signal of even a random MIP-coated gate FET sensor is quantitatively analyzed using the bi-Langmuir adsorption isotherm equation, showing the adsorption mechanism of small biomolecules onto the template-specific MIP membrane. Thus, a platform based on the MIP bioelectrical interface for the bio-FET sensor is suitable for an enzyme-/antibody-free and label-free biosensing system in the fields of clinical diagnostics, drug discovery, the food industry, and environmental research.

A molecularly imprinted polymer (MIP)-based membrane with phenylboronic acid (PBA) molecules, which induces the change in the density of molecular charges, is suitable for the bioelectrical interface of field-effect transistor (FET) sensors.

Recent Advances in Electrochemical and Optical Sensing of Dopamine

Nowadays, several neurological disorders and neurocrine tumours are associated with dopamine (DA) concentrations in various biological fluids. Highly accurate and ultrasensitive detection of DA levels in different biological samples in real-time can change and improve the quality of a patient's life in addition to reducing the treatment cost. Therefore, the design and development of diagnostic tool for in vivo and in vitro monitoring of DA is of considerable clinical and pharmacological importance. In recent decades, a large number of techniques have been established for DA detection, including chromatography coupled to mass spectrometry, spectroscopic approaches, and electrochemical (EC) methods. These methods are effective, but most of them still have some drawbacks such as consuming time, effort, and money. Added to that, sometimes they need complex procedures to obtain good sensitivity and suffer from low selectivity due to interference from other biological species such as uric acid (UA) and ascorbic acid (AA). Advanced materials can offer remarkable opportunities to overcome drawbacks in conventional DA sensors. This review aims to explain challenges related to DA detection using different techniques, and to summarize and highlight recent advancements in materials used and approaches applied for several sensor surface modification for the monitoring of DA. Also, it focuses on the analytical features of the EC and optical-based sensing techniques available.

Preparation and applications of electrochemical chemosensors based on carbon-nanomaterial-modified molecularly imprinted polymers

The past few decades have witnessed a rapid development in electrochemical chemosensors (ECCSs). The integration of carbon nanomaterials (CNMs) and molecularly imprinted polymers (MIPs) has endowed ECCSs with high selectivity and sensitivity toward target detection. Due to the integrated merits of MIPs and CNMs, CNM-modified MIPs as ECCSs have been widely reported and have excellent detection applications. This review systematically summarized the general categories, preparation strategies, and applications of ECCSs based on CNM-modified MIPs. The categories include CNM-modified MIPs often hybridized with various materials and CNM-encapsulated or CNM-combined imprinting silica and polymers on working electrodes or other substrates. The preparation strategies include the polymerization of MIPs on CNM-modified substrates, co-polymerization of MIPs and CNMs on substrates, drop-casting of MIPs on CNM-modified substrates, self-assembly of CNMs/MIP complexes on substrates, and so forth. We discussed the in situ polymerization, electro-polymerization, and engineering structures of CNM-modified MIPs. With regard to potential applications, we elaborated the detection mechanisms, signal transducer modes, target types, and electrochemical sensing of targets in real samples. In addition, this review discussed the present status, challenges, and prospects of CNM-modified MIP-based ECCSs. This comprehensive review is desirable for scientists from broad research fields and can promote the further development of MIP-based functional materials, CNM-based hybrid materials, advanced composites, and hybrid materials.

Carbon Nanotube Chemical Sensors

Carbon nanotubes (CNTs) promise to advance a number of real-world technologies. Of these applications, they are particularly attractive for uses in chemical sensors for environmental and health monitoring. However, chemical sensors based on CNTs are often lacking in selectivity, and the elucidation of their sensing mechanisms remains challenging. This review is a comprehensive description of the parameters that give rise to the sensing capabilities of CNT-based sensors and the application of CNT-based devices in chemical sensing. This review begins with the discussion of the sensing mechanisms in CNT-based devices, the chemical methods of CNT functionalization, architectures of sensors, performance parameters, and theoretical models used to describe CNT sensors. It then discusses the expansive applications of CNT-based sensors to multiple areas including environmental monitoring, food and agriculture applications, biological sensors, and national security. The discussion of each analyte focuses on the strategies used to impart selectivity and the molecular interactions between the selector and the analyte. Finally, the review concludes with a brief outlook over future developments in the field of chemical sensors and their prospects for commercialization.

An Overview of the Recent Progress in the Synthesis and Applications of Carbon Nanotubes

Carbon nanotubes (CNTs) are known as nano-architectured allotropes of carbon, having graphene sheets that are wrapped forming a cylindrical shape. Rolling of graphene sheets in different ways makes CNTs either metals or narrow-band semiconductors. Over the years, researchers have devoted much attention to understanding the intriguing properties CNTs. They exhibit some unusual properties like a high degree of stiffness, a large length-to-diameter ratio, and exceptional resilience, and for this reason, they are used in a variety of applications. These properties can be manipulated by controlling the diameter, chirality, wall nature, and length of CNTs which are in turn, synthesis procedure-dependent. In this review article, various synthesis methods for the production of CNTs are thoroughly elaborated. Several characterization methods are also described in the paper. The applications of CNTs in various technologically important fields are discussed in detail. Finally, future prospects of CNTs are outlined in view of their commercial applications.

An electrodeposited molecularly imprinted quartz crystal microbalance sensor sensitized with AuNPs and rGO material for highly selective and sensitive detection of amantadine

In the present work, a new amantadine (AM) imprinted quartz crystal microbalance (QCM) sensor sensitized by Au nanoparticles (AuNPs) and reduced graphene oxide (rGO) material was fabricated by electrodeposition in the presence of o-aminothiophenol (o-AT) by cyclic voltammetry scanning. AuNPs and graphene, with the advantages of great chemical stability, electrical conductivity, and large surface area, show exceptionally high sensitivity. The results of different modifications of the QCM sensor fabrication process were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy. Under the optimal experimental conditions, the frequency shift of the MIP-QCM sensor showed a linear relationship with the concentration of the AM template in the range of 1.0 × 10⁻⁵ to 1.0 × 10⁻³ mmol L⁻¹ with a limit of detection (LOD) of 5.40 × 10⁻⁶ mmol L⁻¹. The imprinting factor for AM reached 7.1, the selectivity coefficient for the analogues rimantadine (RT), adamantine (AMT) and 1-chloroadamantane (CMT) were 7.3, 5.6, and 6.1, respectively. Here, a highly sensitive, selective and stable QCM sensor prepared via the imprinting approach is reported for the first time for detection of AM from animal-derived food samples.

In the present work, a new amantadine imprinted quartz crystal microbalance sensor sensitized by Au nanoparticles and reduced graphene oxide material was fabricated by electrodeposition of o-aminothiophenol by cyclic voltammetry scanning.

Conducting polymer-based electrochemical biosensors for neurotransmitters: A review

Neurotransmitters are important biochemical molecules that control behavioral and physiological functions in central and peripheral nervous system. Therefore, the analysis of neurotransmitters in biological samples has a great clinical and pharmaceutical importance. To date, various methods have been developed for their assay. Of the various methods, the electrochemical sensors demonstrated the potential of being robust, selective, sensitive, and real time measurements. Recently, conducting polymers (CPs) and their composites have been widely employed in the fabrication of various electrochemical sensors for the determination of neurotransmitters. Hence, this review presents a brief introduction to the electrochemical biosensors, with the detailed discussion on recent trends in the development and applications of electrochemical neurotransmitter sensors based on CPs and their composites. The review covers the sensing principle of prime neurotransmitters, including glutamate, aspartate, tyrosine, epinephrine, norepinephrine, dopamine, serotonin, histamine, choline, acetylcholine, nitrogen monoxide, and hydrogen sulfide. In addition, the combination with other analytical techniques was also highlighted. Detection challenges and future prospective of the neurotransmitter sensors were discussed for the development of biomedical and healthcare applications.

The novel sulfonated polyaniline-decorated carbon nanosphere nanocomposites for electrochemical sensing of dopamine

Herein, a novel dopamine (DA) electrochemical sensor was developed by combining carbon nanospheres (CNSs) and sulfonated polyaniline (SPANI) with their own excellent characteristics.

Nickel–cobalt double hydroxide nanosheets wrapped amorphous Ni(OH)2 nanoboxes: development of dopamine sensor with enhanced electrochemical properties

The Ni(OH)₂/NiCo-LDHs nanocomposites accelerated the electron transfer and successfully realized dopamine catalytic oxidation.

From non-electroactive to electroactive species: highly selective and sensitive detection based on a dual-template molecularly imprinted polymer electrochemical sensor

A selective and sensitive detection of non-electroactive and electroactive molecules has been achieved on a dual-template imprinted electrochemical sensor. And the proposed dual-signal strategy can be used for highly sensitive detection of electroactive analytes.

Electropolymerized molecular imprinting on glassy carbon electrode for voltammetric detection of dopamine in biological samples

A simple and reliable method for preparing a selective dopamine (DA) sensor based on a molecularly imprinted polymer of ethacridine was proposed. The molecularly imprinted polymer electrode was prepared through electrodepositing polyethacridine-dopamine film on the glassy carbon electrode and then removing DA from the film via chemical induced elution. The molecular imprinted sensor was tested by cyclic voltammetry as well as by differential pulse voltammetry (DPV) to verify the changes in oxidative currents of DA. In optimized DPV conditions the oxidation peak current was well-proportional to the concentration of DA in the range from 2.0×10(-8)M up to 1×10(-6)M. The limit of detection (3σ) of DA was found to be as low as 4.4nM, by the proposed sensor that could be considered a sensitive marker of DA depletion in Parkinson's disease. Good reproducibility with relative standard deviation of 1.4% and long term stability within two weeks were also observed. The modified sensor was validated for the analysis of DA in deproteinized human serum samples using differential pulse voltammetric technique.