Fabrication of DNA, o-phenylenediamine, and gold nanoparticle bioimprinted polymer electrochemical sensor for the determination of dopamine

Label-Free Electrochemical Dopamine Biosensor Based on Electrospun Nanofibers of Polyaniline/Carbon Nanotube Composites

The development of conducting polymer incorporated with carbon materials-based electrochemical biosensors has been intensively studied due to their excellent electrical, optical, thermal, physical and chemical properties. In this work, a label-free electrochemical dopamine (DA) biosensor based on polyaniline (PANI) and its aminated derivative, i.e., poly(3-aminobenzylamine) (PABA), composited with functionalized multi-walled carbon nanotubes (f-CNTs), was developed to utilize a conducting polymer as a transducing material. The electrospun nanofibers of the composites were fabricated on the surface of fluorine-doped tin oxide (FTO)-coated glass substrate under the optimized condition. The PANI/f-CNTs and PABA/f-CNTs electrospun nanofibers were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which confirmed the existence of f-CNTs in the composites. The electroactivity of the electrospun nanofibers was investigated in phosphate buffer saline solution using cyclic voltammetry (CV) before being employed for label-free electrochemical detection of DA using differential pulse voltammetry (DPV). The sensing performances including sensitivity, selectivity, stability, repeatability and reproducibility of the fabricated electrospun nanofiber films were also electrochemically evaluated. The electrochemical DA biosensor based on PANI/f-CNTs and PABA/f-CNTs electrospun nanofibers exhibited a sensitivity of 6.88 µA·cm-2·µM-1 and 7.27 µA·cm-2·µM-1 in the linear range of 50-500 nM (R2 = 0.98) with a limit of detection (LOD) of 0.0974 µM and 0.1554 µM, respectively. The obtained DA biosensor showed great stability, repeatability and reproducibility with precious selectivity under the common interferences, i.e., glucose, ascorbic acid and uric acid. Moreover, the developed electrochemical DA biosensor also showed the good reliability under detection of DA in artificial urine.

Redox Sensor Array with 23.5-μm Resolution for Real-Time Imaging of Hydrogen Peroxide and Glutamate Based on Charge-Transfer-Type Potentiometric Sensor

Towards clarifying the spatio-temporal neurotransmitter distribution, potentiometric redox sensor arrays with 23.5-µm resolution were fabricated. The sensor array based on a charge-transfer-type potentiometric sensor comprises 128×128 pixels with gold electrodes deposited on the surface of pixels. The sensor output corresponding to the interfacial potential of the electrode changed logarithmically with the mixture ratio of K3Fe(CN)6 and K4Fe(CN)6, where the redox sensitivity reached 49.9 mV/dec. By employing hydrogen peroxidase as an enzyme and ferrocene as an electron mediator, the sensing characteristics for hydrogen peroxide (H2O2) were investigated. The analyses of the sensing characteristics revealed that the sensitivity was about 44.7 mV/dec., comparable to the redox sensitivity, while the limit of detection (LOD) was achieved to be 1 µM. Furthermore, the oxidation state of the electron mediator can be the key to further lowering the LOD. Then, by immobilizing oxidizing enzyme for H2O2 and glutamate oxidase, glutamate (Glu) measurements were conducted. As a result, similar sensitivity and LOD to those of H2O2 were obtained. Finally, the real-time distribution of 1 µM Glu was visualized, demonstrating the feasibility of our device as a high-resolution bioimaging technique.

Selective Determination of Dopamine in Pharmaceuticals and Human Urine Using Carbon Quantum Dots as a Fluorescent Probe

A cost-effective and environmentally friendly method was formulated for rapid dopamine (DA) detection that was based on the fluorescence (FL) quenching of carbon quantum dots (C-dots). Upon adding DA to the C-dots’ solution, we noticed a regular reduction in their fluorescence intensity. The effects of pH, amount of C-dots, reaction temperature and time on the determination of DA were investigated. Under the optimized experimental conditions, trace amounts of DA could be analyzed. Furthermore, dopamine hydrochloride injection and human urine samples with and without spiked DA were analyzed using the developed sensing system. The procedure was validated following the guidelines of the European Medicines Agency (EMA) in terms of the following: calibration range (0.3–100 μM), linearity (R2 = 0.9991), limit of detection (LOD) (93 nM). Recoveries of dopamine with spiked samples at three different levels were between 95.0 and 105.9%, and the relative standard deviations (RSDs) were within 2.68% (n = 6). This method is simple and suitable for the determination of dopamine in pharmaceuticals and human urine for clinical application. Compared with previous reports, the proposed method offers great advantages including ease of C-dot sensor preparation (one-pot synthesis), environmentally friendly sample preparation by using either water or phosphate buffer solution only, a short response time and selectivity.

Label-free liquid crystal-based biosensor for detection of dopamine using DNA aptamer as a recognition probe

We present a label-free liquid crystal-based biosensor for the detection of dopamine (DA) in aqueous solutions using dopamine-binding aptamers (DBA) as recognition elements. In this system, the dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP) self-assembled monolayers immobilized on glass slides support the long alkyl chains that keep the liquid crystal (LC) molecules in a homeotropic orientation. Glutaraldehyde (GA) is used as a cross-linker to immobilize DBA onto the surface of glass slides. The specific binding of DA and DBA disrupts the homeotropic orientation of LCs, thereby inducing a change in the orientation from homeotropic to a random alignment. This orientation change can be converted and visualized simply as a transition from a dark optical LC image to a brighter image under a polarized optical microscope (POM), enabling the detection of DA. The developed LC-based aptasensor shows a good linear optical response towards DA in the very wide range of 1 pM-10 μM (0.19 pg/mL to 1.9 μg/mL) and has a very low detection limit of 10 pM (∼1.9 pg/mL). The biosensor also exhibited satisfactory selectivity and could be successfully applied to detect DA in human urine. The proposed LC-based aptamer sensing method offers a simple, rapid, highly sensitive and selective, and a label-free method for the analysis of DA in real clinical 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 Electrochemical Sensors: Analytical and Pharmaceutical Applications Based on Ortho-Phenylenediamine Polymerization

Background:

The molecular imprinting technique has been applied in many fields including separation, artificial antibody mimics, catalysis, sensing studies, and drug delivery. The reasons for the popularity of this technique among the researchers are high selectivity due to the cavities that are formed on the polymer surface for the specific analyte, high robustness, high durability under extreme conditions and low cost. When these advantages are combined with the advantages of electrochemical methods such as rapid response time, ease of use, cheapness and miniaturizability, Molecularly Imprinted Polymer (MIP) based electrochemical sensors turn out to be a widely-preferred sensing tool.

Objective:

This article provides the reader with information on MIP-based electrochemical sensors and reviews the applications of the MIP sensors prepared by electropolymerization of orthophenylenediamine, a monomer whose mechanical and chemical stability is very high.

Results and Conclusion:

The literature survey summarized in this review shows that cyclic voltammetry is the most widely preferred electrochemical technique for electropolymerization of o-PD. The media chosen is generally acetate or phosphate buffers with different pH values. Although there are numerous solvents used for template removal, generally methanol and NaOH have been chosen.

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.

Electrochemical molecularly bioimprinted siloxane biosensor on the basis of core/shell silver nanoparticles/EGFR exon 21 L858R point mutant gene/siloxane film for ultra-sensing of Gemcitabine as a lung cancer chemotherapy medication

In search for improvements in bioanalysis electrochemical sensors, for better assessment of anti-cancer drugs, it is necessary for their detection limits to be minimized and the sensitivity and selectivity to be surpassed simultaneously; whereas, resolving any probable interfering with other medical treatments are considered. In this work, a novel approach was adopted for detection and assessment of Gemcitabine (GEM) as an anti-cancer drug based on evaluating its interaction with EGFR exon 21-point mutant gene. An electrochemical nanobiosensor was invented based on a new molecularly bioimprinted siloxane polymer (MBIS) strategy; in which the EGFR exon 21 acts as an identification probe. The roles of multi-walled carbon nanotubes and Ag nanoparticles (NPs) are to perform as a signal amplifier. The MBIS film was prepared by acid-catalysed hydrolysis/condensation of the sample solution, containing Ag NPs, ds-DNA of EGFR exon 21 point mutant gene, GEM as a template molecule, 3-(aminopropyl) trimethoxysilane (APTMS) and tetraethoxysilane. The interaction between the dsDNA and GEM was investigated by employing the modified biosensor and monitoring oxidation signal of guanine and adenine. The produced biosensor was characterized by XRD, FE-SEM, EDS, FT-IR and differential pulse voltammetry. The oxidation signals of adenine and guanine were in linear range when the device was subjected to various concentrations of GEM, from 1.5 to -93 μM, where a low detection limit 12.5 nmol L^-1, and 48.8 nmol L^-1 were recorded by guanine and adenine respectively. The developed biosensor did perform very well when employed for the actual samples; the stability was also approved which was acceptable for a reasonable time.

Electrochemical Detection of Dopamine Based on Functionalized Electrodes

The rapid electrochemical identification and quantification of neurotransmitters being a challenge in the ever-growing field of neuroelectronics, we aimed to facilitate the electrochemical selective detection of dopamine by functionalizing commercially available electrodes through the deposition of a thin film containing pre-formed gold nanoparticles. The influence of different parameters and experimental conditions, such as buffer solution, fiber material, concentration, and cyclic voltammetry (CV) cycle number, were tested during neurotransmitter detection. In each case, without drastically changing the outcome of the functionalization process, the selectivity towards dopamine was improved. The detected oxidation current for dopamine was increased by 92%, while ascorbic acid and serotonin oxidation currents were lowered by 66% under the best conditions. Moreover, dopamine sensing was successfully achieved in tandem with home-made triple electrodes and an in-house built potentiostat at a high scan rate mode.

Fabrication of Au Nanoparticle-Decorated MoS2 Nanoslices as Efficient Electrocatalysts for Electrochemical Detection of Dopamine

Herein, MoS2 nanoslices were simply prepared by using ultrasonic treatment, and were further decorated with Au nanoparticles (AuNPs) through an electrodeposition process to obtain the MoS2/Au nanocomposites. The obtained nanocomposites display synergetic electrocatalytic effect for the oxidation of dopamine due to the large surface area and two-dimensional structure of the MoS2 nanoslices, combining with the high catalytic activity and good conductivity of AuNPs. An electrochemical sensor was constructed based on MoS2/Au-modified carbon paste electrode, for sensitive and quantitative determination of dopamine. The prepared electrochemical sensor proves excellent analytical performances: very high sensitivity, wide linear ranges (0.5–300 μM), and low detection limit (76 nM). Moreover, the dopamine sensor also displays high selectivity, good reproducibility and stability, and can be used in real sample analysis. The method of fabricating high-efficiency electrocatalysts and electrochemical sensors proposed in this study provides a good reference for developing more functionalized nanocomposites and for extending practical applications.

Promising methods for noninvasive medical diagnosis based on the use of nanoparticles: surface-enhanced raman spectroscopy in the study of cells, cell organelles and neurotransmitter metabolism markers

Application of advances in nanomedicine and materials science to medical diagnostics is a promising area of research. Surface-enhanced Raman spectroscopy (SERS) is an innovative analytical method that exploits noble metal nanoparticles to noninvasively study cells, cell organelles and protein molecules. Below, we summarize the literature on the methods for early clinical diagnosis of some neurodegenerative and neuroendocrine diseases. We discuss the specifics, advantages and limitations of different diagnostic techniques based on the use of low- and high molecular weight biomarkers. We talk about the prospects of optical methods for rapid diagnosis of neurotransmitter metabolism disorders. Special attention is paid to new approaches to devising optical systems that expand the analytical potential of SERS, the tool that demonstrates remarkable sensitivity, selectivity and reproducibility of the results in determining target analytes in complex biological matrices.

An electrochemical sensor for attomolar determination of mercury(II) using DNA/poly-L-methionine-gold nanoparticles/pencil graphite electrode

The present work describes an ultrasensitive electrochemical sensor for determination of mercury(II) using deoxyribonucleic acid/poly-L-methionine-gold nanoparticles/pencil graphite electrode (DNA/PMET-AuNPs/PGE). To fabricate this biosensor, L-methionine (L-MET) was electropolymerized on the PGE surface followed by simultaneous electrochemical entrapment of AuNPs. Next, DNA was immobilized on the PMET-AuNPs/PGE by applying a 0.5 V potential. The surface area of modified and unmodified electrodes was determined by chronocoulometric technique. Hg²⁺ was detected in the linear dynamic range of 0.1 aM to 0.1 nM, and the detection limit was determined as 0.004 aM using square wave anodic stripping voltammetry (SWASV) under optimized conditions. The DNA/PMET-AuNPs/PGE demonstrated good selectivity toward Hg²⁺ against other metal ions such as V⁴⁺, Pb²⁺, Cr³⁺, Cd²⁺, Cu²⁺, Zn²⁺, Sn²⁺, In³⁺, Ge⁴⁺, and Fe³⁺. Real samples studies were carried out in sea water and fish samples.

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.

Electrochemical determination of thrombin with molecularly imprinted polymers and multiwalled carbon nanotubes

The preparation and application of reagentless electrochemical thrombin molecularly imprinted sensors were studied using multiwalled carbon nanotubes as sensitivity-enhanced materials. The molecularly imprinted polymer film was prepared by the electropolymerization of o-phenylenediamine with thrombin as the template molecule onto the surface of multiwalled carbon nanotubes modified glassy carbon electrode. After removing thrombin, the poly-o-phenylenediamine molecularly imprinted film was obtained with specific recognition for thrombin. Using the poly-o-phenylenediamine molecularly imprinted polymers as the electron probe, the electrochemical molecularly imprinted sensor was fabricated for the detection of the protein thrombin. Under optimized experimental conditions, the sensor exhibited a good linear response from 10.0 fg/mL to 1.0 μg/mL for thrombin, with correlation coefficient 0.999 and a low detection limit of 1.7 fg/mL. The fabricated molecularly imprinted sensor can be applied to the detection of thrombin in actual sample bovine serum with satisfactory results.

Development of a disposable and low-cost electrochemical sensor for dopamine detection based on poly(pyrrole-3-carboxylic acid)-modified electrochemically over-oxidized pencil graphite electrode

In this study, preparation of a single-use electrochemical sensor for the selective and sensitive determination of dopamine (DOP) was investigated by electrochemical polymerization of pyrrole-3-carboxylic acid on electrochemically over-oxidized pencil graphite electrode (p(P3CA)/EOPGE). Cyclic voltammetry measurements of Fe(CN)₆^4-/3- indicated that the electrochemically over-oxidized PGE (EOPGE) showed superior electron transfer characteristics according to bare PGE. The ionized carboxyl groups found in the structure of poly(pyrrole-3-carboxylic acid) (p(P3CA)) showed high affinity towards positively charged DOP. The combination of the advantages of EOPGE and p(P3CA) in p(P3CA)/EOPGE led to a synergistic effect on the electrochemical oxidation of DOP. The effects of experimental variables on the voltammetric performance of the p(P3CA)/EOPGE were examined by preparing the electrodes at different conditions. The p(P3CA)/EOPGE showed high selectivity towards DOP by discriminating its oxidation potential from the common interfering substances such as ascorbic and uric acids. The p(P3CA)/EOPGE showed linear responses in the electrochemical oxidation of DOP between the concentration values of 0.025µM and 7.5µM. Detection limit was determined as 0.0025µM according to signal to noise ratio (S/N: 3). Analytical application of p(P3CA)/EOPGE was successfully tested in the determination of DOP in blood serum and pharmaceutical samples.

Facile preparation of gold nanoparticles-decorated poly(o-phenylenediamine) hollow microspheres and their application for the detection of dopamine

Gold (Au) nanoparticles-decorated poly( o-phenylenediamine) (PoPD@Au) hollow microspheres were successfully synthesized by a simple two-step process without any other templates or additives. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible absorption spectra were performed to characterize the resulting samples. The results confirmed that the obtained PoPD@Au microspheres had a perfect hollow structure and revealed that there is an interaction between PoPD hollow microspheres and Au nanoparticles. Plausible explanation for the formation of PoPD@Au hollow microspheres has been elaborated. Furthermore, PoPD@Au hollow microspheres were immobilized onto the surface of a glassy carbon electrode and applied to construct a sensor. Cyclic voltammogram experiments indicated that the proposed sensor method had good sensitivity, stability, and repeatability.

Towards a Multifunctional Electrochemical Sensing and Niosome Generation Lab-on-Chip Platform Based on a Plug-and-Play Concept

In this paper, we present a new modular lab on a chip design for multimodal neurotransmitter (NT) sensing and niosome generation based on a plug-and-play concept. This architecture is a first step toward an automated platform for an automated modulation of neurotransmitter concentration to understand and/or treat neurodegenerative diseases. A modular approach has been adopted in order to handle measurement or drug delivery or both measurement and drug delivery simultaneously. The system is composed of three fully independent modules: three-channel peristaltic micropumping system, a three-channel potentiostat and a multi-unit microfluidic system composed of pseudo-Y and cross-shape channels containing a miniature electrode array. The system was wirelessly controlled by a computer interface. The system is compact, with all the microfluidic and sensing components packaged in a 5 cm × 4 cm × 4 cm box. Applied to serotonin, a linear calibration curve down to 0.125 mM, with a limit of detection of 31 μM was collected at unfunctionalized electrodes. Added sensitivity and selectivity was achieved by incorporating functionalized electrodes for dopamine sensing. Electrode functionalization was achieved with gold nanoparticles and using DNA and o-phenylene diamine polymer. The as-configured platform is demonstrated as a central component toward an “intelligent” drug delivery system based on a feedback loop to monitor drug delivery.

A microporous silk carbon–ionic liquid composite for the electrochemical sensing of dopamine

A metal-free silk carbon–ionic liquid composite, synthesized from natural silk cocoons, was prepared for electrochemical determination of dopamine.

Supportless electrochemical sensor based on molecularly imprinted polymer modified nanoporous microrod for determination of dopamine at trace level

In this work, we developed a novel freestanding metallic microrod as working electrode for highly sensitive and selective electrochemical detection of trace dopamine (DA). The electrode was facilely fabricated via first dealloying smooth Au-Ag alloy microrod (AMR) into nanoporous Au-Ag alloy microrod (NPAMR) and further modifying with electro-polymerized molecularly imprinted polymer (MIP). Influencing factors during electro-polymerization process including pH value and molar ratio of monomer to template molecule were optimized. Under the optimal conditions, a linear range from 2 × 10(-13) to 2 × 10(-8)M for measuring DA was obtained with an ultralow detection limit of 7.63 × 10(-14)M (S/N=3). In addition, the MIP-modified electrode (MIP/NPAMR) was successfully employed to test DA in serum and brain samples.

Simultaneous and sensitive determination of melatonin and dopamine with Fe3O4 nanoparticle-decorated reduced graphene oxide modified electrode

An electrochemical sensor based on a new nanocomposite of graphene/Fe₃O₄ has been fabricated for simultaneous determination of melatonin and dopamine.

A novel methionine/palladium nanoparticle modified carbon paste electrode for simultaneous determination of three antiparkinson drugs

A simple and novel method for the simultaneous determination of entacapone (EN), levodopa (LD) and carbidopa (CD) based on a methionine/palladium nanoparticle modified carbon paste electrode is described.