Electrochemical characterization of poly(eriochrome black T) modified glassy carbon electrode and its application to simultaneous determination of dopamine, ascorbic acid and uric acid

Mobile Point-of-Care Device Using Molecularly Imprinted Polymer-Based Chemosensors Targeting Interleukin-1β Biomarker

Molecularly imprinted polymers (MIPs) have garnered significant attention as a promising material for engineering specific biological receptors with superior chemical complementarity to target molecules. In this study, we present an electrochemical biosensing platform incorporating MIP films for the selective detection of the interleukin-1β (IL-1β) biomarker, particularly suitable for mobile point-of-care testing (POCT) applications. The IL-1β-imprinted biosensors were composed of poly(eriochrome black T (EBT)), including an interlayer of poly(3,4-ethylene dioxythiophene) and a 4-aminothiophenol monolayer, which were electrochemically polymerized simultaneously with template proteins (i.e., IL-1β) on custom flexible screen-printed carbon electrodes (SPCEs). The architecture of the MIP films was designed to enhance the sensor sensitivity and signal stability. This approach involved a straightforward sequential-electropolymerization process and extraction for leaving behind cavities (i.e., rebinding sites), resulting in the efficient production of MIP-based biosensors capable of molecular recognition for selective IL-1β detection. The electrochemical behaviors were comprehensively investigated using cyclic voltammograms and electrochemical impedance spectroscopy responses to assess the imprinting effect on the MIP films formed on the SPCEs. In line with the current trend in in vitro diagnostic medical devices, our simple and effective MIP-based analytical system integrated with mobile POCT devices offers a promising route to the rapid detection of biomarkers, with particular potential for periodontitis screening.

Electrocatalytic Determination of Uric Acid with the Poly(Tartrazine)-Modified Pencil Graphite Electrode in Human Serum and Artificial Urine

A novel electrocatalytic sensing strategy was built for uric acid (UA) determination with an exceptionally developed poly(tartrazine)-modified activated pencil graphite electrode (pTRT/aPGE) in human serum and artificial urine. The oxidation signal of UA at 275 mV in pH 7.5 phosphate buffer solution served as the analytical response. Cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the sensing platform, which was able to detect 0.10 μM of UA in the ranges of 0.34-60 and 70-140 μM. The samples of human serum and artificial urine were analyzed by both the pTRT/aPGE and the uricase-modified screen-printed electrode. The results were statistically evaluated and compared with each other within the confidence level of 95%, and no significant difference between the results was found.

Signal-Enhanced Electrochemical Determination of Quercetin with Poly(chromotrope fb)-Modified Pencil Graphite Electrode in Vegetables and Fruits

A novel signal-enhanced electrochemical sensing strategy was constructed for quercetin determination with a peculiarly developed poly(chromotrope fb)-modified activated pencil graphite electrode in vegetables and fruits. The oxidation signal of quercetin at 118 mV in an alcoholic solution served as the analytical response. The produced platform, characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, could detect 1.9 nM of quercetin in the range of 0.01-1.2 μM. The extracted quercetin contents of red onion, red cabbage, cranberry, black mulberry, black raisin, and carob were determined by both the developed method and UV-visible spectroscopy. The results were statistically evaluated at the 95% confidence level, and no significant difference between the results was found.

Detection of Residual 2-Phenylphenol on Lemon Rind by Electrochemically Deposited Poly(hydroxybenzaldehyde) and Poly(hydroxybenzoic acid) Polymeric Stackings as Electrode Modifiers

This study explores the characteristics of electrodeposition of the three hydroxybenzaldehyde isomers and selected hydroxybenzoic acids (4-hydroxybenzoic acid, salicylic acid, 3,5-dihydroxybenzoic acid) from mesityl oxide solvent. Similar to recent advances of this solvent, used by electrochemical studies, the carbon-carbon double bond had significant influence on the formation of polymers from the outlined molecules. In case of most substrates the peak currents increased to a steady-state but electropolymerization of some substrates caused significant deactivation. Scanning electron microscopic and complementary voltammetric studies facilitated that the electrochemically formed polymers are present on the electrode surface in stackings. In viewpoint of analysis of 2-phenylphenol, the modifying deposit formed from 4-hydroxybenzaldehyde was the best with 5 µM detection limit obtained with differential pulse voltammetry. Furthermore, a new procedure was chosen for the involvement of a cavitand derivative into the organic layers with the purpose to improve the layer selectivity (subsequent electrochemical polymerization in an other solution). Further studies showed that in this way the sensitivities of as-modified electrodes were a little worse than without this step, thus indicating that application of this step is disadvantageous. Recovery studies of 2-phenylphenol were carried out on lemon rind without any treatment, and it was compared with the case when the outer yellow layer was removed by rasping. The inner tissues showed very high adsorption affinity towards 2-phenylphenol.

Construction of Electrochemical and Photoelectrochemical Sensing Platform Based on Porphyrinic Metal-Organic Frameworks for Determination of Ascorbic Acid

Highly sensitive and specific detection of biomolecular markers is of great importance to the diagnosis and treatment of related diseases. Herein, Cu-TCPP@MOFs thin films were synthesized with tetrakis(4-carboxyphenyl) porphyrin (H₂TCPP) as organic ligands and copper ions as metal nodes. The as-synthesized Cu-TCPP@MOFs thin films as electrode modifiers were used to modify the pre-treated glassy carbon electrode (GCE) and the electrochemical performances of Cu-TCPP@MOFs/GCE were evaluated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Furthermore, as the working electrode, the constructed Cu-TCPP@MOFs/GCE was used for the investigation of ascorbic acid (AA) due to its outstanding electrocatalytic activities towards AA by several electrochemical methods, including cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA). The well-linear relationship was established based on different AA concentration ranges and the ideal detection limits (LOD) were obtained in the above-mentioned electrochemical methods, respectively. Furthermore, a Cu-TCPP MOFs@GCE sensing platform was used as a photoelectrochemical (PEC) sensor to quantitatively detect AA based on the strong absorption properties of Cu-TCPP ingredients in Cu-TCPP MOFs in a visible light band of 400~700 nm. PEC sensing platform based on Cu-TCPP@MOFs exhibited a more extensive linear concentration range, more ideal detection limit, and better sensitivity relative than the other electrochemical methods for AA. The well linear regression equations were established between the peak current intensity and AA concentrations in different electrochemical technologies, including CV, DPV, and CA, and PEC technology. AA concentration ranges applicable to various electrochemical equations were as follows: 0.45~2.10 mM of CV, 0.75~2.025 mM of DPV, 0.3~2.4 mM of CA, 7.5~480 μM of PEC, and the corresponding detection limits for AA were 1.08 μM (S/N = 3), 0.14 μM (S/N = 3), 0.049 μM (S/N = 3), and 0.084 nA/μM. Moreover, the proposed Cu-TCPP MOFs@GCE electrochemical and photoelectrochemical sensing platform was applied to determine the AA concentration of a real human serum sample; the results reveal that Cu-TCPP MOFs@GCE sensing platform could accurately determine the concentration of AA of the human serum under other potential interferences contained in the human serum samples.

Electrochemical Biosensing of Dopamine Neurotransmitter: A Review

Neurotransmitters are biochemical molecules that transmit a signal from a neuron across the synapse to a target cell, thus being essential to the function of the central and peripheral nervous system. Dopamine is one of the most important catecholamine neurotransmitters since it is involved in many functions of the human central nervous system, including motor control, reward, or reinforcement. It is of utmost importance to quantify the amount of dopamine since abnormal levels can cause a variety of medical and behavioral problems. For instance, Parkinson's disease is partially caused by the death of dopamine-secreting neurons. To date, various methods have been developed to measure dopamine levels, and electrochemical biosensing seems to be the most viable due to its robustness, selectivity, sensitivity, and the possibility to achieve real-time measurements. Even if the electrochemical detection is not facile due to the presence of electroactive interfering species with similar redox potentials in real biological samples, numerous strategies have been employed to resolve this issue. The objective of this paper is to review the materials (metals and metal oxides, carbon materials, polymers) that are frequently used for the electrochemical biosensing of dopamine and point out their respective advantages and drawbacks. Different types of dopamine biosensors, including (micro)electrodes, biosensing platforms, or field-effect transistors, are also described.

Holey nitrogen-doped graphene aerogel for simultaneously electrochemical determination of ascorbic acid, dopamine and uric acid

In this paper, holey nitrogen-doped graphene aerogel (HNGA) was synthesized and applied to the concurrently electrochemical determination of small biological molecules including ascorbic acid (AA), dopamine (DA) and uric acid (UA). Firstly, holey graphene hydrogel was synthesized by the hydrothermal reaction in the presence of H₂O₂, which subsequently was lyophilized and further annealed in the mixed gas of ammonia and argon to obtain HNGA. Electron microscopy characterization exhibited a great number of nanopores formed on the basal surface of graphene sheets, and HNGA possessed a hierarchically porous structure. The unique structure and composition of HNGA make it an ideal material for electroanalytical application through accelerating mass and electron transfer. HNGA modified glassy carbon electrode (HNGA/GCE) displayed significantly enhanced electrochemical response to AA, DA, and UA, namely reducing overpotential, increasing current density, and improving the reversibility. The oxidation peaks of these three biomolecules can be entirely separated with evident peak potential differences which are 0.216 V (AA-DA), 0.120 V (DA-UA), and 0.336 V (AA-UA), which it allowed the determination of the three substances at the same time. This sensor shows high sensitivity for the determination of AA, DA, and UA with the detection limit of 16.7 μM, 0.22 μM, and 0.12 μM (S/N = 3), respectively. The proposed sensor was applicable for the practical sample analysis as well and desirable recovery was obtained.

Ultrasensitive voltammetric detection of benzenediol isomers using reduced graphene oxide-azo dye decorated with gold nanoparticles

The detection of phenolic compounds, i.e. resorcinol (RC) catechol (CC) and hydroquinone (HQ) are important due to their extremely hazardous impact and poor environmental degradation. In this work, a novel and sensitive composite of electrochemically reduced graphene oxide-poly(Procion Red MX-5B)/gold nanoparticles modified glassy carbon electrode (GCE/ERGO-poly(PR)/AuNPs) was assembled for voltammetric detection of benzenediol isomers (RC, CC, and HQ). The nanocomposite displayed high peak currents towards the oxidation of RC, HQ, and CC compared to non-modified GCE. The peak-to-peak separations were 0.44 and 0.10 V for RC-CC and CC-HQ, respectively. The limit of detections were 53, 53, and 79 nM for HQ, CC, and RC with sensitivities of 4.61, 4.38, and 0.56 μA/μM (S/N = 3), respectively. The nanocomposite displayed adequate reproducibility, besides good stability and acceptable recoveries for wastewater and cosmetic samples analyses.

Mechanism of Nanocomposite Formation in the Layer-by-Layer Single-Step Electropolymerization of π-Conjugated Azopolymers and Reduced Graphene Oxide: An Electrochemical Impedance Spectroscopy Study

This work presents a study of the formation mechanism of electrochemically deposited alternating layers of azopolymer and graphene oxide, as well as a systematic study of the physicochemical characteristics of the resulting nanocomposite films by electrochemical impedance spectroscopy. The nanocomposite films were constructed by cyclic electropolymerization, which allowed for the assembly of thin films with alternating azopolymers and reduced graphene oxide (rGO) layers in one step. Morphological characterizations were performed by atomic force microscopy and scanning electron microscopy and verified that the electrodeposition of the poly(azo-BBY) polymeric film occurred during the anodic sweep, and the deposition of graphene oxide sheets took place during the cathodic sweep. By analyzing the electrochemical impedance spectra using equivalent circuit models, variations in the resistance and capacitance values of the system were monitored as a function of the amount of electrodeposited material on the fluorine doped tin oxide electrode. In addition, the interfacial phenomena that occurred during the electroreduction of the rGO sheets were monitored with the same method.

Sensitive and Simultaneous Determination of Hydroquinone and Catechol in Water Using an Anodized Glassy Carbon Electrode with Polymerized 2-(Phenylazo) Chromotropic Acid

Hydroquinone (HQ) and catechol (CT) are considered as environmental pollutants with high toxicity. We have developed a simple electrochemical sensor using an anodized glassy carbon electrode modified with a stable 2-(phenylazo) chromotropic acid- (CH-) conducting polymer (PCH/AGCE). The PCH/AGCE sensor showed good electrocatalytic activity and reversibility towards the redox of HQ and CT in phosphate buffer solution (PBS, pH 7.0). The cyclic voltammetry (CV) in mixed solution of HQ and CT showed that the oxidation peaks of them became well resolved with a peak separation of 0.1 V. The detection limits of HQ and CT were 0.044 and 0.066 μM, respectively, in a wide linear response range of 1–300 μM for both. Moreover, the sensor displayed an excellent selectivity in the presence of common interferences. This study provided a simple, sensitive, and high recovery method for simultaneous and quantitative determination of HQ and CT in aqueous medium.

Synthesis and characterization of tetra-ganciclovir cobalt (II) phthalocyanine for electroanalytical applications of AA/DA/UA

Cobalt (II) phthalocyanine embedded with ganciclovir units has been synthesized by a novel method using tetracarboxylic phthalocyanine reported for the first time. The synthesized dark green colored complexes were characterized by electronic spectroscopy, elemental analysis, FT-IR, MASS and XRD. Thermal stability study reveals that the newly synthesized complex was stable up to 300 °C and XRD patterns showed amorphous nature of the complex. In the present work, the synthesized complex was characterized by cyclic voltammetry and shows the redox behavior corresponding to central metal (Co^+II/Co^+I) of the complex. Three biomolecules are well-separated by their oxidation peaks in simultaneous determination predicting the potentials for (-128, 335, and 723 mV) with highly increasing current. The low detection limit of AA, DA, and UA were 0.33, 0.03 and 0.10 μmol by CV method and good responses of amperometric and DPV technique. The modified tetra substituted CoTGPc/GCE exhibit an excellent electrocatalytic activity, stability, high sensitivity, good linearity, and selectivity without losing its catalytic activity and proves to be a versatile chemical sensor for commercial pharmaceutical samples, vitamin C tablets, and dopamine injections.

Electrochemical study of a glassy carbon electrode modified by poly-4-nitroaniline-reduced/murexide and its sensitivity for metal ions

The electrochemical modification of a glassy carbon electrode using reduced poly-4 nitroaniline (P-4NA) and it's applicability for determination of metallic ions was performed in this study. The electrode modification was performed by cyclic voltammetry in the potential range between 0.9 V and 1.4 V vs Ag/Ag⁺ (in 10 mM AgNO₃) at the scan rate of 100 mV/s by 50 cycles in non-aqueous media. The reduction of nitro groups on the P-4NA modified glassy carbon electrode surface was performed in the potential range between -0.1 V and -0.8 V vs Ag/AgCl(Sat. KCl) at a scan rate of 100 mV/s in 100 mM aqueous HCl solution. The reduced P-4NA glassy carbon surface was modified with the murexide. The affinity of the modified glassy carbon electrode with some metallic ions was investigated by electrochemical impedance spectroscopy method in phosphate buffer solution (pH = 5).

Flexible and conductive titanium carbide-carbon nanofibers for the simultaneous determination of ascorbic acid, dopamine and uric acid

The development of novel materials for facile, cost-effective and quick practical application is a demanding research interest in electroanalytical chemistry. Titanium carbide (TiC), as one of the most important transition metal carbides, exhibits good chemical stability and electrical conductivity, and its electrocatalytic activity resembles that of metals, but is much cheaper. In this work, TiC nanoparticle (NP) loaded carbon nanofiber (CNF) films (TCNFs) are synthesized using an electrospinning and carbothermal technique, which facilely maintains their structural integrity with robust adhesion. Uniform TiC NPs are firmly embedded in the surface of CNFs, which integrates the large surface area and unique 3D, porous network structure of CNFs with the good conductivity and excellent electrocatalytic activity of TiC NPs. Simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA) and uric acid (UA) at TCNFs displays excellent peak current signals with well-defined peak potentials. The linear ranges are 0.001-1.5 mM, 0.05-160 μM and 0.001-0.875 mM for AA, DA and UA, and the corresponding detection limits are 0.3 μM, 20 nM and 0.3 μM, respectively. In addition, TCNFs show long-term sensing stability and potential applications in real samples, and behave as good anti-interference agents towards KNO₃, ZnSO₄, glucose, etc. Most importantly, unlike some common carbon-based electrochemical sensor systems, an adsorption-less response is observed for the test analytes at the TCNF electrode. TCNFs show interesting potential as candidates for the construction of electrochemical sensors.

Carbon ceramic microelectrodes modified with buckyballs for simultaneous determination of redox-active biomolecules

In this report, simultaneous electrochemical determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (Trp) was achieved using buckyball-modified carbon ceramic microelectrodes (CCMEs). A concentration-dependent increase in anodic peak current signals was observed in comparison with those obtained at bare CCMEs. The optimal pH for simultaneous determination of a quaternary mixture of AA–DA–UA–Trp was determined to be pH 4. The peak separations for the mixture containing AA–DA–UA–Trp were well-defined at the scan rate of 50 mV s⁻¹. The catalytic peak current obtained was linearly dependent on the AA, DA, UA and Trp concentrations in the range of 6.0–600, 6.0–600, 6.0–600 and 4.0–440 μM, respectively. The detection limits for AA, DA, UA and Trp were also determined to be 1.64, 0.82, 0.36 and 1.22 μM, respectively. The analytical performance of this sensor has also been challenged for simultaneous electrochemical detection of AA, DA, UA and Trp in real samples.

In this report, simultaneous electrochemical determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (Trp) was achieved using buckyball-modified carbon ceramic microelectrodes (CCMEs).

Novel UIO-66-NO2@XC-72 nanohybrid as an electrode material for simultaneous detection of ascorbic acid, dopamine and uric acid

The UIO-66-NO₂@XC-72 sensor exhibited excellent linear responses to AA, DA and UA due to the synergistic effect of UIO-66-NO₂ and XC-72, as well as the hydrogen bond effect. The detection ranges were 0.2–3.5 μM for AA, 0.03–2.0 μM for DA and 0.75–22 μM for UA.

Molecular engineering of a π-conjugated polymer film of the azo dye Bismarck Brown Y

Herein, we report a novel organic π-conjugated chromophore obtained by the electropolymerization of Bismarck Brown Y (4,4′-[1,3-phenylenedi(E)-2,1-diazenediyl]di(1,3-benzenediamine)). This polymer has potential applications as optical and electrochemical devices.