Electropolymerization Conditions Research Articles

Implementation of quality by design approach for optimization of the green voltammetric analysis of a brain doping agent (Piracetam) using a novel molecular imprinted polymeric sensor

It is encouraging to note that in recent years there has been a growth of high-quality articles detailing molecular imprinted sensors for the detection of biomolecules, illicit narcotics, and explosives, paving the way for the technology’s usage in forensic and medical diagnostics.Thus in this work, a molecularly imprinted polymeric sensor was fabricated, for the first time, for the sensitive and selective determination of a brain doping agent; Piracetam, using a pencil-graphite electrode. This sensor was created by the simple anodic electro-polymerization of o-phenylenediamine (o-PD) with Piracetam as the template. Then the sensor was activated by removing the template using a suitable solvent mixture. Because of Piracetam’s lack of electro-activity, [Fe (CN)6]3−/4− has been used as an electrochemical probe that produces analytically relevant voltammetric signals by competing for the binding sites. Based on UV-spectrophotometric measurements, Job’s approach confirmed the expected stoichiometric ratio between Piracetamand the chosen monomer. X-ray photoelectron spectroscopy and cyclic voltammetry techniques were used for the characterization of the fabricated sensors. Different factors affecting the electro-polymerization conditions as; the effect of scan rate, number of cycles, pH of electro-polymerization, and the incubation time for rebinding were studied and optimized using fractional factorial design, in which the predicted model fits well to the experimental data as proved by ANOVA results. The developed voltammetric platform was applied for the in-line quantification of Piracetam in its pure solutions, pharmaceutical dosage form, and spiked human plasma with high accuracy and selectivity without the interference of the co-formulated drug; Citicoline sodium and excipients. The proposed molecular imprinted sensor was very sensitive with a linearity range (1.00 × 10−13 − 1.00 × 10−12 M), with LOD down to 4.38 × 10−15 M. This method was statistically compared with the reported method, and no statistically significant difference was found. The proposed method was assessed for greenness quantitatively and qualitatively using the Green Analytical Procedure Index (GAPI) and Analytical GREEnness metric (AGREE) as new greenness assessment tools.

Detection of Pseudomonas aeruginosa infection using a sustainable and selective polydopamine-based molecularly imprinted electrochemical sensor

Pyocyanin, a redox-active secondary metabolite produced by Pseudomonas aeruginosa, serves as a crucial virulence factor. Detection and quantification of pyocyanin can aid early diagnosis of infection. A selective and sensitive molecularly imprinted electrochemical sensor was constructed by using a green polymerization technique to deposit an ultrathin polydopamine film on an electrode modified with gold nanoparticles and chitosan. Target recognition was facilitated by specific binding sites within the imprinted polymer matrix that are complementary to the structure of pyocyanin. Various techniques, including cyclic voltammetry, electrochemical impedance spectroscopy, and square wave voltammetry, were employed to characterize the electrochemical behavior of the sensor. We investigated the influence of fabrication components, including chitosan concentration, monomer concentration, electro-polymerization conditions, pH, and rebinding time. Demonstrating a high degree of specificity and sensitivity, the sensor showcased a broad linear detection range of 1–100 µM and a low detection limit of 0.74 µM for pyocyanin. Moreover, the sensor successfully detected pyocyanin in real bacterial culture samples, exhibiting a recovery of the spiked standard ranging from 93 to 103 %. The electrochemical sensor displayed satisfactory stability lasting for at least 5 weeks. We demonstrated the sensor's applicability for clinical measurements by detecting pyocyanin in infected burn wounds using an ex vivo porcine skin model. Leveraging the synergistic advantages of molecularly imprinted polymer and the specific redox window for pyocyanin detection, the electrochemical sensor presents a promising approach for early-stage infection identification, thus contributing to enhanced treatment and more effective healthcare for patients.

Chemically Modified Electrodes Based on 4-((5-Isopropyl-3,8-dimethylazulen-1-yl)methylene)-2-phenyloxazol-5(4H)-one

Novel chemically modified electrodes (CMEs) based on azulene were prepared by electrooxidation of guaiazulene derivative 4-((5-isopropyl-3,8-dimethylazulen-1-yl)methylene)-2-phenyloxazol-5(4H)-one (G). G is based on guaiazulene non-alternating aromatic hydrocarbon exhibiting a less symmetrical structure compared to naphthalene skeletal derivative. Therefore, it can be used as a building block for the preparation of novel materials. To evaluate the chemical structure and surface images, the CMEs based on G (G-CMEs) were characterized by ferrocene redox probe, X-ray photon spectroscopy (XPS), and scanning electron microscopy (SEM). They were also tested for the analysis of synthetic samples of heavy metal (HM) ions. The influence of preparation conditions (electric charge and potential) on the properties of these CMEs was examined. This paper highlights the importance of electropolymerization conditions on electrodeposited film surfaces, especially on their analytical properties vs. Cd(II), Pb(II), Cu(II), and Hg(II) investigated ions. This study is relevant for further design and development of advanced materials based on azulenyl-phenyloxazolone for the HM analysis in water. A linear dependence of the peak currents for Pb(II) ion on the concentration in test aqueous solutions was obtained between 10−7 M and 5·10−5 M. The detection limits of 5·10−6 M; 10−7 M; 5·10−6 M; and 10−5 M were estimated for Cd(II), Pb(II), Cu(II), and Hg(II), respectively, for G-CMEs.

Electropolymerization of a Conjugated Polymer on Top of a Different Conjugated Polymer for Yarn Actuators

Electropolymerization of conjugated polymers is usually performed on highly conductive metallic electrodes. However, for applications such as textile actuators this is not possible. There, the electropolymerization is performed on a different, previously deposited conjugated polymer. This resulted on some new electrochemical phenomena not present when the electropolymerization is done on a metallic substrate. Processes as the oxidation and overoxidation of the underlying conjugated polymer need to be taken into account. In this work we have investigated the best conditions for electropolymerization of polypyrrole on top of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coated textile yarns, when the electropolymerization was performed by either cyclic voltammetry, chronoamperometry or chronopotentiometry in order to achieve the best electroactive and actuating conjugated polymer.

Unraveling the Adhesion Behavior of Different Cell Lines on Biomimetic PEDOT Interfaces: The Role of Surface Morphology and Antifouling Properties.

The poly(3,4-ethylenedioxythiophene) (PEDOT) interface, renowned for its biocompatibility and intrinsic conductivity, holds substantial potential in biosensing and cellular modulation. Through strategic functionalization, PEDOT derivatives can be adaptable for multifaceted applications. Notably, integrating phosphorylcholine (PC) groups into PEDOT, mimicking the hydrophilic headgroups from cell membranes, confers exceptional antifouling properties on the coating. This study systematically investigated biomolecule interactions with distinct forms of PEDOT, incorporating variations in surface modifications and structure. Zwitterionic PEDOT-PC was electropolymerized on smooth and nanostructured surfaces using various feeding ratios in electrolytes to finely control the antifouling properties of the interface. Precise electropolymerization conditions governed the attainment of smooth and nanostructured filamentous surfaces. The study employed a quartz crystal microbalance with dissipation (QCM-D) to assess protein binding behavior. Bovine serum albumin (BSA), lysozyme (LYZ), cytochrome c (cyt c), and fibronectin (FN) were used to evaluate their binding affinities for PEDOT films. FN, a pivotal extracellular matrix component, was included for connecting to cell adhesion behavior. Furthermore, the cellular adhesion behaviors on PEDOT interfaces were evaluated. Three cell lines─MG-63 osteosarcoma, HeLa cervical cancer, and fibroblast NIH/3T3 were examined. The presence of PC moieties significantly altered the adhesive response, including the number of attached cells, their morphologies, and nucleus shrinkage. MG-63 cells exhibited the highest tolerance for PC moieties. A feeding ratio of PEDOT-PC exceeding 70% resulted in cell apoptosis. This study contributes to understanding biomolecule adsorption on PEDOT surfaces of diverse morphologies and degrees of the antifouling moiety. Meanwhile, it also sheds light on the responses of various cell types.

Molecularly Imprinted Electrochemical Sensor Based on Poly (O-Phenylenediamine) for Sensitive Detection of Oxycodone in Water

This work was aimed at the development of a sensitive electrochemical detection method for oxycodone in water. Molecularly imprinted electrodes were formed by electro-polymerization process using o-phenylenediamine as a monomer. The electro-polymerization was performed on glassy carbon electrodes in the presence of oxycodone before the extraction of entrapped oxycodone molecules. Various electrochemical techniques were employed to monitor the polymerization and response of the fabricated electrodes toward oxycodone. These techniques included cyclic voltammetry (CV), square wave voltammetry (SWV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The oxycodone concentration was determined using SWV by measuring the change in the oxidation peak current of [Fe(CN)6]3−/4− in a 0.1 mM acetate buffer solution. At the optimal electro-polymerization conditions, a calibration curve of the current versus the concentration of oxycodone indicated a linear response at a region from 0.4 nM to 5.0 nM with a detection limit of 1.8 ± 0.239 nM. The MIP-modified electrode’s binding isotherm was fitted using a Langmuir model and showed an association constant, KA, of 1.12 × 106, indicating a high affinity of oxycodone molecules to binding sites. This sensor has the potential to act as an alternative method suitable for the on-site analysis of oxycodone.

Electrochemical Considerations for the Electropolymerization of PPy on PEDOT:PSS for Yarn Actuator Applications

AbstractElectrochemical devices as conducting polymer‐based actuators or textile actuators often use layers of different conducting polymers. Although research has been performed on such devices, it is still not very clear how the different layers affect each other. Here we attempt to clarify such influence on yarn actuators using electrochemical methods. Different electrochemical methods as cyclic voltammetry, chronoamperometry or chronopotentiometry were used to electropolymerize polypyrrole on top of a poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coated textile yarns by using different applied electrochemical conditions (potentials/currents). Thus, we found that selecting suitable conditions (as an applied potential of +0.8 V) for such electropolymerization is key to obtain a polypyrrole of high quality. Besides, we show that the underlying layer of PEDOT:PSS has an influence on such electropolymerization conditions and can be subjected to parallel redox reactions as oxidation or electrochemical degradation that influence the electropolymerized polypyrrole.

Impedimetric DNA Sensor Based on Electropolymerized N-Phenylaminophenothiazine and Thiacalix[4]arene Tetraacids for Doxorubicin Determination.

Electrochemical DNA sensors are highly demanded for fast and reliable determination of antitumor drugs and chemotherapy monitoring. In this work, an impedimetric DNA sensor has been developed on the base of a phenylamino derivative of phenothiazine (PhTz). A glassy carbon electrode was covered with electrodeposited product of PhTz oxidation obtained through multiple scans of the potential. The addition of thiacalix[4]arene derivatives bearing four terminal carboxylic groups in the substituents of the lower rim improved the conditions of electropolymerization and affected the performance of the electrochemical sensor depending on the configuration of the macrocyclic core and molar ratio with PhTz molecules in the reaction medium. Following that, the deposition of DNA by physical adsorption was confirmed by atomic force microscopy and electrochemical impedance spectroscopy. The redox properties of the surface layer obtained changed the electron transfer resistance in the presence of doxorubicin due to its intercalating DNA helix and influencing charge distribution on the electrode interface. This made it possible to determine 3 pM-1 nM doxorubicin in 20 min incubation (limit of detection 1.0 pM). The DNA sensor developed was tested on a bovine serum protein solution, Ringer-Locke's solution mimicking plasma electrolytes and commercial medication (doxorubicin-LANS) and showed a satisfactory recovery rate of 90-105%. The sensor could find applications in pharmacy and medical diagnostics for the assessment of drugs able to specifically bind to DNA.

Electrode Based on the MWCNTs and Electropolymerized Thymolphthalein for the Voltammetric Determination of Total Isopropylmethylphenols in Spices.

Isopropylmethylphenols, namely thymol and carvacrol, are natural phenolic monoterpenoids with a wide spectrum of bioactivity making them applicable in the cosmetic, pharmaceutical, and food industry. The dose-dependent antioxidant properties of isopropylmethylphenols require their quantification in real samples. Glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and electropolymerized thymolphthalein has been developed for the sensitive quantification of isopropylmethylphenols. Conditions of thymolphthalein electropolymerization (monomer concentration, number of cycles, and electrolysis parameters) providing the best response to thymol have been found. Scanning electron microscopy and electrochemical methods confirm the effectivity of the electrode developed. The linear dynamic ranges of 0.050-25 and 25-100 µM for thymol and 0.10-10 and 10-100 µM for carvacrol with detection limits of 0.037 and 0.063 µM, respectively, have been achieved in differential pulse mode in Britton-Robinson buffer pH 2.0. The selectivity of the isopropylmethylphenols response in the presence of typical interferences (inorganic ions, saccharides, ascorbic acid) and other phenolics (caffeic, chlorogenic, gallic and rosmarinic acids, and quercetin) is a significant advantage over other electrochemical methods. The electrode has been used in the analysis of oregano and thyme spices. Total isopropylmethylphenols contents have been evaluated after a single sonication-assisted extraction with methanol.

Evaluation of electro-synthesized oligothiophenes as donor materials in vacuum-processed organic photovoltaic devices

2,2′:5′,2″-terthiophene (3Th) was utilized as a precursor in the electro-synthesis of oligothiophenes and their further evaluation as donor materials in the active layer of vacuum-processed organic photovoltaic (OPV) devices. Electro-polymerization conditions were optimized to obtain a controlled fraction of polydisperse oligomers, as demonstrated by size exclusion chromatography (SEC). The polydispersity of the material was further decreased during thermal evaporation, where a reduced fraction of the oligomer was deposited, as observed by SEC, absorption spectroscopy, and the characterization of the fabricated devices. Our results demonstrate for the first time the potential of the electro-synthesis of oligothiophenes as active materials for their application in bulk heterojunction for OPV devices.

Voltammetric Sensor Based on the Poly(p-aminobenzoic Acid) for the Simultaneous Quantification of Aromatic Aldehydes as Markers of Cognac and Brandy Quality.

Cognac and brandy quality control is an actual topic in food analysis. Aromatic aldehydes, particularly syringaldehyde and vanillin, are one of the markers used for these purposes. Therefore, simple and express methods for their simultaneous determination are required. The voltammetric sensor based on the layer-by-layer combination of multi-walled carbon nanotubes (MWCNTs) and electropolymerized p-aminobenzoic acid (p-ABA) provides full resolution of the syringaldehyde and vanillin oxidation peaks. Optimized conditions of p-ABA electropolymerization (100 µM monomer in Britton-Robinson buffer pH 2.0, twenty cycles in the polarization window of -0.5 to 2.0 V with a potential scan rate of 100 mV·s-1) were found. The poly(p-ABA)-based electrode was characterized by scanning electron microscopy (SEM), cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Electrooxidation of syringaldehyde and vanillin is an irreversible two-electron diffusion-controlled process. In the differential pulse mode, the sensor allows quantification of aromatic aldehydes in the ranges of 0.075-7.5 and 7.5-100 µM for syringaldehyde and 0.50-7.5 and 7.5-100 µM for vanillin with the detection limits of 0.018 and 0.19 µM, respectively. The sensor was applied to cognac and brandy samples and compared to chromatography.

Electrosynthesized copper polycorroles as versatile materials in double lateral heterojunctions

Metallocorrole derivatives are an emerging class of coordination complexes successfully exploited in different applications, ranging from catalysis to medical field, due to their peculiar tunable properties. Herein, new polycorroles materials are in situ synthesized and deposited on the electrodes in a one-step electrochemical method from 5,10,15-(4-aminophenyl)corrolato]copper(III) as monomer, generating phenazine bridges containing polymer chains. Conductive films are obtained and the film thickness can be controlled by tuning the number of potential scans. However, the nature of the resulting polymer is affected by the electropolymerization conditions: in neat CH2Cl2 the protonation of polymer chains occurs. The role of proton scavenger 2,6-lutidine is worth mentioning, which prevents demetallation of corrole macrocycle. The polycorrole films are further combined with lutetium bis-phthalocyanine to realize double lateral heterojunction (DLH) sensors for ammonia detection, in which organic-organic interface plays a key role in their charge transport properties. The protonation of polycorrole can tune the p- or n-nature of the semiconducting film, and the highest sensitivity obtained with these devices favorably competes with these reported so far for DLH heterojunctions, with a limit of detection as low as 125 ppb for NH3.

The Thermoelectric Properties of Spongy PEDOT Films and 3D-Nanonetworks by Electropolymerization

Recently, polymers have been attracted great attention because of their thermoelectric materials' excellent mechanical properties, specifically their cost-effectiveness and scalability at the industrial level. In this study, the electropolymerization conditions (applied potential and deposition time) of PEDOT films were investigated to improve their thermoelectric properties. The morphology and Raman spectroscopy of the PEDOT films were analyzed according to their applied potential and deposition time. The best thermoelectric properties were found in films grown at 1.3 V for 10 min, with an electrical conductivity of 158 ± 8 S/cm, a Seebeck coefficient of 33 ± 1 µV/K, and a power factor of 17 ± 2 µW/K·m2. This power factor value is three times higher than the value reported in the literature for electropolymerized PEDOT films in acetonitrile using lithium perchlorate as a counter-ion. The thermal conductivity was found to be (1.3 ± 0.3) × 10-1 W/m·K. The highest figure of merit obtained at room temperature was (3.9 ± 1.0) × 10-2 using lithium perchlorate as a counter-ion. In addition, three-dimensional (3D) PEDOT nanonetworks were electropolymerized inside 3D anodic aluminum oxide (3D AAO), obtaining lower values in their thermoelectric properties.

Electropolymerized 4-Aminobenzoic Acid Based Voltammetric Sensor for the Simultaneous Determination of Food Azo Dyes.

Electrochemical sensors with polymeric films as a sensitive layer are of high interest in current electroanalysis. A voltammetric sensor based on multi-walled carbon nanotubes (MWCNTs) and electropolymerized 4-aminobenzoic acid (4-ABA) has been developed for the simultaneous determination of synthetic food azo dyes (sunset yellow FCF and tartrazine). Based on the voltammetric response of the dyes' mixture, the optimal conditions of electropolymerization have been found to be 30-fold potential scanning between -0.3 and 1.5 V, at 100 mV s-1 in the 100 µmol L-1 monomer solution in phosphate buffer pH 7.0. The poly (4-ABA)-based electrode shows a 10.5-fold increase in its effective surface area and a 17.2-fold lower electron transfer resistance compared to the glassy carbon electrode (GCE). The sensor gives a sensitive and selective response to sunset yellow FCF and tartrazine, with the peak potential separation of 232 mV in phosphate buffer pH 4.8. The electrooxidation parameters of dyes have been calculated. Simultaneous quantification is possible in the dynamic ranges of 0.010-0.75 and 0.75-5.0 µmol L-1 for both dyes, with detection limits of 2.3 and 3.0 nmol L-1 for sunset yellow FCF and tartrazine, respectively. The sensor has been tested on orange-flavored drinks and validated with chromatography.

Co‐detection of Copper and Lead in Artisanal Sugarcane Spirit Using Caffeic Acid‐modified Graphite Electrodes

AbstractCaffeic acid (CA)‐modified graphite electrodes [GE/poly(CA)] was applied to the co‐detection of copper and lead in artisanal sugarcane spirit using square‐wave anodic stripping voltammetry (SWASV). Electrochemical and morphological studies were performed, and a mechanism for polymerization was proposed. Electropolymerization, SWASV, and analysis conditions parameters were optimized. Interferents, repeatability, reproducibility, and addition and recovery tests were carried out. GE/poly(CA) shows a linear range from 15 to 705 μg/L with a limit of detection of 3.01 μg/L for Pb(II) and 4.50 μg/L for Cu(II). Real samples of artisanal sugarcane spirit were used, and the electrochemical results were compared with atomic absorption spectroscopy experiments.

An eco-friendly strategy using a double-current two-phase cell system for electrografting of polyacrylic acid

• Electrochemical synthesis of polyacrylic acid. • Proposed mechanism for the electrochemical synthesis of PAA. • Optimization of conditions for electropolymerization of acrylic acid. • Design of a double-current two-phase cell system. In this study, we succeeded in synthesizing polyacrylic acid in a double-current two-phase cell system containing water and ethyl acetate on a Cu electrode. The more detailed steps for grafting polymerization of acrylic acid on the copper electrode are as follows: (1) Electrochemical reduction of p -dinitrobenzene ( DNB ) to 4-nitroaniline ( 4NA ) in ethyl acetate by applying a potential of -0.1 V vs. Ag/AgCl. (2) Conversion of 4NA to corresponding diazonium cation through its reaction with NaNO 2 in the aqueous phase. (3) Electrochemical generation of Cu + from Cu electrode in the aqueous phase. (4) Reduction of diazonium cation by Cu + and formation of aryl radical and (5) polymerization of acrylic acid on copper electrode initiated by aryl radicals. The structural properties and characteristics of the deposited polyacrylic acid layer is fully characterized using different spectroscopic techniques, electrochemical and surface analysis studies. The present method is efficient (82.2% AE) and the experimental results confirm our strategy in creating an attractive architecture of a non-porous insulating film on the electrode surface.

Polydopamine imprinted polymer-based tunable electrochemical synthesis of copper benzene-1, 3, 5-tricarboxylate metal-organic framework film as a hybrid dual recognition element for ultra-trace sensing of pregabalin (lyrica)

The present study propounds an innovative diagnostic hybrid dual recognition strategy to detect trace amounts of pregabalin (PGB) using the combination of two powerful metal-organic framework (MOF) structures and the molecularly imprinted polymer (MIP) technique. To improve the analytical property of the electrode surface, copper-benzene-1,3,5-tricarboxylic acid frameworks (Cu-BTC MOFs) were directly synthesized on the glassy carbon electrode (GCE). Afterwards, MIP film was synthesized via the in situ dopamine (DA) electropolymerization method. To explore the effect of independent variables on the MIP construction, the Box-Behnken design was considered to determine the response surface methodology. In this sense, the predicted optimum combination variables were DA= 3 mM, pH = 7.4, cycle number = 16, KOH 4 mM, KOH: Et-OH ratio of 5:1 and 18 min elution time. Incubation time was obtained at 12 min. Electrochemical impedance spectroscopy (EIS) was used to determine the PGB analyte. The linear dynamic concentration range and limit of detection (LOD) were 0.05–800 pM and 2.9 fM, respectively. The imprinting calculated factor was 24.60, showing high interaction between the PGB and DA monomer. Inter-day and intra-day reproducibility measurements showed 2.08% and 1.58% and, 98% of the initial current response was maintained. Coefficients of selectivity against the PGB, for tapentadol, gabapentin, levetiracetam, L -Carnitine, and L -Histidine were 1, 5.52, 8.75, 2.8, 6.56 and 6.56 respectively. Cyclic voltammetry (CV) at various scan rates verified that adsorption kinetics follows a diffusion control mechanism. Finally, the efficiency of the GCE/Cu-BTC/ePDA-MIP sensor in real samples was evaluated and satisfactory results were achieved. • Combining two powerful molecularly imprinted polymer and metal-organic framework methods. • Direct growth of copper-organic framework mediated by copper hydroxide nano-strips. • In situ dopamine potentiodynamic electropolymerization. • Optimize electropolymerization conditions with Box-Behnken method. • Ultra-trace detection of pregabalin by prepared sensor.

Ni(OH)2-Type Nanoparticles Derived from Ni Salen Polymers: Structural Design toward Functional Materials for Improved Electrocatalytic Performance.

Herein, we report the potential-driven electrochemical transformation carried out in basic media of two Ni2+ salen polymers, (poly(NiSalen)s), abbreviated as poly(meso-NiSaldMe) and poly(NiSaltMe). These two polymers, with different configurations of methyl substituents on the imine bridge, were used as precursors for the preparation of electrocatalytically active nickel hydroxide [Ni(OH)2]-type nanoparticles (NPs) anchored in the polymeric matrix as poly[SalenNi(OH)2]. The use of potentiodynamic and potentiostatic electropolymerization conditions for the deposition of polymeric precursors allowed us to control the molecular architecture of poly(NiSalen)s and NPs derived from them. Thus, we obtained different arrangements of NPs embedded in morphologically different poly(Salen) matrixes, indicating their electrocatalytic activity toward ethanol to different extents. Moreover, we found a direct relationship between the electrochemical stability of the poly(NiSalen) precursors operating in the organic solvent-based electrolyte solutions and the easiness of their transformation into Ni(OH)2 NPs operating in the aqueous alkaline media. Poly(NiSalen)s and Ni(OH)2-type NPs were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy.

Fast and Efficient Voltammetric Detection of L-Tryptophan in Dietary Supplements Using Carbon Electrodes Modified with Poly(L-Arginine)

Tryptophan (TRYP) is an essential amino acid that plays several key roles in different physiological processes, ranging from acting as a building block for protein synthesis to being involved in neurotransmission and cellular signaling.1 Humans can only obtain TRYP from food intake,1 and therefore this compound is frequently added to dietary supplements. Considering the potential toxic effects that arise from TRYP overdoses,2 an efficient quality control should be performed on products containing TRYP in their formulations. In this way, this work proposes an efficient voltammetric sensor as a cost-effective and feasible tool to detect TRYP in commercial supplements. The sensor was based on glassy carbon electrodes modified with poly(L-arginine) (GCE/p-ARG), which was electrochemically synthesized in situ from L-arginine monomers.3 The conditions for p-ARG electropolymerization were optimized through multivariate statistical approaches in order to enhance the electrode’s sensing capability. Cyclic voltammetry and electrochemical impedance spectroscopy analysis in the presence of [Fe(CN)6]3-/4- redox probe showed that p-ARG significantly improved the electron transfer at the electrode surface. TRYP was irreversibly oxidized on GCE/p-ARG displaying a peak at +0.73 V (vs. Ag/AgCl), which was more intense than the anodic peak showed by the bare GCE. This was due to the presence of p-ARG on the GCE surface, which enabled the occurrence of multiple interactions that favoured TRYP detection. The amino acid oxidation followed a diffusion-controlled mechanism and showed to be dependent on the supporting electrolyte pH. A linear relationship between the anodic peak current (obtained through square wave voltammetry) and the TRYP concentration was observed in the range from 1.0 to 7.0 μmol L-1. Limits of detection and quantification were found to be equal to 0.30 and 0.91 μmol L-1, respectively. The developed electroanalytical method was successfully applied to detect TRYP in dietary supplements, with good precision and accuracy. In conclusion, it can be stated that the GCE/p-ARG is a promising candidate for food and pharmaceutical industry to enable cheap, fast, and reliable quality control of TRYP-based commercial products. References M. Platten, E. A. A. Nollen, U. F. Röhrig, F. Fallarino, and C. A. Opitz, Nature Reviews Drug Discovery, 18, 379–401 (2019).Y. Xia, F. Zhao, and B. Zeng, Talanta, 206 (2020).J. Soleymani et al., Materials Science and Engineering C, 77, 790–802 (2017).

Molecularly imprinted electrochemical sensor based on poly(o-phenylenediamine-co-o-aminophenol) incorporated with poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) ferrocene composite modified screen-printed carbon electrode for highly sensitive and selective detection of prostate cancer biomarker

A molecularly imprinted polymer (MIP) of o-phenylenediamine (o-PD) and o-aminophenol (o-AP), electropolymerized in the presence of prostate specific antigen (PSA), was deposited on a screen-printed carbon electrode (SPCE) modified with a poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) ferrocene composite (PEDOT:PSS@Fc) to create a MIP/PEDOT:PSS@Fc/SPCE electrochemical sensor. The MIP layer was characterized by scanning electron microscopy (SEM). PSA was determined using differential pulse voltammetry by measuring the change in the oxidation peak current of Fc. At the optimal monomer molar ratio, electropolymerization condition, phosphate buffer pH and rebinding time, the MIP sensor produced a linear response over a concentration range of 1.0 × 10−7–1.0 × 10−4 ng mL−1 PSA. The detection limit was (8.3 ± 1.3) × 10−8 ng mL−1 and selectivity, reproducibility, reusability over 12 cycles and long-term stability over 7 weeks were good. Using the Langmuir adsorption isotherm, the dissociation constant (KD) of the MIP sensor was 1.91 × 10−6 ng mL−1. PSA levels detected in blood serum with the present sensor were consistent with the data from the electrochemiluminescence immunoassay (P > 0.05).