Electropolymerization of a conductive β-cyclodextrin polymer on reduced graphene oxide modified screen-printed electrode for simultaneous determination of ascorbic acid, dopamine and uric acid

Electrochemical sensor for simultaneous determination of antiviral favipiravir drug, paracetamol and vitamin C based on host-guest inclusion complex of β-CD/CNTs nanocomposite

Favipiravir (FVI) is extensively used as an effective medication against several diverse infectious RNA viruses. It is widely administered as an anti-influenza drug. Combination therapy formed from FVI, paracetamol (PAR) and vitamin C (VC) is needed for treating patients diseased by RNA viruses. Thus, an efficient electrochemical sensor is developed for detecting FVI in human serum samples. The sensor is fabricated by casting a thin layer of carbon nanotubes (CNTs) over a glassy carbon (GC) electrode surface followed by electrodeposition of another layer of β-cyclodextrin (β-CD). Under optimized conditions, the sensor shows excellent catalytic effect for FVI, PAR and VC oxidation in the concentration ranges (0.08 µM → 80 µM), (0.08 µM → 50 µM) and (0.8 µM → 80 µM) with low detection limits of 0.011 μM, 0.042 μM and 0.21 μM, respectively. The combined effect of host-guest interaction ability of β-CD for the drugs, and a large conductive surface area of CNTs improves the sensing performance of the electrode. The sensor exhibits stable response over 4 weeks, good reproducibility, and insignificant interference from common species present in serum samples. The reliability of using the sensor in serum samples shows good recovery of FVI, PAR and VC.

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.

Resultant inward imbalanced seeding force (RIISF)-induced concave gold nanostar (CAuNS) for non-enzymatic electrocatalytic detection of serotonin and Kynurenine in human serum

CTAC-based gold nanoseed-induced concave curvature evolution of surface boundary planes from concave gold nanocube (CAuNC) to concave gold nanostar (CAuNS) has been achieved by a novel synthetic methodology simply by controlling the extent of seed used and hence the generated 'Resultant Inward Imbalanced Seeding Force (RIISF)'. The resultant CAuNS shows an excellent enhancement in catalytic activity compared to CAuNC and other intermediates as a function of curvature-induced anisotropy. Detailed characterization evaluates the presence of an enhanced number of multiple defect sites, high energy facets, larger surface area, and roughened surface which ultimately results in an increased mechanical strain, coordinately unsaturation, and multifacet-oriented anisotropic behavior suitable for positive influence on the binding affinity of CAuNSs. While different crystalline and structural parameters improve their catalytic activity, the resultant uniform three-dimensional (3D) platform shows comparatively easy pliability and well absorptivity on the glassy carbon electrode surface for increased shelf life, a uniform structure to confine a large extent of stoichiometric systems, and long-term stability under ambient conditions for making this newly developed material a unique nonenzymatic scalable universal electrocatalytic platform. With the help of various electrochemical measurements, the ability of the platform has been established by performing highly specific and sensitive detection of the two most important human bio messengers: Serotonin (STN) and Kynurenine (KYN) which are metabolites of L-Tryptophan in the human body system. The present study mechanistically surveys the role of seed-induced RIISF-modulated anisotropy in controlling the catalytic activity which offers a universal 3D electrocatalytic sensing tenet by an electrocatalytic approach.

Reduced Graphene Oxide as a Platform for the Immobilization of Amino-Cyclodextrins

In the present work, we reported on a method to combine amino β-cyclodextrins (CD1) with reduced graphene oxide (obtained by the electrochemical reduction of graphene oxide, erGO) to produce a glassy carbon electrode (GCE) modified with both CD1 and erGO (CD1-erGO/GCE). This procedure avoids the use of organic solvents such as hydrazine or long reaction times and high temperatures. The material combining both CD1 and erGO (CD1-erGO/GCE) was characterized by SEM, ATR-FTIR, Raman, XPS, and electrochemical techniques. As proof-of-concept, the determination of the pesticide carbendazim was carried out. The spectroscopic measurements, especially XPS, proved that CD1 was covalently attached to the surface of the erGO/GCE electrode. The attachment of cyclodextrin at the reduced graphene oxide produced an increase in the electrochemical behavior of the electrode. The cyclodextrin-functionalized reduced graphene oxide, CD1-erGO/GCE, showed a larger sensitivity (1.01 μA/μM) and a lower limit of detection for carbendazim (LOD = 0.50 μM) compared with the non-functionalized material, erGO/GCE, (sensitivity = 0.63 μA/μM and LOD = 4.32 μM, respectively). Overall, the results of the present work show that this simple method is suitable to attach cyclodextrins to graphene oxide, maintaining their inclusion abilities.

A novel, extreme low-cost poly (Erythrosine) modified pencil graphite electrode for determination of Adrenaline

A simple, novel, and less cost yellow (Erythrosine) modified pencil graphite electrode (Po-ERY/MGPE) was successfully fabricated via electropolymerization method using cyclic voltammetric techniques. The fabricated Po-ERY/MGPE opted as a sensor for the detection of Adrenaline (ADR) in 0.2 M PBS (7.4 pH). This reported senor displayed excellent electrocatalytic activity, increased sensitivity, high stability, superior electron transfer kinetics in the oxidation of ADR once relative to BGPE. The significance of pH, scan rate, and impact of concentration was assessed at the sensor. As per the pH and scan rate study, redox routes carry the same number of electrons and protons, and electro-oxidation of ADR was adsorption controlled respectively. The LOD of ADR was found to be 0.499 µM. The DPV data indicate that there is a significant peak divergence among ADR and uric acid (UA) which could make it easier to determine them alone and simultaneously on the sensor. The described method has been employed for the determination of ADR in injection sample. Good recovery values indicate the efficacy and applicability of the sensor in detecting ADR.

An Electrochemical Sensor Based on Electropolymerization of β-Cyclodextrin on Glassy Carbon Electrode for the Determination of Fenitrothion

An electrochemical sensor enabled by electropolymerization (EP) of β-cyclodextrin on glassy carbon electrode (β-CDP/GCE) is built for the determination of fenitrothion (FNT). The effects of the EP cycles, pH value, and enrichment time on the electrochemical response of FNT were studied. With the optimum conditions, good linear relationships between the current of the reduction peak of the nitroso derivative of FNT and the concentration are obtained in the range of 10-150 and 150-4000 ng/mL, with a detection limit of 6 ng/mL (S/N = 3). β-CDP/GCE also exhibits a satisfactory applicability in cabbage and tap water, with recovery values between 98.43% and 112%. These outstanding results suggest that β-CDP/GCE could be a new effective alternative for the determination of FNT in real samples.

Functionalization of Graphene Derivatives with Conducting Polymers and Their Applications in Uric Acid Detection

In this article, we review recent progress concerning the development of sensorial platforms based on graphene derivatives and conducting polymers (CPs), alternatively deposited or co-deposited on the working electrode (usually a glassy carbon electrode; GCE) using a simple potentiostatic method (often cyclic voltammetry; CV), possibly followed by the deposition of metallic nanoparticles (NPs) on the electrode surface (ES). These materials have been successfully used to detect an extended range of biomolecules of clinical interest, such as uric acid (UA), dopamine (DA), ascorbic acid (AA), adenine, guanine, and others. The most common method is electrochemical synthesis. In the composites, which are often combined with metallic NPs, the interaction between the graphene derivatives-including graphene oxide (GO), reduced graphene oxide (RGO), or graphene quantum dots (GQDs)-and the CPs is usually governed by non-covalent functionalization through π-π interactions, hydrogen bonds, and van der Waals (VW) forces. The functionalization of GO, RGO, or GQDs with CPs has been shown to speed up electron transfer during the oxidation process, thus improving the electrochemical response of the resulting sensor. The oxidation mechanism behind the electrochemical response of the sensor seems to involve a partial charge transfer (CT) from the analytes to graphene derivatives, due to the overlapping of π orbitals.

Reactive argon-plasma activation of screen-printed carbon electrodes for highly selective dopamine determination

Dopamine (DA) deficiency has been linked to several psychiatric disorders. Electrochemical determination of the level of DA suffers from abundant ascorbic acid (AA) and uric acid (UA) in body fluids. In this work, a facile argon (Ar) plasma treatment was utilized to enhance the electrocatalytic reactivity of screen-printed carbon electrodes (SPCEs) for selective DA detection. Surface characterization of the Ar-treated SCPEs verified that the carbon paste binders were successfully removed and single-bonded oxygenated moieties (-OH and C-O-C) were generated. Interestingly, the sharper D* and D'' Raman interbands were new key evidence of a higher exposure of carbon defect sites. Electrochemical studies further revealed that the Ar-treated SPCEs possessed faster heterogeneous electron-transfer rates, larger electroactive surface areas, and much higher conductivity when compared with untreated electrodes. As a result, the oxidation potentials of AA, DA, and UA in the mixture could be well-resolved and the current responses were significantly increased. The selective determination of DA in the presence of AA and UA by differential pulse voltammetry gave two linear responses with the limit of detection of 0.27 μM (0.15-10 μM range). Moreover, this Ar-treated SPCE had high reproducibility and good storage stability. These results suggest that Ar-plasma treatment could be a promising method to enhance the electrocatalytic properties of SPCEs for the detection of biomolecules.

Development of a Redox-Label-Doped Molecularly Imprinted Polymer on β-Cyclodextrin/Reduced Graphene Oxide for Electrochemical Detection of a Stress Biomarker

Cortisol is a major stress biomarker involved in the regulation of metabolic and immune responses. Readily accessible assays with sufficient quantitative and temporal resolution can assist in prevention, early diagnosis, and management of chronic diseases. Whereas conventional assays are costly in terms of time, labor, and capital, an electrochemical approach offers the possibility of miniaturization and detection at the point-of-care. Here, we investigate the biosensor application of molecularly imprinted polypyrrole (PPy) doped with hexacyanoferrate (HCF) and coupled to reduced graphene oxide functionalized with β-cyclodextrin (β-CD). β-CD provides an inclusion site for lipophilic cortisol and was electrochemically grafted simultaneous with reduction of GO. Next, PPy was electrochemically deposited in presence of cortisol template with HCF dopant ions serving as intrinsic redox probe. Thus, the sensor response was evaluated via changes of redox peak current in cyclic voltammetry and demonstrated a broad logarithmic detection range (5 pg/mL to 5000 ng/mL, R ² = 0.995), with a sensitivity of 8.809 μA log^-1 (ng/mL) cm^-2 and LOD of 19.3 pM. The sensor was shown to be specific toward cortisol in reference to salivary cortisol concentration in saliva over structural analogues. The sensor was exhibited to determine cortisol in artificial saliva at normal and elevated levels. The good performance and facile electrochemical fabrication of this antibody- and external label-free interface are promising for the development of affordable point-of-care biosensors.

Poly (Orange CD) sensor for paracetamol in presence of folic acid and dopamine

In the present work, Orange CD was chosen as an intriguing modifier for the electropolymerization on the surface of CPE by the CV technique. A novel, sensitive, and cost-effective poly (Orange CD) MCPE (PoOCD/MCPE) sensor was utilized for the selective detection of paracetamol (PA) in 0.2 M phosphate buffer solution (PBS) of pH 7.4. The oxidation peak current of PA was vastly enhanced at the sensor. The scan rate study is suggested that electro-oxidation of PA was adsorption-controlled. The pH study testifies the redox pathways transport with the same quantity of electrons and protons. The detection limit of PA is found to be 2.64 µM. DPV results show that substantial peak separation between PA, folic acid (FA), and dopamine (DA) could be facilitating their individual and simultaneous determination on the sensor. The decorated sensor demonstrates high sensitivity, stability, reproducibility, repeatability and has been successfully exploited for the detection of PA in a tablet with promising results.

Sensitive identification of silibinin as anticancer drug in human plasma samples using poly (β-CD)-AgNPs: A new platform towards efficient clinical pharmacotherapy

Silibinin is effective in significantly inhibiting the growth of cancer cells which shown significant anti-neoplastic effects in a variety of in vitro and in vivo cancer models, including skin, breast, lung, colon, bladder, prostate and kidney carcinomas. So, development of a new method to its biomedical analysis in clinical samples in highly demanded. In this study, an innovative electroanalysis method for the accurate, sensitive and rapid recognition of silibinin in human plasma samples was proposed and validated. The sensing platform was designed using silver nanoparticles (AgNPs) dispersed on the polymeric layer of β-cyclodextrin (β-CD). AgNPs with cubic shape providing a large effective surface area for β-CD electropolymerization. So, a layer with high electron conductivity boosting the detection electrochemical signals. Also, poly(β-CD) providing an efficient substrate with cavities to interact with silibinin and its oxidation. Differential pulse voltammetry technique was conducted to measure silibinin concentration in human real samples. Under optimized conditions, proposed sensor indicated linear relationship between the anodic peak current and concentration of silibinin in the range of 0.0103-10.3 µM on the standard and human plasma samples. Based on obtained results, proposed sensor is an efficient platform to efficient therapy of cancer based on recognition of silibinin in clinical samples.

Electrochemical aptasensor for 17β-estradiol using disposable laser scribed graphene electrodes

17β-Estradiol (E2), the strongest of the three major physiological estrogens in females, is an important factor in the female reproductive system. The abnormal level of E2 causes health issues, such as weak bones, urinary tract infections and even depression. Here, we present a novel, sensitive and selective, electrochemical aptasensor for detection of 17β-estradiol (E2). The E2 recognition aptamer was split into two fragments: the first fragment, functionalised with adamantane, is attached to poly(β-cyclodextrin) (poly(β-CD))-modified electrode surface through host-guest interactions between the adamantane and poly(β-CD). The second fragment, labelled with gold nanoparticles, forms the stem-loop structure with the first fragment only in the presence of E2. That specific recognition process triggers the change in the electrochemical signal (a change in the peak current from reduction of AuNPs), recorded by means of differential pulse voltammetry (DPV). The feasibility of the sensing design was firstly investigated on the commercially available glass carbon electrodes (GCE), with achieved a linear detection range of 1.0 × 10^-13 to 1.0 × 10^-8 M and a limit of detection (LoD) 0.7 fM. The sensing methodology was then translated onto single-use, disposable, laser-scribed graphene electrodes (LSGE) on a plastic substrate. The dynamic sensing range of E2 on LSGE was found to be 1.0 × 10^-13 to 1.0 × 10^-9 M, with a LoD of 63.1 fM, comparable to these of GCE. The successful translation of the developed E2 aptasensor from GCE to low-cost, disposable LSGE highlights a potential of this sensing platform in commercial, portable sensing detection systems for E2 and similar targets of biological interest.

da Silva Alves D, Okeke C, Breslin CB. Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.

Enhancement of graphene oxide through β-cyclodextrin composite to sensitive analysis of an antidepressant: Sulpiride

In this study, the electrochemical behavior of sulpiride (SUL) was examined deeply by using pyrolytic graphite electrode modified with graphene oxide (GO) and β-cyclodextrin (β-CD). The developed nanosensor indicated considerable impact by significantly increasing the signal of SUL compared with the bare electrode. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) methods were utilized to investigate the SUL electrochemical analysis in aqueous solutions. Under optimum experimental conditions, calibration plot for SUL with a limit of detection of 2.83 × 10−9 M was obtained at accumulation time of the 30 s using square wave adsorptive stripping voltammetric technique (AdSSWV) in the range of 1.0 × 10−7 to 5.0 × 10−5 M. The effects of accumulation potential, accumulation time, pH, scan rate, electrolyte, and interfering agents were studied to obtain the intensive peak signal of the analyte. The presented method is validated and successfully performed for the determination of the SUL tablet and capsule. The fabricated nanosensor was carried out for the detection of SUL in the urine. Excellent recoveries among 104.37, 103.82, and 101.95% were obtained for tablet and capsule forms and urine analysis.

Chemical binding of horseradish peroxidase enzyme with poly beta-cyclodextrin and its application as molecularly imprinted polymer for the monitoring of H2 O2 in human plasma samples

In this study, a selective and sensitive molecular imprinting-based electrochemical sensors, for horseradish peroxidase (HRP) entrapment was fabricated using electro polymerization of ß-Cyclodextrin (ß-CD) on the surface of glassy carbon electrode. Poly beta-cyclodextrin P(ß-CD) provide efficient surface area for self-immobilization of HRP as well as improve imprinting efficiency. The proposed imprinted biosensor successfully utilized for detection of HRP with excellent analytical results which linear range is 0.1 mg/mL to 10 ng/mL with LOD of 2.23 ng/mL. Furthermore, electrocatalytical activity of the prepared biosensor toward the reduction of hydrogen peroxide was investigated in the ranges of 1 to 15 μM with a detection limit of 0.4 μM by using chronoamperometry technique. The developed biosensor was used for the detection of hydrogen peroxide in unprocessed human plasma sample.

Molecularly Imprinted Sensor for Ascorbic Acid Based on Gold Nanoparticles and Multiwalled Carbon Nanotubes

Background:

L-Ascorbic acid (AA) is a kind of water soluble vitamin, which is mainly present in fruits, vegetables and biological fluids. As a low cost antioxidant and effective scavenger of free radicals, AA may help to prevent diseases such as cancer and Parkinson’s disease. Owing to its role in the biological metabolism, AA has also been utilized for the therapy of mental illness, common cold and for improving the immunity. Therefore, it is very necessary and urgent to develop a simple, rapid and selective strategy for the detection of AA in various samples.

Methods:

The molecularly imprinted poly(o-phenylenediamine) (PoPD) film was prepared for the analysis of L-ascorbic acid (AA) on gold nanoparticles (AuNPs) - multiwalled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE) by electropolymerization of o-phenylenediamine (oPD) and AA. Experimental parameters including pH value of running buffer and scan rates were optimized. Scanning electron microscope (SEM), fourier-transform infrared (FTIR) spectra, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized for the characterization of the imprinted polymer film.

Results:

Under the selected experimental conditions, the DPV peak currents of AA exhibit two distinct linear responses ranging from 0.01 to 2 μmol L-1 and 2 to 100 μmol L-1 towards the concentrations of AA, and the detection limit was 2 nmol L-1 (S/N=3).

Conclusion:

The proposed electrochemical sensor possesses excellent selectivity for AA, along with good reproducibility and stability. The results obtained from the analysis of AA in real samples demonstrated the applicability of the proposed sensor to practical analysis.

Design of A Low-Cost and Disposable Paper-Based Immunosensor for the Rapid and Sensitive Detection of Aflatoxin B1

We report a paper-based electrochemical immunosensor made with sustainable materials to detect aflatoxin B1 (AFB1), a highly toxic, carcinogenic mycotoxin found in food. The immunosensor was prepared with a waterproof paper substrate and low-cost graphite-based conductive ink through a simple cut-printing method. The working electrode was functionalized with a drop-cast film of multiwalled carbon nanotubes (MWCNT)/chitosan on which a layer of anti-AFB1 monoclonal antibodies was immobilized covalently. The architecture of the immunosensor was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and electrochemical impedance spectroscopy (EIS), including the effective immobilization of the active layer of anti-AFB1. With EIS as the principle of detection, the immunosensor could detect AFB1 in the range from 1 to 30 ng·mL−1, and detection limit of 0.62 ng·mL−1. This sensitivity is sufficient to detect AFB1 in food according to regulatory agencies. The immunosensor exhibited good repeatability, reproducibility, stability, and selectivity in experiments with a possible interferent. Furthermore, detection of AFB1 in maize flour samples yielded recovery of 97–99%, in a demonstration of the possible use of the paper-based immunosensor to detect AFB1 using extraction solutions from food samples.

Enhanced Electrocatalytic Behaviour of Poy(aniline-co-2-hydroxyaniline) Coated Electrodes for Hydrogen Peroxide Electrooxidation

Polymer-coated electrodes are widely used for the detection and oxidation of hydrogen peroxide (H2O2). Conducting polyaniline (PANI), poly (2-hydroxyanilne) (PHA), and their copolymer poly(aniline-co-2-hydroxyaniline) (PACHA) were electrochemically synthesized on a gold substrate for H2O2 detection and analysis. Cyclic voltammetry (CV), square wave voltammetry (SWV), and differential pulse voltammetry (DPV) techniques were used for electroanalysis. Both PACHA and PANI greatly reduced the gold overpotential for H2O2 oxidation with enhanced current densities. The PACHA- and PANI-coated electrodes showed oxidative peaks at 0.30 and 0.50 V, respectively, in the presence of 1.4 × 10−6 M H2O2, while PHA-coated electrodes exhibited no response. The fabricated electrodes displayed a linear response towards H2O2 in range of 2 × 10−7 to 1.4 × 10−6 M, with very low detection limits (LODs) of 1 × 10−7 M (for PACHA) and 1.15 × 10−7 M (for PANI) evaluated from CV data. In case of SWV and DPV, the LODs were found to be 1.78 × 10−7 M (for PACHA) and 1 × 10−7 M (for PANI), respectively. The materials exhibit high sensitivity of 650 A/Mcm2 and show good stability. The PACHA-coated electrode shows better capacitance (1.84 × 10−3 F) than PHA- (2.52 × 10−4 F) and PANI-coated (1.17 × 10−3 F) electrodes.

Nanosized iron telluride for simultaneous nanomolar voltammetric determination of dopamine, uric acid, guanine and adenine

Herein, an efficient electrochemical sensor based on nano-sized iron telluride material (FeTe₂) have been developed for the first time for simultaneous nanomolar determination of dopamine, uric acid, guanine and adenine molecules.

A Nanostructured Sensor Based on Gold Nanoparticles and Nafion for Determination of Uric Acid

The paper discusses the mechanism of uric acid (UA) electrooxidation occurring on the surface of gold nanoparticles. It has been shown that the electrode process is purely electrochemical, uncomplicated with catalytic stages. The nanoeffects observed as the reduction of overvoltage and increased current of UA oxidation have been described. These nanoeffects are determined by the size of particles and do not depend on the method of particle preparation (citrate and "green" synthesis). The findings of these studies have been used to select a modifier for carbon screen-printed electrode (CSPE). It has been stated that CSPE modified with gold nanoparticles (5 nm) and 2.5% Nafion (Nf) may serve as non-enzymatic sensor for UA determination. The combination of the properties of nanoparticles and Nafion as a molecular sieve at the selected pH 5 phosphate buffer solution has significantly improved the resolution of the sensor compared to unmodified CSPE. A nanostructured sensor has demonstrated good selectivity in determining UA in the presence of ascorbic acid. The detection limit of UA is 0.25 μM. A linear calibration curve has been obtained over a range of 0.5-600 μM. The 2.5%Nf/Au(5nm)/CSPE has been successfully applied to determining UA in blood serum and milk samples. The accuracy and reliability of the obtained results have been confirmed by a good correlation with the enzymatic spectrophotometric analysis (R² = 0.9938) and the "added-found" technique (recovery close to 100%).

A ratiometric strategy -based electrochemical sensing interface for the sensitive and reliable detection of imidacloprid

A ratiometric electrochemical sensor was developed for selective and sensitive detection of imidacloprid. Modified poly(thionine) provided a built-in correction to endow the sensor with good accuracy and stability.

Low-cost screen-printed electrodes based on electrochemically reduced graphene oxide-carbon black nanocomposites for dopamine, epinephrine and paracetamol detection

A green approach for the preparation of carbon black (CB) and electrochemically reduced graphene oxide composite (ERGO) is described based on screen printed carbon electrodes (SPCEs) fabricated on poly(ethylene terephthalate) (PET) as electrochemical sensors. This approach leads to a heterogeneous hydrophilic surface with high concentration of defect sites according to scanning electron microscopy, contact angle and Raman spectroscopy measurements. The SPCE/CB-ERGO sensor was tested with dopamine (DA), epinephrine (EP) and paracetamol (PCM), exhibiting an enhanced electrocatalytic performance compared to the bare SPCE. It displayed a wider linear range, lower limit of detection and a remarkably higher analytical sensitivity, viz. 1.5, 0.13 and 0.028 A L mol^-1 for DA, EP and PCM, respectively, being also capable of simultaneous determination of the three analytes. Such high performance is demonstration that SPCE/CB-ERGO may serve as generic platform for cost-effective flexible electrochemical sensors.