Surface Of Screen-printed Carbon Electrode Research Articles

Capacitive nanobiosensing of β-1,4-galactosyltransferase-V colorectal cancer biomarker

β-1,4-GalT-V is an enzyme with glycosyltransferase activity that glycosylates proteins and synthesizes the lactosylceramide sphingolipid in the Golgi apparatus. Colorectal cancer (CRC) tumor cells produce these biomolecules in high concentrations concerning normal cells, releasing them into the blood serum. Hence, β-1,4-GalT-V glycoprotein has emerged as a promising CRC biomarker, and its detection opens opportunities for the diagnosis/prognosis of CRC. We report the first capacitive nanobiosensor for the detection of β-1,4-GalT-V based on disposable screen-printed carbon electrodes (SPCEs) nanostructured with gold nanorods (AuNRs) and the Prussian blue (PrB) redox-active compound. AuNRs increased the SPCE surface area for antibody immobilization by physical adsorption and promoted the deposition of PrB onto the SPCE surface. Antibody-glycoprotein molecular biorecognition event onto the SPCE/AuNRs/PrB surface perturbed the PrB redox density-of-states and hence redox capacitance (Cμ̅). We found that changes in the inverse of Cμ̅ correlated well with the increasing concentrations of β-1,4-GalT-V in the linear range from 50 to 400 fM with a sensitivity of 1.5 µF fM-1 cm-2 and a limit of detection of 20 fM. The nanobiosensor detected the β-1,4-GalT-V glycoprotein from raw human serum samples with high specificity, ultrasensitivity, and reagentless label-free electrochemical transduction. The nanobiosensor could be applied as a CRC diagnosis/prognosis tool in a decentralized setting, with minimal patient sample manipulation and rapid response.

Novel Electrochemical Aptasensor Based on Ordered Mesoporous Carbon/2D Ti3C2 MXene as Nanocarrier for Simultaneous Detection of Aminoglycoside Antibiotics in Milk.

Herein, a novel electrochemical aptasensor using a broad-spectrum aptamer as a biorecognition element was constructed based on a screen-printed carbon electrode (SPCE) for simultaneous detection of aminoglycoside antibiotics (AAs). The ordered mesoporous carbon (OMC) was firstly modified on 2D Ti3C2 MXene. The addition of OMC not only effectively improved the stability of the aptasensor, but also prevented the stacking of Ti3C2 sheets, which formed a good current passage for signal amplification. The prepared OMC@Ti3C2 MXene functioned as a nanocarrier to accommodate considerable aptamers. In the presence of AAs, the transport of electron charge on SPCE surface was influenced by the bio-chemical reactions of the aptamer and AAs, generating a significant decline in the differential pulse voltammetry (DPV) signals. The proposed aptasensor presented a wide linear range and the detection limit was 3.51 nM. Moreover, the aptasensor, with satisfactory stability, reproducibility and specificity, was successfully employed to detect the multi-residuals of AAs in milk. This work provided a novel strategy for monitoring AAs in milk.

Porous graphene oxide based disposable non-enzymatic electrochemical sensor for the determination of nicotinamide adenine dinucleotide

Electrochemical detection of β-nicotinamide adenine dinucleotide (NADH) has fascinated the scientific community due to its significance in pharmaceuticals, food supplements as well as in various biological reactions and pathways. Herein, a facile and low-cost disposable non-enzymatic electrochemical sensor for the selective and sensitive determination of NADH was developed using porous graphene oxide (PGO) modified screen printed carbon electrode (SPE). PGO has received growing attention owing to its high internal porosity, improved conductivity, large surface area, excellent stability, improved active sites, and hence expected to show excellent electrocatalytic activity than graphene and other derivatives of carbon. Firstly, graphene oxide (GO) sheets were synthesized, after which pores were created on these GO sheets through simple base reduction and acid treatment and the pore formation was confirmed using different characterization techniques. The PGO was directly dropcasted on the surface of SPE to form PGO/SPE and the fabricated electrode demonstrated eminent electrocatalytic activity towards NADH oxidation. Further, the fabricated sensor has shown significant response over a broad-range of concentration from 30 to 1071 μM with a good sensitivity of 21.83 μA mM −1 cm −2 and a low detection limit of 8.6 μM. Moreover, the fabricated PGO/SPE has advantages like cost-effectiveness, robustness, disposability, ease of fabrication, high stability, and excellent reproducibility. • Porous graphene oxide was synthesized via base reduction and acidification. • Fabricated a disposable electrochemical sensor by dropcasting PGO on SPE (PGO/SPE) • PGO/SPE effectively utilized for the electrocatalytic oxidation of NADH. • Compared to GO/SPE and ERGO/SPE, PGO/SPE showed superior analytical performance. • PGO/SPE exhibits good selectivity for NADH with excellent stability and sensitivity.

Facile synthesis of electrocatalytically active bismuth oxide nanosheets for detection of palladium traces in pharmaceutical wastewater

Current synthesis routes of bismuth oxide nanosheets (BiONS) are relatively complicated, requiring the use of halogens or metalloids. Herein, a facile method to synthesize BiONS without the addition of halogens or other metalloids was developed. The synthesized BiONS were identified to have flake-shaped structures (300–1000 nm in width) with the thickness of 6–10 nm, which were predominantly made of β-Bi2O3. Such BiONS were applied to modify the surface of screen-printed carbon electrodes (BiONS-SPCEs) for the development of a robust palladium (Pd2+) sensor. After optimizing the electrochemical parameters of the sensor, it was found that the linear sensor response range and limit of detection for Pd2+ were 40–400 and 1.4 ppb, respectively. The electrocatalytic activity of the Pd2+-sensor was validated in the competing environment of other metal and metalloid ions. Real samples collected during a Pd recovery process from pharmaceutical wastewater were used to verify the application of BiONS-SPCEs in control of palladium recovery process. The quantitative results of post recovery palladium concentrations obtained using BiONS-SPCEs in treated pharmaceutical wastewater samples were in good agreement with those obtained by inductively coupled plasma-optical emission spectrometry (ICP-OES). Thus, such Pd2+-sensor provided the possibility of on-site process control of complex industrial samples for obtaining near-instant information that would lead to better management of resources used in the process, and same time assure environmental standards for both recovered products and processed discharge.

Disposable Electrochemical Aptasensor Based on Graphene Oxide-DNA Complex as Signal Amplifier towards Ultrasensitive Detection of Ochratoxin A.

Signal amplification is crucial in developing a reliable disposable screen-printed carbon electrodes (SPCEs)-based biosensor for analyte detection with a narrow detection window. This work demonstrated a novel label-free electrochemical aptasensor based on SPCEs for the ultrasensitive detection of ochratoxin A (OTA). The graphene oxide-DNA (GO-DNA) complex as a signal amplifier with easy preparation was investigated for the first time. The proposed aptasensor based on the SPCEs/GO/cDNA-aptamer/3D-rGO-AuNPs structure was formed through the hybridization of aptamer-linked 3D-rGO/AuNPs and its complementary DNA-linked GO (GO-cDNA). The presence of OTA was discerned by its specific aptamer forming a curled OTA-aptamer complex and releasing the GO-cDNA from the surface of SPCEs. The resulting OTA-aptamer complex hindered interfacial electron transfer on the sensing surface, leading to the decreased peak current. The GO-cDNA further amplified the peak current change. This electrochemical aptasensor showed a low limit of detection of 5 fg/mL as well as good reproducibility with the relative standard deviation (RSD) of 4.38%. Moreover, the detection result of OTA in the rice and oat samples was comparable with that of the enzyme-linked immunosorbent assay (ELISA) kit. In general, the OTA aptasensor used in this work with convenient preparation, low-cost, good selectivity, high sensitivity and acceptable reproducibility can be proposed as a reliable point-of-care (POC) technique for OTA determination.

Screen-Printed Carbon Electrodes with Macroporous Copper Film for Enhanced Amperometric Sensing of Saccharides.

A porous layer of copper was formed on the surface of screen-printed carbon electrodes via the colloidal crystal templating technique. An aqueous suspension of monodisperse polystyrene spheres of 500 nm particle diameter was drop-casted on the carbon tracks printed on the substrate made of alumina ceramic. After evaporation, the electrode was carefully dipped in copper plating solution for a certain time to achieve a sufficient penetration of solution within the polystyrene spheres. The metal was then electrodeposited galvanostatically over the self-assembled colloidal crystal. Finally, the polystyrene template was dissolved in toluene to expose the porous structure of copper deposit. The morphology of porous structures was investigated using scanning electron microscopy. Electroanalytical properties of porous copper film electrodes were evaluated in amperometric detection of selected saccharides, namely glucose, fructose, sucrose, and galactose. Using hydrodynamic amperometry in stirred alkaline solution, a current response at +0.6 V vs. Ag/AgCl was recorded after addition of the selected saccharide. These saccharides could be quantified in two linear ranges (0.2–1.0 μmol L−1 and 4.0–100 μmol L−1) with detection limits of 0.1 μmol L−1 glucose, 0.03 μmol L−1 fructose, and 0.05 μmol L−1 sucrose or galactose. In addition, analytical performance of porous copper electrodes was ascertained and compared to that of copper film screen-printed carbon electrodes, prepared ex-situ by the galvanostatic deposition of metal in the plating solution. After calculating the current densities with respect to the geometric area of working electrodes, the porous electrodes exhibited much higher sensitivity to changes in concentration of analytes, presumably due to the larger surface of the porous copper deposit. In the future, they could be incorporated in detectors of flow injection systems due to their long-term mechanical stability.

A membrane-less Glucose/O2 non-enzymatic fuel cell based on bimetallic Pd–Au nanostructure anode and air-breathing cathode: Towards micro-power applications at neutral pH

Herein, the authors propose a miniaturized glucose/O2 n-EFC based on a new direct electron transfer. The anode is a screen-printed carbon electrode (SPCE) modified with functionalized carbon nanotubes (f-CNTs) and cauliflower-like PdAu nanostructures (PdAuNS). The PdAuNS/f-CNT biomimetic nanocatalyst was prepared using a cost-effective and straightforward method, which consisted of drop-casting well-dispersed f-CNTs over the SPCE surface before PdAuNS electrodeposition. This enzyme-free interface was used for glucose electrooxidation at neutral medium (pH 7.4). The electrochemical behaviour of the PdAuNS/f-CNT/SPCE was investigated using cyclic voltammetry, linear sweep voltammetry, and amperometry. Several parameters were optimized and discussed, including the metal precursor concentration (HAuCl4, PdCl2) and the electrodeposition conditions. The cathode for oxygen electroreduction is an air-cathode which is composed of Pt-coated carbon cloth. The electrochemical performances of the anode and the cathode were evaluated separately for glucose oxidation and oxygen reduction, respectively. Both electrodes were then assembled in a membrane-less single chamber n-EFC with an innovative architecture. Electrical characterization of the n-EFC supplied with a neutral buffered solution containing 20 mM glucose showed a maximal power output of 129 ± 11 μW cm−2, a current density of 600 ± 39 μA cm−2 with a cell voltage of 0.35 V, and an open circuit potential of 0.56 V. The proposed electrocatalyst possesses several advantages such as fast response, low cost, reusability, poison-free characteristics, and good stability. Hence, glucose/O2 n-EFC could be of great interest in direct glucose fuel cell applications (e.g., powering mountable/implantable biomedical micro-devices running at low electrical power supply) or in self-powered biosensing.

Conductive electrospun composite fibers based on solid-state polymerized Poly(3,4-ethylenedioxythiophene) for simultaneous electrochemical detection of metal ions.

Conductive composite fibers containing poly (3,4-ethylenedioxythiophene) (PEDOT) and silver nanoparticles (AgNPs) were fabricated by emulsion electrospinning of 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) in toluene together with aqueous solution of poly (vinyl alcohol) (PVA) and silver nanoparticles (AgNPs) in the presence of sodium dodecylsulfate followed by heat treatment at 70°C to convert DBEDOT to conductive PEDOT via solid state polymerization (SSP). The composite fibers were characterized by scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and thermogravimetric analysis. The PEDOT/PVA/AgNPs composite fibers deposited on a screen-printed carbon electrode (SPCE) surface exhibited good electrochemical response and was applied for simultaneous detection of heavy metal ions in a mixture, namely Zn(II), Cd(II), and Pb(II) via square wave anodic stripping voltammetry (SWASV). With added Bi+3 into the detection system, the bismuth film formed on the electrode allows effective alloy formation with the deposited heavy metals obtained upon reduction of the heavy metal ions, the detection of heavy metal ions after stripping was successfully accomplished with a linear range of 10-80ppb and limits of detections (LOD) of 6, 3 and 8ppb for Zn(II), Cd(II), and Pb(II), respectively.

Nanochannel Array on Electrochemically Polarized Screen Printed Carbon Electrode for Rapid and Sensitive Electrochemical Determination of Clozapine in Human Whole Blood.

Rapid and highly sensitive determination of clozapine (CLZ), a psychotropic drug for the treatment of refractory schizophrenia, in patients is of great significance to reduce the risk of disease recurrence. However, direct electroanalysis of CLZ in human whole blood remains a great challenge owing to the remarkable fouling that occurs in a complex matrix. In this work, a miniaturized, integrated, disposable electrochemical sensing platform based on the integration of nanochannel arrays on the surface of screen-printed carbon electrodes (SPCE) is demonstrated. The device achieves high determination sensitivity while also offering the electrode anti-fouling and anti-interference capabilities. To enhance the electrochemical performance of SPCE, simple electrochemical polarization including anodic oxidation and cathodic reduction is applied to pretreat SPCE. The electrochemically polarized SPCE (p-SPCE) exhibits an enhanced electrochemical peak signal toward CLZ compared with bare SPCE. An electrochemically assisted self-assembly method (EASA) is utilized to conveniently electrodeposit a vertically ordered mesoporous silica nanomembrane film (VMSF) on the p-SPCE, which could further enrich CLZ through electrostatic interactions. Owing to the dual signal amplification based on the p-SPCE and VMSF nanochannels, the developed VMSF/SPCE sensor enables determination of CLZ in the range from 50 nM to 20 μM with a low limit of detection (LOD) of 28 nM (S/N = 3). Combined with the excellent anti-fouling and anti-interference abilities of VMSF, direct and sensitive determination of CLZ in human blood is also achieved.

Nanoporous Cauliflower-like Pd-Loaded Functionalized Carbon Nanotubes as an Enzyme-Free Electrocatalyst for Glucose Sensing at Neutral pH: Mechanism Study.

In this work, we propose a novel functionalized carbon nanotube (f-CNT) supporting nanoporous cauliflower-like Pd nanostructures (PdNS) as an enzyme-free interface for glucose electrooxidation reaction (GOR) in a neutral medium (pH 7.4). The novelty resides in preparing the PdNS/f-CNT biomimetic nanocatalyst using a cost-effective and straightforward method, which consists of drop-casting well-dispersed f-CNTs over the Screen-printed carbon electrode (SPCE) surface, followed by the electrodeposition of PdNS. Several parameters affecting the morphology, structure, and catalytic properties toward the GOR of the PdNS catalyst, such as the PdCl2 precursor concentration and electrodeposition conditions, were investigated during this work. The electrochemical behavior of the PdNS/f-CNT/SPCE toward GOR was investigated through Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV), and amperometry. There was also a good correlation between the morphology, structure, and electrocatalytic activity of the PdNS electrocatalyst. Furthermore, the LSV response and potential-pH diagram for the palladium–water system have enabled the proposal for a mechanism of this GOR. The proposed mechanism would be beneficial, as the basis, to achieve the highest catalytic activity by selecting the suitable potential range. Under the optimal conditions, the PdNS/f-CNT/SPCE-based biomimetic sensor presented a wide linear range (1–41 mM) with a sensitivity of 9.3 µA cm−2 mM−1 and a detection limit of 95 µM (S/N = 3) toward glucose at a detection potential of +300 mV vs. a saturated calomel electrode. Furthermore, because of the fascinating features such as fast response, low cost, reusability, and poison-free characteristics, the as-proposed electrocatalyst could be of great interest in both detection systems (glucose sensors) and direct glucose fuel cells.

Electrocatalytic determination of hydrazine concentrations with polyelectrolyte supported AuCo nanoparticles on carbon electrodes

Gold–cobalt alloy nanoparticles (AuCo NPs) deposited on a screen-printed carbon electrode (SPCE) surface modified with a combination of polystyrene sulfonate (PSS) and poly-3,4-ethylenedioxythiophene (PEDOT) is demonstrated for monitoring the direct oxidation of hydrazine. The surface morphology and properties of PSS:PEDOT supported AuCo NPs modified carbon electrodes were characterized using field-emission scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopic analysis. The current change with respect to the electrocatalytic oxidation of hydrazine on AuCo NPs/PSS:PEDOT/SPCE was used for the quantitative analysis in conjunction with cyclic, linear sweep, and differential pulse voltammetries alongside chronoamperometry (CA). The voltammetric response for the oxidation of hydrazine using AuCo NPs/PSS:PEDOT/SPCE was also compared with those of bare SPCE and PSS:PEDOT/SPCE. Under optimum conditions using CA, the modified electrode offered a linear range from 0.5 to 1000 μM, a sensitivity of 1.64 µA µM−1 and a limit of detection of 0.17 µM. The stability, reproducibility, sensitivity, and selectivity were also investigated. Finally, the AuCo NPs/PSS:PEDOT/SPCE platform was employed to determine native hydrazine concentrations in local river water samples.

A Broad-Range Disposable Electrochemical Biosensor Based on Screen-Printed Carbon Electrodes for Detection of Human Noroviruses.

Human noroviruses (HuNoVs) are the major non-bacterial pathogens causing acute gastroenteritis in people of all ages worldwide. No stable culture system in vitro is available for routing the detection of multiple strains of HuNoVs. A simple and rapid method for detection of HuNoVs is of great significance for preventing and controlling this pathogen. In this work, an electrochemical biosensor for sensitive and fast detection of HuNoVs was constructed based on a screen-printed carbon electrode (SPCE). Gold nanoparticles and protein-A were applied on the SPCE surface for enhancement of the electrical signals and the linkage of antibodies with a fixed orientation, respectively. A monoclonal antibody (MAb) against the S domain protein of the viral capsid (VP1) was further immobilized on the SPCE to bind HuNoVs specifically. The binding of VP1 to the coated MAbs resulted in the reduction of conductivity (current) measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The reduction in the current was correlated to the concentration of VP1/HuNoVs. The detection limitation of Genogroup I.1 (GI.1) VP1 and Genogroup II.4 (GII.4) VP1 was 0.37 ng/ml (≈1.93×107 HuNoVs/mL) and 0.22 ng/ml (≈1.15×107 HuNoVs/mL), respectively. The detection limitation of both GI and GII HuNoVs in clinical fecal samples was 104 genomic copies/mL. The results could be obtained in 1 h. We demonstrated that this disposable electrochemical biosensor was a good candidate for rapid detection of different genogroup and genotype HuNoVs.

Innovative modification of the surface of screen-printed carbon electrodes by nanofilms directly deposited in cold acrylonitrile plasma

This work describes a pioneering example of the application of plasma-enhanced chemical vapor deposition (PECVD) for the direct modification of commercially available screen-printed carbon electrodes (SPCEs) with plasma-deposited (polymerized) acrylonitrile (pp-AN) nanofilms. The developed method enables fast and simple deposition of the films directly on the surface of the working electrode with excellent reproducibility and repeatability. The films were deposited at various plasma power levels (P = 10–80 W) and deposition times (2–4 min), with thicknesses in the range 50–500 nm. The films were characterized in terms of surface morphology (SEM and AFM analysis) and DC electrical conductivity. The cyclic voltammetry measurements performed in the presence of [Fe(CN)6]4−\\3− indicated that, depending on the type of deposited film, the sensors have radically different electrochemical properties. An electrode covered with pp-AN film deposited at P = 10 W with a thickness of approx. 60 nm exhibits the highest sensitivity of the materials studied, and has a favorable peak current ratio, an improved peak separation value, and a well-developed surface area. In general, sensors with pp-AN films deposited at P ≥ 40 W show the microelectrode effect (characterized by the sigmoidal shape of cyclic voltammograms). The excellent homogeneity and mechanical durability of the resulting nanofilms, as well as their outstanding long-term stability (up to six months), demonstrate that PECVD technology offers a real opportunity for the mass production of sensors that can be almost freely functionalized to provide properties such as selectivity and sensitivity.

Screen-printed electrochemical immunosensor based on a novel nanobody for analyzing aflatoxin M1 in milk

This study aimed to devise a nontoxic electrochemical immunosensor to quantitatively determine aflatoxin M1 by chronoamperometry with novel anti-idiotypic nanobody-functionalized screen-printed carbon electrodes (SPCEs). Anti-idiotype nanobodies (AIdnb) were developed to replace the high toxic chemically synthesized antigen. AIdnb was immobilized on the surface of SPCE via covalent coupling as capture reagent. The functionalized SPCEs were followed by characterization using electrochemical impedance spectroscopy, fourier-transform infrared spectroscopy, transmission electron microscopy mapping, and atomic force microscopy. After optimizing experimental parameters, the assembled immunosensor exhibited a good linearity range of 0.25–5.0 ng/mL, with the limit of detection of 0.09 ng/mL. The immunosensor showed a satisfactory selectivity to AFM1, without interference from analogs, including zearalenone, ochratoxin, and fumonisin B1. For practical application, the developed immunosensor was validated using real spiked samples with the recovery range 82.0%–108.0% and relative standard deviation (RSD) 10.1%–13.0%, indicating that it could be used in milk samples.

Electrochemical evaluation of Cd2+ and Hg2+ ions in water using ZnO/Cu2ONPs/PANI modified SPCE electrode

Metal oxides NPs synthesized using orange peels extract (OE) and lemon peels extract (LE) and polyaniline (PANI) were used to modify the surface of screen printed carbon electrode (SPCE). The electrochemical responses of the various working electrode in potassium hexacyanoferrate (III) probe, and HCl electrolyte were evaluated using cyclic voltammetry. Integrating bimetal oxides NPs Cu2O/ZnO NPs with PANI on SPCE surface increased the electron transport properties of the sensors. The analytical performance of the SPCE treated with OE/Cu2O/ZnONPs/PANI composite, (OE/ZnO/Cu2ONPs/PANI/SPCE) and their counterpart LE/Cu2O/ZnONPs/PANI composite (LE/ZnO/Cu2ONPs/PANI/SPCE), on Cd2+, and Hg2+ ions in 0.1 M HCl electrolyte, was investigated using square voltammetry (SWV). The limits of detection at concentration range of 2.2–12.0 μM, and 0.17–1.5 μM for Cd2+ were 3.04 ppb, and 1.08 ppb, while for Hg2+ at concentration range of 2.95–11.8 μM, and 0.12–1.2 μM, the values were 5.08 ppb, and 2.72 ppb at LE/Cu2O/ZnONPs/PANI/SPC, and OE/Cu2O/ZnONPs/PANI/SPC modified electrodes respectively. The sensitivities of 108 μA/μM, and 27 μA/μM towards Hg2+, and Cd2+ were realized at OE/Cu2O/ZnONPs/PANI/SPCE, despite the narrow linear range. Relative standard deviations (RSD) at 6.55 μM concentrations for Cd2+ were 2.54%, and 6.50% for LE/Cu2O/ZnONPs/PANI/SPCE, and OE/Cu2O/ZnONPs/PANI/SPCE respectively, while the RSDs for Hg2+ at 2.94 μM concentration were 2.92%, and 4.44% using LE/Cu2O/ZnONPs/PANI/SPCE, and OE/Cu2O/ZnONPs/PANI/SPCE respectively. At OE/Cu2O/ZnONPs/PANI/SPCE, there was no significant drop in the anodic peak current for both target trace metals, in the presence of interferences, like Co2+, Mg2+, Fe2+, Ni2+, Zn2+ and Cu2+, except for 11.39% drop of the stripping peak current of Cd2+ in the presence of Zn2+. Hence, the economy of nanotechnology and sensing could profit from the recycling of biomass wastes, which are frequently poorly managed.

Architecting of an aptasensor for the staphylococcus aureus analysis by modification of the screen-printed carbon electrode with aptamer/Ag–Cs-Gr QDs/NTiO2

Given the many issues bacterial infections cause to humans and the necessity for their detection, in this work we developed a robust aptasensor for prompt, ultrasensitive, and selective analysis of staphylococcus aureus bacterium (S. aureus). A nanocomposite of Ag nanoparticles, chitosan, graphene quantum dots, and nitrogen-doped TiO2 nanoparticles (Ag–Cs-Gr QDs/NTiO2) was synthesized, and thoroughly characterized by XRD, FT-IR, and FE-SEM spectroscopic methods. The surface of screen-printed carbon electrodes modified with Ag–Cs-Gr QDs/NTiO2 nanocomposite was utilized as a compatible platform for aptamer attachment. The aptasensor accurately determined S. aureus in the dynamic range of 10–5 × 108 CFU/mL with detection limit of 3.3 CFU/mL. The monitoring of the practical performance of aptasensor in human serum samples revealed its superiority over the conventional methods (relative recovery of 96.25–103.33%). The Ag–Cs-Gr QDs/NTiO2-based aptasensor offers facile, biocompatibility, good repeatability, reproducibility (RSD = 3.66%), label free and stabile strategy for sensitive S. aureus analysis free from biomolecules interferences in actual specimens.

Bismuth-coated screen-printed electrodes for the simple voltammetric determination of formaldehyde.

For the first time, bismuth modified electrodes have been used for the voltammetric detection of formaldehyde (FM). The well-known method of forming formaldehyde hydrazone (FAH) in the presence of hydrazine sulphate was used to convert the hydrated form of FM into its electrochemically active derivative. Various experimental conditions for differential pulse voltammetry were studied to achieve the best analytical performance. The FAH reduction current (FM response) reaches its maximum value at a pH of a phosphate buffer solution of 5.2 ± 0.1 in the presence of 0.09-0.12 M hydrazine sulfate on a bismuth film preliminarily precipitated for 8-12 min from acidic Bi(III) acetate solutions at an electrolysis potential of -1.0 V on the surface of a screen-printed carbon electrode (SPCE). A dendritic-like film structure was created on the SPCE surface. Under the optimized conditions a linear calibration curve over the range of 0.01-5 mg L-1 (0.33-167 μM) FM was achieved, with a detection limit of 0.002 mg L-1 (0.06 μM). The determination of FM in waste water, melt water from snow within the city industrial zone, and a widely used pharmaceutical preparation "Endofalk®" with good results revealed the potential applicability of a bismuth modified SPCE (BiSPCE) for trace analysis.

Rational design of manganese oxide/tin oxide hybrid nanocomposite based electrochemical sensor for detection of prochlorperazine (Antipsychotic drug)

The development of hybrid metal oxides nanocomposite has been utilized for the electrochemical sensor with low detection limits, and excellent sensitivity. In this present study, the co-precipitation synthesis of manganese oxide/tin oxide (Mn2O3/SnO2) hybrid nanocomposite was developed and applied for prochlorperazine (PCP) electrochemical detection. The structural and morphological properties of the prepared hybrid nanocomposite were characterized with various analytical techniques. The synthesized Mn2O3/SnO2 was modified on a screen-printed carbon electrode (SPCE) surface and utilized cyclic voltammetric (CV) and differential pulse voltammetric (DPV) analysis. The linking advantages of Mn2O3, SnO2, and SPCE show superior electrochemical performance in PCP detection, displaying high oxidation response than that of the unmodified SPCE and other modified electrodes (Mn2O3 and SnO2). The optimized voltammetric results exhibited that the hybrid modified electrode shows a broad linear range of 0.03–421.45 µM, the lowest limit of detection, and the limit of quantification of 8 nM, and 29 nM with high sensitivity of 1.415 µA µM−1 cm−2 for PCP oxidation. Besides, the constructed sensor reveals excellent selectivity, stability, and precision for the detection of PCP. Finally, the viability of the hybrid sensor was performed to PCP determination in real human samples with satisfactory results.

Fabrication of GQD-Electrodeposited Screen-Printed Carbon Electrodes for the Detection of the CRP Biomarker.

The traditional three-electrode electrochemical system used in the development of biosensors for detecting various biomarkers of interest necessitates the use of bulk electrodes, which precludes the deployment of handheld electrochemical devices in clinical applications. Affordable screen-printed carbon electrodes (SPCEs) modified with functional interfaces are being developed to enhance the sensitivity of a compact sensing system as a whole. In this work, SPCEs were fabricated on an overhead projection (OHP) sheet in three different active areas of 2 × 2, 3 × 3, and 4 × 4 mm2 using a screen printing technique, and then ∼2 nm sized graphene quantum dots (GQDs) were electrodeposited over the SPCE surface to add functionality for the detection of ultralow levels of one of the cardiac biomarkers, C-reactive protein (CRP). The proposed mediator-dependent voltammetric biosensor exhibited good sensitivity, a low detection limit, and a linear range of 2.45 μA ng–1 mL–1 cm–2, 0.036 ng mL–1, and 0.5–10 ng mL–1, respectively. The fabricated SPCE/GQDs/anti-CRP biosensor could rapidly detect CRP in less than 25 s. The intra- and interassays were performed with five sensor strips, which showed a minimum standard deviation of 1.85 and 2.8%, respectively. The SPCE/GQDs/anti-CRP electrode was used to detect CRP concentrations in a ringer lactate solution. Thus, the developed biosensor has all of the characteristics such as rapidity, inexpensive disposable electrodes, miniaturization, and a lower detection limit needed to evolve as a point-of-care (PoC) application.

Probeless and label-free impedimetric biosensing of D-dimer using gold nanoparticles conjugated with dihexadecylphosphate on screen-printed carbon electrodes

D-dimer (DD) is a clinical biomarker of emerging significance. Its fast analysis and quantification, preferably by the bedside, helps a medical doctor make crucial decisions. Electrochemical biosensors are point-of-care technologies that can address such issues. Herein, it is developed a probeless and label-free impedimetric DD biosensor. Gold nanoparticles (AuNPs) are dispersed along with dihexadecylphosphate (DHP) on the surface of screen-printed carbon electrodes (SPCEs) to attach anti-DD monoclonal antibody as sensing recognition element, and the measurements are performed using electrochemical impedance spectroscopy (EIS). Two different analytical models are used to interpret raw impedance spectra. The first model is based on the capacitive response within the DHP monolayer and its electrochemical occupancy described by the complex capacitance value at the frequency of 200 mHz, noted as M1. The second model is based on the charge transfer resistance changes (Rct) occurring upon the mAb-DD binding event, fitted by two different Randles types of the equivalent circuits (noted as M2a and M2b). The models are compared, and with the obtained high linearity in the clinically relevant range (up to 500 ng mL−1) and low levels of detection (as low as 8.92 ng mL−1), a potential POC sensor is demonstrated. Additionally, the proposed sensor is applied in real whole blood samples showing good recovery values with certain discrepancies from the standard laboratory assay result, making a cheap and straightforward way for semi-quantitative bedside clinical evaluation.