Surface Of Screen-printed Carbon Electrode Research Articles

Calf thymus ds-DNA intercalation with pendimethalin herbicide at the surface of ZIF-8/Co/rGO/C3N4/ds-DNA/SPCE; A bio-sensing approach for pendimethalin quantification confirmed by molecular docking study

Pendimethalin (PND) is a herbicide that is regarded to be possibly carcinogenic to humans and toxic to the environment. Herein, we fabricated a highly sensitive DNA biosensor based on ZIF-8/Co/rGO/C3N4 nanohybrid modification of a screen-printed carbon electrode (SPCE) to monitor PND in real samples. The layer-by-layer fabrication pathway was conducted to construct ZIF-8/Co/rGO/C3N4/ds-DNA/SPCE biosensor. The physicochemical characterization techniques confirmed the successful synthesis of ZIF-8/Co/rGO/C3N4 hybrid nanocomposite, as well as the appropriate modification of the SPCE surface. The utilization of ZIF-8/Co/rGO/C3N4 nanohybrid as a modifier was analyzed using. The electrochemical impedance spectroscopy results showed that the modified SPCE exhibited significantly lowered charge transfer resistance due to the enhancement of its electrical conductivity and facilitation of the transfer of charged particles. The proposed biosensor successfully quantified PND in a wide concentration range of 0.01–35 μM, with a limit of detection (LOD) value of 8.0 nM. The PND monitoring capability of the fabricated biosensor in real samples including rice, wheat, tap, and river water samples was verified with a recovery range of 98.2–105.6%. Moreover, to predict the interaction sites of PND herbicide with DNA, the molecular docking study was performed between the PND molecule and two sequence DNA fragments and confirmed the experimental findings. This research sets the stage for developing highly sensitive DNA biosensors that will be used to monitor and quantify toxic herbicides in real samples by fusing the advantages of nanohybrid structures with crucial knowledge from a molecular docking investigation.

Nanoengineered disposable sensor fabricated with lanthanum stannate nanocrystallite for detecting animal feed additive: Ractopamine

Ractopamine (RA) has been at the forefront of feed additives as a nutrient repartitioning mediator that recuperates the growth rate, decreases animal fat, and guarantees food safety. However, inappropriate and abusive usage of RA to enhance economic efficiency can negatively impact the environment–animal–human interactions. Therefore, the call for monitoring and quantifying RA is highly desired. In this work, the potentiality of La2Sn2O7 as an electrode modifier on the surface of the portable screen-printed carbon electrode (SPCE) was examined for its precision, disposability, and ability to detect RA. The superior electrocatalytic activity of the fabricated La2Sn2O7/SPCE fortifies its standpoints by displaying a wide linear working range of 0.01–501.2 µM, an enhanced sensitivity, a better stability, a lower LOD of 0.86 nM, and an increased selectivity toward the detection of RA. Furthermore, the investigation of the constructed electrochemical sensor with real-time food samples underpins its practicality and feasibility.

Self-assembling nanomaterial-based peptide surface for target cell adhesion

Non-covalent modification of electrode surfaces with nanoparticle-based peptides does not change the chemical properties of the electrode but allows electrochemical measurement of cell adhesion. This study examines the effect of self-modified nanomaterial/peptide surfaces on cell adhesion. This adhesion to the surface is caused by the negative Gibs free energy formed in the system because of the presence of -0H, sulfur, carbonyl, or reactive groups. A cheaper and more practical method for electrode surfaces targeting cell adhesion, which does not use heavy chemicals and EDC/NHS chemistry, is used in this work. Thanks to the bioactive materials immobilized on the screen-printed carbon electrode (SPCE) surface in a controlled manner and the surface chemistry offered by these materials, a biocompatible self-assembling nanomaterial-based peptide surface platform is created, and cell adhesion is measured by an electrochemical technique. After the characterization steps, electro­chemical techniques created a calibration curve of the current value as a function of concentration for each cell line. The adhesion of the generated bioactive electrode surfaces to the selected cell lines was examined comparatively.

Point-of-care detection of Japanese encephalitis virus biomarker in clinical samples using a portable smartphone-enabled electrochemical "Sensit" device.

Japanese encephalitis (JE), a neglected tropical zoonotic disease prevalent in south-east Asian and western pacific countries, caused by the flavivirus JE virus (JEV), has a dearth of electrochemical point-of-care (PoC) diagnostic tools available to manage endemic breakouts. To overcome this, we have developed a screen-printed carbon electrode (SPCE) immunosensor for rapid PoC detection of JEV nonstructural 1 (NS1) antigen (Ag), found circulating in serum of infected individuals using a smartphone based portable "Sensit" device. The modification of SPCE surface with JEV NS1 antibody (Ab) was confirmed via observation of globular protein structures via scanning electron microscopy (SEM), increase in electrode surface hydrophilicity via contact angle measurement and decrease in current via differential pulse voltammetry (DPV). The fabrication and testing parameters were optimized based on highest current output obtained using DPV. The SPCE was tested for detection limit of target JEV NS1 Ag ranging from 1fM to 1μM, which was determined as 0.45 fM in spiked serum. The disposable immunosensor was also found to be highly specific in detecting JEV NS1 Ag over other flaviviral NS1 Ag. Finally, the modified SPCE was clinically validated by testing 62 clinical JEV samples using both a portable miniaturized electrochemical "Sensit" device coupled with a smartphone and a laboratory-based potentiostat. The results were corroborated with gold-standard RT-PCR and showed 96.77% accuracy, 96.15% sensitivity, and 97.22% specificity. Hence, this technique may further be developed into a one-step rapid diagnostic tool for JEV, especially in rural areas.

Hollow carbon spheres decorated by silver nanocubes as the advanced aptasensing interface for sensitive and selective tracing of methamphetamine in human biofluids

This study presents a sensitive and selective aptasensor for the detection of trace amounts of MAMP. The aptasensing principle relies on modifying the planar screen-printed carbon electrode (SPCE) with the synthesized nanostructures of N-doped hollow carbon spheres (N-HCSs) and silver nanocubes (AgNCs). The nanocomposite has presented high active surface area and more electron transfer ability than bare SPCE surface. Furthermore, AgNCs in the nanocomposite acts as a linker to load high amounts of aptamer (Apt) biocaptures on the modified SPCE surface. By MAMP incubation on the embedded interface sensing, Apt arm wrapped around MAMP and the more space barrier induced on the surface and reduced the electrochemical signal of ferro/ferri cyanide as the anion redox probe. The aptasensor affinity toward MAMP led to a wide linear dynamic range (LDR) value from 1.00 pM to 50.00 mM with a low limit of detection (LOD) value of 3.33 × 10−4 pM compared to other electrochemical sensors with no significant interference from other common species. The aptasensor efficiency for MAMP measurement was satisfactory evaluated in some spiked and non-spiked serum, urine and saliva samples from a healthy and addicted person for MAMP. These acceptable results may promise the reliability of the proposed methodology for routine MAMP tests, especially saliva monitoring as the non-invasive analysis. The sensitivity and selectivity of the aptasensor, which is a bonus to accurate and valid discrimination of MAMP, holds great promise to provide technical support for routine analysis of real-world clinical samples.

Heavy metal‐free electrochemical detection of pyrophosphate ions by Nafion/carbon dots decorated screen printed carbon electrodes

AbstractWe employ Nafion‐mixed carbon dots (CDs) and low‐cost screen‐printed carbon electrodes (SPCEs) as foundation matrices for the fabrication of electrochemical biosensors. The NH2 and COOH functional groups present on the SPCE surface after Nafion/CDs deposition allow for pyrophosphate ions (PPis) collection. Using Fe(CN)63− as the electrochemical mediator, the SPCE‐Nafion/CDs are applied to the detection of aqueous PPi by square wave voltammetry. Between 50 and 1 μM, a linear connection is established between the square wave voltammetry current and the PPi concentration. The limit of detection is determined to be 1.01 μM, and recoveries of 113% (±1.9%) and 108% (±3.9%) are achieved for human urine samples spiked with 6 and 3 μM of PPi, respectively. Furthermore, this PPi assay is suitable for the usage of complicated urine matrices without the inclusion of heavy metals. We anticipate that this unique approach will be beneficial for PPi level monitoring in urine during therapeutic treatments of illnesses and malignancies.

Electrochemical immunoplatform to help managing pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the solid tumor with the worst prognosis, representing today the third cause of cancer-related deaths in developed countries and expected to be the second in 2030. Today, CA19-9 remains the only clinically used marker for management of PDAC (FDA-approved as a disease monitoring marker). This work reports a disposable amperometric immunoplatform for the determination of CA19-9. The immunoplatform skilfully combines the advantages of magnetic microsupports (MBs) for implementation of the immunoassay and amperometric transduction on screen-printed carbon electrodes (SPCEs). The method involves the preparation of sandwich immunocomplexes enzymatically labeled with the enzyme horseradish peroxidase (HRP) on the MBs and uses a detection antibody conjugated to HRP. Once the HRP-labeled sandwich immunocomplexes-bearing MBs were trapped on the SPCE surface, the variation of the cathodic current was measured in the presence of H2O2 and hydroquinone (HQ), which was directly proportional to the concentration of CA19-9. Under the optimized experimental conditions, the immunoplatform allowed the amperometric determination of CA19-9 standards over the 5.0 to 500 U mL−1 concentration range, with a limit of detection (LOD) value of 1.5 U mL−1 in 1 h. The method exhibits good reproducibility and selectivity and the magnetic immunoconjugates shows a good storage stability. The immunoplatform was applied to the determination of CA19-9 in serum samples of a medium-sized cohort (22 individuals) of healthy subjects and patients diagnosed with PDAC. The obtained results demonstrated the immunoplatform ability to discriminate both types of individuals within 1 h after sample dilution. The developed immunoplatform represents an improvement in terms of cost, applicability and accessibility compared to the ELISA-based techniques currently used in the clinic.

Differential pulsed voltammetry of Δ9‐Tetrahydrocannabinol (THC) on disposable screen‐printed carbon electrodes: A potential in‐field method to detect Δ9‐THC in saliva

AbstractDue to recent legalization of marijuana across many states in the U.S., there is an increased concern of users driving while impaired/intoxicated with Δ9‐tetrahydrocannabinol (Δ9‐THC), the principal psychoactive constituent of cannabis/marijuana. Hence, there is a need for a rapid roadside detection of this drug that can be used to accurately screen drivers. Current field sobriety tests rely on a series of physical and mental exercises administered during DUI investigations to help determine a driver's level of impairment. Due to their portability and effectiveness, screen printed carbon electrodes (SPCEs) are ideal to work with when it comes to devising a low‐cost screening device for roadside testing. SPCE's can potentially detect low levels of Δ9‐THC in an individual's saliva via electrochemical oxidation of Δ9‐THC. Herein we report a fast, cheap, and accurate approach to electrochemically detect 1–20 μM Δ9‐THC in a 1 mL sample of artificial oral fluid (AF‐OF) diluted to 50 % with a buffer/electrolyte solution using differential pulse voltammetry (DPV) at the surface of a small SPCE. Implications for the use of this method to screen intoxicated drivers are discussed.

Gold nanoparticles enhanced molecularly imprinted poly(3-aminophenylboronic acid) sensor for myo-inositol detection

Myo-inositol (MI) is a secondary messenger that can be used to treat a variety of metabolic syndromes (MS), from diabetes to cancer, and ongoing research is reassuring a bright future for therapies. In this study, two molecular imprinting polymer (MIP) sensor matrixes were created and investigated for the determination of MI; (i) 3-aminophenylboronic acid (3-APBA) electropolymerization with MI as the template on the SPCE surface (ii) gold nanoparticles (AuNPs) initially electrodeposited on a screen-printed carbon electrode (SPCE) surface and further the molecularly imprinted poly-3-aminophenylboronic acid (PAPBA) sensor film was electropolymerized with MI on the modified AuNPs/SPCE surface. Here, the surface modification with AuNPs on SPCE better enhances the electrochemical signal compared with unmodified SPCE. The electrochemical characterization of molecularly imprinted sensors was evaluated via Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Differential Pulse Voltammetry (DPV) techniques. The morphological changes of the modified electrodes were analyzed by Scanning Electron Microscope (SEM). The performances of the imprinted sensors (such as extraction of the template, rebinding conditions, and interference study) were investigated and optimized. The overall analytical data of the MI/PAPBA/AuNPs/SPCE based imprinted sensor (linear range: 500 nM to 60 μM; limit of detection: 1.0 nM; sensitivity: 0.042 μA μM−1) was better than the MI/PAPBA/SPCE (linear range: 500 nM to 50 μM; limit of detection: 4.7 nM; sensitivity: 0.019 μA μM−1). Further, the MI/PAPBA/AuNPs/SPCE imprinted sensor was successfully validated by applying for the sensitive and selective detection of myo-inositol in human plasma samples, and the results agreed well with the HPLC literature data.

Polyaniline-chitosan modified on screen-printed carbon electrode for the electrochemical detection of perfluorooctanoic acid

The overwhelming utilisation of perfluorooctanoic acid (PFOA) for household and industrial applications has posed a severe risk to human health and environmental pollution. Therefore, this study was performed to fabricate a polyaniline-chitosan (PANI-CHT) composite using CHT extracted from crab shells and modified with Screen-Printed Carbon Electrode (SPCE) for the development of an electrochemical sensor to detect PFOA. The physicochemical properties of CHT, PANI, and PANI-CHT were characterised using ATR-FTIR, XRD and SEM-EDX. In addition, the electrochemical performance of the SPCE-modified PANI-CHT 1:1 composite was evaluated through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Based on the results, PANI-CHT 1:1 showed a linear correlation coefficient of R2 = 0.9954 with a LOD of 1.08 ppb in a linear range of 5–150 ppb. The physicochemical analyses demonstrate the successful blending of CHT with PANI, which enhanced the effective active sites on the surface of SPCE. Upon the practical assessment of the fabricated composite using spiked water samples, the sensor recorded an acceptable recovery percentage range of 96–103 %. Overall, the proposed sensor exhibited great sensitivity, excellent reproducibility, and good stability for the detection of PFOA and with a promising performance.

Flexible, Bifunctional Sensing Platform Made with Biodegradable Mats for Detecting Glucose in Urine

We report on a flexible, bifunctional platform made with solution-blow spinning fiber mats of polylactic acid (PLA) and polyethylene glycol (PEG). The PLA/PEG mats were designated bifunctional because they were used as a substrate for screen-printed carbon electrodes (SPCEs) and as a matrix to attach glucose oxidase (GOx) covalently. By attaching GOx only on the fiber mats, and not on the SPCE, the detection of hydrogen peroxide generated from glucose oxidation by the enzyme was efficient, especially with Prussian blue (PB) nanoparticles electrodeposited on the SPCE surface. The bifunctional device detected hydrogen peroxide (H2O2) in synthetic and human urine at a low applied potential (0 V vs Ag/AgCl) in the range from 1.0 to 6.0 mM, with a detection limit of 0.197 mM, being also interference-free. The biosensor whose cost is <US$ 0.25 per unit (estimated from the price of the materials used) had performance comparable to the gold standard method while measuring glucose in human urine samples, in addition to exhibiting a rapid response and long lifetime. The design of the bifunctional device is generic and may be extended to other biosensors for on-site monitoring as well as for wearable devices and in monitoring the environment and water in varied resources.

Construction of a point-of-care electrochemical biosensor for Escherichia coli 16S rRNA analysis based on MoS2 nanoprobes.

Foodborne pathogens are harmful to human health because they can contaminate food and induce diseases. To efficiently distinguish and determine foodborne bacteria, an ultrasensitive point-of-care electrochemical biosensor was designed for 16S rRNA detection by coupling a signal amplification strategy with MoS2-based nanoprobes. Gold nanoparticles and thionine co-functionalized molybdenum disulfide (MoS2) nanocomposites (MoS2-Thi-AuNPs) were used to construct nanoprobes, which can efficiently monitor the detection process and amplify the detection signal. In the presence of Escherichia coli (E. coli) 16S rRNA, a classical sandwiched DNA structure was formed on the surface of a hierarchical flower-like gold nanostructure-decorated screen-printed carbon electrode (HFGN-SPCE), generating an obvious electrochemical signal from Thi. Under optimal conditions, this designed electrochemical biosensor showed a wide dynamic range (0-1.0 × 106 fM), low detection limit (2.8 fM), high selectivity and accepted stability for E. coli 16S rRNA detection in ideal buffers. Moreover, this biosensor can efficiently determine 16S rRNA in milk samples and 10 CFU mL-1 bacterial lysate. All experimental results suggested that this biosensor has a promising application in the detection of foodborne pathogens.

Design of a label-free aptasensor for electrochemical determination of hemoglobin: investigation of the peroxidase-like activity of hemoglobin for the sensing of different substrates.

The unbalanced hemoglobin level in biological fluids can cause several diseases; hence it can be used as a biomarker for diagnosis. We aim, in the present study, to construct a label-free electrochemical aptasensor for the quantification of hemoglobin. For that, a conjugate of L-cysteine and gold nanoparticles was used for the aptamer immobilization on screen printed carbon electrodes. Using square wave voltammetry, the calibration plot was obtained and it was linear in the range of 50 ng ml-1 to 36 000 ng ml-1 while the detection limit was 1.2 ng ml-1. After the binding of Hb on the modified screen-printed carbon electrode surface, the peroxidase-like activity of the bound hemoglobin was explored in the quantification of different substrates. Hydrogen peroxide and nitrite were chosen as model analytes. Amperometric measurements showed wide linear ranges: 0.2 μM-7.7 mM and 3.6 nM-1.3 mM for H2O2 and nitrite, respectively, with detection limits of 0.044 μM and 0.55 nM. In the proposed strategy, the aptamer provides excellent orientation and a biocompatible environment for hemoglobin whose catalytic activity plays a key role in H2O2 and nitrite analysis.

Gold Nanospikes Formation on Screen-Printed Carbon Electrode through Electrodeposition Method for Non-Enzymatic Electrochemical Sensor

In this study, we reported the construction of Gold Nanospike (AuNS) structures on the surface of screen-printed carbon electrode (SPCE) used for non-enzymatic electrochemical detection. This modification was prepared with a one-step electrodeposition method by controlling the electrodeposition parameters, such as applied potential and deposition time, via Constant Potential Amperometry (CPA). Those parameters and precursor solution concentration were varied to investigate the optimum electrodeposition configuration. The results confirmed that AuNS were homogenously deposited and well-dispersed on the working electrode surface of SPCE. The AuNS-modified SPCE was implemented as a non-enzymatic sensor toward dopamine and could enhance the electrocatalytic ability compared with the bare SPCE. Further examination shows that the sensing performance of the AuNS-modified SPCE produced an increase in electrochemical surface area (ECSA) at 17.25 times higher than the bare electrode, a sensitivity of 0.056 µA mM−1 cm−2 with a wide linear range of 0.2–50 µM and a detection limit of 0.33 µM. In addition, AuNS-modified SPCE can selectively detect dopamine among other interfering analytes such as ascorbic acid, urea, and uric acid, which commonly coexist in the body fluid. This work demonstrated that AuNS-modified SPCE is a prospective sensing platform for non-enzymatic dopamine detection.

Anti-Biofouling Electrochemical Sensor Based on the Binary Nanocomposite of Silica Nanochannel Array and Graphene for Doxorubicin Detection in Human Serum and Urine Samples.

A disposable and portable electrochemical sensor was fabricated by integrating vertically-ordered silica mesoporous films (VMSF) and electrochemically reduced graphene (ErGO) on a screen-printed carbon electrode (SPCE). Such VMSF/ErGO/SPCEs could be prepared by a simple and controllable electrochemical method. Stable growth of VMSF on SPCE could be accomplished by the introduction of an adhesive ErGO nanolayer owing to its oxygen-containing groups and two-dimensional (2D) planar structure. An outer VMSF layer acting as a protective coating is able to prevent the leakage of the inner ErGO layer from the SPCE surface. Thanks to the electrostatic permselectivity and anti-fouling capacity of VMSF and to the good electroactive activity of ErGO, binary nanocomposites of VMSF and ErGO endow the SPCE with excellent analytical performance, which could be used to quantitatively detect doxorubicin (DOX) in biological samples (human serum and urine) with high sensitivity, good long-term stability, and low sample amounts.

Tuberculosis detection from raw sputum samples using Au-electroplated screen-printed electrodes as E-DNA sensor.

Tuberculosis (TB) remains a leading cause of death globally, especially in underdeveloped nations. The main impediment to TB eradication is a lack of efficient diagnostic tools for disease diagnosis. In this work, label free and ultrasensitive electrochemical DNA biosensor for detecting Mycobacterium tuberculosis has been developed based on the electrodeposition of gold nanoparticles on the surface of carbon screen-printed carbon electrode (Zensors) for signal amplification. Particularly, screen-printed electrodes were modified by electrochemical deposition of Au to enhance the conductivity and facilitate the immobilization of ssDNA probes via Au-S bonds. The electrochemically modified SPEs were characterized using Scanning electron microscopy/Energy Dispersive X-Ray Analysis (SEM/EDX) and X-Ray Diffraction (XRD). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used to investigate the DNA hybridization between single-stranded (ssDNA) probe and target DNA (tDNA). Under the ideal conditions, DPV exhibited a correlation coefficient R2 = 0.97, when analyzed with different tDNA concentrations. The proposed DNA biosensor exhibits a good detection range from 2 to 10nm with a low detection limit of 1.91nm, as well as high selectivity that, under ideal conditions, distinguishes non-complementary DNA from perfectly matched tDNA. By eliminating the need for DNA purification, this work paves the path for creating disposable biosensors capable of detecting DNA from raw sputum samples.

Novel Co MOF with Ionic Liquid Comprised Portable Molecularly Imprinted Polymer-Based Electrochemical Sensor for the Point-of-Care Detection of a Breast Cancer Biomarker

A cobalt metal-organic framework (Co MOF)-ionic liquid (IL) nanocomposite comprising the base matrix of the electrode was developed with electropolymerized molecularly imprinted polymer (MIP) consisting of o-phenylenediamine (oPD) to detect carcinoembryonic antigen (CEA), a biomarker of breast cancer. Firstly, Co MOF was synthesized using hydrothermal synthesis, which was used as an electrically conductive skeleton and functionalized with an IL. Then, CEA was employed as a template in the electropolymerization of oPD-imprinted films on the surface of screen-printed carbon electrode (SPCE). Finally, the template protein was removed to form a molecularly imprinted film capable of qualitatively and quantitatively signaling CEA. Under optimized conditions, the sensor for CEA exhibits a wide detection range of 1.0 × 10−4−10 ng·ml−1 (0.32 V vs Ag/AgCl) with a limit of detection (LOD) and limit of quantification (LOQ) of 0.024 pg·ml−1 and 0.082 pg·ml−1, respectively. Besides, other parameters including the selectivity, reproducibility (RSD 2.2%), and recovery rate (92.16%–103.35%) are all satisfactory. The proposed strategy provides a new route for the development of rapid breast cancer diagnostic tools.

Impedance–based haptenation of skin sensitizers with self–assembled monolayer of gold nanoparticles and cysteine modified screen printed carbon electrode

Haptenation of skin sensitizer is indicated because of the covalent attachment of a skin sensitizer to a skin protein. The idea of this research is to explore the haptenation of skin sensitizer with a modified screen printed carbon electrode (SPCE) and a self–assembled monolayer of gold nanoparticles (AuNPs) and cysteine (designated as ACC modified SPCE) using the impedance technique. The ACC modified SPCE was characterized using Fourier–Transform infrared spectroscopy–attenuated total reflectance (FTIR–ATR), atomic force microscopy (AFM), and Energy Dispersive X–Ray Spectroscopy (EDX). The presence of AuNPs and cysteine on the working electrode of the ACC modified electrode was detected by FTIR–ATR and EDX. AuNPs, possessing a homogeneous dot shape, and cysteine was randomly distributed on the carbon surface of SPCE shown by FESEM images. The AFM images indicated the possibility of a monolayer of adsorption of skin sensitizer onto ACC modified SPCE. The ACC modified SPCE has good reproducibility and stability with an RSD of 8.43 %. In addition, the interaction of extreme/strong skin sensitizer with the ACC modified SPCE was discovered with a high value of changes of charge transfer resistance of skin sensitizer (ΔRCTskinsensitizer) when compared to moderate and weak/non skin sensitizers. A total of 9 min was reported to be the optimum contact time of the skin sensitizer onto ACC modified SPCE. The adsorption isotherm studies of skin sensitizers with ACC modified SPCE showed Langmuir isotherm adsorption and spontaneous mechanism. Maleic anhydride (as a model of extreme/strong skin sensitizers) showed a fast–binding rate (18.2149 M−1) with the addition of a slow dissociation rate of 0.0549 M, while glycerol (as a model of weak/non skin sensitizer) showed a slow binding rate of 4.5977 M−1 as a result of a rapid dissociation rate of 0.2175 M. The change in Gibbs free energy (ΔG°) was calculated for ACC modified SPCE with glycerol and maleic anhydride to be at –3.78 × 10+03 kJ/mol and –7.19 × 10+03 kJ/mol, respectively. This study proved that the ACC modified SPCE could be used for routine screening during the early product development stage in qualitative skin sensitization measurements.

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.