Differential Pulse Voltammetric Research Articles

Fabrication of a novel molecularly imprinted biosensor assisted by higher-order calibration methods and a computer-generated experimental design for determination of thyroglobulin in the presence of thyroxine and triiodothyronine as uncalibrated interference

In this work, a novel electrochemical biosensor was fabricated by modification of a rotating glassy carbon electrode (GCE) with fullerene C60-ionic liquid (C60-IL), and electrochemical synthesis of molecularly imprinted polymers (MIPs) on its surface for selective and sensitive determination of thyroglobulin (TG) in the presence of thyroxine (T4) and triiodothyronine (T3) as uncalibrated interference. The MIPs were synthesized onto the surface of electrochemically activated C60-IL/GCE by electropolymerization of 4-aminothiophenol, methacrylic acid, ethylene glycol dimethacrylate (as cross linker), and TG (as template molecule). By incubation of the biosensor in TG solution, the TGs were entrapped within the pathways of the MIPs, and by incubation of the biosensor in electrochemical probe solution, the pathways for reaching the probe molecules to biosensor were decreased which caused the hydrodynamic differential pulse voltammetric (HDPV) response of the biosensor to be decreased. The effects of experimental parameters on response of the biosensor were optimized by a quadratic central composite design, and at optimized conditions determination of TG in the presence of T4 and T3 as uncalibrated interference was performed. The selectivity of the biosensor was further assisted by supporting the biosensor response with the help of second-order calibration methods and generation of second-order HDPV data with the aim of exploiting second-order advantage. Second-order calibration models were developed by MCR-ALS, PARAFAC2, N-PLS/RBL, and U-PLS/RBL with the aim of choosing the best model for assisting the biosensor for selective determination of the TG in the presence of T4 and T3 as uncalibrated interference. The results confirmed the best performance was observed for the biosensor assisted by PARAFAC2 in both synthetic and real matrices which was comparable with HPLC-UV as the reference method, and can be suggested as an alternative method for chromatographic methods.

Electrochemical Sensor Based on N–Doped Carbon Nanodots Derived from the Agro-Waste Cotton Boll Peel Extracts for Nano Molar Determination of an Anti-Cancer Drug, Pemetrexed

A green and facile one-step synthetic route was proposed for the synthesis of nitrogen-doped carbon nanodots (N-CDs) from agro-waste cotton boll peel extract as a natural carbon source and glycine as a nitrogen source. The prepared N-CDs were utilized further in the fabrication of an electrochemical sensor for the nanomolar determination of an anti-cancer drug, pemetrexed (PMT). The electrode material was characterized by XRD, FTIR, TEM, Raman, EDX, UV–vis, fluorescence, cyclic voltammetric and electrochemical impedance spectroscopic studies. The N-CDs drop-casted on the surface of glassy carbon electrode (GCE) served as a good sensing material and exhibited electrocatalytic activity as evident from ∼20-fold enhancement in the oxidation peak current of PMT at N-CDs/GCE with 130 mV lesser positive oxidation peak potential than that at bare GCE. This was attributed to excellent conductivity, higher electroactive surface area, graphitic cores of N-CDs besides the interactions between PMT and N-CDs via hydrogen bonding and π–π stacking. The sensing performance of the demonstrated electrode was optimized by varying the peak current dependant parameters and also by investigating the influence of interfering substances in the determination of PMT. The electrochemical behaviour of PMT at different pH revealed the adsorption controlled electrode process with the involvement of protons. Under optimized conditions, differential pulse voltammetric (DPV), square wave voltammetric (SWV) and adsorptive differential pulse voltammetric (AdSDPV) methods were developed for sensitive determination of PMT at nano molar level. Further, these developed analytical methods were applied successfully for the determination of PMT in analyte fortified human urine samples and pharmaceutical formulations.

Non-targeted and targeted analytical approaches for estimating the features of wine spirits

Non-targeted UV–Vis/synchronous fluorescence (SF) spectroscopic and differential pulse voltammetric (DPV) fingerprinting have been tested to discriminate between caramel-containing and caramel-free wine spirits using partial least squares-discriminant analysis (PLS-DA), variable importance in projection (VIP)-PLS-DA, VIP-principal component analysis-linear discriminant analysis (PCA-LDA) and VIP-support vector machine (SVM). A 96 % total correct classification in VIP-PLS-DA and VIP-PCA-LDA was achieved using, among others, of 115 variables corresponding to a potential range from 0.43 to 1.00 V in DPV, or 45 variables selected from SF spectra recorded at a difference between the emission and excitation wavelengths of 100 nm for diluted samples. The conclusions resulting from the non-targeted methods were verified and confirmed by the targeted quantitative analysis of the samples using the HPLC-DAD method, focused on 5-hydroxymethylfurfural, furfural, syringaldehyde and vanilline. In targeted SF spectroscopic quantitative analysis, the PLS regression model based on 21 variables selected from SF spectra recorded at a difference between the emission and excitation wavelengths of 100 nm was suitable for the determination of caramel in the range from 0.1 to 4.0 g/L. High coefficients of determination R2 and small root mean squared error (RMSE) values for both cross-validation and prediction (R2 = 0.9811 and 0.9736, respectively, and RMSE = 0.046 and 0.047, respectively) prove good quantitative properties of the VIP-PLS regression model.

A novel and intelligent molecularly imprinted enzymatic biosensor for biosensing of human serum albumin in the presence of gamma-globulin, and glucose as uncalibrated interference

Human serum albumin (HSA) is not electroactive, because the electroactive amino acids have been buried in its structure. Therefore, direct electrochemical determination of the HSA as the most abundant protein in human plasma cannot be performed. In this work, a novel electrochemical biosensor has been developed based on synthesis of dual templates molecularly imprinted polymers (DTMIPs) having trypsin (TRP) and HSA as template molecules onto the surface of a glassy carbon electrode (GCE) modified with graphene-ionic liquid (Gr-IL). By incubation of the biosensor with TRP, and HSA, tryptic hydrolysis of the HSA is occurred which breaks the HSA down into free amino acids. The HSA involves five electroactive amino acids including cysteine, tryptophan, tyrosine, methionine and histidine whose differential normal pulse voltammetric (DNPV) responses are overlapped and generated a single peak. In order to increase the sensitivity of the DTMIP/Gr-IL/GCE for determination of the HSA, hydrodynamic DNPV (HDNPV) data were generated, and used for analytical purposes. The second-order HDNPV data were generated at different pulse amplitudes and used to develop four second-order calibration models by multivariate curve resolution-alternating least squares (MCR-ALS), parallel factor analysis2 (PARAFAC2), multi-way partial least squares/residual bilinearization (N-PLS/RBL), and unfolded partial least squares/residual bilinearization (U-PLS/RBL) to select the best procedure for determination of the HSA in the presence of gamma-globulin and glucose as uncalibrated interferences. The results confirmed the best performance for the biosensor assisted by MCR-ALS for ultrasensitive and selective determination of the HSA in both synthetic and real matrices which was comparable with HPLC-UV as a reference method.

Thioglycolic acid-capped gold nanoparticle/cytochrome P450-2E1 electrochemical biosensor for isoniazid

Tuberculosis (TB) is one of the deadliest diseases in Africa and it is classified as a serious global health problem. A new threat associated with the disease is the emergence of multidrug-resistant TB (MDR-TB), which results from improper dose or non-compliance with a treatment regime. It is, therefore, important to determine a patient’s rate of TB drug metabolism at a point-of-care, in order to enable appropriate dose prescription. This work presents a novel enzymatic nanobiosensor for real-time determination of isoniazid (INH), which is a highly prescribed drug for TB treatment. The nanobiosensor consists of a cytochrome P450-2E1 (CYP2E1) isoenzyme covalently attached to a screen printed or disk gold electrode (Au), functionalized with thioglycolic acid-capped gold nanoparticle (TGA-AuNP). The nanomaterial was green-synthesized with banana peel extract (BPE) as the reducing agent. It exhibited an ultraviolet-visible spectroscopy (UV–Vis) signature absorption band for AuNP at 536 nm and a direct bandgap energy (Eg) value of 2.00 eV. Fourier transform infra-red spectroscopy (FTIR) was used to confirm the reduction of Au3+ to Au0. High-resolution transmission electron microscopy (HR-TEM) and high-resolution scanning electron microscopy (HR-SEM) studies indicated that TGA-AuNPs were polydisperse and exhibited spherical morphology. Bovine serum albumin (BSA) and CYP2E1 were attached to the TGA-AuNPs-modified Au electrode using glutaraldehyde (Glu) as binder, to form the nanobiosensor (BSA/CYP2E1/Glu/TGA-AuNPs/Au). Differential pulse voltammetric (DPV) responses of the nanobiosensor for INH were determined in 10 mM phosphate buffer (pH 7.4). The limit of detection (LOD) and the limit of quantification (LOQ) values of the nanobiosensor were 0.0556 μM INH and 0.1683 μM INH, respectively.

Voltammetric determination of sulfamethoxazole using commercial screen-printed carbon electrodes

A differential pulse voltammetric (DPV) method using commercial screen-printed carbon electrodes (SPCE) is developed for a fast and cost-effective determination of the antibiotic sulfamethoxazole (SMX). Optimal measurements are carried out at pH 5.5 in acetate buffer and yield a detection limit of 15 µg/L and a linearity range of 50 – 600 µg/L with good repeatability (1.1%) and reproducibility (2.5%). The method is successfully applied to the analysis of a spiked tap water sample with very high reproducibility (0.4%) and good trueness (Recovery 95.2%).Additional considerations are made about the irreversible electrochemical oxidation of SMX, which is notoriously pH-dependent according to a process involving 2e- and 2H+, in agreement with several reported mechanisms in the literature. Besides, the analysis of other sulfonamide antibiotics is discussed, showing the key role of the free terminal amino group in oxidation, which makes almost undistinguishable voltammetric signals from different molecules sharing this moiety. In contrast, the acetylation of the mentioned group (e.g., in sulfonamide metabolites) drastically reduces the sensitivity of voltammetric measurements.

Determination of Dipyridamole Using a MIP-Modified Disposable Pencil Graphite Electrode

A new method for the determination of the antiplatelet drug dipyridamole (DIP) in pharmaceuticals using a molecularly imprinted polymer (MIP)-modified pencil graphite electrode (PGE) is proposed. The modified electrode was prepared simply and rapidly by electropolymerization of caffeic acid (CA) in the presence of DIP and subsequent DIP extraction with ethanol, resulting in a cost-effective, eco-friendly disposable modified electrode (MIP_PGE). Several working conditions (monomer and template concentration, number of voltametric cycles, scan rate extraction time, and solvent) for the MIP_PGE preparation were optimized. The differential pulse voltammetric (DPV) oxidation signal of DIP obtained at MIP_PGE was 28% higher than that recorded at bare PGE. Cyclic voltammetry emphasized DIP irreversible, pH-dependent, diffusion-controlled oxidation at MIP_PGE. Differential pulse and adsorptive stripping voltammetry at MIP_PGE in phosphate buffer solution pH = 7.00 were applied for the drug quantitative determination in the range of 1.00 × 10−7–1.00 × 10−5 and 1.00 × 10−8–5.00 × 10−7 mol/L DIP, respectively. The obtained limits of detection were at the tens nanomolar level.

An electrochemical sensor based on graphene nanoribbon nano-catalyst for determination of etoposide as an approved drug in lung cancer

Monitoring of anticancer drugs is an important strategy in clinical investigation. Determining the level of these drugs in chemotherapy processes provides useful information about the treatment process. The etoposide is one of the important drugs approved to lung cancer with many side effects. Therefore, monitoring of it is so important in clinical process and specially chemotherapy processes. The presence study focused on design of a new, simple, electrical-based, safe and fast response sensor to trace level monitoring of etoposide in biological fluids and pharmaceutical samples. The sensor successfully determined etoposide in nano-level concentration that is very important to investigation role of this anticancer drug in biological fluids. To this goal, the graphene nanoribbon nano-catalyst (GNR) was synthesized and characterized by MAP and SEM methods. The electrochemical catalytic activity of it was investigated by electrochemical impedance spectroscopy method. In continuous, glassy carbon electrode (GCE) modified with GNR was fabricated and ability of sensor to sensing of etoposide was investigated by differential pulse voltammetric (DPV) method. The GNR/GCE monitored etoposide in the concentration range 0.4–150 µM with detection limit 0.1 µM by DPV methods. At biological condition (pH = 7.4), the GNR/GCE was successfully used to monitoring of etoposide in urine, serum and injection samples and data confirmed with HPLC method and Statistical tests.

Comparative DNA-/BSA-binding, DNA cleavage, and cytotoxic properties of copper(II) amino/salicyl-phenolate Schiff bases (phen) complexes that induce generation of phenoxyl radicals

A series of mixed-ligand Cu(II) complexes of the type [Cu(L1-5)(diimine)(H2O)](ClO4) (1–5) and [Cu(L6)(diimine)](ClO4) (6), where HL1-HL4 are aminophenolate Schiff base ligands viz., 2-(benzylideneamino)phenol (HL1, 1), 2-(4-fluorobenzylideneamino)phenol (HL2, 2), 2-(4-chlorobenzylideneamino)phenol (HL3, 3), and 2-(4-nitrobenzylideneamino)phenol (HL4, 4) whereas HL4 and HL5 are salicyl-phenolate Schiff base ligands viz.,2-((phenylimino)methyl)phenol (HL5, 5) and (E)-2-(((2-(dimethylamino)ethyl)imino)methyl)phenol (HL6, 6) as primary ligands and the diimine 1,10-phenanthroline (phen) as co-ligand have been isolated. TheSchiffbaseligandsand their mixedligandchelates were characterizedby spectral techniques (UV–Visible, IR, mass, 1H, and 13C NMR), elemental analysis, cyclic voltammetry (CV), and differential pulse voltammetric (DPV) techniques. The molecular structure of 6, which alone formed appreciable crystals, was determined by single-crystal X-ray studies, and two crystallographically independent molecules (a and b) existed in square pyramidal distorted trigonal bipyramidal (SPDTBP) geometry. The complexes 1–4 showed a reversible (ΔEp for 3; 64), quasi-reversible (2; 105 and 4; 115), and irreversible (1; 181 mV) oxidation waves discernible at E1/2 ranging from + 0.035 V to −0.120 V (DPV) which are attributed to the formation of copper(II)-phenoxyl radical species. Among them, 2 and 3 showed a well-defined reversible phenoxyl radical formation in CV and DPV. Also, these two complexes exhibited more stable phenoxyl radical in the presence of CAN (cerium ammonium nitrate). The DNA binding studies revealed that the fluoro- and chloro-substituted complexes 2 and 3 exhibited higher DNA binding propensity than the other complexes. All the complexes displayed moderate to high oxidative DNA cleavage property in the presence of H2O2, wherein complexes 2 and 3 exhibited higher DNA cleavage than the others. Interestingly, complex 3 exhibited less AC50 value (18.26 µM) than complex 2 (43.3 µM). The mechanistic study led to the inference that the DNA cleavage is possibly mediated via copper(II)-bound phenoxyl-radical. The cytotoxicity of complexes 1–6 was investigated in A549 non-small cell lung carcinoma cell. The amino-phenolate complexes 2 (IC50 = 3.52 µM) and 3 (IC50 = 3.4 µM) brought about higher cytotoxicity and ≈ 3.8-times more potency than cisplatin. The complex 3 showed to be 47-times less toxic to non-cancerous peripheral blood mononuclear cells (PBMC). Fluorescent staining assay revealed that the complexes 1–6 induced apoptotic cell death with some degree of necrosis. JC-1 staining assay revealed that complex 3 efficiently depolarized the mitochondrial membrane potential. Put together, the results substantiate that amino-phenolate-containing copper(II) mixed ligand complexes are more cytotoxic than salicyl-phenolate-containing copper(II) complexes.

Cu-MOF/Pd derived oxide nanoparticles based carbon composite - An innovative electrochemical sensing platform for Bisphenol A

Bisphenol A (BPA), an endocrine disrupting chemical, had been used worldwide as a raw material in water bottles and food packages. It leaches into food products and water sources and hence, it should be monitored effectively. Herein, an electrochemical sensing platform based on Cu-MOF@Pd-500 modified glassy carbon (GC) electrode was fabricated for the sensing of BPA. The material was synthesized by a simple solvothermal method, carbonized at 500 ⁰C, and characterized by various surface analytical techniques. Cyclic voltammetric (CV) analysis reveals that the Cu-MOF@Pd-500 modified GCE exhibits 1.5 folds hike in peak current and a considerable shift in peak potential towards the anodic side when compared to Cu-MOF@ 500, suggesting the higher electrocatalytic activity of the former than that of the later. The electrochemical oxidation of BPA provides an irreversible diffusion-controlled process involving two electrons and two protons. Differential pulse voltammetric (DPV) analysis reveals that the constructed sensor material provides a linear response over BPA concentration of 1 − 150 µM with a low detection limit (LOD) of 0.06 µM, (S/N = 3) and amperometric studies deliver a linear range of 1–22 µM with a LOD of 0.025 µM in 0.1 M PBS at a pH 7.0. Additionally, the Cu-MOF@Pd-500 delivers good repeatability, stability, and anti-interference capabilities. The results obtained also support the effectiveness of Cu-MOF@Pd-500 for quantifying and identifying BPA in real sample analysis (plastic water bottles) with an average recovery of the ratio of 101.93 having a relative standard deviation (RSD) of 0.42%.

Bioresource-derived multifunctional carbon quantum dots as a fluorescence and electrochemical sensing platform for picric acid and noncytotoxic food storage application

This work deals with the synthesis of facile, water-soluble, and blue-emitting carbon quantum dots (CQDs) from Plumbago indica leaves by a hydrothermal method with a quantum yield of 16 %. The biomass Plumbago indica leaves exhibit several advances such as easy availability, cost-effectiveness, non-toxic, green source, and not requiring any sophisticated techniques to develop the sensor. The optical, morphological, structural, and compositional properties of the CQDs were confirmed by various characterization methods. As a fluorescent probe, CQDs exhibited good linear response to picric acid (PA) with a limit of detection (LOD) of 18 nM. The sensing mechanism involves a combination of static quenching and fluorescence resonance energy transfer (FRET). In the electrochemical sensing method, the differential pulse voltammetric (DPV) technique was performed using a CQD-modified gold electrode with a LOD of 0.35 nM for PA. Using fresh carrots as a model sample, the antioxidant activity of PVA, CQD, and a PVA-CQD mixture was qualitatively determined. The in vitro cytotoxicity analysis of CQDs by MTT assay using the L6 cell line confirmed its non-toxic behaviour. This work is noteworthy because it offers a new attempt to identify toxic PA from biomass-derived precursor material and finds future applications in the food industry.

Eutectic solvent-mediated synthesis of manganese molybdate nanosheets: Rapid and real-time electrochemical detection of p-methylaminophenol sulfate(metol)

The present study explores the design of MnMoO4 modified sensing platform for the electrochemical detection of metol. The green synthesis of MnMoO4 nanosheets was accomplished by a low-temperature deep eutectic solvents (DES) assisted hydrothermal protocol. According to structural and electrochemical studies, the large surface area and pore volume of the MnMoO4-based working electrode assembly provided a conduit for the anchoring of the target analytes. Under optimized electrochemical conditions, the modified sensor demonstrated an exceptionally low detection limit (LOD = 0.98 nM) with a sensitivity of 88.8 μA μM−1 cm−2 within a substantial linear working range from 0.01 to 375.6 μM by differential pulse voltammetric (DPV) technique. Benefiting from the significantly improved stability, sensitivity, and reproducibility, the proposed MnMoO4 electrocatalyst showed amplified current responses of metol. The possibility of metol detection without any foreign interference and % recovery between ±99.20–99.90 % opens up new prospects for the efficacious on-site detection of metol.

Poly(3,4-ethylenedioxythiophene):Polystyrene Sulfonate-Modified Electrode for the Detection of Furosemide in Pharmaceutical Products.

Furosemide (4-chloro-2-(furan-2-ylmethylamino)-5-sulfamoyl benzoic acid) is a widely used, FDA-approved drug prescribed for several symptoms associated with heart, kidney, liver failure, or chronic high blood pressure. In this work, a glassy carbon working electrode modified with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate is developed to detect furosemide (FURO) with high sensitivity and precise selectivity. The modified electrode was also characterized using field emission scanning electron microscopy, attenuated total reflectance-Fourier transform infrared, and cyclic voltammetry. Here, an efficient and cost- and time-efficient technique to study the furosemide mechanism of reaction in an acidic liquid medium is presented. An electrochemical oxidation of loop diuretic furosemide was investigated in a supporting electrolyte, 0.01 M of phosphate buffer (at a pH level of 4.0) at 25 ± 0.1 °C using a differential pulse voltammetric (DPV) technique. Under optimized parameters, the developed sensor displays a wide detection range of furosemide concentrations of 6.0 × 10-6 to 1.0 × 10-4 M with a detection limit of 2.0 × 10-6 M using DPV. The presented sensor offers a robust and high-precision technique with an excellent reproducibility to detect furosemide in as a real sample such as urine and pharmaceutical products.

Simultaneous electrochemical determination of the tumour biomarkers homovanillic acid and vanillylmandelic acid using a modified pencil graphite electrode

This study describes the fabrication of an electrochemical sensor for the simultaneous detection of the tumour biomarkers homovanillic acid (HVA) and vanillylmandelic acid (VMA). The electrooxidation of HVA and VMA were studied at a pencil graphite electrode (PGE) modified with an electropolymer of 4- Aminosalicylic acid (ASA). Cyclic voltammetric (CV) studies of HVA and VMA on PGE and poly-ASA modified PGE (PASA-PGE) showed that simultaneous resolution of these analytes was possible only on PASA-PGE. The differential pulse voltammetric (DPV) response of HVA and VMA on PASA-PGE was found to be linear in a concentration range of 3.00 μM- 61.40 μM and 0.50 μM − 15.35 μM with a respective lower detection limit (LOD) of 1.82 μM and 0.28 μM. This is the first work reporting the electrochemical quantification of HVA and VMA simultaneously on PGE and was analytically applied for the determination of these analytes from human urine samples.

Fabrication of a novel electrochemical biosensor based on easy and efficient modifications of a glassy carbon electrode for sensitive and selective determination of morphine

In this study, a selective and sensitive electrochemical determination of morphine at low concentration was carried out using electropolymerization of 3-methyl-1-phenyl-pyrazole-5-one (MPP) at the surface of a glassy carbon electrode (GCE) which was further modified by electrodeposition of cobalt nanoparticles (Co NPs) onto its surface. The electrochemical studies of morphine were performed using cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques. Modification of the electrode surface increased its response to morphine which yielded a relatively wide linear range (2 to 100 μM) and a low limit of detection of 0.12 μM. The analytical characteristics of the sensor towards determination of the morphine were investigated which confirmed a good analytical performance for the sensor. Finally, the sensor was used for monitoring morphine in serum and urine samples as real matrices whose performance was both acceptable and admirable which motivated us to introduce it as a reliable method for determination of morphine in biological fluids.

Synergetic effects of Mo2C sphere/SCN nanocatalysts interface for nanomolar detection of uric acid and folic acid in presence of interferences

Till to date, the application of sulfur-doped graphitic carbon nitride supported transition metal carbide interface for electrochemical sensor fabrication was less explored. In this work, we designed a simple synthesis of molybdenum carbide sphere embedded sulfur doped graphitic carbon nitride (Mo2C/SCN) catalyst for the nanomolar electrochemical sensor application. The synthesized Mo2C/SCN nanocatalyst was systematically characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with elemental mapping. The SEM images show that the porous SCN network adhered uniformly on Mo2C, causing a loss of crystallinity in the diffractogram. The corresponding elemental mapping of Mo2C/SCN shows distinct peaks for carbon (41.47%), nitrogen (32.54%), sulfur (1.37%), and molybdenum (24.62%) with no additional impurity peaks, reflecting the successful synthesis. Later, the glassy carbon electrode (GCE) was modified by Mo2C/SCN nanocatalyst for simultaneous sensing of uric acid (UA) and folic acid (FA). The fabricated Mo2C/SCN/GCE is capable of simultaneous and interference free electrochemical detection of UA and FA in a binary mixture. The limit of detection (LOD) calculated at Mo2C/SCN/GCE for UA and FA was 21.5 nM (0.09 – 47.0 μM) and 14.7 nM (0.09 – 167.25 μM) respectively by differential pulse voltammetric (DPV) technique. The presence of interferons has no significant effect on the sensor’s performance, making it suitable for real sample analysis. The present method can be extended to fabricate an electrochemical sensor for various molecules.

An Aptamer Biosensing Strategy for Label-Free Assay of Dual Acute Myocardial Infarction Biomarkers Built upon AuNPs/Ti3C2-MXenes

The sensitive quantification of cardiac troponin I (cTnI) and myoglobin (Myo) in blood is essential for an early emergency diagnosis of acute myocardial infarction (AMI). Attributed to AuNPs and a titanium element on the surface of the AuNPs/Ti3C2-MXenes hybrid, each respective aptamer strand can be immobilized on. In this work, a nanohybrid was deposited on amino-functionalized indium tin oxide (ITO) via an Au–N bond; thereafter, it could catch cTnI-specific, thiol-functionalized DNA aptamer through Au–S self-assembly or Myo-aptamer via adsorption and metal chelate interaction between phosphate groups and titanium for specific recognition. Both using [Fe(CN)6]3−/4− as a signaling probe, the differential pulse voltammetric (DPV) current of the cTnI-aptasensor decreased after binding with cTnI, while the other responded to Myo via the impedimetric measurement. These developed biosensors enable the response to the femtogram/mL level cTnI or nanogram/mL level Myo. Remarkably, the proposed aptasensors exhibit high sensitivity and specificity for targets and display great potential for applications in clinic diagnosis.

Highly Efficient versus Null Electrochemical Enantioselective Recognition Controlled by Achiral Colinkers in Homochiral Metal-Organic Frameworks.

Chiral materials capable of electrochemical enantiomeric recognition are highly desirable for many applications, but it is still very challenging to achieve high recognition efficiency for lack of the knowledge of structure-property relationships. Here, we report the completely distinct enantiomeric recognition related to slightly different achiral colinkers in isomorphic homochiral metal-organic frameworks with the same chiral linker. Cu-TBPBe, for which the achiral colinker has two pyridyl rings connected by ─CH═CH─, shows excellent enantioselectivity and sensitivity for electrochemical recognition of l-tryptophan (Trp) with a detection limit of 3.16 nM. The l-to-d ratio of differential pulse voltammetric (DPV) currents reaches 53, which is much higher than the values (2-14) reported for previous electrochemical sensors. By contrast, Cu-TBPBa, in which the achiral colinker has -CH2-CH2- between pyridyl rings, is incapable of discrimination between l-Trp and d-Trp. Structural and spectral analyses suggest that the achiral conjugated colinker and the chiral moieties around it cooperate to produce a chiral pocket in favor of enantioselective adsorption through multiple hydrogen-bonding and π-π stacking interactions. The work demonstrated that Cu-TBPBe can be used to fabricate reliable electrochemical sensors for ultrasensitive quantification of Trp enantiomers in racemic mixtures and in complex biological systems such as urine. The work also highlights that an achiral coligand can be of vital importance in determining enantiomeric discrimination, opening up a new avenue for the design of chiral sensing materials.

A novel triple templates molecularly imprinted biosensor assisted by first derivatives of second-order hydrodynamic differential normal pulse voltametric data and multi-way calibration methods for simultaneous biosensing of penicillin, tetracycline and amoxicillin in dairy products: A novel multi-disciplinary study

In this work, a screen printed carbon electrode (SPCE) was used as a platform to fabricate a novel electrochemical biosensor assisted by the first derivatives of the second-order hydrodynamic differential normal pulse voltammetric (HDNPV) data modeled by multivariate curve resolution alternating least squares (MCR-ALS) and parallel factor analysis applied to shift invariant amplitude spectra (PARASIAS) for simultaneous determination of penicillin (PC), tetracycline (TC), and amoxicillin (AC) in dairy products. The SPCE was modified with poly(3,4-ethylenedioxythiophene) (PEDOT) by electropolymerization of the EDOT. Triple templates molecularly imprinted polymers (TTMIPs) were synthesized by using acrylic acid as the functional monomer, and TC, PC, and AC as the template molecules, and epichlorohydrin as a crosslinking agent. The TTMIPs were mixed with multi-walled carbon nanotubes-graphene-ionic liquid (MWCNTs-GR-IL), and drop-casted onto the surface of PEDOT/SPCE. The first derivatives of individual HDNPV responses of the TTMIPs-MWCNTs-GR-IL/PEDOT/SPCE to TC, PC and AC were univariately calibrated, and their linear ranges were used to develop second-order calibration models using MCR-ALS and PARASIAS whose performances were validated by application of them to a validation set with the aim of choosing the best model to assist the biosensor for the analysis of yogurt, milk, and yogurt drink as real samples. The biosensor assisted by MCR-ALS showed a better performance than PARASIAS which forced us to make a final decision on choosing it to assist the biosensor for the analysis of real matrices. The methodology developed in this work was benefited from TTMIIPs, good structure of the biosensor, and three-way calibration models which helped us to develop a novel electroanalytical method for simultaneous determination of TC (0.1–9 pM), PC (1–10 pM), and AC (0.35–8 pM) whose performance in analysing real matrices was comparable with the HPLC-UV as the reference method.

Molecularly imprinted graphene based biosensor as effective tool for electrochemical sensing of uric acid

Graphene oxide based molecularly imprinted polymer was designed by incorporating vinyltrimethoxysilane into the layers of graphene oxide, which was copolymerized with functional monomers such as Itaconic acid (IA) and methyl methacrylate (MMA) was developed via bulk imprinting technique. The prepared polymer was studied for selective sensing the uric acid (UA) in blood serum. The electrode was constructed by modifying bare glassy carbon electrodes with the prepared molecularly imprinted polymer (MIP) via drop cast method. Electrochemical measurements were made by Cyclic voltammetric (CV) and Differential Pulse Voltammetric (DPV) response of the sensor. The physical and chemical properties of the resultant material will be characterized by FTIR spectroscopy, XRD and FESEM. The constructed sensor showed a regression coefficient (R2) of 0.9302 with limit of detection (LOD) of about 0.565 ​μM. The developed sensor is reusable without any compromise in its selectivity. All the results confirm that the constructed biosensor requires no pre-treatment of samples and is suitable for real sample analysis.