A label-free aptasensor based on electrodeposition of gold nanoparticles on silver-based metal-organic frameworks for measuring ochratoxin A in black and red pepper.

Since ochratoxin A (OTA) is immunotoxic, teratogenic and carcinogenic, it is very important to monitor this compound in food samples. In the present work, the development and fabrication of a label-free electrochemical aptasensor based on the gold nanoparticles/silver-based metal-organic framework (AuNPs/Ag-MOF) for the determination of ochratoxin A (OTA) is introduced. The aptasensor was fabricated by electrodeposition of AuNPs on a glassy carbon electrode modified with Ag-MOF. The characteristics of the synthesized Ag-MOF were determined by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy. The aptamer was immobilized on the modified electrode and then OTA was incubated on it. The process of different stages of the aptasensor construction has been confirmed by two methods of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and using [Fe(CN)6]3-/4- as a redox probe. The EIS method has also been used for the OTA quantitative determination. The difference in charge transfer resistance (Rct) before and after the interaction of OTA with the immobilized aptamer was considered as the analytical response of the aptasensor. Using the developed aptasensor, it is possible to measure OTA in the concentration range of 1.0 × 10-3 to 200.0 ng mL-1 with a detection limit of 2.2 × 10-4 ng mL-1. Finally, the ability of the aptasensor to measure OTA in red and black pepper was investigated and completely satisfactory results were obtained.

Alprazolam Detection Using an Electrochemical Nanobiosensor Based on AuNUs/Fe-Ni@rGO Nanocomposite.

Despite all the psychological advantages of alprazolam, its long list of toxic properties and interactions has caused concern and highlighted the need for a reliable sensing method. In this study, we developed a simple, highly sensitive electrochemical nanobiosensor to determine the desirable dose of alprazolam, averting the undesirable consequences of overdose. Gold nanourchins (AuNUs) and iron-nickel reduced graphene oxide (Fe-Ni@rGO) were immobilized on a glassy carbon electrode, which was treated beforehand. The electrode surface was characterized using cyclic voltammetry, Fourier transform infrared spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and differential pulse voltammetry. The fabricated sensor showed two linear ranges (4 to 500 µg L-1 and 1 to 50 mg L-1), low limit of detection (1 µg L-1), high sensitivity, good repeatability, and good recovery. Increased -OH and carboxyl (-COOH) groups on the electrode surface, resulting in improved the adsorption of alprazolam and thus lower limit of detection. This nanobiosensor could detect alprazolam powder dissolved in diluted blood serum; we also studied other benzodiazepine drugs (clonazepam, oxazepam, and diazepam) with this nanobiosensor, and results were sensible, with a significant difference.

Fabrication of a label-free electrochemical aptasensor to detect cytochrome c in the early stage of cell apoptosis.

A label-free direct electrochemical aptasensor is presented for the identification of cytochrome c (Cyt c) at the nM concentration level. Carbon nanofibers (CNF), as a highly conductive material, were used to modify a glassy carbon electrode (GCE) and thus increase its conductivity. Moreover, to enhance the immobilization of aptamers (Apt) on the electrode surface, graphene oxide functionalized with aspartic acid (GOAsp) was added to the surface. Aspartic acid with countless carboxyl groups (-COOH) on its surface caused more aptamers to be immobilized on the electrode surface. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) were used to monitor the step-by-step fabrication of the label-free direct electrochemical aptasensor. The label-free quantification of Cyt c was also done by the direct electron transfer between the Fe(III)/Fe(II)-heme redox-active sites which were selectively bound to the aptamers on the GCE and the surface of the electrode. Under optimum conditions, the peak currents of differential pulse voltammograms at 0.26 V (vs. Ag/AgCl) were used for calibration. The proposed aptasensor performs in a wide dynamic range from 10 nM to 100 µM with a low detection limit of 0.74 nM for cytochrome c. It also has high selectivity as well as acceptable stability. These advantages make the biosensor capable of detecting early-stage apoptotic cells that contribute to early cancer diagnosis.

Development of an electrochemical aptasensor based on Au nanoparticles decorated on metal-organic framework nanosheets and p-biphenol electroactive label for the measurement of aflatoxin B1 in a rice flour sample.

This study purposes designing a new aptasensor to detect aflatoxin B1 (AFB1). The AFB1 aptasensor was developed by growing gold nanoparticles on the surface of nickel-based metal-organic framework nanosheets (AuNPs/Ni-MOF) and an electroactive indicator (p-biphenol, PBP). The AFB1 aptamer was immobilized on the AuNPs/Ni-MOF and then hybridized with the complementary DNA (cDNA). PBP was intercalated within the double helix of the cDNA-aptamer. The difference between electrochemical responses of intercalated PBP before and after incubation of AFB1 with the immobilized aptamer was considered as an analytical response. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to monitor the construction processes of the aptasensor. By recording the differential pulse voltammograms of PBP in phosphate buffer (pH 7.0, 0.1 M), the linear range and the detection limit of AFB1 were found to be 5.0 × 10-3-150.0 ng mL-1 and 1.0 × 10-3 ng mL-1 (S/N = 3), respectively. Finally, the designed aptasensor has been successfully used to measure AFB1 in a rice flour sample with satisfying results. Schematic illustrated the different steps of constructing the electrochemical aptasensor based on Au nanoparticles decorated on Ni-metal-organic framework nanosheets and p-biphenol electroactive label for measuring aflatoxin B1 (AFB1).

Determination of lead ions in fish and oyster samples using a nano-adsorbent of functionalized magnetic graphene oxide nanosheets-humic acid and the flame atomic absorption technique.

This study aims at the functionalization of magnetic graphene oxide nanosheets and the binding of humic acid as a lead complex ligand. Graphene oxide nanosheets possess a large surface area and various carboxylic acid groups which can be activated easily by activating agents. Therefore, they are suitable to be used for the extraction of heavy metals. To have a better process of extracting lead ions, magnetic graphene oxide was used in this research. Humic acid, as a lead metal complex agent, has an amine functional group which can be bound to modified graphene oxide from one side. The process of constructing the nano-adsorbent proposed for the preconcentration of lead ions as well as its characterization was studied by infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-visible), field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM). The designed nano-adsorbent was tested to measure lead ions in simulated and real samples of sea water, fish, and oysters. The detection limit obtained in the simulated samples was 0.07 µg/L, and the linear range was 0.2-12 µg/L. The apparatus used to measure the ions was a flame atomic absorption device. In the analysis of the real samples, the values obtained through flame atomic absorption were compared with those obtained through furnace atomic absorption. The proposed technique is advantageous due to being cheap, precise, and sensitive for the trace measurement of lead ions.

Monitoring the mechanism of anti-cancer agents to inhibit colorectal cancer cell proliferation: Enzymatic biosensing of glucose combined with molecular docking.

Glucose, a major energy source in cellular metabolism, has a significant role in cell growth. The increase in glucose uptake is a distinguishing hallmark in cancer cells. A key step in glucose utilization is the transport of glucose to the cancer cells for supplying their additional energy. The glucose transporter (or GLUT) family is a membrane protein which facilitates the uptake of glucose in most cancer cell types. Given the increased glucose level in cancer cells and the regulatory role of GLUTs in glucose uptake, it is required to combine both experimental and theoretical studies to develop new methods to monitor cell proliferation. Herein, for the first time, a new strategy was proposed to evaluate the cell proliferation of HT-29 based on glucose consumption in the presence of resveratrol (RSV) as an anticancer agent. A hybrid nanocomposite of carbon nanofibers and nitrogen-doped graphene quantum dots was used to design an enzymatic sensor for the selective and sensitive determination of glucose in cancer cells. The results obtained from the voltammetric technique were compared with the conventional colorimetric assay. A good correlation was observed between the proliferation rate and glucose utilization by cancer cells. As it was observed, RSV induces a decrease in glucose consumption, indicating lower glucose uptake efficiency for HT-29 cells. Molecular docking studies reveal that RSV can block the interaction of glucose with the GLUT family. This is one of the possible mechanisms for the decrease of glucose level followed by the reduction of cell proliferation in the presence of RSV. Compared with traditional methods, in vitro electrochemical techniques benefit from simple, nontoxic, sensitive and low-cost detection assays and hence serve as a novel tool to pursue the growth inhibition of cancer cell in response to anti-cancer agents.

Experimental and theoretical study for miR-155 detection through resveratrol interaction with nucleic acids using magnetic core-shell nanoparticles.

A novel electrochemical nanobiosensor for the detection of miR-155 (as breast cancer biomarker) is introduced . Fe3O4NPs@Ag core-shell nanoparticles were synthesized and their shape and characteristics were confirmed by scanning electron microscope (SEM) imaging, Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) methods. Synthesized nanoparticles were applied onto the magnetic bar carbon paste electrode and then the amine-modified anti-miR-155 (single-stranded probes) was applied on the modified electrode surface and upon hybridization with target miR-155, resveratrol (RSV) was eventually applied as an electrochemical label on the double-strand oligonucleotide. Differential pulse voltammetry (DPV) of the oxidation peak of RSV was assumed as the final signal by sweeping potential from 0 to 0.6 V (vs. Ag/AgCl). The fabrication process was optimized through a series of experiments and the optimized process was confirmed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The linear range of the fabricated nanobiosensor was 0.5 fM to 1.0 nM and the detection limit was 0.15 fM. The nanobiosensor was able to pass reproducibility and specificity tests using different types of mismatched target sequences.Spiked real samples of human serum were used to confirm that the nanobiosensor enables detection of miR-155 without any significant interferences from other moieties and molecules. Finally, the molecular dynamics simulation of the RSV interaction with single- and double-stranded oligonucleotide was performed and confirmed the preferential binding of RSV to double-stranded DNA; therefore, it can be used as the electrochemical label of DNA and/or miRNA hybridization-based biosensors. Graphical abstract.

The extraction and measurement of nickel metal ion in crab, shellfish and rice samples using magnetic silk fibroin - EDTA ligand and furnace atomic absorption spectrometry.

The main aim of the present study was the measurement of nickel metal ion in the real samples of crab, oyster and rice by the designed magnetic nano adsorbent silk fibroin-EDTA ligand (SF-Fe3O4-EDTA). Due to the structure of silk fibroin (possessing lots of functional groups which are suitable for attachment of ligands and high surface area), it was used in the structure of fabricated nano-adsorbent. To follow the fabrication processes of the magnetic nano-adsorbent, different techniques of fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Visible), vibrating sample magnetometer (VSM), and field emission scanning electron microscopy (FE-SEM) were used. The optimization processes were performed with the chemometric method of response surface modeling with sufficient accuracy and precision. Using this chemometric method, the optimum values of pH, absorption time, the concentration of nano-adsorbent and temperature were calculated to be 6, 21 min, 4 mg L-1 and 28 °C, respectively. Due to the magnetic nature of the constructed nano-adsorbent, a magnet bar was used to separate the nano-adsorbent from the solution and then inject to the furnace atomic absorption device. Using the magnetic nano-adsorbent of silk fibroin-EDTA ligand and furnace atomic absorption a detection limit of 0.0017 µg L-1 and a linear range of 0.0030-5.0 µg L-1 for determination of nickel metal ion were obtained. The determination of nickel metal ion in the crab tissue, oyster tissue and rice samples were performed and the obtained results revealed the successful applicability of the designed method for determination of nickel metal ion in the real samples.

Highly selective sensing and measurement of microRNA-541 based on its sequence-specific digestion by the restriction enzyme Hinf1.

In this study, a genosensor is introduced to detect microRNA-541 through an enzymatic digestion method and using a restriction enzyme (RE). Hinf1 is a type of RE which can cut the double helix DNA at specific sequences. The hybridization event and the corresponding enzymatic reactions are studied through guanine signal tracing on a pencil graphite electrode modified with graphene quantum dots (GQDs/PGE). The stages of fabricating the electrode are monitored by atomic force microscopy, and its electrochemical behavior is studied by cyclic voltammetry. The results indicate that the guanine current response of a 25-mer oligonucleotide of 7-guanine immobilized on the electrode surface decreases after hybridization despite an increase in the number of the guanine bases. Also, after enzyme treatment, the current decreases further due to the separation of a number of guanine bases from ds-DNA. A comparison of the analytical parameters of the proposed method with those of the conventional guanine oxidation method indicates that the linear concentration range in the proposed method, i.e. 1.0 fM to 1.0 nM, is lower than that in the conventional method, i.e. 10.0 pM-1.0 µM. On the basis of these findings, it is concluded that the use of Hinf1 enzyme makes it possible to measure microRNA at a femtomolar level. The selectivity of the designed biosensor has been proved using a non-complementary sequence with a one-base mismatch in the recognition site, rather than a complementary sequence. Finally, the proposed genosensor can be satisfactorily applied to measure microRNA-541 in human plasma samples.

Identification of molecular features necessary for selective inhibition of B cell lymphoma proteins using machine learning techniques.

Selective inhibition of Bcl-2 and Bcl-xL proteins due to their dual inhibition toxicity plays an important role in treatment of cancer and chemotherapy effectiveness; therefore, in the last decade, discovery of selective inhibitors for Bcl-2 and Bcl-xL proteins has become a significant and important research topic. The present contribution paves the way for characterization of molecular features which induce selectivity for inhibition of Bcl-2 and Bcl-xL. In this line, a total of 1534 molecules related to inhibition of Bcl-2 and Bcl-xL proteins were collected from Binding Database. A diverse set of molecular descriptors was calculated for each molecule, and the best subset of descriptors were selected using variable importance in projection (VIP) approach. The molecules were classified according to their therapeutic targets (Bcl-2/Bcl-xL) and activities. Partial least square-discriminate analysis (PLS-DA) and supervised Kohonen network (SKN) models were utilized to relate the molecular structures of chemicals to their activities and selectivities. According to the VIP-selected descriptors physicochemical properties, such as polarity number, number of branches, size and cyclicity of the molecule, flexibility, functional counts and constitutional descriptors, all affect the activities of Bcl-2 and Bcl-xL inhibitors. The performances of PLS-DA and SKN methods were evaluated based on statistical parameters derived from the confusion matrices. The models were validated using tenfold cross-validation and an external test set. The best statistical results were obtained by implementing the SKN model. The classification rates range from 93.5 to 79.1% for the training and validation procedure for the optimized SKN models. The high values of the obtained classification rates demonstrate that the information provided in this work would be useful to design new drugs with selective inhibitory activities toward Bcl-2 or Bcl-xL proteins for more effective treatment of cancer.

Deciphering the inhibition effect of thymoquinone on xanthine oxidase activity using differential pulse voltammetry in combination with theoretical studies.

Xanthine oxidase (XO) catalyzes the oxidation of xanthine to uric acid. Over-production of uric acid is a risk factor for hyperuricemia and other diseases. Although allopurinol decreases uric acid levels, it causes severe adverse effects. Therefore, more effort is needed in finding novel XO inhibitors with fewer side effects. In this study, differential pulse voltammetry was used to investigate the inhibitory effect of thymoquinone (TQ) on the XO activity while the major problem was the overlap of the obtained signals. Thus, Parallel Factor Analysis (PARAFAC) was applied to extract the useful information. Also, docking was used to investigate how TQ and the active site of XO fit together. PARAFAC results based on the voltammetry studies revealed that TQ blocks the catalytic centers of XO, which leads to a decrease in the electrochemical signal of Mo center in XO. The results also indicated the dose-dependent inhibition of XO with TQ. Molecular docking studies were shown TQ surrounds the active sites of XO and reduces the oxidation of xanthine to uric acid. Therefore, the electrochemical response of Mo decreases in the presence of TQ. This finding is in good agreement with the results obtained from molecular docking studies.

Potentiality of PARAFAC approaches for simultaneous determination of N-acetylcysteine and acetaminophen based on the second-order data obtained from differential pulse voltammetry.

N-acetylcysteine (N-AC) has widespread application such as pharmaceutical drug and nutritional supplement. Its adverse effects are rash, urticaria, and itchiness and large doses of N-AC could potentially cause damage to the heart and lungs. Therefore, in this work, a sensitive voltammetric sensor based on a carbon paste electrode modified with silica nano particles (i.e. Mobil Composition of Matter (No. 41) modified with Boron Trifluoride or BF3@MCM-41) with a combination of 4,4'-dihydroxybiphenyl (DHB) (BF3@MCM-41/DHB/CPE) was designed for determination of N-AC. The electrochemical oxidation of N-AC was examined using various techniques such as cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV). Under the optimum conditions, some parameters such as electron transfer coefficient (α) and heterogeneous rate constant (ks) were estimated for N-AC. Due to the use of N-AC for the treatment of acetaminophen (AC) overdose, the application of modified electrode was investigated for the simultaneous determination of N-AC and AC in blood serum and tablet samples. Since, the signals of these species overlap and due to the presence of interfering species in blood samples, the simultaneous determination of mentioned species is difficult or impossible. To overcome this challenge, parallel factor analysis (PARAFAC) was used for the analysis of the complex matrices to obtain the spectral profile of each component and interference. To achieve this goal, electrochemical second-order data were generated using a simple change in pulse height of differential pulse voltammetry. The results of the presently proposed strategy for the real samples analysis are similar to those obtained with HPLC. Thus, the proposed method has acceptable performance for simultaneous determination of the two species in real samples.

Dual-aptamer based electrochemical sandwich biosensor for MCF-7 human breast cancer cells using silver nanoparticle labels and a poly(glutamic acid)/MWNT nanocomposite.

This paper reports on a sensitive and selective method for the detection of Michigan Cancer Foundation-7 (MCF-7) human breast cancer cells and MUC1 biomarker by using an aptamer-based sandwich assay. A biocompatible nanocomposite consisting of multiwall carbon nanotubes (MWCNT) and poly(glutamic acid) is placed on a glassy carbon electrode (GCE). The sandwich assay relies on the use of a mucin 1 (MUC1)-binding aptamer that is first immobilized on the surface of modified GCE. Another aptamer (labeled with silver nanoparticles) is applied for secondary recognition of MCF-7 cells in order to increase selectivity and produce an amplified signal. Differential pulse anodic stripping voltammetry was used to follow the electrochemical signal of the AgNPs. Under the optimal condition, the sensor responds to MCF-7 cells in the concentration range from 1.0 × 102 to 1.0 × 107 cells·mL-1 with a detection limit of 25 cells. We also demonstrate that the MUC1 tumor marker can be detected by the present biosensor. The assay is highly selective and sensitive, acceptably stable and reproducible. This warrants the applicability of the method to early diagnosis of breast cancer. Graphical abstract Schematic of the fabrication of an aptamer-based sandwich biosensor for Michigan Cancer Foundation-7 cells (MCF-7). A MWCNT-poly(glutamic acid) nanocomposite was used as a biocompatible matrix for MUC1-aptamer immobilization. Stripping voltammetry analysis of AgNPs was performed using aptamer conjugated AgNPs as signalling probe.

An in-depth view of potential dual effect of thymol in inhibiting xanthine oxidase activity: Electrochemical measurements in combination with four way PARAFAC analysis and molecular docking insights.

Xanthine oxidase (XO) can catalyze xanthine to uric acid and has also been linked with the extension of some serious diseases such as cancer, gout, diabetes and so on. Thymol is a part of diet in the form of spices. Due to the high antioxidant activity, its inhibitory effect on XO was studied in the present work. XO organized in four redox domains which exhibiting electrochemical signals. Therefore, voltammetric methods can be used to obtain the valuable information about the action mechanism of thymol on XO. However, there are extreme complexities in these biological sample matrices which make the deeper understanding of inhibition mechanism of thymol on XO activity is difficult. Thus, development of electrochemical techniques coupled with the four-way parallel factor analysis (PARAFAC) has provided promising solutions for analyzing of complex matrix. To better explore this inhibitory effect, electrochemical technologies have been used as a complement with ultraviolet and visible (UV-Vis) spectroscopy and molecular docking studies. For the first time, molecular docking studies were used to gain a fundamental understanding to explain how the electron transfer coupling occurs at XO active sites in the presence of thymol. It is in good agreement with the experimental data. These studies reveal that thymol could enter into the catalytic centers of XO. Also, it inhibits the XO activity through the direct binding to flavin adenine dinucleotides (FAD) center. The results display dose-dependent inhibition of XO with thymol. Its inhibitory activity was linked to its antioxidant properties to reduce the formation of free radicals (FRs) and related diseases.

Chemometric studies of thymol binding with bovine serum albumin: A developing strategy for the successful investigation of pharmacological activity.

Thymol (Thy) is a hydrophobic active ingredient present in thyme essential oils. It is marginally soluble in water which is one of the challenging limitations for its application in foods or as drugs. An important aspect of our understanding from this system is to quantitatively comprehend how albumin interacts with Thy. Herein, this study has been focused on the interactions between thymol and bovine serum albumin (BSA) using electrochemical methods and ultraviolet and visible (UV-Vis) spectroscopy. Due to the overlap between obtained signals of existing species, it is apparent that multivariate methods can resolve overlapping signal trough unique decomposition. These obtained profiles are then analyzed to give the thermodynamic parameters, concentration and structural information of BSA binds to Thy. The thermodynamic results show that hydrogen bonding formation and van der Waals forces play major role in the binding process. Also, docking studies suggested that Thy binds mainly to the subdomain IIA of BSA through the formation of hydrogen bonding with Arg 217. Good agreement was found between the results obtained from experimental and theoretical studies. Thus, the current approaches seem to be promising that are not only for the transport of thymol in blood but also for its effective action in food applications.

A Highly Selective DNA Sensor Based on Graphene Oxide-Silk Fibroin Composite and AuNPs as a Probe Oligonucleotide Immobilization Platform3667.

In this study, a simple and novel electrochemical biosensor based on a glassy carbon electrode (GCE) modified with a composite of graphene oxide (GO) - silk fibroin nanofibers (SF) and gold nanoparticles (MCH/ssDNA/AuNPs/SF/GO/GCE) was developed for detection of DNA sequences. The fabrication processes of electrochemical biosensor were characterized by scanning electron microscopy (SEM), FT-IR and electrochemical methods. Some experimental conditions such as immobilization time of probe DNA and MCH incubation time, time and temperature of hybridization were optimized. The designed biosensor revealed a wide linear range of 1.0 × 10-16 - 1.0 × 10-8 mol L-1 and a low detection limit (3.3 × 10-17 mol L-1) for detection of BRCA1 5382 mutation by EIS technique. The designed biosensor revealed high selectivity for discrimination of the complementary (P1C) sequences from various non-complementary sequences of (P1nC1, P1nC2 and P1nC3). Also, the biosensor revealed a high reproducibility (RSD of 7.5% (n=4)) and high stability (92% of its initial response after 8 days). So, the fabricated biosensor has a suitable potential to be applied for detection of breast cancer sequences in the initial stages of the cancer.

New insights into the efficiency of thymol synergistic effect with p-cymene in inhibiting advanced glycation end products: A multi-way analysis based on spectroscopic and electrochemical methods in combination with molecular docking study.

Protein glycation in the body is one of the main reasons of diabetes complications. The electrochemical studies on the inhibitory mechanism of glycation are rather scarce. Thus, it is important to investigate the role of electrochemistry in the glycation process with basic chemometric frameworks. The aim of the current study is to investigate the anti-glycation effects of candidate compounds from thyme species i.e. thymol and p-cymene. To gain this objective, the electrochemical and absorption responses of glycated bovine serum albumin (BSA) in the absence and presence of inhibitors were recorded after 20 day of incubation. Due to the presence of multiple binding sites on BSA for the interaction with glucose, there are overlapping between the signals of these sites. Therefore, it is reasonable to use chemometric methods such as parallel factor analysis (PARAFAC) and alternating penalty trilinear decomposition (APTLD). The obtained results from chemometric methods showed that the solution of thymol at 5.0 mg mL-1 mixture with p-cymene (2.5 mg mL-1) was effective than thymol of 5.0 mg mL-1. Computational docking studies revealed the interaction pattern of thymol with BSA. The binding affinity of thymol was greater than glucose which it is in well agreement with the experimental data.

Monitoring the protective ability of thymoquinone mixture with p-cymene against bovine serum albumin (BSA) glycation: MCR-ALS analysis based on combined spectroscopic and electrochemical methods.

Protein glycation with sugars such as glucose start by the initial reaction between the carbonyl group of sugars and the amino group of proteins such as albumin and hemoglobin. This leads to the generation of Schiff base and following that the amadori and advanced glycation end products (AGEs). AGEs products can store in tissues and blood of diabetic patients. So, they play key roles to generate free radicals, which cause the development of diabetes complications. Inhibition of protein glycation plays an important role in controlling diabetes, so the identification of anti-glycation compounds is now receiving considerable interest. In this study, the protection effects of thymoquinone and its mixture with p-cymene on the glycation of bovine serum albumin (BSA) have been investigated by differential pulse voltammetry (DPV) and UV-vis spectrophotometry (UV-vis) techniques. Also, the multivariate curve resolution-alternating least squares (MCR-ALS) method was used since the results of the experimental measurements have a strongly overlapping signals. Molecular docking was applied to determine the site specific binding of inhibitor with residues of BSA. This study demonstrates that thymoquinone and its mixture with p-cymene have the potent ability to use as a dietary adjuvant against glycation.

Developing an electrochemical sensor based on a carbon paste electrode modified with nano-composite of reduced graphene oxide and CuFe2O4 nanoparticles for determination of hydrogen peroxide.

In this paper, a highly sensitive voltammetric sensor based on a carbon paste electrode with CuFe2O4 nanoparticle (RGO/CuFe2O4/CPE) was designed for determination of hydrogen peroxide (H2O2). The electrocatalytic reduction of H2O2 was examined using various techniques such as cyclic voltammetry (CV), chronoamperometry, amperometry and differential pulse voltammetry (DPV). CuFe2O4 nanoparticles were synthesized by co-precipitation method and characterized with scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) techniques. Then, a high conductive platform based on a carbon paste electrode modified with RGO and CuFe2O4 nanoparticles was prepared as a suitable platform for determination of hydrogen peroxide. Under the optimum conditions (pH5), the modified electrode indicated a fast amperometric response of <2s, good linear range of 2 to 200µM, low detection limit of 0.52µM for determination of hydrogen peroxide. Also, the peak current of differential pulse voltammetry (DPV) of hydrogen peroxide is increased linearly with its concentration in the ranges of 2 to 10µM and 10 to 1000µM. The obtained detection limit for hydrogen peroxide was evaluated to be 0.064µM by DPV. The designed sensor was successfully applied for the assay of hydrogen peroxide in biological and pharmaceutical samples such as milk, green tea, and hair dye cream and mouthwash solution.

Impedimetric PSA aptasensor based on the use of a glassy carbon electrode modified with titanium oxide nanoparticles and silk fibroin nanofibers.

This article describes an impedimetric aptasensor for the prostate specific antigen (PSA), a widely accepted prostate cancer biomarker. A glassy carbon electrode (GCE) was modified with titanium oxide nanoparticles (TiO2) and silk fibroin nanofiber (SF) composite. The aptasensor was obtained by immobilizing a PSA-binding aptamer on the AuNP-modified with 6-mercapto-1-hexanol. The single fabrication steps were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The assay has two linear response ranges (from 2.5 fg.mL-1 to 25 pg.mL-1, and from 25 pg.mL-1 to 25 ng.mL-1) and a 0.8 fg.mL -1 detection limit. After optimization of experimental conditions, the sensor is highly selective for PSA over bovine serum albumin and lysozyme. It was successfully applied to the detection of PSA in spiked serum samples. Graphical abstract Schematic of the fabrication of an aptasensor for the prostate specific antigen (PSA). It is based on the use of a glassy carbon electrode modified with gold nanoparticles and titanium oxide-silk fibroin. The immobilization process of aptamer and interaction with PSA were followed by electrochemical impedance spectroscopy technique.