A Sensitive Aptamer-Based Biosensor for Electrochemical Quantification of PSA as a Specific Diagnostic Marker of Prostate Cancer.

PURPOSE: The current project aimed to design a simple, highly sensitive, and economical label-free electrochemical aptasensor for determination of prostate-specific antigen (PSA), as the gold standard biomarker for prostate cancer diagnosis. The aptasensor was set up using a screen-printed carbon electrode (SPCE) modified by gold nanoparticles (Au NPs) conjugated to thiolated aptamers. METHODS: Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were implemented for electrochemical (EC) characterization of the aptasensor. The determination of PSA was also performed through differential pulse voltammetry (DPV) in [Fe (CN) 6]3-/4- electrolyte solution. RESULTS: The present aptasensor was shown an outstanding linear response in the concentration range of 1 pg/mL - 200 ng/mL with a remarkably lower limit of detection of 0.077 pg/mL. The optimum concentration for PSA separation and the optimum incubation time for antigen-aptamer binding were determined by observing and electing the highest electrochemical responses in a specified time or concentration. CONCLUSION: According to the results of the specificity tests, the designed aptasensor did not show any significant interactions with other analytes in real samples. Clinical functionality of the aptasensor was appraised in serum samples of healthy individuals and patients examining the PSA level through the fabricated aptasensor and the reference methods. Both methods are comparable in sensitivity. The present fabricated PSA aptasensor with substantial characteristics of ultra- sensitivity and cost-effectiveness can be conventionally built and used for the routine check-up of the men for prostate problems.

Simple and effective label free electrochemical immunosensor for Fig mosaic virus detection.

Here, the construction and characterization of the first immunosensor for highly sensitive and label free detection of Fig mosaic virus (FMV) is reported. The specific antibody against nucleocapsid of the virus was raised and immobilized at the surface of 11-mercaptoundecanoic acid (MUA) and 3-mercapto propionic acid (MPA) modified gold electrode, via carbodiimide coupling reaction. The immunosensor fabrication steps were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical detection of FMV was conducted using differential pulse voltammetry in ferri/ferrocyanide solution as a redox probe. The proposed immunosensor exhibited high selectivity, good reproducibility and high sensitivity for FMV detection in a range from 0.1 nM to 1 µM with a detection limit of 0.03 nM. Moreover, good results were obtained for determination of FMV in real samples, indicating the feasibility of the developed immunosensor for detection of fig mosaic disease, without the need for molecular (e.g. PCR) amplification.

Simultaneous extraction and determination of trace amounts of diclofenac from whole blood using supported liquid membrane microextraction and fast Fourier transform voltammetry.

A novel, simple, and inexpensive analytical technique based on flat sheet supported liquid membrane microextraction coupled with fast Fourier transform stripping cyclic voltammetry on a reduced graphene oxide carbon paste electrode was used for the extraction and online determination of diclofenac in whole blood. First, diclofenac was extracted from blood samples using a polytetrafluoroethylene membrane impregnated with 1-octanol and then into an acceptor solution, subsequently it was oxidized on a carbon paste electrode modified with reduced graphene oxide nanosheets. The optimal values of the key parameters influencing the method were as follows: scan rate, 6 V/s; stripping potential, 200 mV; stripping time, 5 s; pH of the sample solution, 5; pH of the acceptor solution,7; and extraction time, 240 min. The calibration curves were plotted for the whole blood samples and the method was found to have a good linearity within the range of 1-25 µg/mL with a determination coefficient of 0.99. The limits of detection and quantification were 0.1 and 1.0 µg/mL, respectively. Using this coupled method, the extraction and determination were merged into one step. Accordingly, the speed of detection for sensitive determination of diclofenac in complex samples, such as blood, increased considerably.

Cerium(III) Ion Sensing Based on Graphene Quantum Dots Fluorescent Turn-Off.

In this work, graphene quantum dots (GQDs) was synthesized through hydrothermal method and used as a photoluminescent bulk nano-chemosensor for detection of Ce3+ ion in the aqueous solution. The synthesized GQD was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Visible absorption and fluorescence emission spectroscopy. The sheet diameters of the synthesized GQDs were mainly distributed in the range of 15-20 nm. The interactions of GQDs with common cations and lanthanide ions were studied by fluorescence spectroscopy. Among the tested cations, Ce3+ ions was able to quench the fluorescence emission intensity of the GQD selectively. This quenching can be attributed to a redox mechanism between Ce3+ ion on the GQDs surface.

Biosensors and their applications in detection of organophosphorus pesticides in the environment.

This review discusses the past and recent advancements of biosensors focusing on detection of organophosphorus pesticides (OPs) due to their exceptional use during the last decades. Apart from agricultural benefits, OPs also impose adverse toxicological effects on animal and human population. Conventional approaches such as chromatographic techniques used for pesticide detection are associated with several limitations. A biosensor technology is unique due to the detection sensitivity, selectivity, remarkable performance capabilities, simplicity and on-site operation, fabrication and incorporation with nanomaterials. This study also provided specifications of the most OPs biosensors reported until today based on their transducer system. In addition, we highlighted the application of advanced complementary materials and analysis techniques in OPs detection systems. The availability of these new materials associated with new sensing techniques has led to introduction of easy-to-use analytical tools of high sensitivity and specificity in the design and construction of OPs biosensors. In this review, we elaborated the achievements in sensing systems concerning innovative nanomaterials and analytical techniques with emphasis on OPs.

A fluorescent aptasensor for sensitive analysis oxytetracycline based on silver nanoclusters.

A fluorescent aptasensor for detection of oxytetracycline (OTC) was presented based on fluorescence quenching of DNA aptamer-templated silver nanoclusters (AgNCs). The specific DNA scaffolds with two different nucleotides fragments were used: one was enriched with a cytosine sequence fragment (C12) that could produce DNA-AgNCs via a chemical reduction method, and another was the OTC aptamer fragment that could selectively bind to the OTC antibiotic. Thus, the as-prepared AgNCs could exhibit quenched fluorescence after binding to the target OTC. The fluorescence ratio of the DNA-AgNCs was quenched in a linearly proportional manner to the concentration of the target in the range of 0.5 nM to 100 nM with a detection limit of 0.1 nM. This proposed nanobiosensor was demonstrated to be sensitive, selective, and simple, introducing a viable alternative for rapid determination of toxin OTC in honey and water samples. Copyright © 2016 John Wiley & Sons, Ltd.

A Novel Cobalt-Sensitive Fluorescent Chemosensor Based on Ligand Capped CdS Quantum Dots.

In this work, a ligand capped CdS QDs was synthesized, characterized and its fluorescence behavior was studied. The surface of the CdS QDs was modified using N-(3-methyl-2-(thiophene-2-carboxamido) phenyl) thiophene-2-carboxamide. The immobilized ligand on the surface of the CdS QDs can interact by cationic species due to the existence of donating atoms in its structures. Thus, effect of some metal cations on the fluorescent intensity of the ligand capped CdS QDs were studied. It was found that fluorescence intensity of the modified CdS QDs quenched selectively by addition of Co(II) ion in comparison with other cations tested. The ligand capped CdS QDs can be used as a fluorescent bulk chemosensor for detection of Co(II) ions. The fluorescent quenching is linear in the range of 1.0 × 10(-5) to 1.5 × 10(-4) mol L(-1) of Co(II) ions. The limit of detection was obtained 8.3 × 10(-7) mol L(-1). The nanosensor exhibits high selectivity toward Co(II) ions in comparison with common metal ions.

Sensitive determination of carbidopa through the electrochemiluminescence of luminol at graphene-modified electrodes.

Using the concept of electrogenerated chemiluminescence (ECL), a sensitive analytical method for the determination of carbidopa is described. Electro-oxidation of carbidopa on the surface of a graphene oxide (GO)-modified gold electrode (GE) leads to enhancement of the weak emission of oxidized luminol. Under optimum experimental conditions, the ECL signal increases linearly with increasing carbidopa concentrations over a range of 1.0 × 10(-9) -1.7 × 10(-7) M, with a detection limit of 7.4 × 10(-10) M. The proposed ECL method was successfully used for the determination of carbidopa in urine samples.

Development of label-free electrochemical OMP-DNA probe biosensor as a highly sensitive system to detect of citrus huanglongbing.

The fabrication of the first label-free electrochemical DNA probe biosensor for highly sensitive detection of Candidatus Liberibacter asiaticus (CLas), as the causal agent of citrus huanglongbing disease, is conducted here. An OMP probe was designed based on the hybridization with its target-specific sequence in the outer membrane protein (OMP) gene of CLas. The characterization of the steps of biosensor fabrication and hybridization process between the immobilized OMP-DNA probe and the target ssDNA oligonucleotides (OMP-complementary and three mismatches OMP or OMP-mutation) was monitored using cyclic voltammetry and electrochemical impedance spectroscopy based on increasing or decreasing in the electron transfer in [Fe (CN)6]3-/4- on the modified gold electrode surface. The biosensor sensitivity indicated that the peak currents were linear over ranges from 20 to 100 nM for OMP-complementary with the detection limit of 0.026 nM (S/N = 3). The absence of any cross-interference with other biological DNA sequences confirmed a high selectivity of fabricated biosensor. Likewise, it showed good specificity in discriminating the mutation oligonucleotides from complementary target DNAs. The functional performance of optimized biosensor was achieved via the hybridization of OMP-DNA probe with extracted DNA from citrus plant infected with CLas. Therefore, fabricated biosensor indicates promise for sensitivity and early detection of citrus huanglongbing disease.

Non-invasive and probeless rapid in-vitro monitoring and quantification of HUVECs counts based on FFT impedimetery.

Introduction: The endothelial cells derived from the human vein cord (HUVECs) are used as in-vitro models for studying cellular and molecular pathophysiology, drug and hormones transport mechanisms, or pathways. In these studies, the proliferation and quantity of cells are important features that should be monitored and assessed regularly. So rapid, easy, noninvasive, and inexpensive methods are favorable for this purpose. Methods: In this work, a novel method based on fast Fourier transform square-wave voltammetry (FFTSWV) combined with a 3D printed electrochemical cell including two inserted platinum electrodes was developed for non-invasive and probeless rapid in-vitro monitoring and quantification of human umbilical vein endothelial cells (HUVECs). The electrochemical cell configuration, along with inverted microscope images, provided the capability of easy use, online in-vitro monitoring, and quantification of the cells during proliferation. Results: HUVECs were cultured and proliferated at defined experimental conditions, and standard cell counts in the initial range of 12 500 to 175 000 were prepared and calibrated by using a hemocytometer (Neubauer chamber) counting for electrochemical measurements. The optimum condition, for FFTSWV at a frequency of 100 Hz and 5 mV amplitude, were found to be a safe electrochemical measurement in the cell culture medium. In each run, the impedance or admittance measurement was measured in a 5 seconds time window. The total measurements were fulfilled at 5, 24, and 48 hours after the seeding of the cells, respectively. The recorded microscopic images before every electrochemical assay showed the conformity of morphology and objective counts of cells in every plate well. The proposed electrochemical method showed dynamic linearity in the range of 12 500-265 000 HUVECs 48 hours after the seeding of cells. Conclusion: The proposed electrochemical method can be used as a simple, fast, and noninvasive technique for tracing and monitoring of HUVECs population in in-vitro studies. This method is highly cheap in comparison with other traditional tools. The introduced configuration has the versatility to develop electrodes for the study of various cells and the application of other electrochemical designations.

Advancing chirality analysis through enhanced enantiomer characterization and quantification via fast Fourier transform capacitance voltammetry.

The exploration of the chiral configurations of enantiomers represents a highly intriguing realm of scientific inquiry due to the distinct roles played by each enantiomer (D and L) in chemical reactions and their practical utilities. This study introduces a pioneering analytical methodology, termed fast Fourier transform capacitance voltammetry (FFT-CPV), in conjunction with principal component analysis (PCA), for the identification and quantification of the chiral forms of tartaric acid (TA), serving as a representative model system for materials exhibiting pronounced chiral characteristics. The proposed methodology relies on the principle of chirality, wherein the capacitance signal generated by the adsorption of D-TA and L-TA onto the surface of a platinum electrode (Pt-electrode) in an acidic solution is harnessed. The capacitance voltammograms were meticulously recorded under optimized experimental conditions. To compile the final dataset for the analyte, the average of the FFT capacitance voltammograms of the acidic solution (without the presence of the analyte) was subtracted from those containing the analyte. A distinct arrangement was obtained by employing PCA as a linear data transformation method, representing D-TA and L-TA in a two/three-dimensional space. The outcomes of the study reveal the successful detection of the two chiral forms of TA with a considerable degree of precision and reproducibility. Moreover, the proposed method facilitated the establishment of two linear response ranges for the concentration values of each enantiomer, spanning from 1 to 20 µM, and 50 to 500 µM. The respective detection limits were also determined to be 0.4 µM for L-TA and 1.3 µM for D-TA. These findings underscore the satisfactory sensitivity and efficiency of the proposed method in both qualitative and quantitative assessments of the chiral forms of TA.

Highlighting and trying to overcome a serious drawback with QSPR studies; data collection in different experimental conditions (mixed-QSPR).

The experimental conditions in quantitative structure-property relationship (QSPR) studies need to be the same for each dataset in case one wishes to relate the property, only to the structure. This major drawback limits QSPR studies due to two reasons: (1) Gathering of physicochemical data obtained under the same experimental condition is difficult. (2) The obtained model is just useful to predict the physicochemical properties under the specific experimental condition. In this article, we report an attempt to highlight the shortcoming of QSPR studies for a property that was measured under different experimental conditions. In addition, we reveal inadequacies that correlating the fluorescence properties and the descriptor of the solvent has. These defects are eventually removed by taking into account the solvent-solute interactions in descriptor calculations. Quantum chemical calculations (HF/6-31G*) were carried out to optimize geometry and calculate the structural descriptors. The genetic algorithm combined with multiple linear regression method was utilized to construct the linear QSPR models. Because of the better nonlinear relationship between the quantum yield of fluorescence and structural descriptors in comparison with those of a linear relationship, support vector machine was used to construct the nonlinear QSPR model. Result analyses demonstrated that the proposed models meet our goal.

Simultaneous electrochemical determination of morphine and methadone by using CMK-5 mesoporous carbon and multivariate calibration.

For the first time, a sensitive electrochemical sensor using a glassy carbon electrode modified with CMK-5 Ordered mesoporous carbon was fabricated for simultaneous analysis of morphine and methadone. Modern electrochemical FFT-SWV techniques and partial least-squares as a multivariable analysis were used in this method. CMK-5 nanostructures were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. Variables such as accumulation time and pH for the proposed sensor were optimized before quantitative analysis. To train the proposed sensor, standard mixtures of morphine (MOR), and methadone (MET) were prepared in the established linear ranges of the analyzes. The results obtained from training samples were used for PLS modeling. The efficiency of the model was determined using test and real matrix samples. The root mean square error of prediction and the squared correlation coefficients (R2p) for MET and MOR were estimated to be 0.00772 and 0.00892 and 0.948 to 0.990, respectively. The recoveries in urine samples were reported to be 97.0 and 105.6% for both MOR and MET, respectively.

The global trend of exosome in diabetes research: A bibliometric approach.

BACKGROUND AND AIMS: Exosome as a novel biomarker reflecting cell behavior in normal and pathological conditions such as diabetes is being the center of academic attention. Therefore, we aimed to study the research output of exosome in diabetes globally. METHODS: We conducted a bibliometric approach to analyze publications on exosome and diabetes from the beginning to 2021 based on keyword search in the Scopus. Annual publications, citations, contributions, co-authorships, and co-occurrences were analyzed and plotted using VOSviewer and GraphPad Prism. RESULTS: 410 original articles and 149 reviews have published between 2009 and 2021. China and the USA were top countries in research output, sponsorship, and international collaborations. The top journals were Scientific Reports, Stem Cell Research and Therapy and Diabetes. The top institution was the University of Queensland in Australia. The top author was Chopp M. Co-occurrence analysis indicated that researchers focused on 1) extracellular vesicles in insulin resistance induced by metabolic disorders like obesity and diabetes mellitus; 2) diagnostic applicability of exosomal microRNAs as biomarkers for diabetic nephropathy; 3) therapeutic effect of exosome in wound healing and endothelial dysfunction during diabetes mellitus; and 4) The oxidative stress, autophagy, apoptosis, fibrosis, inflammation and angiogenesis mediated by exosomes during diabetes. CONCLUSION: The trend in research output has been increased in this field, and advanced countries are involved much more than other countries in terms of research, financial support, and international collaboration. The bibliometric results could be beneficial for further studies in better understanding of novel ideas in exosome and diabetes fields.

Carcinoembryonic antigen admittance biosensor based on Au and ZnO nanoparticles using FFT admittance voltammetry.

In this work, a highly sensitive carcinoembryonic antigen fast Fourier transform admittance biosensor is introduced. The proposed biosensor is based on bilayer films of ZnO/Au nanoparticles as an immobilization matrix. These layers are prepared by self-assembly and deposition method on a gold electrode surface, respectively. Carcinoembryonic antibody (anti-CEA) was immobilized on gold nanoparticles and positively charged horseradish peroxidase (HRP) was used to block sites against nonspecific binding. The admittance biosensor was developed based on fast Fourier transform continuous square wave voltammetry, which produces a sensitive, fast (less than 20 s) and reliable response for determination of carcinoembryonic antigen. The technique was applied as a detector in a flow injection system. The admittances reduction current of the biosensor decreases linearly in two concentrations ranges of CEA from 0.1 to 70 ng/mL and from 70 to 200 ng/mL with a detection limit of 0.01 ng/mL in presence of 0.5 mM H(2)O(2) as an eluent solution.

Pyrophosphate selective recognition in aqueous solution based on fluorescence enhancement of a new aluminium complex.

A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)(2)Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10(-7) to 1.0 × 10(-5) mol/L of PPi and the detection limit of 2.3 × 10(-8) mol/L. The association constant of L-PPi complex was calculated 2.6 × 10(5) L/mol. L was found to show selectively and sensitively fluorescence enhancement toward PPi over than I(3)(-), NO(3)(-), CN(-), CO(3)(2-), Br(-), Cl(-), F(-), H(2)PO4(-) and SO(4)(2-), which was attributed to higher stability of inorganic complex between pyrophosphate and L.

QSAR study of C allosteric binding site of HCV NS5B polymerase inhibitors by support vector machine.

Multiple linear regressions (MLR) and support vector machine (SVM) were used to develop quantitative structure-activity relationship (QSAR) models of novel Hepatitis C virus (HCV) NS5B polymerase inhibitors. Various kinds of molecular descriptors were calculated to represent the molecular structures of compounds, such as chemical, topological, geometrical, and quantum descriptors. Principal component analysis (PCA) was used to select the training set. A variable selection method utilizing a genetic algorithm (GA) was employed to select from the large pool of calculated descriptors, an optimal subset of descriptors which have significant contribution to the overall inhibitory activity. The models were validated using Leave-One-Out (LOO) and Leave-Group-Out (LGO) crossvalidation, and Y-randomization test. Results demonstrated the SVM model offers powerful prediction capabilities.

Sample preparation method for the analysis of some organophosphorus pesticides residues in tomato by ultrasound-assisted solvent extraction followed by dispersive liquid-liquid microextraction.

A very simple and economic method for organophosphorus pesticides (OPPs) residues analysis in tomato by means of gas chromatography-flame photometric detection (GC-FPD) has been developed. The method involves a rapid and small-scale extraction. The sample was homogenised and extraction of the OPPs with acetone was carried out assisted by sonication. No clean-up or evaporation were required after extraction. Pre-concentration of the OPPs from the acetone extract was done by using dispersive liquid-liquid microextraction (DLLME) technique. Chlorobenzene was added in micro-level volume as extraction solvent and triphenylphosphate as internal standard in DLLME procedure. The method showed good linearity over the range assayed (0.5-1000µgkg(-1)) and the detection limits for the pesticides studied varied from 0.1 to 0.5µgkg(-1). Repeatability studies resulted a relative standard deviation lower than 10% in all cases. The proposed method was used to determine pesticides levels in tomatoes grown in open field.

Review on oxidative stress relation on COVID-19: Biomolecular and bioanalytical approach.

COVID-19 disease has put life of people in stress worldwide from many aspects. Since the virus has mutated in absolutely short period of time the challenge to find a suitable vaccine has become harder. Infection to COVID-19, especially at severe life threatening states is highly dependent on the strength of the host immune system. This system is partially dependent on the balance between oxidative stress and antioxidant. Besides, this virus still has unknown mechanism of action companied by a probable commune period. From another hand, some reactive oxygen species (ROS) levels can be helpful on the state determination of the disease. Thus it could be possible to use modern bioanalytical techniques for their detection and determination, which could indicate the disease state at the golden time window since they have the potential to show whether specific DNA, RNA, enzymes and proteins are affected. This also could be used as a preclude study or a reliable pathway to define the best optimized time of cure beside effective medical actions. Herein, some ROS and their relation with SARS-CoV-2 virus have been considered. In addition, modern bioelectroanalytical techniques on this approach from quantitative and qualitative points of view have been reviewed.

Quantitative structure-activity relationship (QSAR) study of interleukin-1 receptor associated kinase 4 (IRAK-4) inhibitor activity by the genetic algorithm and multiple linear regression (GA-MLR) method.

A linear quantitative structure-activity relationship (QSAR) model is presented for the modelling and prediction for the interleukin-1 receptor associated kinase 4 (IRAK-4) inhibition activity of amides and imidazo[1,2-α] pyridines. The model was produced using the multiple linear regression (MLR) technique on a database that consisted of 65 recently discovered amides and imidazo[1,2- α] pyridines. Among the different constitutional, topological, geometrical, electrostatic and quantum-chemical descriptors that were considered as inputs to the model, seven variables were selected using the genetic algorithm subset selection method (GA). The accuracy of the proposed MLR model was illustrated using the following evaluation techniques: cross-validation, validation through an external test set, and Y-randomisation. The predictive ability of the model was found to be satisfactory and could be used for designing a similar group of compounds.