A nitrogen-doped hollow carbon nanospheres-based aptasensor for non-invasive salivary detection of progesterone.

Developing an easy-to-use and non-invasive sensor for monitoring progesterone (P4) as a multi-functional hormone is highly demanded for point-of-care testing. In this study, an ultrasensitive electrochemical aptasensor is fabricated for monitoring P4 in human biofluids. The sensing interface was designed based on the porous nitrogen-doped hollow carbon spheres (N-HCSs). The N-HCSs covalently immobilized high-dense aptamer (Apt) sequences as the bioreceptor of P4. The electron transfer of the redox probe was hindered by incubating P4 on the aptasensor surface and forming the P4-Apt complexes. Meanwhile, the signaling was decreased under two wide linear dynamic ranges (LDRs) from 10 fM to 5.6 µM with a limit of detection (LOD) value of 3.33 fM. The aptasensor presented satisfactory selectivity in the presence of different off-target species with successful feasibility for P4 detection in some human urine and saliva samples. The aptasensor with high sensitivity, as an advantage for on-site and sensitive measurement of P4, can be considered a non-invasive tool for routine analysis of real-world clinical samples method.

Copper corrosion prevention in 3.5% NaCl solution by Spartium junceum petals extract as an eco-friendly bio-inhibitor: kinetic and thermodynamic studies.

During the last decades, numerous studies were performed to introduce green corrosion inhibitors. So, various materials were utilized due to their being bio-degradable, available, and inexpensive. Because of the aforementioned aspects, Spartium Junceum petals extract (SJPE) was used as a new bio-inhibitor for the prevention of copper corrosion in a 3.5 wt% NaCl solution. This extract was obtained in water as a non-toxic solvent. Also, gas chromatography-mass spectrometry (GC-MS) confirmed the presence of organic molecules containing O, N, and F heteroatoms in SJPE, which are important for inhibitors. Also, Fourier-transform infrared spectroscopy (FT-IR) was used to identify the functional groups of the inhibitor molecules. Moreover, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques were used which verified the great effect of this procedure to promote resistance corrosion of copper substrate. In addition, scanning electron microscopy (SEM) exhibited the surface morphology of copper substrate in the presence of SJPE which demonstrated the improvement of corrosion resistance in comparison to the absence of this bio-inhibitor. It should be noted that by increasing the amount of SJPE, the inhibition efficiency was ameliorated up to 87.8%. Furthermore, variation in temperature magnitude between 298 and 338 K implied that SPJE can improve inhibition behavior in higher temperatures. By applying temperature effect study data, the value of activation energy in the presence of the inhibitor was calculated (37.9 kJ mol-1), and the adsorption isotherm was Langmuir. Also, these data showed the inhibition mechanism is physical adsorption. The proposed inhibitor can be used as an efficient, eco-friendly, and inexpensive bio-inhibitor for the prevention of copper corrosion.

Advanced Cellulose-Nanocarbon Composite Films for High-Performance Triboelectric and Piezoelectric Nanogenerators.

Natural polymers such as cellulose have interesting tribo- and piezoelectric properties for paper-based energy harvesters, but their low performance in providing sufficient output power is still an impediment to a wider deployment for IoT and other low-power applications. In this study, different types of celluloses were combined with nanosized carbon fillers to investigate their effect on the enhancement of the electrical properties in the final nanogenerator devices. Cellulose pulp (CP), microcrystalline cellulose (MCC) and cellulose nanofibers (CNFs) were blended with carbon black (CB), carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). The microstructure of the nanocomposite films was characterized by scanning electron and probe microscopies, and the electrical properties were measured macroscopically and at the local scale by piezoresponse force microscopy. The highest generated output voltage in triboelectric mode was obtained from MCC films with CNTs and CB, while the highest piezoelectric voltage was produced in CNF-CNT films. The obtained electrical responses were discussed in relation to the material properties. Analysis of the microscopic response shows that pulp has a higher local piezoelectric d33 coefficient (145 pC/N) than CNF (14 pC/N), while the macroscopic response is greatly influenced by the excitation mode and the effective orientation of the crystals relative to the mechanical stress. The increased electricity produced from cellulose nanocomposites may lead to more efficient and biodegradable nanogenerators.

Highly sensitive electrochemical sensor based on carbon paste electrode modified with graphene nanoribbon-CoFe2O4@NiO and ionic liquid for azithromycin antibiotic monitoring in biological and pharmaceutical samples.

In this report, Azithromycin (Azi) antibiotic was measured by carbon paste electrode (CPE) improved by graphene nanoribbon-CoFe2O4@NiO nanocomposite and 1-hexyl-3 methylimidazolium hexafluorophosphate (HMIM PF6) as an ionic liquid binder. The electrochemical behavior of Azi on the graphene nanoribbon-CoFe2O4@NiO/HMIM PF6/CPE is investigated by voltammetric methods, and the results showed that the modifiers improve the conductivity and electrochemical activity of the CPE. According to obtained data, the electrochemical behavior of Azi is related to pH. under optimum conditions, the sensor has linear ranges from 10 µM to 2 mM with a LOD of 0.66 µM. The effect of scan rate and chronoamperometry were studied, which showed that the Azi electro-oxidation is diffusion controlled with the diffusion coefficient of 9.22 × 10-6 cm2/s. The reproducibility (3.15%), repeatability (2.5%), selectivity, and stability (for 30 days) tests were investigated, which results were acceptable. The actual sample analysis confirmed that the proposed sensor is an appropriate electrochemical tool for Azi determination in urine and Azi capsule.

A caffeic acid electrochemical sensor amplified with GNR/CoFe2O4@NiO and 1-Ethyl-3-methylimidazolium acetate; a new perspective for food analysis.

Determining Caffeic acid is important as an antioxidant compound in food. In this study, caffeic acid (CA) was measured using a carbon paste electrode modified with GNR/CoFe2O4@NiO and 1-Ethyl-3-methylimidazolium acetate (EMIM Ac) as ion liquid. A simple sensor showed a higher current than a bare carbon paste; thus, it can be said that the modified electrode has a higher sensitivity for detecting CA. The linear range of this sensor and its detection limit was equal to 0.01-100.0 µM and 0.01 µM, respectively. Moreover, the developed electrode indicated outstanding selectivity in the presence of several interferences, high sensitivity, reproducibility, and long-term stability. The percentage recovery of CA obtained with the developed sensor affirmed its reliability for CA determination in real samples. The modified sensor's accuracy was confirmed to identify this analyte according to the results.

Electrochemical nano-genosensor for highly sensitive detection of miR-21 biomarker based on SWCNT-grafted dendritic Au nanostructure for early detection of prostate cancer.

MicroRNAs (miRNAs) appear as a novel reliable candidate in biomarkers for early diagnosis of cancer. Due to their roles in various types of cancer, their potential as a diagnostic biomarker is getting more attention. Here, a novel electrochemical biosensor for detection of miR-21 was demonstrated, through combining the advantages of electrochemical methods and nanomaterials with the selectivity of oligonucleotides, based on thiolated receptor probe-functionalized dendritic gold nanostructures (den-Au) via the self-assembly monolayer (SAM) process which grafted on the single-wall carbon nanotubes (SWCNTs) platform on the surface of the fluorine-doped tin oxide (FTO) electrode. Cadmium ions (Cd2+) were used as signal units and also signal amplification substance which labeled before on miR-21 target. The oxidation signal of Cd2+ as a signal unit was measured by differential pulse voltammetry (DPV) technique that had a very wide linear relationship with the concentration of miR-21 target (0.01 fmol L-1 to 1 µmol L-1) and low experimental detection limit of 0.01 fmol L-1. Furthermore, fabricated biosensor showed acceptable performance in human serum samples and also good selectivity indiscriminate between the complementary target and non-complementary one, so this nano-genosensor can clinically be used for prostate cancer diagnosis through the detection of miR-21 in human serum samples.

Multifunctional Magnetic Nanoparticles-Labeled Mesenchymal Stem Cells for Hyperthermia and Bioimaging Applications.

Magnetic nanoparticles have demonstrated considerable capacity for theranosis purposes due to their unique characteristics, including magnetic properties, comparable size to biomolecules, favorable conjugations of drugs and biomolecules, ability to labeling, and capability of sensing, separation, detection, and targeted drug delivery. They could be exploited in magnetic resonance imaging as the contrast agents and also warmed as exposed to an external magnetic AC field that could be applied in hyperthermia. Here, progresses and advances in the strategy and assembly of fluorescent magnetic nanoparticles are presented for stem cell tracing and drugs/biomolecules targeting into cells.

An electrochemical paper based nano-genosensor modified with reduced graphene oxide-gold nanostructure for determination of glycated hemoglobin in blood.

Hemoglobin A1c (HbA1c) is a standard biomarker to measure long-term average glucose concentration for diagnosis and monitoring of diabetes. Various methods have been reported for measuring HbA1c, however, portable and precise determination is still challenging. Herein, a new highly sensitive electrochemical nanobiosensor is developed for the specific determination of HbA1c. A nanocomposite of reduced graphene oxide (rGO) and gold with hierarchical architecture structure was electrochemically deposited on a cheap and flexible graphite sheet (GS) electrode. The nanocomposite increased the surface area, improved the electron transfer on the electrode surface and augmented the signal. It also provided a suitable substrate for linkage of thiolated DNA aptamer as a bioreceptor on the electrode surface by strong covalent bonding. The quantitative label free detection was carried out by differential pulse voltammetry (DPV) in a phosphate-buffered saline (PBS) solution containing redox probe Fe(CN)63-/4-. The detection is based on insulating the surface in presence of HbA1c and decreasing the current, which is directly related to the HbA1c concentration. The nanobiosensor demonstrated high sensitivity of 269.2 µA. cm-2, wide linear range of 1 nM-13.83 µM with a low detection limit of 1 nM. The biosensor was successfully used for measuring HbA1c in blood real sample. Furthermore, it is promising to use it as a part of a point of care device for low-invasive screening and management of diabetes.

Electrochemical sensor for L-cysteine by using a cobalt(II)/aluminum(III) layered double hydroxide as a nanocatalyst.

A voltammetric sensor is described for the determination of L-cysteine (Cys). A pencil graphite electrode (PCE) was modified with a Co(II)-Al(III) layered double hydroxide (LDH) to obtain a disposable, inexpensive and sensitive sensor for Cys. The LDH was electrochemically deposited on the PGE by chronoamperometry. The electrochemical behavior of the modified PGE was investigated by cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. The structure and morphology of the electrodes surface were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Experiments were conducted in optimal condition, scan rate of 10 mV. s-1 and the oxidation peak potential 0.15 V vs. saturated calomel electrode. The sensor has a linear response in the 100 pM to 0.1 µM Cys concentration range and a 100 pM detection limit. It was used to quantify Cys in a drug sample. Graphical abstract Schematic presentation of pencil graphite electrode modification with Co-Al layered double hydroxide nanaocatalyst by chronoamperometry, and its usage as an electrochemical sensor for L-cysteine determination.

Sandwich-structured nanoparticles-grafted functionalized graphene based 3D nanocomposites for high-performance biosensors to detect ascorbic acid biomolecule.

We present a highly sensitive and selective nano-biosensor for rapid, stable and highly reproducible detection of ascorbic acid (AA) in the presence of dopamine, uric acid and other interferences by a three-layer sandwich arrangement of nitrogen-doped functionalized graphene (NFG), silver nanoparticles (AgNPs) and nanostructured polyaniline (PANI) nanocomposite. The enhanced AA electrochemical properties of the NFG/AgNPs/PANI electrode is attributed to the superior conductivity of the NFG-PANI and the excellent catalytic activity of AgNPs. The critical modification of the AgNPs-grafted NFG-PANI coated on very low-cost fluorine doped tin oxide electrode (FTOE) increased the charge transfer conductivity of the electrode (the resistance drops down from 11,000 Ω to 6 Ω). The nano-biosensor was used to accurately detect AA in vitamin C tablets with the recovery of 98%. The sensor demonstrated a low detection limit of 8 µM (S/N = 3) with a very wide linear detection range of 10-11,460 µM, good reproducibility and excellent selectivity performance for AA detection. The results demonstrate that this nanocomposite is a promising candidate for rapid and selective detection of AA in practical clinical samples.

Label-free ultrasensitive detection of breast cancer miRNA-21 biomarker employing electrochemical nano-genosensor based on sandwiched AgNPs in PANI and N-doped graphene.

MicroRNAs (miRNAs) are small, endogenous, noncoding RNAs, shown to be expressed abnormally in many tumors and identified as predictive biomarkers for early diagnosis of several cancers including the breast. Therefore, the label-free and highly sensitive detection of miRNAs is of critical significance. In this work, a highly sensitive and label-free nano-genosensor is developed for the detection of miRNA-21, a known breast cancer biomarker, based on a specific architecture of nitrogen-doped functionalized graphene (NFG), silver nanoparticles (AgNPs), and polyaniline (PANI) that resulted in a remarkable effect on signal amplification. Following the successful functionalization of the nanocomposite and immobilization of the specific sequence of the aminated complementary oligonucleotide of miRNA-21, the detection was performed using differential pulse voltammetry (DPV). The oxidation peak current of the redox probe under optimal conditions was determined to monitor the event hybridization of miRNA-21 biomarker. Applying this highly sensitive and optimized nano-biosensor enabled detection of a wide dynamic range of 10 fM-10 µM with a sensitivity of 2.5 µA cm-2 and a low detection limit of 0.2 fM. This nano-biosensor also demonstrated highly reproducible results in the analysis of blood samples, with recoveries between 94% and 107%, and could be used for early detection of breast cancer by direct detection of the miRNA-21 in real clinical samples without any need to sample preparation, RNA extraction and/or amplification.

Nano-biosensor for highly sensitive detection of HER2 positive breast cancer.

Nanocomposite materials have provided a wide range of conductivity, sensitivity, selectivity and linear response for electrochemical biosensors. However, the detection of rare cells at single cell level requires a new class of nanocomposite-coated electrodes with exceptional sensitivity and specificity. We recently developed a construct of gold nanoparticle-grafted functionalized graphene and nanostructured polyaniline (PANI) for high-performance biosensing within a very wide linear response and selective performance. Further, replacing the expensive gold nanoparticles with low-cost silver nanoparticles as well as optimizing the nanocomposite synthesis and functionalization protocols on the electrode surface in this work enabled us to develop ultrasensitive nanocomposites for label-free detection of breast cancer cells. The sensor presented a fast response time of 30 min within a dynamic range of 10 - 5 × 106 cells mL-1 and with a detection limit of 2 cells mL-1 for the detection of SK-BR3 breast cancer cell. The nano-biosensor, for the first time, demonstrated a high efficiency of > 90% for the label-free detection of cancer cells in whole blood sample without any need for sample preparation and cell staining. The results demonstrated that the optimized nanocomposite developed in this work is a promising nanomaterial for electrochemical biosensing and with the potential applications in electro-catalysis and super-capacitances.

Enhanced visible light photocurrent response and photodegradation efficiency over TiO2-graphene nanocomposite pillared with tin porphyrin.

In this study, a nanostructure material of pillared graphene made of tin porphyrin functionalized graphene-TiO2 composite (TG) was successfully synthesized. The prepared compound showed high activity in the photodegradation reaction under irradiation of visible light. To investigate the effect of graphene as well as dye sensitization on the photoactivity of the catalysts, photocatalytic properties and photocurrent responses of the photocatalyst were examined. Results showed that the composite of graphene-TiO2 containing 3% graphene had the highest photoactivity. Besides, tin porphyrin-pillared TG composite (TGSP) material exhibited an excellent visible light photocatalytic performance in degradation of methyl orange dye. The photoelectrochemical investigations determined that compared with the pure TiO2 electrode, the TGSP electrode exhibited a 23-fold enhancement of photocurrent intensity, suggesting the synergistic effect of the TiO2, the graphene, and the tin porphyrin photosensitizer in these photocatalysts. Furthermore, the mechanism of the photocatalytic process of the synthesized catalysts and the charge transfer mechanism in the prepared TGSP via its band edge positions was also discussed.

A simple method for determination of D-penicillamine on the carbon paste electrode using cupric ions.

The interaction of D-penicillamine (PA) with copper at the carbon paste electrode (CPE) in the presence of cupric ions (Cu(2+)) was used for the determination of PA at very low potential (0.1 V vs. Ag/AgCl) without applying of any modifier. The electrochemical response of copper is changed considerably in the presence of negligible amount of PA. In this report some important parameters, such as pH effect, Cu(2+) concentration and scan rate are studied, which the selected conditions were acetate buffer (pH=6) and 1 mM Cu(2+). The linear range for PA was from 1.0×10(-6) to 1.0×10(-4) M with an experimental detection limit of 1.0×10(-7) M. The relative standard deviation for 6 measurements was 3.8%. The interfering effects of some important inorganic ions were investigated, which there was no significant effect on the PA measurements. Also three organic interferences including ascorbic acid (AA), uric acid (UA) and l-cysteine (Cys) were examined, which the effect of AA was not notable, the interference of UA was moderate and for Cys was significant, but moderate at the levels which fined in the urine samples. This method was applied successfully for the determination of PA in urine sample.

Depression. Does it affect the comprehension of receptive skills?

OBJECTIVE: To compare the comprehension of depressed and non-depressed male and female Iranian learners of English as a Foreign Language (EFL) in receptive skills, and to investigate whether inefficiency in learning English could be due to depression. METHODS: We selected 126 boys and 96 girls aged between 15 and 18 by simple random sampling from 2 high schools in Kerman, Iran to examine whether there was any significant relationship between depression and comprehension of receptive skills in males and females. We undertook this descriptive, correlational study between January and May 2011 in Kerman, Iran. After administration of the Beck Depression Inventory (BDI), we found that 93 students were non-depressed, 65 had minimal depression, 48 mild depression, and 16 suffered from severe depression. RESULTS: The correlation between participants` scores on listening and reading test with depression level indicated a significant relationship between depression and comprehension of both listening, and reading. Males had higher scores in both reading and listening. In listening, there was no significant difference among the levels of depression and males and females. Regarding the reading skill, there was no significant difference among levels of depression; however, the reading comprehension of males and females differed significantly. CONCLUSION: Learners who show a deficiency in receptive skills should be examined for the possibility of suffering from some degree of depression.

Periodic catatonia. Challenging diagnosis for psychiatrists.

Periodic catatonia (PC) is a rare type of catatonia syndrome, in which the catatonic phases often repeat regularly. Between the catatonic periods, the symptoms totally disappear and make the diagnosis difficult. We report a case with PC who did not show any catatonic symptoms except anxiety and restlessness in his first referral to the hospital. Although it was reported that he showed the symptoms of the disorder such as mutism, and immobility, he was not hospitalized. In his next referral (24 hours later), he was referred with catatonic symptoms and was hospitalized. The periods of catatonia were repeated regularly before electroconvulsive therapy, so the primary diagnosis was PC. During treatment with ECT, based on the semi-structured interview, a diagnosis of bipolar mood disorder was made. Due to the disappearance of symptoms between catatonic periods, this disorder may be underestimated and treatment postponed.

Method for preparation of a sol-gel-derived carbon ceramic electrode using microwave irradiation.

A fast and new method for preparation of a sol-gel carbon ceramic electrode (CCE) by microwave (MW) irradiation is introduced. In comparison to previous preparation methods which require a very long time (mostly 48 h for ceramic completion and drying in air), this method requires only a few minutes. Furthermore, before MW irradiation an ultrasonic wave was applied to influence the gelation time and dispersion of particles in the sol-gel. The composition of the proposed carbon ceramic was characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy, which was very similar to the air-dried sol-gel carbon ceramics. The proposed electrode was used for determination of dopamine (DA); the results show that this method has a wider linear range (LR) and lower detection limit (DL) than the air-dried CCE and exhibits a greater sensitivity for determination of DA compared to a recently reported CCE.

A simple and cost-effective method, as an appropriate alternative for visible spectrophotometry: development of a dopamine biosensor.

In this study, a new, simple, fast and inexpensive method as an alternative to visible spectrophotometry is developed. In this method the cells containing the sample solution were scanned with a scanner, then the color of each cell was analyzed with software written in visual basic (VB 6) media to red, green and blue values. The cells were built by creating holes in the Plexiglas sheet. The dimensions of identical cells were examined by Cr (III) solution with known concentrations. The validity of this new method was studied by determination of dopamine (DA) without using any other reagent. The parameters which affect the system were optimized. The comparison between the current and traditional UV-Vis spectrophotometry methods was studied and the results revealed similar trends in both methods. The developed method was successfully applied to the determination of dopamine in serum and urine without using any pretreatment. Finally comparing the results obtained in the developed method showed that microwave irradiation of the solution can decrease the experimental time, increase sensitivity and improve the limit of detection.