Porous carbohydrate-graphene aerogels synthesized by green method as electroactive supercapacitor materials.

Various graphene derivatives have been known as electrode-active materials for fabricating supercapacitors. Interconnected graphene networks with adjustable porous structures, i.e., 3D graphene aerogels (GAs), can control the restacking of graphene sheets very well and, thus, lead to the enhanced performance supercapacitors. In this study, carbohydrates (sucrose and fructose) were used to make two types of 3D porous carbohydrates-graphene aerogels, sucrose-graphene aerogel (SCR) and fructose-graphene aerogel (FRC). Carbohydrates operate as a cross-linking and reductant agent. Voltammograms of supercapacitor electrodes based on the FRC and SCR indicate a more rectangular shape with a larger area and a superior current than the GA (graphene aerogel without using carbohydrates) electrode. They have better capacitive performance, more electron transportation ability, and higher specific capacitance (CS) values than GA. The supercapacitor electrodes based on FRC, SCR, and GA demonstrate the CS values of 257.2 F g -1, 221.0 F g -1, and 95 F g -1 at ѵ = 10 mV.s-1, respectively. Improvement in the performance of SCR and FRC supercapacitor electrodes, in comparison to GA, is attributed to the porous interconnected feature of their structures and their suitable available surface area, which facilitates electron and ion transportation throughout graphene networks. These supercapacitors also show excellent stability after recording 5000 consecutive voltammograms.

Ag nanorod@PEI-Ag nanohybrid as an excellent signal label for sensitive and rapid detection of serum HER2.

The accurate detection of Human epidermal growth factor receptor-2 (HER2) as a critical breast cancer biomarker can be essential for the early selection of therapeutic approaches. HER2 is a prominent component of a signaling network. Overexpression of the HER2 protein due to amplification of its gene leads to the development of an aggressive subtype of breast cancer. Patients with tumors that overexpress HER2 are eligible for treatment that significantly reduces mortality rates. Herein, we present a fast and simple method for detecting serum HER2. A new electrochemical label has been developed using charged Ag nanorod@ polyethylenimine-Ag (Ag NR@ PEI-Ag) nanohybrid. The synthesized Ag NR@PEI-Ag nanohybrid simultaneously has the electroactive property of silver and the large surface area of the PEI, which results in the enhancement of the detection signal. So, using Ag NR@PEI-Ag nanohybrid as the electrochemical label, a simple, fast, and sensitive electrochemical biosensor was designed to detect HER2. This way, after immobilizing HER2 aptamer on the Au electrode surface, HER2 or human serum was exposed to the aptamer. Then, the positively charged Ag NR@PEI-Ag nanohybrid was adsorbed onto the negatively charged aptamer-HER2 complex, and the current that was produced due to the Ag/AgCl reaction was measured as the electrochemical signal. The aptasensor shows a broad linear response from 10-12 to 10-7 g, a low detection limit (LOD) of 10 pg, and a total assay time of ~ 30 min.

Highly Efficient Enzyme-Free Glutamate Sensors Using Porous Network Metal-Organic Framework-Ni-NiO-Ni-Carbon Nanocomposites.

This study introduces an innovative electrochemical sensor designed to detect glutamate using a nonenzymatic approach. The sensor utilizes a porous network metal-organic framework (Ni-MOF)-NiO-Ni-Carbon nanocomposite (PNM-NiO-Ni-Carbon) as an electrode modifier, which was synthesized and assessed for its effectiveness. Cyclic voltammetry measurements demonstrated that the PNM-NiO-Ni-Carbon nanocomposite, synthesized at 450 °C, displayed remarkable electrocatalytic activity for glutamate oxidation. The linear range for detection spanned from 5 to 960 µmol/L, and the sensor achieved a low detection limit of 320 nmol/L (S/N = 3), which was comparable to previously reported data. Moreover, the sensor exhibited high accuracy and favorable recovery rates when tested with real samples, thus, demonstrating its potential for rapid glutamate detection. The real samples were analyzed using both electrochemical and high-performance liquid chromatography methods, and the results obtained from the two methods did not differ significantly, validating the sensor's excellent practical performance. Based on our findings, the PNM-NiO-Ni-Carbon system exhibits potential for a wide range of biomedical applications.

Facile preparation of a cost-effective platform based on ZnFe2O4 nanomaterials for electrochemical cell detection.

Circulating tumor cells (CTCs) are important tumor markers that indicate early metastasis, tumor recurrence, and treatment efficacy. To identify and separate these cells from the blood, new nanomaterials need to be developed. The present study explored the potential application of ZnFe2O4 magnetic nanoparticles in capturing CTCs with cell surface markers. Folic acid was coupled to L-cysteine-capped ZnFe2O4 nanoparticles (ZC) to provide binding sites on ZnFe2O4 nanoparticles for the recognition of folate bioreceptors, which are highly expressed in MCF-7 breast cancer cells. The cytotoxicity of ZnFe2O4 nanoparticles and ZC against MCF-7 was analyzed with the MTT assay. After 24 h of incubation, there were IC50 values of 702.6 and 805.5 µg/mL for ZnFe2O4 and ZC, respectively. However, after 48 h of incubation, IC50 values of ZnFe2O4 and ZC were reduced to 267.3 and 389.7 µg/mL, respectively. The cell quantification was conducted with magnetically collected cells placed on a glassy carbon electrode, and the differential pulse voltammetry (DPV) responses were analyzed. This cost-effective ZnFe2O4-based biosensing platform allowed cancer cell detection with a limit of detection of 3 cells/mL, ranging from 25 to 104 cells/mL. In future, these functionalized zinc ferrites may be used in electrochemical cell detection and targeted cancer therapy.

Hierarchal polyaniline-folic acid nanostructures act as a platform for electrochemical detection of tumor cells.

The fabrication of electrochemical sensing platforms for cancer monitoring by quantifying circulating tumor cells (CTCs) in blood holds promise for providing a low-cost, rapid, feasible, and safe approach for cancer diagnosis. Here, we isolate cancer cells using CoFe2O4 nanoparticles functionalized with folic acid and chitosan as an inexpensive magnetic nanoprobe. This electrochemical cytosensing platform was realized using polyaniline-folic acid nanohybrids with a three-dimensional hierarchical structure that presents abundant affinity sites toward overexpressed folate bioreceptors on cancer cells, in addition to retaining satisfied conductivity. Furthermore, 3D modeling and simulation of the polyaniline-folic acid structures were conducted to investigate the stable complex between aniline and folate, and the interaction between the polyaniline-folate complex and folate receptor alpha1, a bioreceptor on MCF-7 was revealed for the first time. The limit of detection was calculated to be 4 cells mL-1 with a linear range from 50 to 106 cells mL-1.

Glutaraldehyde crosslinked doxorubicin promotes drug delivery efficiency using cobalt ferrite nanoparticles.

Doxorubicin (DOX) is a common chemotherapy agent that is used in clinics for the treatment of a wide spectrum of cancers. Herein, a novel approach for improving doxorubicin loading on nanoparticles and also controlled release is suggested using crosslinking doxorubicin molecules with glutaraldehyde. We investigated the loading efficiency of doxorubicin on CoFe2O4 nanoparticles in the absence and presence of glutaraldehyde. Based on the feasible, one-pot, and time-saving approach suggested here, the crosslinked DOX showed loading efficiency about twice more in comparison with the non-crosslinked DOX. In vitro doxorubicin release of three formulations including DOX crosslinked with glutaraldehyde (DOXGA), DOX loaded on CoFe2O4 (CFDOX) and DOX loaded on CoFe2O4 using glutaraldehyde (CFDOXGA) yielded a sustained release. The kinetic models such as first-order, Sahlin-Peppas, and Higuchi were employed for further exploration of DOX release profile. Our suggested method might extend to other nanomaterial-based drug delivery formulations to promote drug delivery efficiency.

A green protocol for the electrochemical synthesis of a fluorescent dye with antibacterial activity from imipramine oxidation.

Electrochemical oxidation of imipramine (IMP) has been studied in aqueous solutions by cyclic voltammetry and controlled-potential coulometry techniques. Our voltammetric results show a complex behavior for oxidation of IMP at different pH values. In this study, we focused our attention on the electrochemical oxidation of IMP at a pH of about 5. Under these conditions, our results show that the oxidation of IMP leads to the formation of a unique dimer of IMP (DIMP). The structure of synthesized dimer is fully characterized by UV-visible, FTIR, 1H NMR, 13C NMR and mass spectrometry techniques. It seems that the first step in the oxidation of IMP is the cleavage of the alkyl group (formation of IMPH). After this, a domino oxidation-hydroxylation-dimerization-oxidation reaction, converts IMPH to (E)-10,10',11,11'-tetrahydro-[2,2'-bidibenzo[b,f]azepinylidene]-1,1'(5H,5'H)-dione (DIMP). The synthesis of DIMP is performed in an aqueous solution under mild conditions, without the need for any catalyst or oxidant. Based on our electrochemical findings as well as the identification of the final product, a possible reaction mechanism for IMP oxidation has been proposed. Conjugated double bonds in the DIMP structure cause the compound to become colored with sufficient fluorescence activity (excitation wave-length 535 nm and emission wave-length 625 nm). Moreover, DIMP has been evaluated for in vitro antibacterial. The antibacterial tests indicated that DIMP showed good antibacterial performance against all examined gram-positive and gram-negative bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Shigella sonnei).

Optical cytosensors for the detection of circulating tumour cells.

Blood analysis is an established approach to monitor various diseases, ranging from heart defects and diabetes to cancer. Among various tumor markers in the blood, circulating tumor cells (CTCs) have received increasing attention due to the fact that they originate directly from the tumors. Capturing and detecting CTCs represents a promising approach in cancer diagnostics and clinical management of cancers. CTCs in blood progress to self-seeding a tumour or initiating a new lesion mass. Cytosensors are biosensors intended to identify CTCs in a blood sample of cancer patients and provide information about the cancer status. Herein, we firstly discuss different detection methods of state-of-the-art optical cytosensors, including colorimetry, fluorescence, surface plasmon resonance, photoelectrochemistry and electrochemiluminescence. Then we review the significant advances made in implementing biorecognition elements and nanomaterials for the detection of cancer cells. Despite great progress in optical cytosensors, and their integration with smartphones, they have still only been explored to prototype stages. Much more effort is needed to fulfil their potential in modern cancer diagnostics and in monitoring the state of disease for cancer patients.

MXene-based cytosensor for the detection of HER2-positive cancer cells using CoFe2O4@Ag magnetic nanohybrids conjugated to the HB5 aptamer.

MXenes are a new class of conductive two-dimensional material which have received growing attention in biosensing for their significant surface area and unique surface chemistry. Here, gold electrodes were modified with MXene nanosheets of about 2 nm thickness and 1.5 µm lateral size for the electrochemical detection of tumor cells. An HB5 aptamer with high selectivity for HER-2 positive cells was immobilized on the MXene layers via electrostatic interactions. To minimize electrode biofouling with blood matrix, magnetic separation of HER-2 positive circulating tumor cells was carried out using CoFe2O4@Ag magnetic nanohybrids bonded to the HB5. The formation of sandwich-like structures between the magnetically captured cells and the functionalized MXene electrodes effectively shields the electron transfer of a redox probe, enabling quantitative cell detection using the change in current. This label-free MXene-based cytosensor platform yielded a wide linear range of 102-106 cells/mL, low detection limit of 47 cells/mL, and good sensitivity and selectivity in the detection of HER2-posetive cells in blood samples. The presented aptacytosensor demonstrates the great potential of using CoFe2O4@Ag magnetic nanohybrids and MXenes to monitor cancer progression via circulating tumor cells in blood at low cost.

Vesicular release dynamics are altered by the interaction between the chemical cargo and vesicle membrane lipids.

The release of the cargo from soft vesicles, an essential process for chemical delivery, is mediated by multiple factors. Among them, the regulation by the interaction between the chemical cargo species and the vesicular membrane, widely existing in all vesicles, has not been investigated to date. Yet, these interactions hold the potential to complicate the release process. We used liposomes loaded with different monoamines, dopamine (DA) and serotonin (5-HT), to simulate vesicular release and to monitor the dynamics of chemical release from isolated vesicles during vesicle impact electrochemical cytometry (VIEC). The release of DA from liposomes presents a longer release time compared to 5-HT. Modelling the release time showed that DA filled vesicles had a higher percentage of events where the time for the peak fall was better fit to a double exponential (DblExp) decay function, suggesting multiple kinetic steps in the release. By fitting to a desorption-release model, where the transmitters adsorbed to the vesicle membrane, the dissociation rates of DA and 5-HT from the liposome membrane were estimated. DA has a lower desorption rate constant, which leads to slower DA release than that observed for 5-HT, whereas there is little difference in pore size. The alteration of vesicular release dynamics due to the interaction between the chemical cargo and vesicle membrane lipids provides an important mechanism to regulate vesicular release in chemical and physiological processes. It is highly possible that this introduces a fundamental chemical regulation difference between transmitters during exocytosis.

In situ monitoring of gating approach on mesoporous silica nanoparticles thin-film generated by the EASA method for electrochemical detection of insulin.

An innovative label-free electrochemical aptasensing platform has been designed for detection of insulin using functionalized mesoporous silica thin-film (MSTF) coated on a glassy carbon electrode through the one-step electrochemically assisted self-assembly (EASA) method. This strategy is contingent upon the covalent attachment of a complementary DNA (cDNA) oligonucleotide sequence on the mesoporous silica surface, for which further hybridization with its labeled aptamer as a gating molecule restricts the diffusion of the electroactive probe (Fe(CN)63-/4-) toward the electrode surface by the closing of mesochannels. Upon insulin introduction as the stimulus target molecule, hybridization between aptamer and cDNA is efficiently destroyed, which triggers the opening of nanochannels to facilitate redox probe diffusion toward the electrode with a noticeable increase in differential pulse voltammetry signal. The proposed aptasensor showed a wide detection ranging from 10.0 to 350.0 nM and a suitable detection limit of 3.0 nM. This method offers the sensitive and rapid detection of insulin without the need for cargo (dye/fluorophore) as an electrochemical marker inside the pore, at low cost and with a fast modification time.

Metal oxide-based gas sensors for the detection of exhaled breath markers.

Exhaled breath test is a typical disease monitoring method for replacing blood and urine samples that may create discomfort for patients. To monitor exhaled breath markers, gas biomedical sensors have undergone rapid progress for non-invasive and point-of-care diagnostic devices. Among gas sensors, metal oxide-based biomedical gas sensors have received remarkable attention owing to their unique properties, such as high sensitivity, simple fabrication, miniaturization, portability and real-time monitoring. Herein, we reviewed the recent advances in chemoresistive metal oxide-based gas sensors with ZnO, SnO2 and In2O3 as sensing materials for monitoring a range of exhaled breath markers (i.e., NO, H2, H2S, acetone, isoprene and formaldehyde). We focused on the strategies that improve the sensitivity and selectivity of metal oxide-based gas sensors. The challenges to fabricate a functional gas sensor with high sensing performance along with suggestions are outlined.

Advances in aptasensor technology.

Aptasensors form a class of biosensors that function on the basis of a biological recognition. An aptasensor is advantageous because it incorporates a unique biologic recognition element, i.e., an aptamer, coupled to a transducer to convert a biological interaction to readable signals that can be easily processed and reported. In such biosensors, the specificity of aptamers is comparable to and sometimes even better than that of antibodies. Using the SELEX technique, aptamers with high specificity and affinity to various targets can be isolated from large pools of different oligonucleotides. Nowadays, new modifications of the SELEX technique and, as a result, easy generation and synthesis of aptamers have led to the wide application of these materials as biological receptors in biosensors. In this regard, aptamers promise a bright future. In the present research a brief account is initially provided of the recent developments in aptasensors for various targets. Then, immobilization methods, design strategies, current limitations and future directions are discussed for aptasensors.

Electrochemical cytosensors for detection of breast cancer cells.

Breast cancer is one of lethal cancers among women with its metastasis leading to cancer-related morbidity and mortality. Circulating tumor cells (CTCs) derived from a primary tumor can be detected in the venous blood of cancer patients. Monitoring CTCs in blood samples has increased exponentially over the past decades and holds great promise in the diagnosis and treatment of metastatic breast cancer. Electrochemical cytosensors, classified as a class of electrochemical biosensors for sensitive detection and enumeration of targeted cells with minimally invasive methods, have the advantages of electrochemical biosensors, such as simplicity, low cost, and low limit of detection. Here, we review recent progress in the detection of CTCs from breast cancer with a focus on electrochemical cytosensors. This review describes platforms benefiting from these cytosensors to identify cancerous breast cells. Furthermore, strategies for signal amplification and also generation of reusable electrochemical cytosensors are introduced. In addition, breast cancer markers and biorecognition elements for cell capturing are reviewed.

Designing and optimization of an electrochemical substitute for the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay.

For the first time ever, this paper reports the development of an easily operated and cost-effective electrochemical assay to be used as an appropriate substitute for the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay. The proposed assay is based on the electrochemical reaction of Saccharomyces cerevisiae (S. cerevisiae) with toxic materials, and it overcomes most of the limitations of MTT such as evaporation of volatile solvents, cytotoxic effects of MTT reagents, high cost, and sensitivity to light. The novel electrochemical assay can be used to detect diazinon in the range of 10-6 g mL-1 to 10-2 g mL-1 with the detection limit of 1.5 × 10-7 g mL-1.

A distinguished cancer-screening package containing a DNA sensor and an aptasensor for early and certain detection of acute lymphoblastic leukemia.

A disposable package of biosensors was developed along with the corresponding guidelines for early detection of the acute lymphoblastic leukemia cancer. This proposed cancer-screening package included a DNA sensor and an aptasensor as two main types of biosensors. The biosensors were used simultaneously. This combination of sensors can detect not only the presence of mutant genes but also the biomarkers of cancer. At current work, the combination of sensors were used to detect the presence of BCR-ABL1 as a mutant gene and CEA as a biomarkers of cancer, such a capability makes the package liable for early and certain detection of acute lymphoblastic leukemia. To construct both the DNA sensor and the aptasensor, a nanocomposite consisting of electrosynthesis carbon quantum dots and biosynthesized gold nanoparticles was applied. The construction of these biosensors was characterized using four different electrochemical methods including DPV (Differential Pulse Voltammetry), EIS (Electrochemical Impedance Spectroscopy), CV (Cyclic Voltammetry) and chronoamperometry. The peak current of a catechol solution that was used as an electroactive probe on the biosensor was linearly related to the logarithm of the concentrations of the target DNA and the target antigen in the range of 10 pM to 100 µM and 1 pg mL-1 to 0.001 g mL-1 with the detection limits of 1.5 pM and 0.26 pg mL-1 respectively, which are quite good results.

Latest Trends in Electrochemical Sensors for Neurotransmitters: A Review.

Neurotransmitters are endogenous chemical messengers which play an important role in many of the brain functions, abnormal levels being correlated with physical, psychotic and neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's disease. Therefore, their sensitive and robust detection is of great clinical significance. Electrochemical methods have been intensively used in the last decades for neurotransmitter detection, outclassing more complicated analytical techniques such as conventional spectrophotometry, chromatography, fluorescence, flow injection, and capillary electrophoresis. In this manuscript, the most successful and promising electrochemical enzyme-free and enzymatic sensors for neurotransmitter detection are reviewed. Focusing on the activity of worldwide researchers mainly during the last ten years (2010-2019), without pretending to be exhaustive, we present an overview of the progress made in sensing strategies during this time. Particular emphasis is placed on nanostructured-based sensors, which show a substantial improvement of the analytical performances. This review also examines the progress made in biosensors for neurotransmitter measurements in vitro, in vivo and ex vivo.

Improving the effective photovoltaic performance in dye-sensitized solar cells using an azobenzenecarboxylic acid-based system.

In this research, an azobenzenecarboxylic acid was used as a sufficient co-adsorbent in combination with N719 dye. As it is found from the results, an optimized concentration of the co-absorbent leads to the highest efficiency. The dye-sensitized solar cells (DSSCs) parameters such as short-circuit current (Jsc), open-circuit voltage (Voc) and conversion efficiency (η) were obtained -14.87 mA/cm2, 0.765 V and 5.20% respectively. Based on the results, the N719/Azobenzenecarboxylic-based system shows a significant increase in Voc and Jsc, resulting in an ∼21% improvement in the efficiency. A higher conversion efficiency for the co-adsorbent-based systems was assigned to their enhanced η, which is attributed to reduced dye aggregation, higher electron injection and increased Voc. This corresponded to the improved electron density in the TiO2 conduction band of the photoanode and reduced charge recombination revealed through electrochemical impedance spectroscopy measurements. Also, evidence was provided for a long charge life time and a high resistance of charge recombination for the co-absorbed solar cells.

Fabrication of an ultrasensitive and selective electrochemical aptasensor to detect carcinoembryonic antigen by using a new nanocomposite.

A lable-free electrochemical aptasensor was successfully developed for the sensitive detection of carcinoembryonic antigen as a tumor biomarker. To do this, a ternary nanocomposite of hemin, graphene oxide and multi-walled carbon nanotubes was used. The aptamer can be attached to the surface of a hemin, graphene oxide and multi-walled carbon nanotubes glassy carbon electrode through -NHCO- covalent bonds to form a sensing surface. Through fourier transform infrared spectroscopy and scanning electron microscopy, it was indicated that hemin can be successfully incorporated into hemin, graphene oxide and multi-walled carbon nanotubes. Hemin, which protects graphene nanosheets, also serves as an in-situ probe owing to its well-defined redox properties. Multi-walled carbon nanotubes in the modifier enhance conductivity and facilitate the electron transfer between hemin and the glassy carbon electrode. In this study, carcinoembryonic antigen got specifically bound to the aptamer, and the current changes were used for selective and specific detection of that antigen. The devised aptasensor proved to have excellent performance with a wide linear range of 1.0 × 10-15 - 1.0 × 10-8 gmL-1 and a detection limit of 0.82 fg mL-1. The inter-day and intra-day values of RSD% were obtained in the range of 0.10-2.91 and 2.21-4.56 respectively. According to the experiments conducted on real samples, it may be claimed that the proposed label-free electrochemical aptasensor is capable enough of determining carcinoembryonic antigen in clinical diagnostics.

Recent advancements in compact layer development for perovskite solar cells.

Herein, we will present recent progress in the compact layer (CL) or hole blocking layer (HBL) which is known as an important layer and not as an essential layer for perovskite solar cells (PSCs). The CL involves an effective role to enhance efficiency in PSCs. Thus, any change, modification, and replacement in this layer will have a profound effect on the performance and improvement of some characteristics such as photo-stability, durability and hysteresis effect. These changes can improve the applications of PSCs in the flexible cell, industrial mass production, high-scale manufacturing. In this review, we will present recent studies on CLs.