CNT-FET for sensitive hydrogen peroxide biosensing via immobilized Cytochrome c.

H2O2 is an effective substance in the body which contributes to gene expression, insulin metabolism and determining cell shapes. However, a high concentration of H2O2 is harmful to the body and can cause various diseases such as colitis wounds, sepsis disease, lymphocyte proliferation and macrophage apoptosis in systemic lupus erythematosus. In this study, a Cyt c/cMWCNTs/FET was designed to real-time detect H2O2 via immobilized Cyt c on the cMWCNTs/FET surface. The performance of the Cyt c/cMWCNTs/FET biosensor was studied under various parameters such as cMWCNTs and Cyt c concentrations, as well as different pH values. When H2O2 was added to the reaction chamber of the Cyt c/cMWCNTs/FET, the output current of the Bio-FET was reduced, which was attributed to H2O2 detection. The linear response range of this Cyt c/cMWCNT/FET was 10.0 fM to 1.0 nM. The limit of detection and response time of this platform were determined to be 9.13 fM and around 1.0 s, respectively. Also, the operation of the Cyt c/cMWCNTs/FET in the presence of glucose, leucine, tyrosine and ascorbic acid as interfering substances was selective towards H2O2.

A new strategy to design label-free electrochemical biosensor for ultrasensitive diagnosis of CYFRA 21-1 as a biomarker for detection of non-small cell lung cancer.

Lung cancer is one of the most dangerous cancers with high mortality rate among other cancers therefore, early detection of this cancer is very important. Many studies have been reported in ways of diagnostic lung cancer early. According to reports, one of the most important biomarkers to detect lung cancer is Cytokeratin 19 fragment 21-1 (CYFRA21-1), which is significantly related to non-small cell lung cancer, in particular, squamous cell carcinoma. Thus, finding a new method for the early diagnosis of CYFRA 21-1 (DNA target probe) is essential. In the present report, we design a novel label-free electrochemical DNA-biosensor related to the signal of guanine oxidation. The proposed DNA biosensor is fabricated by a modified glassy carbon electrode (GCE) with reduced-graphene oxide (rGO), poly pyrrole (PPy), silver nanoparticles (AgNPs) and single-strand DNA (ssDNA as capture probe) GCE/rGO/PPy/AgNPs/ssDNA. The differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques are used to verify the hybridization process between capture and target probes. Electrochemical impedance spectroscopy (EIS), energy diffraction X-ray (EDX) and field-emission scanning microscopy (FE-SEM) techniques are applied to the characterization of different modified GCE surfaces as well as X-ray diffraction (XRD) for graphene oxide synthesis. The XRD pattern of the synthesized GO that its diffraction peak appears at 10.2. The applied CV and DPV for the guanine oxidation are determined under optimal conditions. The label-free DNA biosensor showed a great result for the determination of CYFRA21-1 with a wide linear range from two consecutive linear relationships of peak current and CYFRA21-1 concentration were found (1.0 × 10-14 - 1.0 × 10-10 M, R2 = 0.9936 and 1.0 × 10-9 - 1.0 × 10-6 M, R2 = 0.9955). Proposed electrochemical biosensor displayed low detection limit (2.4 fM).

Non-Coding RNA-Based Biosensors for Early Detection of Liver Cancer.

Primary liver cancer is an aggressive, lethal malignancy that ranks as the fourth leading cause of cancer-related death worldwide. Its 5-year mortality rate is estimated to be more than 95%. This significant low survival rate is due to poor diagnosis, which can be referred to as the lack of sufficient and early-stage detection methods. Many liver cancer-associated non-coding RNAs (ncRNAs) have been extensively examined to serve as promising biomarkers for precise diagnostics, prognostics, and the evaluation of the therapeutic progress. For the simple, rapid, and selective ncRNA detection, various nanomaterial-enhanced biosensors have been developed based on electrochemical, optical, and electromechanical detection methods. This review presents ncRNAs as the potential biomarkers for the early-stage diagnosis of liver cancer. Moreover, a comprehensive overview of recent developments in nanobiosensors for liver cancer-related ncRNA detection is provided.

Prolactin receptor expression as a novel prognostic biomarker for triple negative breast cancer patients.

Prolactin receptor (PRLR) is a novel emerging prognostic biomarker in different cancers, especially in breast cancer. However, there is limited information about the association of PRLR expression and triple-negative breast cancers (TNBC) prognosis. In this study, 80 TNBC patients were evaluated for PRLR expression by immunohistochemistry. The correlation of PRLR expression with clinicopathological features, patient recurrence, and survival was investigated. PRLR expression was considered positive if >10% of tumor cells were stained. The Fisher's exact test was used to analyze PRLR expression relation with the clinicopathological parameters. Survival distribution was estimated by the Kaplan-Meier method. Positive immunoreactivity for PRLR was observed in 50 out of 80 (62%) specimens. Although expression of PRLR was associated with TNBC patients' stage, no-correlation was observed between its expression and tumor size, grade, lymph node status, and Ki-67 expression. In addition, patients with positive expression of PRLR exhibited lower recurrence (P = 0.0027) and higher overall survival (P = 0.0285) in comparison with negative expression group. In multivariate analyses, positive expression of PRLR was an independent prognostic marker for lower recurrence (P < 0.001) and higher overall survival (P < 0.001). Therefore, PRLR plays a crucial role in TNBC and has to be considered as an independent prognostic biomarker for TNBC patients.

Immobilization of cytochrome c and its application as electrochemical biosensors.

Cytochrome c (Cyt c) has been used as a model protein to investigate the characters of modified electrodes by many researchers. It has been also employed to construct biosensors to detect hydrogen peroxide, nitrate, superoxide, and etc. Cyt c immobilization techniques, including physical adsorption, entrapment in hydrogel or polymers, layer-by-layer assembly, Langmuir-Blodgett, and covalent attachment are discussed followed by various electrochemical methods applied in the electrode modification. The exploration of some modified protein electrodes, for example, screen printed, microperoxidase and engineered Cyt c are also presented. The preparation, characterizations and some properties of nanocomposites to modify electrode surface for immobilizing Cyt c are highlighted. This review is attempted to discuss the influences of the physical and chemical properties of the substrate materials, such as specific area and surface charge on the protein loading and electron transfer of Cyt c briefly. The comparative information of Cyt c-based electrochemical modified electrodes, such as average surface coverage, sensitivity, linear range, and detection limit of the analyte of interest is also summarized.

A novel label-free electrochemical miRNA biosensor using methylene blue as redox indicator: application to breast cancer biomarker miRNA-21.

Small noncoding microRNAs (miRNAs) have emerged as ideal noninvasive biomarkers for early-phase cancer detection. In this report, a label-free and simple electrochemical miRNA biosensor is developed based on employing methylene blue (MB) as a redox indicator. The successfully immobilization of the single strand DNA (ss-DNA) probe and hybridization with the target miRNA sequence were confirmed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. Differential pulse voltammetry (DPV) technique was used to record the oxidation peak current of MB under optimal condition and an increase in the peak current was observed after hybridization. By employing this strategy, miRNA can detect in a range from 0.1 to 500.0 pM with a relatively low detection limit of 84.3 fM. The electrochemical response of MB on ss-DNA and duplex of miRNA/DNA was characterized by CV and chronocoulometry method. The linear relation between the redox peak currents (Ip) and scan rate (ν) indicates that the electron transfer (ET) between MB and the electrode surface was mediated by the miRNA/DNA π-stacked duplex. The value of surface coverage (Γ) was calculated that indicated increase amount of MB on the surface of modified electrode after hybridization event and revealed the adsorption of MB at modified electrode is monolayer. Also, the electron transfer rate constants (ks) of MB were estimated. The results of kinetic analysis were confirmed by chronocoulometry method. The discrimination ability of miRNA biosensor even against a noncomplementary target was also studied. Consequently, this strategy will be valuable for sensitive, selective and label-free detection of miRNA.

Superoxide radical biosensor based on a nano-composite containing cytochrome c.

A biosensor for the quantification of superoxide radical (O(2)˙(-)) was developed based on a nano-composite containing cytochrome c (Cyt c), carboxylated multi-walled carbon nanotubes and a room temperature ionic liquid (RTIL). The immobilized Cyt c was characterized by field emission scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. Using this biosensor a formal potential of -280 mV (vs. Ag/AgCl) and electron transfer rate constant of 1.24 was recorded for the immobilized Cyt c in 0.1 M phosphate buffer solution (pH 7.0). The biosensor showed a relatively high sensitivity (7.455 A M(-1) cm(-2)) and a long term stability (180 days) towards O(2)˙(-) in the concentration range from 0.05 to 8.1 µM with a detection limit of 0.03 µM. The selectivity of the biosensor to O(2)˙(-) was verified when its response was compared with those obtained by four potential interfering substances (ascorbic acid, uric acid, acetaminophen and hydrogen peroxide).

Ionic-liquid/NH2-MWCNTs as a highly sensitive nano-composite for catalase direct electrochemistry.

A nano-composite material consisting of amine functionalized multi-walled carbon nanotubes and a room temperature ionic-liquid (1-butyl-3-methylimidazolium tetrafluoroborate) was prepared and used to construct a novel catalase (Ct) based biosensor for the determination of hydrogen peroxide. The modified electrode exhibited a quasi-reversible cyclic voltammogram corresponding to the Fe(II)/Fe(III) redox couple in the heme prosthetic group of Ct with a formal potential of -460 mV in 0.1M phosphate buffer solution at pH 7.0. The nano-composite film showed an obvious promotion of the direct electron transfer between Ct and the underlying electrode. The apparent charge transfer rate constant and transfer coefficient for electron transfer between the electrode surface and enzyme were calculated as 2.23s(-1) and 0.45, respectively. The immobilized Ct exhibited a relatively high sensitivity (4.9 nA/nM) toward hydrogen peroxide. Under the optimized experimental conditions, hydrogen peroxide was detected in the concentration range from 8.6 to 140 nM with a detection limit of 3.7 nM at S/N=3. The modified electrode was stable for two weeks with no observable change in the cyclic voltammograms.

Determination of pore/protein size via electrophoresis and slit sieve model.

We used electrophoresis for three purposes: (i) estimation of the mean pore size of polyacrylamide gels via measuring electrophoretic mobility of globular proteins of known sizes in combination with simple sieve (cylindrical and slit) models; (ii) determination of the average size of protein molecules (native or denatured) by the use of the same models; (iii) monitoring the changes in molecular dimensions of proteins in the course of their denaturation. Both models yield results that are in good agreement with those found via the more elaborate techniques (considering the principal differences involved). The approach provides a direct and convenient way of monitoring the variations in protein sizes during the course of their denaturation in gels having a gradient of denaturants, and possibly the number of conformational states involved in the process, a facet that is quite unique and useful. The simpler slit model seems to yield better results in the latter case and is moreover supported by the recently reported data on electrophoresis of DNA molecules through the 1 microm slits of a microbrush matrix made of micropillars arranged in a hexagonal lattice.