Superior graphdiyne self-powered biosensing platform with highly sensitivity and reliability for dual-mode detection of MicroRNA by integrating T7 Exonuclease and 3D DNA walker induced rolling circle amplification.

A highly sensitivity self-powered biosensor is developed based on T7 exonuclease (T7 Exo) and 3D DNA walker induced rolling circle amplification (RCA) for electrochemical/colorimetric dual-mode detection of microRNA-21 (miRNA-21) with improved reliability. Taking its advantage of fascinating properties, such as high structure defects and good conductivity, graphdiyne is prepared and used to prepare high-performance enzyme biofuel cell. T7 Exo-assisted 3D DNA walker target recognition triggers RCA reaction to obtain a significantly amplified signal response. A capacitor is integrated to the enzyme biofuel cell to further amplify the electrochemical output signal of the self-powered biosensor. In detection system, glucose oxidase catalyzes glucose oxidation to produce hydrogen peroxide, and 3,3',5,5'-tetramethylbenzidine (TMB) is then catalyzed to generate colored products, so as to achieve the colorimetric detection of the target. Analysis signals of diverse modes are recorded independently. Consequently, detection of microRNA with improved reliability and wider signal response range are achieved by electrochemical/colorimetric dual-mode with detection limits of 0.15 and 33 fM (S/N = 3) respectively. In addition, the proposed self-powered biosensor successfully applied for the detection of miRNA-21 in human serum samples, confirming its practical applicability in clinical diagnosis. It is powerfully anticipated the proposed self-powered biosensor possesses great potential to be applied to other biomedical domains.

AuNPs/graphdiyne self-powered sensing platform for sensitive detection of microRNA with DNAzyme walker for signal amplification.

A novel self-powered biosensor is engineered by the integration of DNAzyme walker and AuNPs/graphdiyne biosensing interface, realizing sensitive detection of target microRNA. The cleverly constructed DNAzyme walker with outstanding signal transduction ability to obtain an amplified signal response. In addition, the AuNPs/graphdiyne significantly improves electron transport speed of biosensing interface for improving the sensitivity of biosensor. A dynamic linear range of 0.05 fM-10 pM with a low detection limit of 0.015 fM (S/N = 3) is obtained by utilizing the self-powered biosensor. Meanwhile, the developed self-powered biosensor is capable of assaying miRNA-21 in human serum samples with satisfactory recoveries. This strategy provides a valid method for the sensitive microRNA detection, and shows great potential in point-care detection of tumor biomarker.

All-carbon sandwich-type self-powered biosensor for ultrasensitive detection of femtomolar miRNA-141.

The latest research shows that the expression level of microRNA-141 can predict the number of prostate cancer cells in the human body and has become an important biomarker. In this paper, an all-carbon sandwich self-powered biosensor based on graphene and carbon cloth is constructed for the highly sensitive detection of the prostate tumor marker miRNA-141. First, gold nanoparticles modified carbon cloth is applied for substrate electrode, and bilirubin oxidase is then immobilized on it to prepare the biocathode of the biofuel cell. Then, aptamer 1 is immobilized on gold nanoparticles-modified carbon cloth as the electrode substrate. The bioconjugate is prepared by immobilizing the aptamer 2-glucose oxidase complex on gold nanoparticles/graphene. In the biofuel cell-based self-powered sensing system, when the target microRNA-141 is present, it undergoes complementary base pairing with aptamer 1 and aptamer 2, and the bioconjugates are immobilized on the anode to form the sandwich structure. The enzyme on the anode undergoes an oxidation reaction to catalyze the reduction of oxygen, and the electrochemical respond of the system increases significantly. The results show that the concentration of microRNA-141 is proportional to the open-circuit voltage value ranging from 0.0001 to 1000 pmol/L with a detection limit of 50 amol/L (S/N = 3). The method has high sensitivity and excellent selectivity and can be applied to sensitively detect tumor marker microRNA-141 in biological matrix.

Prognostic value of the NLR combined with CIP2A in the serum of patients with colorectal cancer.

OBJECTIVE: This study aimed to investigate the prognostic value of CIP2A (cancerous inhibitor of protein phosphatase 2A) and the NLR (neutrophil-lymphocyte ratio) in the serum of patients with CRC (colorectal cancer) after resection. METHODS: The clinicopathological data of 61 patients who underwent resection between January 2012 and December 2013 were collected. The NLR and CIP2A were divided into low score groups (0) and high score groups (1) with 2.03 and 6.07 as the optimal cut-off value according to the receiver operating characteristic (ROC) curve analysis. To identify the COCN (combination of CIP2A and the NLR) score, we added CIP2A and NLR points together and categorized CRC patients into three groups. Kaplan-Meier curves were used to identify the overall survival (OS) rates of the different groups. Finally, a ROC curve was plotted to evaluate the prognostic efficacy of COCN. RESULTS: The CIP2A was associated with location (P = 0.046) and CEA (P = 0.037) in patients with CRC. Kaplan-Meier survival curves showed that the 5-year OS of patients with low level of serum CIP2A was better than that of high level. The 5-year OS of the patients in the low NLR group was better than that of those in the high NLR group. The COCN score was associated with CEA (P < 0.001) and CA19-9 (P = 0.001). The 5-year OS of the patients in the COCN 0 group was highest, followed by that of those in the COCN 1 and COCN 2 groups. Age, N stage and M stage were factors associated with 5-year OS according to the univariate and multivariate analyses (P < 0.05). The area under the curve (AUC) for COCN was largest, indicating that COCN has better prognostic power than CIP2A or the NLR alone. CONCLUSION: COCN could be used as a better prognostic biomarker for CRC than the NLR or CIP2A alone.

A Cross-Disciplinary Successful Aging Intervention and Evaluation: Comparison of Person-to-Person and Digital-Assisted Approaches.

Background: Successful aging has been the paradigm of old-age life. The purpose of this study was to implement and evaluate a cross-disciplinary intervention program using two approaches for community-based older adults in Taichung, Taiwan. Methods: The content of the intervention included successful aging concepts and preparation, physical activity, chronic disease and health management, dietary and nutrition information, cognitive training, emotional awareness and coping skills, family relationship and resilience, legal concepts regarding financial protection, and Internet use. The traditional person-to-person (P2P) intervention approach was implemented among participants at urban centers, and the personal-and-digital (P&D) intervention approach was implemented among participants at rural centers; before the P&D group received the intervention, participants were assessed as the control group for comparison. Results: Healthy behavior and nutrition improved for the P2P group, although not significantly. Strategies for adapting to old age and reducing ineffective coping were significantly improved in the P2P group. The ability to search for health information improved in the P&D group, and knowledge of finance-related law increased in the P2P group. Conclusion: A continuous, well-designed and evidence-based intervention program is beneficial for improving the health of older adults, or at least delaying its decline.

Direct electrochemistry and electrocatalysis of hemoglobin on carbon ionic liquid electrode.

Hemoglobin in agarose was successfully immobilized on a carbon ionic liquid electrode and the direct electrochemical behavior of hemoglobin was investigated. Room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was used as the modifier. Ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry were used to characterize the hemoglobin on the modified electrode. The results showed that the immobilized hemoglobin retained its bioelectrocatalytic activity. The electrochemistry of hemoglobin provided an opportunity to manufacture a third generation of biosensors. Experimental conditions influencing the biosensor performances such as pH, and potential were optimized and assessed. Under the optimal conditions, hydrogen peroxide was detected in the concentration range from 2x10(-6) to 1.2x10(-3)M with a detection limit of 0.2 microM at S/N=3. The apparent Michaelis-Menten constant was 1.495 mM. The biosensor exhibited some advantages, such as short time respond, high sensitivity, good reproducibility and long-term stability.

A disposable electrochemical immunosensor for carcinoembryonic antigen based on nano-Au/multi-walled carbon nanotubes-chitosans nanocomposite film modified glassy carbon electrode.

In this paper, a disposable electrochemical immunosensor for the detection of carcinoembryonic antigen (CEA) based on Au nanoparticles (AuNPs)/multi-walled carbon nanotubes (MWCNTs)-chitosans (Chits) composite film was developed. MWCNTs-Chits homogeneous composite was first dispersed in acetic acid solution and then the AuNPs was in situ synthesized at the composite. The mixture was dripped on the glassy carbon electrode (GCE) and then CEA antibody (anti-CEA) was immobilized on the resulted modified electrode to construct the immunosensor. The stepwise assembly process of the immunosensor was characterized by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody-antigen complexes decreased peak current of [Fe(CN)(6)](3-/4-) redox pair at the AuNPs/MWCNTs-Chits/GCE. The optimization of the pH of supporting electrolyte, the incubation temperature and time were studied in detail. Under optimal conditions, the peak current of DPV of the immunosensor decreased linearly with increasing CEA concentration in two ranges of 0.3-2.5 and 2.5-20 ng mL(-1), with a detection limit of 0.01 ng mL(-1) (S/N=3). This electrochemical immunoassay combines the specificity of the immunological reaction with the sensitivity of the AuNPs and MWCNTs amplified electrochemical detection. It would be valuable for diagnosis and monitoring of carcinoma.

The investigation of the interactions between CdSe quantum dots and human serum albumin by resonance Rayleigh scattering and second-order scattering spectra.

Human serum albumin (HSA) was the most abundant protein in human plasma and has significant physiological function. In Tris-HCl buffer solution (pH 7.4), water-soluble semiconductor CdSe quantum dots (QDs) reacted with HSA and the products resulted in a great enhancement of the intensity of resonance Rayleigh scattering (RRS) and second-order scattering (SOS). Based on this, a new method was developed to investigate the interactions between QDs and HSA. The parameters with regard to determination were optimized, and the reaction mechanism was discussed. Under optimal conditions, the increments of scattering intensity (DeltaI) were directly proportional to the concentrations of HSA in the range of 0.4-48.0 micromol L(-1). The detection limits were 0.10 micromol L(-1) for RRS method and 0.25 micromol L(-1) for SOS method. The proposed method was sensitive, simple and rapid. It has been successfully applied to the determination of HSA in human urine samples. Analytical results obtained with this novel assay were satisfactory.

Electrochemical behavior and voltammetric determination of tryptophan based on 4-aminobenzoic acid polymer film modified glassy carbon electrode.

Herein, a novel electrochemical method was developed for the determination of tryptophan based on the poly(4-aminobenzoic acid) film modified glassy carbon electrode (GCE). The electrochemical behaviors of tryptophan at the modified electrode were investigated. It was found that the oxidation peak current of tryptophan at the modified GCE was greatly improved compared with that at the bare GCE. The effects of supporting electrolyte, pH value, scan rate, accumulation potential and time were examined. The oxidation peak current of tryptophan was proportional to its concentration over the range from 1.0 x 10(-6) to 1.0 x 10(-4)mol L(-1). The limit of detection was evaluated to be 2.0 x 10(-7)mol L(-1). The proposed method was sensitive and simple. It was successfully employed to determine tryptophan in pharmaceutical samples.

Ultrasound-assisted dispersive liquid-liquid microextraction combined with high-performance liquid chromatography-fluorescence detection for sensitive determination of biogenic amines in rice wine samples.

Ultrasound-assisted dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography-fluorescence detection was used for the extraction and determination of three biogenic amines including octopamine, tyramine and phenethylamine in rice wine samples. Fluorescence probe 2,6-dimethyl-4-quinolinecarboxylic acid N-hydroxysuccinimide ester was applied for derivatization of biogenic amines. Acetonitrile and 1-octanol were used as disperser solvent and extraction solvent, respectively. Extraction conditions including the type of extraction solvent, the volume of extraction solvent, ultrasonication time and centrifuging time were optimized. After extraction and centrifuging, analyte was injected rapidly into high-performance liquid chromatography and then detected with fluorescence. The calibration graph of the proposed method was linear in the range of 5-500 microg mL(-1) (octopamine and tyramine) and 0.025-2.5 microg mL(-1) (phenethylamine). The relative standard deviations were 2.4-3.2% (n=6) and the limits of detection were in the range of 0.02-5 ng mL(-1). The method was applied to analyze the rice wine samples and spiked recoveries in the range of 95.42-104.56% were obtained. The results showed that ultrasound-assisted dispersive liquid-liquid microextraction was a very simple, rapid, sensitive and efficient analytical method for the determination of trace amount of biogenic amines.

Electrochemical behavior and voltammetric determination of norfloxacin at glassy carbon electrode modified with multi walled carbon nanotubes/Nafion.

A simple and rapid electrochemical method is developed for the determination of trace-level norfloxacin, based on the excellent properties of multi-walled carbon nanotubes (MWCNTs). The MWCNTs/Nafion film-coated glassy carbon electrode (GCE) is constructed and the electrochemical behavior of norfloxacin at the electrode is investigated in detail. The results indicate that MWCNTs modified glassy carbon electrode exhibited efficiently electrocatalytic oxidation for norfloxacin (NFX) with relatively high sensitivity, stability and life time. Under conditions of cyclic voltammetry, the current for oxidation of selected analyte is enhanced significantly in comparison to the bare GCE. The electrocatalytic behavior is further exploited as a sensitive detection scheme for the analyte determinations by linear sweep voltammetry (LSV). Under optimized condition in voltammetric method the concentration calibration range and detection limit (S/N=3) are 0.1-100 micromol/L and 5 x 10(-8)mol/L for NFX. The proposed method was successfully applied to NFX determination in tablets. The analytical performance of this sensor has been evaluated for detection of the analyte in urine as a real sample.

Ultra-trace determination of S-nitrosothiols in blood samples by spectrofluorimetry with 8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene.

Increasing evidence suggests that S-nitrosothiols (RSNO) may represent naturally occurring nitric oxide (NO) surrogates and function as intermediates in NO metabolism. In this work, a simple, sensitive, and selective micromethod is developed and validated for quantification of RSNO. A fluorescent probe 8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacence (DABODIPY) is firstly used to label RSNO. The derivatization reaction is performed in aqueous medium at 30 degrees C for 15min in the presence of 6x10(-5)molL(-1)Hg2+ and the derivative is detected by fluorescence at lambda(ex)/lambda(em)=500/510nm. A linear function of concentration in the range of (2.0-600.0)x10(-8)molL(-1) is observed with a correlation coefficient of 0.9992 and detection limit of 1.2x10(-9)molL(-1) (S/N=3). This technique has been successfully applied to quantify RSNO in some human blood samples including healthy persons and patients suffering from cardiovascular diseases.

Sensitive voltammetric determination of tyrosine using multi-walled carbon nanotubes/4-aminobenzeresulfonic acid film-coated glassy carbon electrode.

A chemically modified electrode is constructed based on the multi-walled carbon nanotubes (MWNTs)/4-aminobenzeresulfonic acid (4-ABSA) film-coated glassy carbon electrode. The electrocatalytic oxidation of tyrosine (Tyr) is investigated on the surface of the MWNTs/4-ABSA-modified electrode using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The prepared modified electrode shows voltammetric responses with high sensitivity and selectivity for Tyr in optimal conditions, which makes it very suitable for sub-micromolar detection of Tyr. A sensitive oxidation peak at +0.64 V is employed to determine Tyr. Good linear relationship between the oxidation peak current and the Tyr concentration in the range of 1x10(-7) to 5x10(-5) mol/L is obtained in phosphate buffer solution with pH 7.0. By use of modified electrode, the voltammetric detection limit for Tyr in DPV measurements is 8x10(-8) mol/L (S/N=3). Good sensitivity, selectivity and stability of the low-cost modified electrode make it very suitable for the determination of trace amounts of Tyr in pharmaceutical and clinical preparations.

Determination of nitric oxide in hydrophytes using poly(methacrylic acid-ethylene glycol dimethacrylate) monolith microextraction coupled to high-performance liquid chromatography with fluorescence detection.

Nitric oxide (NO) is a bioactive molecule that has recently emerged as a cellular messenger in numerous physiological processes in plants. A novel high-performance liquid chromatography (HPLC) method combined with poly(methacrylic acid-ethylene glycol dimethacrylate) (MAA-EGDMA) monolith microextraction (PMME) is developed for sensitive determination of NO in hydrophytes. NO is derivatized using a fluorescent probe, 1,3,5,7-tetramethyl-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene (DAMBO), and then the derivatives are extracted with PMME and analyzed by high-performance liquid chromatography (HPLC) with fluorescence detection. The conditions for the derivatization and the subsequent extraction of NO derivatives are optimized in detail. The detection limit (S/N=3) of NO is determined to be 2x10(-12)mol L(-1). Close correlation coefficient and excellent method reproducibility are obtained for the analyte over a linear range of 9x10(-11)-4.5x10(-8)mol L(-1). The inter- and intraday relative standard deviations (R.S.D.s) are less than 5%. The proposed method is successfully applied to the determination of NO levels in hydrophytes samples.

Sensitive determination of nitric oxide in some rat tissues using polymer monolith microextraction coupled to high-performance liquid chromatography with fluorescence detection.

A simple, sensitive, selective, and low-cost method is proposed for rapidly determining nitric oxide (NO) in some rat tissues. Polymer monolith microextraction (PMME) using a poly(methacrylic acid-ethylene glycol dimethacrylate) (MAA-EGDMA) monolithic column was combined with derivatization of NO using 1,3,5,7-tetramethyl-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene (TMDABODIPY), and this was used to analyze the derivatives of NO by high-performance liquid chromatography (HPLC) with fluorescence detection at lambda (ex)/lambda (em) = 498/507 nm. The baseline separation of TMDABODIPY and its NO derivative is performed under simple conditions in which a C(18) column is used and eluted with 50 mmol L(-1) ethanolamine and methanol. The conditions for the extraction of NO derivatives were optimized. The limit of detection of NO was 2 x 10(-12) mol L(-1) (S/N = 3). The linearity range of the method was 9 x 10(-11)-4.5 x 10(-8) mol L(-1). The interday and intraday relative standard deviations were less than 5%. The proposed method was successfully applied to the determination of NO levels in some rat tissue samples including heart, kidney, and liver with recoveries varying from 87.1 to 95.2%.

Sensitive determination of ultra-trace nitric oxide in blood using derivatization-polymer monolith microextraction coupled with reversed-phase high-performance liquid chromatography.

Nitric oxide (NO) plays a very important role in human blood system. In this work, a novel approach has been developed for the quantitation of ultra-trace NO derivatized with 1,3,5,7-tetramethyl-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene (DAMBO) using a polymer monolith microextraction (PMME) with a poly(methacrylic acid-ethylene glycol dimethacrylate) (MAA-EGDMA) monolith in conjunction with high-performance liquid chromatography (HPLC). Both derivatization and PMME conditions have been optimized in detail. The detection limit of derivatized NO was 2x10(-12) mol L(-1) (signal to noise=3) and linear range was 9x10(-11)-4.5x10(-8) mol L(-1). The proposed DAMBO-based derivatization-PMME-HPLC-fluorescence detection method has been successfully applied for the determination of NO in 10 microL blood samples of healthy persons and patients suffering from ischemic cardio-cerebrovascular diseases with recoveries varying from 87.40 to 91.60%.

Investigation of the effect of tanshinone IIA on nitric oxide production in human vascular endothelial cells by fluorescence imaging.

Nitric oxide (NO) has been proved to be a potent vasodilator that played an important role in regulating vascular tones. Tanshinone, one of the active components of Radix Salvia miltiorrhiza, was used widely in clinics in China for treating cardiovascular diseases. The objective of this study was to sensitively and specifically investigate the effects of tanshinone IIA, one important pharmacological constituent of tanshinone, on the release of NO from human vascular endothelial cells (HVECs) by fluorescence imaging with an excellent fluorescent probe 1,3,5,7-tetramethyl-2,6-dicarbethoxy-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacence (TMDCDABODIPY). After cells were incubated with tanshinone IIA, TMDCDABODIPY was employed to label NO. Following the tagging, real-time imaging of NO release from the cells was performed with inverted fluorescence microscope. The results of the experiments showed that tanshinone IIA could induce NO production significantly enhanced in HVECs. The activation of NO by tanshinone IIA may be employed therapeutically in modulating NO production in HVECs.

Sensitive determination of S-nitrosothiols in human blood by spectrofluorimetry using a fluorescent probe: 1,3,5,7-tetramethyl-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene.

S-Nitrosothiols (RSNO) have been proved to be potent smooth muscle relaxants and inhibitors of platelet aggregation. It has been reported as the best candidate for the endogenous storage and transport of nitric oxide (NO) in vivo. Sensitive determination of RSNO in biosamples seems to be of great significance. In this work, a novel spectrofluorimetric method is proposed to determine RSNO. An excellent fluorescence probe 1,3,5,7-tetramethyl-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacence (DAMBO) is used to label RSNO. The derivatization reaction performs in aqueous medium at 30 degrees C for 15 min in the presence of 1.0 x 10(-4)mol L(-1) Hg(2+). The derivative is detected by fluorescence at an emission wavelength of 507 nm with excitation at 498 nm. The response is a linear function of concentration in the range of 6.0-400.0 x 10(-9)mol L(-1). The detection limit is 1.2 x 10(-10)mol L(-1) (S/N=3). The method is applied to determine RSNO in the blood of healthy persons and patients suffering from cardiovascular diseases. Recoveries of RSNO from spiked blood samples are between 97.52 and 102.81%. The studies indicate that the method presented here is rapid, simple, sensitive and feasible.