Dual-Shaped Silver Nanoparticle Labels for Electrochemical Detection of Bioassays.

In this paper we demonstrate the use of dual-shaped silver nanoparticles (AgNPs) as detection labels for electrochemical bioassays. The key finding is that by using AgNP labels having two different shapes simultaneously, the limit of detection (LOD) for the assays is lowered compared to using either of the two shapes separately. The two shapes were silver nanocubes (AgNCs) having edge lengths of 40 ± 4 nm and spherical AgNPs (sAgNPs) having diameters of 20 ± 3 nm. Two different bioassays were examined. In both cases the Ag labels were functionalized with antibodies. In the one assay, the labels are directly linked to a second antibody immobilized on magnetic beads. In the second assay, the antibodies on the AgNP labels and the antibodies on the magnetic beads are linked via a peptide. The peptide is N-terminal prohormone brain natriuretic peptide (NT-proBNP), which is a heart failure marker. The efficacy of the two electrochemical assays as a function of the ratio of the two labels was investigated using a galvanic exchange/anodic stripping voltammetry method. The key finding is that by optimizing the ratio of the two types of AgNP labels, it is possible to decrease the LOD of the assays without compromising the dynamic range compared to using either of the two labels independently. This made it possible to achieve the clinically relevant range for NT-proBNP analysis used by physicians for heart failure risk stratification.

Electrochemical Detection of NT-proBNP Using a Metalloimmunoassay on a Paper Electrode Platform.

In this paper, we demonstrate an electrochemical method for detection of the heart failure biomarker, N-terminal prohormone brain natriuretic peptide (NT-proBNP). The approach is based on a paper electrode assembly and a metalloimmunoassay; it is intended for eventual integration into a home-use sensor. Sensing of NT-proBNP relies on the formation of a sandwich immunoassay and electrochemical quantification of silver nanoparticle (AgNP) labels attached to the detection antibodies (Abs). There are four important outcomes reported in this article. First, compared to physisorption of the detection Abs on the AgNP labels, a 27-fold increase in signal is observed when a heterobifunctional cross-linker is used to facilitate this labeling. Second, the assay is selective in that it does not cross-react with other cardiac natriuretic peptides. Third, the assay forms in undiluted human serum (though the electrochemical analysis is carried out in buffer). Finally, and most important, the assay is able to detect NT-proBNP at concentrations between 0.58 and 2.33 nM. This performance approaches the critical NT-proBNP concentration threshold often used by physicians for risk stratification purposes: ∼0.116 nM.

Comparison of prognostic values of high-sensitivity cardiac troponin T and N-terminal prohormone brain natriuretic peptide to assess mortality in elderly inpatients.

BACKGROUND: Studies have shown that increases in low-level high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal prohormone brain natriuretic peptide (NT-proBNP) in the elderly population lead to high risk of adverse clinical outcomes, such as mortality. In this study, associations between the two biomarkers and long-term mortality in elderly patients hospitalized for medical conditions other than acute cardiovascular events were investigated. A comparison of the predictive value of hs-cTnT and NT-proBNP for all-cause mortality was conducted. METHODS: A cohort of 715 elderly inpatients free of acute cardiovascular events was initially recruited. Based on tertiles of baseline hs-cTnT and NT-proBNP levels, the elderly were arranged into low, middle, and high groups. The mortality of each group was observed and the predictive values of hs-cTnT and NT-proBNP compared. Additionally, all-cause mortality was analyzed for hs-cTnT and NT-proBNP combined. RESULTS: There were 135 (18.9%) all-cause mortality cases identified during follow-up (median 47 months). The upper tertile of hs-cTnT was significantly associated with an increased risk of mortality (HR 3.29, 95% CI 1.85-5.85), even after adjustment for potential confounders. However, there were no significant differences observed in mortality rates among the three NT-proBNP groups after adjustment for potential confounders (HR 1.77, 95% CI 0.83-3.17). Compared to NT-proBNP, hs-cTnT was a better predictor of mortality, as area under curves for hs-cTnT and NT-proBNP at 60 months were 0.712 (95% CI 0.616-0.809) and 0.585 (95% CI 0.483-0.6871), respectively. Also, the combination of the two cardiac biomarkers did not render a better predictive value for mortality than hs-cTnT alone. CONCLUSION: Unlike hs-cTnT, baseline NT-proBNP levels failed to show an independent association with all-cause mortality in hospitalized elderly without acute cardiovascular events. hs-cTnT provided significant prognostic value for mortality in the study cohort.

Association of left atrial pressure with left atrial volume and N-terminal prohormone brain natriuretic peptide in children with cardiomyopathy.

BACKGROUND: Enlargement of the left atrium is a non-invasive marker of diastolic dysfunction of the left ventricle, a determinant of prognosis in children with cardiomyopathy. Similarly, N-terminal prohormone brain natriuretic peptide is a useful marker in the management of children with cardiomyopathy and heart failure. The aim of this study is to evaluate the association of left atrial pressures with left atrial volume and N-terminal prohormone brain natriuretic peptide in children with cardiomyopathy. METHODS: This was a retrospective study reviewing the medical records of patients <18 years of age, who were diagnosed with cardiomyopathy or acute myocarditis with eventual development of cardiomyopathy. Left atrial volume by transthoracic echocardiogram and pulmonary capillary wedge pressure, a surrogate of left atrial pressure, obtained by means of cardiac catheterisation were analysed. In addition, N-terminal prohormone brain natriuretic peptide levels obtained at the time of the cardiac catheterisation were also reviewed. Statistical analysis was performed to evaluate the association of left atrial pressures with left atrial volume and N-terminal prohormone brain natriuretic peptide levels. RESULTS: There was a linear correlation of left atrial pressure estimated in the cardiac catheterisation with indexed left atrial volume (r=0.63; p<0.001) and left atrial volume z-scores (r=0.59; p<0.001). We found no statistically significant association between the left atrial pressure and N-terminal prohormone brain natriuretic peptide levels. CONCLUSIONS: Left atrial volume measured non-invasively by echocardiography can be used as a surrogate for left atrial pressure in assessing diastolic dysfunction of the left ventricle in children with cardiomyopathy. The larger the size of the left atrium, worse is the diastolic function of the left ventricle.

Pre-Clinical Tests of an Integrated CMOS Biomolecular Sensor for Cardiac Diseases Diagnosis.

Coronary artery disease and its related complications pose great threats to human health. In this work, we aim to clinically evaluate a CMOS field-effect biomolecular sensor for cardiac biomarkers, cardiac-specific troponin-I (cTnI), N-terminal prohormone brain natriuretic peptide (NT-proBNP), and interleukin-6 (IL-6). The CMOS biosensor is implemented via a standard commercialized 0.35 µm CMOS process. To validate the sensing characteristics, in buffer conditions, the developed CMOS biosensor has identified the detection limits of IL-6, cTnI, and NT-proBNP as being 45 pM, 32 pM, and 32 pM, respectively. In clinical serum conditions, furthermore, the developed CMOS biosensor performs a good correlation with an enzyme-linked immuno-sorbent assay (ELISA) obtained from a hospital central laboratory. Based on this work, the CMOS field-effect biosensor poses good potential for accomplishing the needs of a point-of-care testing (POCT) system for heart disease diagnosis.

Vector synthesis high-resolution electrocardiography, atrial natriuretic peptide and N-terminal prohormone brain natriuretic peptide for estimation of cardiac load in pregnancy.

AIM: We analyzed atrial natriuretic peptide (ANP), N-terminal pro-brain natriuretic natriuretic peptide (NT-proBNP) and vector synthesis high-resolution electrocardiography (ECG), to estimate cardiac load with circulatory dynamic change from pregnancy through the post-partum period. METHODS: The subjects were singleton pregnant women (n = 19), who were divided into three stages: stage 1, 34-36 weeks of gestation; stage 2, 2-6 post-partum days; and stage 3, 1-3 months after delivery. Vector synthesis high-resolution ECG, ANP and NT-proBNP were analyzed for all subjects. RESULTS: A pregnant woman with massive uterin liomyoma expressed largest the corrected recover time (RTc) dispersion in I + II of tow Dimensional (2D) color distribution map ANP and NT-proBNP were significantly higher in stage 2 than in stages 1 and 3. CONCLUSIONS: ANP, NT-proBNP and vector synthesis high-resolution ECG there might be able to evaluate cardiac load of normal pregnancy.

Biological significance of miR-126 expression in atrial fibrillation and heart failure

We investigated the biological significance of microRNA-126 (miR-126) expression in patients with atrial fibrillation (AF) and/or heart failure (HF) to examine the possible mechanism of miR-126-dependent AF and development of HF. A total of 103 patients were divided into three groups: AF group (18 men and 17 women, mean age: 65.62±12.72 years), HF group (17 men and 15 women, mean age: 63.95±19.71 years), and HF-AF group (20 men and 16 women, mean age: 66.56±14.37 years). Quantitative real-time PCR was used to measure relative miR-126 expression as calculated by the 2−ΔΔCt method. miR-126 was frequently downregulated in the 3 patient groups compared with controls. This reduction was significantly lower in permanent and persistent AF patients than in those with paroxysmal AF (P<0.05, t-test). Moreover, miR-126 expression was markedly lower in the HF-AF group compared with the AF and HF groups. The 3 patient groups had higher N-terminal prohormone brain natriuretic peptide (NT-proBNP) levels, lower left ventricular ejection fraction (LVEF), larger left atrial diameter, and higher cardiothoracic ratio compared with controls. There were significant differences in NT-proBNP levels and LVEF among the AF, HF, and HF-AF groups. Pearson correlation analysis showed that relative miR-126 expression was positively associated with LVEF, logarithm of NT-proBNP, left atrial diameter, cardiothoracic ratio, and age in HF-AF patients. Multiple linear regression analysis showed that miR-126 expression was positively correlated with LVEF, but negatively correlated with the logarithm of NT-pro BNP and the cardiothoracic ratio (all P<0.05). Serum miR-126 levels could serve as a potential candidate biomarker for evaluating the severity of AF and HF. However, to confirm these results, future studies with a larger and diverse patient population are necessary.