Metal-Enhanced Fluorescence from Silver Nanowires with High Aspect Ratio on Glass Slides for Biosensing Applications

High enhancement of fluorescence emission, improved fluorophore photostability, and significant reduction of fluorescence lifetimes have been obtained from high aspect ratio (>100) silver (Ag) nanowires. These quantities are found to depend on the surface loading of Ag nanowires on glass slides, where the enhancement of fluorescence emission increases with the density of nanowires. The surface loading dependence was attributed to the creation of intense electric fields around the network of Ag nanowires and to the coupling of fluorophore excited states that takes place efficiently at a distance of 10 nm from the surface of nanowires, which was confirmed by theoretical calculations. The enhancement of fluorescence emission of fluorescein isothiocyanate (FITC) was assessed by fluorescence spectroscopy and fluorescence-lifetime imaging microscopy (FLIM) to demonstrate the potential of high aspect ratio Ag nanowires. Fluorescence enhancement factors exceeding 14 were observed on Ag nanowires with high loading by FLIM. The photostability of FITC was the highest on nanowires with medium loading under continuous laser excitation for 10 min because of the significant reduction in the fluorescence lifetime of FITC on these surfaces. These results clearly demonstrate the potential of Ag nanowires in metal-enhanced fluorescence-based applications of biosensing on planar surfaces and cellular imaging

Tumour exosomes display differential mechanical and complement activation properties dependent on malignant state:implications in endothelial leakiness

Background: Exosomes have been implicated in tumour progression and metastatic spread. Little is known of the effect of mechanical and innate immune interactions of malignant cell-derived exosomes on endothelial integrity, which may relate to increased extravasation of circulating tumour cells and, therefore, increased metastatic spread. Methods: Exosomes isolated from non-malignant immortalized HCV-29 and isogenic malignant non-metastatic T24 and malignant metastatic FL3 bladder cells were characterized by nanoparticle tracking analysis and quantitative nanomechanical mapping atomic force microscopy (QNM AFM) to determine size and nanomechanical properties. Effect of HCV-29, T24 and FL3 exosomes on human umbilical vein endothelial cell (HUVEC) monolayer integrity was determined by transendothelial electrical resistance (TEER) measurements and transport was determined by flow cytometry. Complement activation studies in human serum of malignant and non-malignant cell-derived exosomes were performed. Results: FL3, T24 and HCV-29 cells produced exosomes at similar concentration per cell (6.64, 6.61 and 6.46×104 exosomes per cell for FL3, T24 and HCV-29 cells, respectively) and of similar size (120.2 nm for FL3, 127.6 nm for T24 and 117.9 nm for HCV-29, respectively). T24 and FL3 cell-derived exosomes exhibited a markedly reduced stiffness, 95 MPa and 280 MPa, respectively, compared with 1,527 MPa with non-malignant HCV-29 cell-derived exosomes determined by QNM AFM. FL3 and T24 exosomes induced endothelial disruption as measured by a decrease in TEER in HUVEC monolayers, whereas no effect was observed for HCV-29 derived exosomes. FL3 and T24 exosomes traffic more readily (11.6 and 21.4% of applied exosomes, respectively) across HUVEC monolayers than HCV-29 derived exosomes (7.2% of applied exosomes). Malignant cell-derived exosomes activated complement through calcium-sensitive pathways in a concentration-dependent manner. Conclusions: Malignant (metastatic and non-metastatic) cell line exosomes display a markedly reduced stiffness and adhesion but an increased complement activation compared to non-malignant cell line exosomes, which may explain the observed increased endothelial monolayer disruption and transendothelial transport of these vesicles

Are isolated anti-HBc blood donors in high risk group? The detection of HBV DNA in isolated anti-HBc cases with nucleic acid amplification test (NAT) based on transcription-mediated amplification (TMA) and HBV discrimination

Aim: Hepatitis B virus (HBV) can be transmitted by blood transfusions even so using serological tests having high sensitivity and specificity. We aimed to detect HBV DNA in isolated Anti-HBc donors and show if they have transfusion risk or not

Can the nucleic acid amplification test (NAT) be an alternative to the serologic tests? A prospective study, the results of 18,200 blood donors from the Turkish Red Crescent

Aim: Serologic tests having high sensitivity and specificity are used in order to prevent contamination with infectious agents from blood and blood products for transfusion safety. The present serologic tests have problems such as low sensitivity and weak detection capacity of infectious agents in the "window period". We aimed to test the use of NAT (Nucleic Acid Amplification Test) in routine blood screening in the Blood Bank