A highly sensitive electrochemical genosensor based on Co-porphyrin-labelled DNA

We report the use of Co-porphyrins as electrochemical tags for a highly sensitive and selective genosensor. An avian influenza virus-based DNA sequence characteristic of H5N1 was detected at femtomolar levels from competing non-complementary sequences through hybridisation with the labeled DNA

Electrochemical genosensor based on disc and screen printed goldelectrodes for detection of specific DNA and RNA sequences derivedfrom Avian Influenza Virus H5N1

tThe genosensors based on thiolated ssDNA probe deposited on the two types of gold electrodes: screen-printed (miniaturized) and disc electrodes destined for determination of specific sequences of DNA andRNA derived from Avian Influenza Virus H5N1 have been proposed. The working principle of genosensor isbased on the ion-channel mechanism. The analytical signals generated upon hybridization processes wererecorded using electrochemical technique – Osteryoung square wave voltammetry in the presence of aredox active marker [Fe(CN)6]3−/4−in the sample solution. The miniaturized genosensor based on screenprinted gold electrodes was able to detect the 20-mer complementary DNA oligonucleotide sequence aswell as ∼280-mer RNA sequences containing the complementary 20-mer sequence in various positions:at 3�-terminus, at 5�-terminus and in the middle of the RNA transcript at the 1 pM concentration. Themeasuring systems were selective. Non-complementary 20-mer oligonucleotide sequence as well asRNA transcript without complementary region generated weak response. The RNA transcripts were alsotested with gold disc electrodes modified in the same manner. This device was able to detect ∼280-mer RNA sequences, but at higher concentration of 10 pM. The good discrimination of the position ofcomplementary part in the ∼280-mer RNA sequences was observed with using both types of modifiedelectrodes

Ultrasensitive electrochemical genosensor for direct detection of specific RNA sequences derived from avian influenza viruses present in biological samples

An electrochemical genosensor based on an epoxyphenanthroline–Fe(III)–NH2-ssDNA layer for the detection of RNA derived from Avian Influenza is presented. The biosensor preparation consists of: (I) modification of gold electrodes with aminoethanethiol, (II) modification of the self-assembled monolayer of aminoethanethiol with 5,6-epoxy-5,6-dihydro-[1,10]-phenanthroline using “click” chemistry, (III) a first step of complexation of Fe(III) by 5,6-epoxy-5,6-dihydro-[1,10]-phenanthroline, (IV) a second step of complexation of Fe(III) by 5,6-epoxy-5,6-dihydro-[1,10]-phenanthroline, (V) immobilization of the single stranded amino-DNA probe via “click” chemistry between epoxy and amino groups. The interactions between the ssDNA probe and RNA targets were explored with Osteryoung Square Wave Voltammetry. The genosensor showed a remarkable detection limit of 3 copies/μL (5 aM) for RNA extracted from A/swan/Poland/305/06 (H5N1) containing a fully complementary sequence. A linear dynamic range for this sequence was observed from 3.0×103 to 3.0×105 [copies/μl]. RNA extracted from A/mallard/Poland/446/09 (H7N7), containing a non-complementary sequence, generated a much weaker response. Moreover, the developed genosensor allows to distinguish RNA present in biological samples having 2, 3 and 4 mismatches. This biosensing approach can become a potential alternative tool for detecting RNA samples in biomedical research and early clinical diagnosis of avian influenza viruses

The Kinetics of Primary Alpha Plate Growth in Titanium Alloys

The kinetics of primary alpha-Ti colony/Widmanstatten plate growth from the beta are examined, comparing model to experiment. The plate growth velocity depends sensitively both on the diffusivity D(T) of the rate-limiting species and on the supersaturation around the growing plate. These result in a maxima in growth velocity around 40 K below the transus, once sufficient supersaturation is available to drive plate growth. In Ti-6246, the plate growth velocity was found to be around 0.32 um min-1 at 850 oC, which was in good agreement with the model prediction of 0.36 um min-1 . The solute field around the growing plates, and the plate thickness, was found to be quite variable, due to the intergrowth of plates and soft impingement. This solute field was found to extend to up to 30 nm, and the interface concentration in the beta was found to be around 6.4 at.% Mo. It was found that increasing O content will have minimal effect on the plate lengths expected during continuous cooling; in contrast, Mo approximately doubles the plate lengths obtained for every 2 wt.% Mo reduction. Alloys using V as the beta stabiliser instead of Mo are expected to have much faster plate growth kinetics at nominally equivalent V contents. These findings will provide a useful tool for the integrated design of alloys and process routes to achieve tailored microstructures.Comment: Revised version resubmitted to journa

An electrochemical immunosensor based on a 4,4′-thiobisbenzenethiol self-assembled monolayer for the detection of hemagglutinin from avian influenza virus H5N1

An electrochemical immunosensor for the detection of hemagglutinin from avian influenza virus H5N1 is presented in this paper. The following steps lead up to the construction of immunosensor: (i) modification of gold electrodes with 4,4′-thiobisbenzenethiol, (ii) modification of self-assembled monolayer of 4,4′-thiobisbenzenethiol with gold colloidal nanoparticles, (iii) immobilization of single chain variable fragments of antibodies (scFv) against hemagglutinin H5 via Ssingle bondAu covalent bonds, (iv) blocking of the remaining free space with bovine serum albumin. The interactions between the scFv and hemagglutinin variants have been explored with electrochemical impedance spectroscopy in the presence of [Fe(CN)6]3−/4− as an electroactive marker. The immunosensor was able to detect two different His-tagged variants of recombinant hemagglutinin from H5N1 viruses: the short fragment (17–340 residues) of A/swan/Poland/305-135V08/2006 and the long (17–530 residues) of A/Bar-headed Goose/Qinghai/12/2005. The strongest response has been observed for the long variant with a detection limit of 0.6 pg/mL and a dynamic range from 4.0 to 20.0 pg/mL. The recombinant hemagglutinin (17–527 residues) from A/chicken/Netherlands/1/03 (H7N7), used as the negative control generated a weak response. This confirms the selectivity of the immunsensor proposed. A miniaturized version of the immunosensor, based on screen-printed gold electrodes, was tested with the same set of recombinant hemagglutinins and it achieved a linear range from 1 to 8 pg/mL with a detection limit of 0.9 pg/mL for the long fragment of hemagglutinin

Causative Pathogens of Endophthalmitis after Intravitreal Anti-VEGF Injection: An International Multicenter Study

Purpose: The main objective of this study was to investigate the microbiological spectrum of endophthalmitis after anti- VEGF injections and to compare streptococcal with nonstreptococcus- associated cases with regard to baseline characteristics and injection procedure. Methods: Retrospective,international multicenter study of patients with culture-positive endophthalmitis after intravitreal anti-VEGF injection at 17 different retina referral centers. Results: Eighty-three cases with 87 identified pathogens were included. Coagulasenegative staphylococci (59%) and viridans streptococci (15%) were the most frequent pathogens found. The use of postoperative antibiotics and performance of injections in an operating room setting significantly reduced the rate of streptococcus-induced endophthalmitis cases (p = 0.01 for both). Conclusion: We found a statistically significant lower rate of postinjectional local antibiotic therapy and operating room-based procedures among the streptococcus-induced cases compared to cases caused by other organisms

Ordering and the micromechanics of Ti-7Al

The evolution of intergranular lattice strain in the α titanium alloy Ti–7Al wt% was characterised using in situ time-of-flight (TOF) neutron diffraction during room temperature tensile loading. Samples were aged to promote ordering and the formation of nanometre-scale α2 (Ti3Al). On ageing, at 550°C and 625°C, dislocations were observed to travel in pairs, and in planar arrays, which has been attributed to the presence of ordering. A slight change in c/a was observed, from 1.6949 to 1.6945, and a slight increase in the macroscopic modulus. However, no changes were observed in the residual lattice strains, which are the grain-orientation average elastic strains produced by plasticity. Therefore it is inferred that the changes in deformation mechanisms caused by ordering that result in an enhanced vulnerability to dwell fatigue affect primarily the extent of slip localisation. The overall strain distributions between grains in different orientations are not changed