75 research outputs found
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
DNA probe modified with 3-iron bis(dicarbollide) for electrochemical determination of DNA sequence of Avian Influenza Virus H5N1
An electrochemical immunosensor based on a 4,4′-thiobisbenzenethiol self-assembled monolayer for the detection of hemagglutinin from avian influenza virus H5N1
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