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Background and purpose: The magnetic resonance imaging in multiple sclerosis consensus guidelines currently mandate three sagittal non-contrast enhanced sequences of T2-weighted fast spin echo, proton density-weighted fast spin echo and short tau inversion recovery; however, these particular three sequences have not previously been compared at 3T. This study compared T2-weighted fast spin echo, proton density-weighted fast spin echo, short tau inversion recovery as well as the double inversion recovery sequence for the sagittal detection of multiple sclerosis lesions in the cervical spinal cord at 3T. Method(s): Nineteen multiple sclerosis patients underwent magnetic resonance imaging with 3T sagittal T2-weighted fast spin echo, proton density-weighted fast spin echo, short tau inversion recovery and double inversion recovery between November 2012 and April 2013. Two neuroradiologists independently reviewed the images, and the number of lesions detected on each sequence was recorded. Lesion conspicuity was quantitatively assessed with the lesion-to-cord-contrast ratio and lesion contrast-to-noise ratio. The Wilcoxon signed rank test was performed for statistical analysis. Result(s): Proton density-weighted fast spin echo and short tau inversion recovery detected 32% more lesions compared to T2-weighted fast spin echo, and 37% more lesions compared to double inversion recovery. The lesion-to-cord-contrast ratio was highest in short tau inversion recovery, while the lesion contrast-to-noise ratio was highest for proton density-weighted fast spin echo. Conclusion(s): This study provides the necessary evidentiary support at 3T for the magnetic resonance imaging in multiple sclerosis spinal magnetic resonance imaging protocol consensus guidelines. At 3T sagittal proton density-weighted fast spin echo and short tau inversion recovery sequences allowed improved detection of cervical spinal cord multiple sclerosis lesions, compared to T2-weighted fast spin echo and three-di

The detection principle of nanopore sensors relies on measuring changes in electrical signal as analyte molecules translocate through a nanoscale pore. There are two challenges with this experimental construct when using nanopores for quantitative sensing with low detection limits in complex samples. The first is getting the analyte to the nanopore in a reasonable time frame and the second is other species in the sample also translocating through the nanopore and generating erroneous signals. We have developed a nanopore blockade sensor that alleviates the limitations of diffusion-limited mass transport and non-specific signals. Antibody-modified magnetic nanoparticles are utilized to deliver analytes of interest extracted from sample to an array of antibody-modified nanopores under a controlled electromagnet, resulting in long-term nanopore blocking events due to the formation of sandwiched immunocomplexes. Herein, this study reports on understanding some of important parameters in determining the performance of nanopore blockade sensing system, where prostate-specific antigen (PSA) is used as a model analyte. We describe the characterization of nanopore blockade sensing of PSA by (1) tuning on/off the electromagnet, (2) varying nanopore number in a nanopore chip, and (3) deploying the sensor in human plasma. Results show that magnetophoresis effectively facilitates active delivery and selective sensing of PSA to the nanopore. Nanopore chips with a larger number of nanopores are shown to receive more nanopore blockades for a given concentration of analyte. Furthermore, identifiable blockade events accounted for successful detection of PSA in plasma, indicate the high specificity of the sensing system.

Nanopore sensors detect individual species passing through a nanoscale pore. This experimental paradigm suffers from long analysis times at low analyte concentration and non-specific signals in complex media. These limit effectiveness of nanopore sensors for quantitative analysis. Here, we address these challenges using antibody-modified magnetic nanoparticles ((anti-PSA)-MNPs) that diffuse at zero magnetic field to capture the analyte, prostate-specific antigen (PSA). The (anti-PSA)-MNPs are magnetically driven to block an array of nanopores rather than translocate through the nanopore. Specificity is obtained by modifying nanopores with anti-PSA antibodies such that PSA molecules captured by (anti-PSA)-MNPs form an immunosandwich in the nanopore. Reversing the magnetic field removes (anti-PSA)-MNPs that have not captured PSA, limiting non-specific effects. The combined features allow detecting PSA in whole blood with a 0.8 fM detection limit. Our ‘magnetic nanoparticle, nanopore blockade’ concept points towards a strategy to improving nanopore biosensors for quantitative analysis of various protein and nucleic acid species.

Gold-coated magnetic nanoparticles (Au@MNPs) have attracted significant interest in electrochemistry in recent years. This is especially the case with their application as dispersible electrodes where modified Au@MNPs are dispersed into a solution, selectively bind to the analyte of interest and are then brought to an electrode via application of a magnetic field for measurement. This paper characterizes four types of Au@MNPs with different sizes, shapes, and method of synthesis as dispersible electrodes. The Au@MNPs were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy and scanning electron microscopy. In addition, the electrochemical behaviour of Au@MNPs was investigated using cyclic voltammetry. The four sorts of Au@MNPs were evaluated with regards to the three main features required in the dispersible electrodes approach, well-defined morphology, well-defined electrochemistry and fast response to a magnetic field. The Cubic-Au@MNPs, which presents the simplest synthetic route, showed the best electrochemical stability and performance, responding quickly to a magnet and had a well defined shape.

PURPOSE: Double inversion recovery (DIR) brain imaging at 3T has greater diagnostic value in detection of multiple sclerosis (MS) lesions compared to T2-weighted turbo spin-echo (T2-TSE) imaging. Our aim was to compare cervical cord MS lesion detection using 3T sagittal DIR imaging to the sagittal T2-TSE, proton density (PD) and short-tau inversion recovery (STIR) magnetic resonance (MR) sequences recommended by the Consortium of MS Centers. MATERIALS AND METHODS: We prospectively enrolled patients with MS and imaged the cervical cord with 3T sagittal DIR, sagittal and axial T2-TSE, sagittal PD, sagittal STIR and axial multi-echo recombined gradient echo (MERGE) MRI sequences. Two neuroradiologists blinded to clinical and demographic data reviewed the MR images. A definite MS lesion was defined by either detection on 2 sagittal sequences, or if seen on 1 sagittal sequence alone, then by detection of the same lesion by axial T2-TSE or axial MERGE MR imaging. The cervical cord was divided into 13 segments - C1, C1/2, C2, C2/3, C3, C3/4, C4, C4/5, C5, C5/6, C6, C6/7, and C7. For each MR sequence, we analysed the total number of involved cord segments and compared the normalised lesion-to-cord contrast ratio (LCCR) and the contrast-to-noise ratio (CNR). The Wilcoxon signed-rank test was used for statistical correlation. RESULT(S): Nineteen patients (13 females) with mean age of 47 years (range 23-74 years) were included. Eighty percent had definite cervical cord MS lesions. DIR cervical cord imaging detected definite MS lesions in 48 cervical cord segments. PD detected the greatest number of involved cord segments (n=75), significantly greater than DIR (p=0.0005) and T2-TSE (p=0.01), but similar to STIR (p=0.17). STIR and T2-TSE also detected a significantly greater number of involved cord segments than DIR (STIR, n=67;p=0.01 and T2, n=61;p=0.01). The LCCR was highest for STIR; significantly greater than DIR (p=0.0009). The CNR was highest for PD; significantly greater

Herein we combined the use of self-assembled monolayer (SAM) modified electrodes and gold coated magnetic nanoparticles (Au@MNPs) to modulate faradaic electrochemistry when nanoparticles are absorbed on and removed from, a passivated electrode using an external magnetic field. Substantial faradaic electrochemistry of potassium ferricyanide in solution is first prevented by modifying gold electrodes with 11-mercaptoundecanoic acid to form a passivating SAM. Restoration of the faradaic electrochemistry is then achieved by introducing Au@MNPs which are brought to the surface using an external magnetic field. The faradaic electrochemistry can again be suppressed by removing Au@MNPs from the SAM using another external magnetic field.

Purpose: Current MRI guidelines from the Consortium of Multiple Sclerosis Centers recommend the use of both T2 and proton density (PD) weighted sequences in the assessment of multiple sclerosis (MS) spinal cord lesions. However, there is a paucity of literature comparing the utility of these two sequences for spinal cord lesion detection. We sought to compare cervical cord MS lesion detection and conspicuity on sagittal 1.5T PD and T2 weighted MRI. Methods and Materials: Nineteen patients with MS or clinically isolated syndromes were included in this retrospective analysis. All patients were examined with sagittal PD and T2 cervical cord imaging on a 1.5T Siemens Magnetom Avanto MRI scanner with a 4-channel neck matrix coil. Two neuroradiologists identified MS lesions, with consensus agreement for single viewer lesions. Regions of interest were obtained within lesions using the software program, Osirix v3.0.2. Quantitative analysis comparing the normalised lesion-to-cord contrast ratio (LCCR) and the signal-to-noise ratio (SNR) for each sequence was performed using the Wilcoxon rank-sum test, where P < 0.05 was considered statistically significant. Result(s): Fifteen patients were found to have cervical cord lesions - 20 lesions were identified on T2 and 34 lesions on PD weighted imaging. Twenty-two lesions seen on PD imaging were not seen on T2 imaging, and eight lesions seen on T2 imaging were not seen on PD imaging. PD and T2 weighted imaging were comparable for both the LCCR (PD 0.25 +/- 0.02 vs. T2 0.30 +/- 0.03, P = 0.24) and SNR (PD 50.87 +/- 3.80 vs. T2 50.82 +/- 4.50, P = 0.85). Conclusion(s): Although MS lesion conspicuity is similar with both T2 and PD weighted cervical cord MRI, several MS lesions detected on PD weighted imaging were not seen on T2 imaging. For cervical cord MS lesion detection, PD weighted imaging may be superior than T2 weighted imaging.

PURPOSE Double inversion recovery (DIR) has been shown to be more sensitive than T2 turbo spin echo (TSE) and FLAIR for detection of multiple sclerosis (MS) lesions in the brain. However DIR sensitivity in the cervical cord remains unexplored. The cervical cord to C6 is routinely included as part of brain DIR imaging. We hypothesised that detection of cervical cord lesions on brain DIR may mitigate the need for dedicated cervical cord T2/PD imaging. The aim of the study was to compare cervical cord MS lesion detection and conspicuity on sagittal 1.5 T DIR brain to PD TSE and T2 TSE cervical cord imaging. METHODS 40 patients being treated or investigated for MS over a six-month period with brain and cervical cord MRI were included in this retrospective analysis. Sagittal DIR, PD TSE and T2 TSE images were acquired on a 1.5 T Siemens Magnetom Avanto MRI scanner. A head and neck matrix coil combination was utilised for brain DIR, which included the cervical cord to C6. A 4-channel neck matrix coil was employed for PD TSE and T2 TSE sequences. Two neuroradiologists identified MS lesions, with consensus agreement for single viewer lesions. Regions of interest were obtained within lesions using Osirix v3.0.2. Quantitative analysis comparing the normalised lesion-to-cord contrast ratio (LCCR) and the signal-to-noise ratio (SNR) for each sequence was performed using sample T-tests, where P>0.05 was considered statistically significant. RESULTS 81 cervical cord lesions were detected in 19 patients - 25 on DIR, 25 on T2 TSE and 31 on PD TSE. Five patients with positive T2 TSE scans had negative DIR imaging. Compared to PD and T2, DIR had greater LCCR (DIR 1.51+/-0.09 vs. PD TSE 0.26+/-0.02, P<0.0001; DIR vs. T2 TSE 0.30+/-0.03, P<0.0001), and higher SNR (DIR 126.90+/-5.94 vs. PD TSE 52.63+/-4.00, P<0.0001; DIR vs. T2 TSE 53.02+/-4.99, P<0.0001). CONCLUSIONS DIR detected lesions demonstrate superior contrast resolution and SNR compared to T2 TSE and PD TSE imaging. However mul

A simple and economical process for fabricating gold electrodes on paper is presented. Gold nanoparticles stabilised with 4-(dimethylamino)pyridine were applied to nail-polish coated filter paper and made conductive using a camera flash sintering step. To test the ability of the sintered gold nanoparticle film to function as a sensing platform, cysteine was self-assembled on gold and used for the electrochemical determination of copper ions. The cysteine-sintered gold nanoparticle film was able to successfully complex copper ions, with only minor differences in performance compared with a standard cysteine-modified solid-state gold disk electrode. Investigations by Raman spectroscopy revealed the successful removal of the 4-(dimethylamino)pyridine coating during sintering, whereas electrochemical impedance spectroscopy and scanning electron microscopy suggested that differences in the sensing performance could be attributed to the rougher morphology of the sintered gold nanoparticle electrode. © The Royal Society of Chemistry 2013.