Plasmonic heating of gold nanoparticles and its exploitation

Nanoscale particles of metals such as gold can interact with light by means of a plasmon resonance, even though they are much smaller than the wavelengths of visible light. The proportions of light that are absorbed and scattered vary with wavelength. Any light that is absorbed will cause heating of the particles, and this effect may potentially be exploited for solar glazing coatings, nanoscale lithography or medical treatments. The position of maximum absorption of an isolated spherical nanoparticle is 518 nm, but this may be significantly red-shifted by means of decreasing the symmetry to an prolate spheroid or 'nanorod', or by producing a metal 'nanoshell' on a dielectric core, or by aggregating insulated spherical particles. Absorption peaks in the vicinity of 655 nm for aggregated particles and 780 nm for prolate spheroids are demonstrated here. Absorbed energy is released as heat into the environment of the particles, and will cause a temperature rise within the particle the magnitude of which depends upon the value of the effective heat transfer coefficient between particle and environment. The latter is not known, but we show how highly localized temperature rises of some tens of Celsius might be conceivable in systems illuminated by sunlight

Modelling and verification of the electrical properties of organic dielectric monolayers in capacitive configurations

The possible role of self-assembled monolayers (SAMs) as the dielectric component of nanoscale capacitors is considered. SAMs of two rather different molecules, α,α-p-xylyldithiol ('XYL') and dodecanedithiol ('C12') were produced on a gold {111} substrate, and characterized with respect to their conductivity. The data were fitted with a double tunnel barrier model, in which the two SAMs are primarily differentiated by barrier height and thickness with that of XYL having a thickness of 1.0 nm and a barrier height of 0.78 eV compared to 1.69 nm and 1.39 eV for C12. The remaining parameters of the model were determined by Monte Carlo optimization. Assuming perfect connection of top and bottom electrodes, the leakage current through the XYL at 1 volt is calculated to be 1.4×105 A/cm2, compared to 2.7×104 A/cm2 through C12. These values are not as low as can be obtained with SiO2 of the same thickness. However, SAMs are readily and precisely produced by simple, low temperature processes, a factor which may allow them a niche in the future

How reliable are scanning tunneling microscopy measurements of electron transport in molecules ?

Scanning tunneling microscopy measurements of tunneling through molecules adsorbed on a surface have been simulated using a standard empirical model based upon the Wentzel-Kramer-Brillouin method applied to tunneling through a barrier. The Gaussian noise inherent in these experiments has been added to the model data using a Monte Carlo technique. By generating multiple sets of current-voltage curves and fitting these to the model we have evaluated how reliably barrier height can be determined as a function of noise level. The results suggest that for constant percentage standard deviation in the noise greater than 5% the barrier height cannot be determined reliably. At this level, the standard deviation in the estimate of the barrier height is about 10%. Weighted fits give more reliable estimates of the barrier height. If the height of the tip above the molecule is known, so that the fit is only a single parameter the barrier height can be determined reliably even at percentage noise levels as high as 20%. However, in this case unweighted fits must be used otherwise the estimated value deviates by up to 15% from the true value. Data with constant absolute noise give similar results. The effects of experimental resolution have been evaluated in a similar manner and are shown to have a significant influence on the reliability. At a resolution of about 0.1% of full scale the standard deviation in the estimate of barrier height is only about 2% but increases rapidly to 10% for a resolution of about 1%

Improved efficacy of a dendritic cell-based vaccine against a murine model of colon cancer: The helper protein effect

Purpose Targeted immunotherapy using dendritic cells (DCs) has been employed in numerous investigations aiming at combating neoplasms. We previously showed that copulsing of an antigen with a helper protein could considerably enhance antigen presenting capacity of ex vivo-generated DCs. In this study, we attempted to administer an effective treatment in a murine model of colon cancer with DCs pulsed with the mixture of a tumor-specific gp70-derived peptide (AH1) and a helper protein, ovalbumin (OVA). Materials and Methods First, the presence of gp70 in CT26 tumor cells and tumor tissues was verified using immunofluorescence and Western blot analyses. Next, DCs were purified from normal mice, loaded ex vivowith AH1 and OVA (DC-Pep-OVA), and injected into tumor-bearing mice. Tumor volume, in vitro antigen (Ag)-specific proliferation of splenic cells, and survival rate were measured to determine the efficacy of DC-Pep-OVA. As the control groups, tumor-bearing mice were vaccinated with DC-Pep, unpulsed DC, and DCs loaded with a mixture of OVA and an irrelevant peptide (P15), or were not vaccinated at all. Results DC-Pep-OVA showed superior efficacy over other groups, as indicated by smaller tumor volume, higher Ag-specific proliferation rate of splenic cells, and prolonged survival. Conclusion Overall, in the present study we showed for the first time that DCs copulsed with AH1 (tumor Ag) and OVA (helper molecule) could be considered as potentially robust weapons for use in future antitumor immunotherapies. © 2015 by the Korean Cancer Association

Label-free nanometer-resolution imaging of biological architectures through surface enhanced raman scattering

Label free imaging of the chemical environment of biological specimens would readily bridge the supramolecular and the cellular scales, if a chemical fingerprint technique such as Raman scattering can be coupled with super resolution imaging. We demonstrate the possibility of label-free super-resolution Raman imaging, by applying stochastic reconstruction to temporal fluctuations of the surface enhanced Raman scattering (SERS) signal which originate from biomolecular layers on large-area plasmonic surfaces with a high and uniform hot-spot density (>1011/cm2, 20 to 35 nm spacing). A resolution of 20 nm is demonstrated in reconstructed images of self-assembled peptide network and fibrilated lamellipodia of cardiomyocytes. Blink rate density is observed to be proportional to the excitation intensity and at high excitation densities (>10 kW/cm2) blinking is accompanied by molecular breakdown. However, at low powers, simultaneous Raman measurements show that SERS can provide sufficient blink rates required for image reconstruction without completely damaging the chemical structure

Label-Free Nanometer-Resolution Imaging of Biological Architectures through Surface Enhanced Raman Scattering

Label free imaging of the chemical environment of biological specimens would readily bridge the supramolecular and the cellular scales, if a chemical fingerprint technique such as Raman scattering can be coupled with super resolution imaging. We demonst

The International comparison of Systems of care and patient outcomes In minor Stroke and Tia (InSIST) study: A community-based cohort study

This is the author accepted manuscript. The final version is available from Sage Publications via the DOI in this record.Rationale: Rapid response by health-care systems for transient ischemic attack and minor stroke (TIA/mS) is recommended to maximize the impact of secondary prevention strategies. The applicability of this evidence to Australian non-hospital-based TIA/mS management is uncertain. Aims: Within an Australian community setting we seek to document processes of care, establish determinants of access to care, establish attack rates and determinants of recurrent vascular events and other clinical outcomes, establish the performance of ABC2-risk stratification, and compare the processes of care and outcomes to those in the UK and New Zealand for TIA/mS. Sample size estimates: Recruiting practices containing approximately 51 full-time-equivalent general practitioners to recruit 100 TIA/mS per year over a four-year study period will provide sufficient power for each of our outcomes. Methods and design: An inception cohort study of patients with possible TIA/mS recruited from 16 general practices in the Newcastle-Hunter Valley-Manning Valley region of Australia. Potential TIA/mS will be ascertained by multiple overlapping methods at general practices, after-hours collaborative, and hospital in-patient and outpatient services. Participants’ index and subsequent clinical events will be adjudicated as TIA/mS or mimics by an expert panel. Study outcomes: Process outcomes—whether the patient was referred for secondary care; time from event to first patient presentation to a health professional; time from event to specialist acute-access clinic appointment; time from event to brain and vascular imaging and relevant prescriptions. Clinical outcomes—recurrent stroke and major vascular events; and health-related quality of life. Discussion: Community management of TIA/mS will be informed by this study.Nationale Health and Medical Research Council (NHMRC

The characteristics of patients with possible Transient Ischemic Attack and Minor Stroke in the Hunter and Manning Valley regions, Australia (the INSIST Study)

This is the final version. Available on open access from the American Academy of Neurology via the DOI in this record. Background: Transient ischemic attack (TIA) and minor stroke (TIAMS) are risk factors for stroke recurrence. Some TIAMS may be preventable by appropriate primary prevention. We aimed to recruit “possible-TIAMS” patients in the INternational comparison of Systems of care and patient outcomes In minor Stroke and TIA (INSIST) study. Methods: A prospective inception cohort study performed across 16 Hunter–Manning region, Australia, general practices in the catchment of one secondary-care acute neurovascular clinic. Possible-TIAMS patients were recruited from August 2012 to August 2016. We describe the baseline demographics, risk factors and pre-event medications of participating patients. Results: There were 613 participants (mean age; 69 ± 12 years, 335 women), and 604 (99%) were Caucasian. Hypertension was the most common risk factor (69%) followed by hyperlipidemia (52%), diabetes mellitus (17%), atrial fibrillation (AF) (17%), prior TIA (13%) or stroke (10%). Eighty-nine (36%) of the 249 participants taking antiplatelet therapy had no known history of cardiovascular morbidity. Of 102 participants with known AF, 91 (89%) had a CHA2DS2-VASc score ≥ 2 but only 47 (46%) were taking anticoagulation therapy. Among 304 participants taking an antiplatelet or anticoagulant agent, 30 (10%) had stopped taking these in the month prior to the index event. Conclusion: This study provides the first contemporary data on TIAMS or TIAMS-mimics in Australia. Community and health provider education is required to address the under-use of anticoagulation therapy in patients with known AF, possibly inappropriate use of antiplatelet therapy and possibly inappropriate discontinuation of antiplatelet or anticoagulation therapy.National Health and Medical Research Counci

One-year risk of stroke after transient ischemic attack or minor stroke in Hunter New England, Australia (INSIST Study)

Background: One-year risk of stroke in transient ischemic attack and minor stroke (TIAMS) managed in secondary care settings has been reported as 5–8%. However, evidence for the outcomes of TIAMS in community care settings is limited. Methods: The INternational comparison of Systems of care and patient outcomes In minor Stroke and TIA (INSIST) study was a prospective inception cohort community-based study of patients of 16 general practices in the Hunter–Manning region (New South Wales, Australia). Possible-TIAMS patients were recruited from 2012 to 2016 and followed-up for 12 months post-index event. Adjudication as TIAMS or TIAMS-mimics was by an expert panel. We established 7-days, 90-days, and 1-year risk of stroke, TIA, myocardial infarction (MI), coronary or carotid revascularization procedure and death; and medications use at 24 h post-index event. Results: Of 613 participants (mean age; 70 ± 12 years), 298 (49%) were adjudicated as TIAMS. TIAMS-group participants had ischemic strokes at 7-days, 90-days, and 1-year, at Kaplan-Meier (KM) rates of 1% (95% confidence interval; 0.3, 3.1), 2.1% (0.9, 4.6), and 3.2% (1.7, 6.1), respectively, compared to 0.3, 0.3, and 0.6% of TIAMS-mimic-group participants. At one year, TIAMS-group-participants had twenty-five TIA events (KM rate: 8.8%), two MI events (0.6%), four coronary revascularizations (1.5%), eleven carotid revascularizations (3.9%), and three deaths (1.1%), compared to 1.6, 0.6, 1.0, 0.3, and 0.6% of TIAMS-mimic-group participants. Of 167 TIAMS-group participants who commenced or received enhanced therapies, 95 (57%) were treated within 24 h post-index event. For TIAMS-group participants who commenced or received enhanced therapies, time from symptom onset to treatment was median 9.5 h [IQR 1.8–89.9]. Conclusion: One-year risk of stroke in TIAMS participants was lower than reported in previous studies. Early implementation of antiplatelet/anticoagulant therapies may have contributed to the low stroke recurrence