Raman spectroscopic identification of size-selected airborne particles for quantitative exposure assessment

In this paper we present a method for the quantification of chemically distinguished airborne particulate matter, required for health risk assessment. Rather than simply detecting chemical compounds in a sample, we demonstrate an approach for the quantification of exposure to airborne particles and nanomaterials. In line with increasing concerns over the proliferation of engineered particles we consider detection of synthetically produced ZnO crystals. A multi-stage approach is presented whereby the particles are first aerodynamically size segregated from a lab-generated single component aerosol in an impaction sampler. These size fractionated samples are subsequently analysed by Raman spectroscopy. Imaging analysis is applied to Raman spatial maps to provide chemically specific quantification of airborne exposure against background which is critical for health risk evaluation of exposure to airborne particles. Here we present a first proof-of-concept study of the methodology utilising particles in the 2-4 μm aerodynamic diameter range to allow for validation of the approach by comparison to optical microscopy. The results show that the combination of these techniques provides independent size and chemical discrimination of particles. Thereby a method is provided to allow quantitative and chemically distinguished measurements of aerosol concentrations separated into exposure relevant size fractions. © 2016 IOP Publishing Ltd

Nanomedicines and microneedles: a guide to their analysis and application

The fast-advancing progress in the research of nanomedicine and microneedles application in the past two decades have suggested that the combination of the two concepts could help to overcome some of the challenges we are facing in healthcare. These include poor patient compliance with medication and the lack of appropriate administration forms that enable the optimal dose to reach the target site. Nanoparticles as drug vesicles can protect their cargo and deliver it to the target site, while evading the body’s defence mechanisms. Unfortunately, despite intense research on nanomedicine in the past 20 years, we still haven’t answered some crucial questions, e.g. about their colloidal stability in solution and their optimal formulation, which makes the translation of this exciting technology from lab bench to a viable product difficult. Dissolvable microneedles could be an effective way to maintain and stabilise nano-sized formulations, whilst enhancing the ability of nanoparticles to penetrate the stratum corneum barrier. Both concepts have been individually investigated fairly well and many analytical techniques for tracking the fate of the nanomaterial with their precious cargo, both in vitro and in vivo, have been established. Yet, to the best of our knowledge, a comprehensive overview of the analytical tools encompassing the concepts of microneedles and nanoparticles with specific and successful examples is missing. In this review, we have attempted to briefly analyse the challenges associated with nanomedicine itself but crucially, we provide an easy-to-navigate scheme of methods, suitable for characterisation and imaging the physico-chemical properties of the material matrix

Application of OCT to examination of easel paintings

We present results of applying low coherence interferometry to gallery paintings. Infrared low coherence interferometry is capable of non-destructive examination of paintings in 3D, which shows not only the structure of the varnish layer but also the paint layers

Quantitative assessment of rat bone regeneration using complex master-slave optical coherence tomography

Background: The need for hard and soft tissues in oral implantology determined the development of methods and techniques to increase bone volume and their quality with different alternative materials used as substituents of patient’s natural bone. In addition, laser radiation can be used to accelerate the repair of fractures and to produce an increased volume of formed callus, as well as an increased bone mineral density. Methods: The aim of this work is to evaluate the capability of an in-house developed multimodal complex master slave (CMS) enhanced swept source (SS) optical coherence tomography (OCT) imaging instrument to analyze the increase in the quantity and the improvement of the quality of newly-formed bone using low level laser therapy (LLLT). Bone formation is quantitatively assessed in 5 mm cylindrical defects made in the calvaria part of the skull of living rats. Samples are divided in three study groups: A, a negative control group, for which the natural healing process of the defect is investigated; B, a positive control group, for which bovine graft is used to stimulate bone formation, and C, a study group, in which bovine graft is added to the created defects and LLLT is applied throughout the entire healing period. The animals are sacrificed after 14, 21, and 30 days, and the samples are imaged using the multimodal CMS/SS-OCT instrument. Results: The method allows for the simultaneous monitoring of the bone tissue via two perpendicular cross-sections and nine en-face images taken at adjustable depths into the sample. A global image with course axial resolution allows for the positioning of the field-of-view of the system on the area of interest on the tissue. The quantitative assessment of the process of bone formation is completed using the differences in brightness between the native bone, the artificial bone graft, and the newly-formed bone. Conclusions: Group C is demonstrated to have a higher volume of newly-formed bone than Group B, which is better from this point of view than Group A. By analyzing the evolution of this volume of new bone in time, the most significant difference was after 21 days, therefore approximately after two thirds of the total time interval analyzed. After 30 days, the volumes of bone tend to move closer, as they begin to fill the available gap. The study demonstrates that OCT can assess quantitatively the positive impact of LLLT on bone regeneration

Mathematical Modelling of Optical Coherence Tomography

In this chapter a general mathematical model of Optical Coherence Tomography (OCT) is presented on the basis of the electromagnetic theory. OCT produces high resolution images of the inner structure of biological tissues. Images are obtained by measuring the time delay and the intensity of the backscattered light from the sample considering also the coherence properties of light. The scattering problem is considered for a weakly scattering medium located far enough from the detector. The inverse problem is to reconstruct the susceptibility of the medium given the measurements for different positions of the mirror. Different approaches are addressed depending on the different assumptions made about the optical properties of the sample. This procedure is applied to a full field OCT system and an extension to standard (time and frequency domain) OCT is briefly presented.Comment: 28 pages, 5 figures, book chapte

Research activities arising from the University of Kent

In this paper I describe research activities in the field of optical fiber sensing undertaken by me after leaving the Applied Optics Group at the University of Kent. The main topics covered are long period gratings, neural network based signal processing, plasmonic sensors, and polymer fiber gratings. I also give a summary of my two periods of research at the University of Kent, covering 1985–1988 and 1991–2001

Are Compression Stockings an Effective Treatment for Orthostatic Presyncope?

Syncope, or fainting, affects approximately 6.2% of the population, and is associated with significant comorbidity. Many syncopal events occur secondary to excessive venous pooling and capillary filtration in the lower limbs when upright. As such, a common approach to the management of syncope is the use of compression stockings. However, research confirming their efficacy is lacking. We aimed to investigate the effect of graded calf compression stockings on orthostatic tolerance

MASked-unconTrolled hypERtension management based on office BP or on ambulatory blood pressure measurement (MASTER) Study: a randomised controlled trial protocol.

Masked uncontrolled hypertension (MUCH) carries an increased risk of cardiovascular (CV) complications and can be identified through combined use of office (O) and ambulatory (A) blood pressure (BP) monitoring (M) in treated patients. However, it is still debated whether the information carried by ABPM should be considered for MUCH management. Aim of the MASked-unconTrolled hypERtension management based on OBP or on ambulatory blood pressure measurement (MASTER) Study is to assess the impact on outcome of MUCH management based on OBPM or ABPM

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe

Effect of Systemic Hypertension With Versus Without Left Ventricular Hypertrophy on the Progression of Atrial Fibrillation (from the Euro Heart Survey).

Hypertension is a risk factor for both progression of atrial fibrillation (AF) and development of AF-related complications, that is major adverse cardiac and cerebrovascular events (MACCE). It is unknown whether left ventricular hypertrophy (LVH) as a consequence of hypertension is also a risk factor for both these end points. We aimed to assess this in low-risk AF patients, also assessing gender-related differences. We included 799 patients from the Euro Heart Survey with nonvalvular AF and a baseline echocardiogram. Patients with and without hypertension were included. End points after 1 year were occurrence of AF progression, that is paroxysmal AF becoming persistent and/or permanent AF, and MACCE. Echocardiographic LVH was present in 33% of 379 hypertensive patients. AF progression after 1 year occurred in 10.2% of 373 patients with rhythm follow-up. In hypertensive patients with LVH, AF progression occurred more frequently as compared with hypertensive patients without LVH (23.3% vs 8.8%, p = 0.011). In hypertensive AF patients, LVH was the most important multivariably adjusted determinant of AF progression on multivariable logistic regression (odds ratio 4.84, 95% confidence interval 1.70 to 13.78, p = 0.003). This effect was only seen in male patients (27.5% vs 5.8%, p = 0.002), while in female hypertensive patients, no differences were found in AF progression rates regarding the presence or absence of LVH (15.2% vs 15.0%, p = 0.999). No differences were seen in MACCE for hypertensive patients with and without LVH. In conclusion, in men with hypertension, LVH is associated with AF progression. This association seems to be absent in hypertensive women