Quantifying the hygroscopic properties of cyclodextrin containing aerosol for drug delivery to the lungs.

Aerosol dynamics is important to quantify in drug delivery to the lungs with the aim of delivering therapeutics to a target location and optimising drug efficacy. The macrocycle (2-hydroxypropyl)-ß-cyclodextrin (2-HP-ß-CD) is thought to alleviate symptoms associated with neurodegenerative diseases when inhaled but the hygroscopic response is not well understood. Here we measure the hygroscopic growth of individual aqueous aerosol containing 2-HP-ß-CD in optical tweezers through analysis of morphology-dependent resonances arising in Raman spectra. Droplets are analysed in the size range of 3-5 µm in radius. The evolving radius and refractive index of each droplet are measured in response to change in relative humidity from 98-20% to determine mass and radius based hygroscopic growth factors, and compared with dynamic vapour sorption measurements. Bulk solution refractive index and density measurements were used in accordance with the self-consistent Lorenz-Lorentz rule to determine melt solute and droplet properties. The refractive index of 2-HP-ß-CD was determined to be 1.520 ± 0.002 with a density of 1.389 ± 0.005 g cm-3. To our knowledge, we show the first aerosol measurements of 2-HP-ß-CD and determine hygroscopicity. By quantifying the hygroscopic growth and physicochemical properties of 2-HP-ß-CD, the impact of aerosol dynamics can be accounted for in tailoring drug formulations and informing models used to predict drug deposition patterns within the respiratory system.

Optical path clearing and enhanced transmission through colloidal suspensions.

We utilize advanced laser fields to clear a path through a dynamic turbid medium, a concept termed "Optical path clearing (OPC)." Particles are evacuated from a volume of the medium using the gradient and/or scattering forces due to an applied laser field with a suitably tailored spatial profile. Our studies encompass both an analytical model and proof-of-principle experiments where paths are cleared in dense bulk colloidal suspensions. Based on our results we suggest that high-performance and high efficiency OPC will be achieved by multiple-step clearing using dynamic laser fields based on Airy or inverted axicon beams.

Longitudinal optical trapping and sizing of aerosol droplets.

We present evidence that aerosol droplets, approximately 1-2microm in diameter, can be optically bound over a 4mm distance within a volume formed by the overlap of the central cores and rings of two counterpropagating Bessel beams. The sizes of the individual polydisperse aerosol particles can be estimated from the angular variation of the elastic light scattering. Scattered light from the two orthogonally polarized trapping beams and from a Gaussian probe beam of different wavelength can be used to provide independent estimations of size. The coalescence of two droplets was observed and characterized.

Optical micromanipulation using supercontinuum Laguerre-Gaussian and Gaussian beams.

We characterize a single beam supercontinuum "white light" trap and determine the trap stiffness in the transverse trapping plane. We realize a holographic white light trapping system using a spatial light modulator, and explore the generation of a dual beam trap and characterize its performance. We also demonstrate optical trapping and rotation of particles using a supercontinuum vortex beam. It is shown that orbital angular momentum can be transferred to spheres trapped in a supercontinuum vortex. Quantified rotation rates are demonstrated.

Enhanced optical guiding of colloidal particles using a supercontinuum light source.

We demonstrate enhanced optical guiding distances for microscopic particles using a supercontinuum light beam. The enhanced spectral bandwidth of the source leads to an elongated focal region. As a result we obtain a significant radial gradient force and axial radiation pressure force over a longer distance when compared to a monochromatic Gaussian beam. The guiding distances of up to 3mm that are observed for micron-sized particles with the supercontinuum beam are approximately twice those observed using continuous wave and femtosecond laser sources when considering beams of equivalent diameter. This guiding scheme is expected to be applicable to colloidal particles, biological cells and cold atom ensembles.

Optically bound microscopic particles in one dimension.

Counterpropagating light fields have the ability to create self-organized one-dimensional optically bound arrays of microscopic particles, where the light fields adapt to the particle locations and vice versa. We develop a theoretical model to describe this situation and show good agreement with recent experimental data [Phys. Rev. Lett. 89, 128301 (2002)] for two and three particles, if the scattering force is assumed to dominate the axial trapping of the particles. The extension of these ideas to two- and three-dimensional optically bound states is also discussed.

One-dimensional optically bound arrays of microscopic particles.

A one-dimensional optically coupled array of colloidal particles is created in a potential well formed by two counterpropagating Gaussian light beams. This array has analogies to linear chains of trapped atomic ions. Breathing modes and oscillations of the center of mass are observed. The stability of the array is in accordance with the Kramers model.

Adjusting the balance in health-care quality.

In an increasingly informed society there has been a growing interest by consumers in evaluating the quality-of-care provided by their practitioners. This task is complicated by an asymmetry in the technical knowledge required to assess health-care quality between consumers and health providers. Recently attempts have been made to incorporate patient views into the assessment of quality to try and address this asymmetry. A number of quality initiatives have been developed to help provide consumers with markers of practitioner competency including professional training programmes and examinations, quality standards and quality assurance activities. International trends include federal funding for quality improvement activities within practices, and greater use of information technology to provide error warning systems for practitioners, to monitor practice patterns, and to promote better communication of information between health services. It is important in developing these new initiatives that 'symmetrical' approaches which capture consumers' views on quality are employed.