Vascular retinal biomarkers improves the detection of the likely cerebral amyloid status from hyperspectral retinal images.

Introduction: This study investigates the relationship between retinal image features and β-amyloid (Aβ) burden in the brain with the aim of developing a noninvasive method to predict the deposition of Aβ in the brain of patients with Alzheimer's disease.

Methods: Retinal images from 20 cognitively impaired and 26 cognitively unimpaired cases were acquired (3 images per subject) using a hyperspectral retinal camera. The cerebral amyloid status was determined from binary reads by a panel of 3 expert raters on F-florbetaben positron-emission tomography (PET) studies.

Non-invasive in vivo hyperspectral imaging of the retina for potential biomarker use in Alzheimer's disease.

Studies of rodent models of Alzheimer's disease (AD) and of human tissues suggest that the retinal changes that occur in AD, including the accumulation of amyloid beta (Aβ), may serve as surrogate markers of brain Aβ levels. As Aβ has a wavelength-dependent effect on light scatter, we investigate the potential for in vivo retinal hyperspectral imaging to serve as a biomarker of brain Aβ. Significant differences in the retinal reflectance spectra are found between individuals with high Aβ burden on brain PET imaging and mild cognitive impairment (n = 15), and age-matched PET-negative controls (n = 20).

Hyperspectral multiplex single-particle tracking of different receptor subtypes labeled with quantum dots in live neurons.

The efficacy of existing therapies and the discovery of innovative treatments for central nervous system (CNS) diseases have been limited by the lack of appropriate methods to investigate complex molecular processes at the synaptic level. To improve our capability to investigate complex mechanisms of synaptic signaling and remodeling, we designed a fluorescence hyperspectral imaging platform to simultaneously track different subtypes of individual neurotransmitter receptors trafficking in and out of synapses. This imaging platform allows simultaneous image acquisition of at least five fluorescent markers in living neurons with a high-spatial resolution.

Preliminary investigation of multispectral retinal tissue oximetry mapping using a hyperspectral retinal camera.

Oximetry measurement of principal retinal vessels represents a first step towards understanding retinal metabolism, but the technique could be significantly enhanced by spectral imaging of the fundus outside of main vessels. In this study, a recently developed Hyperspectral Retinal Camera was used to measure relative oximetric (SatO2) and total hemoglobin (HbT) maps of the retina, outside of large vessels, in healthy volunteers at baseline (N = 7) and during systemic hypoxia (N = 11), as well as in patients with glaucoma (N = 2). Images of the retina, on a field of view of ∼30°, were acquired between 500 and 600 nm with 2 and 5 nm steps, in under 3 s.

A prototype hyperspectral system with a tunable laser source for retinal vessel imaging.

Purpose: To describe the technology and determine the within-session repeatability of manual retinal reflectance measurements of arterioles and venules using a prototype hyperspectral retinal camera.

Methods: Six healthy young volunteers (three males, average age 26 ± 4 years) had five repeated sets of retinal images captured between 500 and 600 nm at 5-nm intervals using a newly developed hyperspectral retinal camera. Optical densities were manually extracted for first-degree arterioles and venules and the repeatability of retinal reflectance was compared sequentially.

Nanonization of megestrol acetate by laser fragmentation in aqueous milieu.

Nanonization is a simple and effective method to improve dissolution rate and oral bioavailability of drugs with poor water solubility. There is growing interest to downscale the nanocrystal production to enable early preclinical evaluation of new drug candidates when compound availability is scarce. The purpose of the present study was to investigate laser fragmentation to form nanosuspensions in aqueous solution of the insoluble model drug megestrol acetate (MA) using very little quantities of the drug.

Fabrication of paclitaxel nanocrystals by femtosecond laser ablation and fragmentation.

Nanonization, which involves formulating the drug powder as nanometer-sized particles, is a known method to improve drug absorption and allow the intravenous administration of insoluble drugs. This study investigated a novel femtosecond (fs) laser technique for the fabrication of nanocrystals in aqueous solution of the insoluble model drug paclitaxel. Two distinct methods of this technology, ablation and fragmentation, were investigated and the influence of laser power, focusing position and treatment time on the particle size, drug concentration, and degradation was studied.

Reverse iontophoresis of amino acids: identification and separation of stratum corneum and subdermal sources in vitro.

Purpose: To differentiate the stratum corneum (SC) and subdermal sources of amino acids (AAs) extracted by reverse iontophoresis.

Methods: 13 zwitterionic AAs were quantified in this in vitro study. Repetitive tape-stripping permitted the distribution of the analytes to be determined in the SC.

In vitro optimization of dexamethasone phosphate delivery by iontophoresis.

Background And Purpose: This study was designed to evaluate the effects of competing ions and electroosmosis on the transdermal iontophoresis of dexamethasone phosphate (Dex-Phos) and to identify the optimal conditions for its delivery.

Methods: The experiments were performed using pig skin, in side-by-side diffusion cells (0.78 cm(2)), passing a constant current of 0.

Stabilization and size control of gold nanoparticles during laser ablation in aqueous cyclodextrins.

Femtosecond laser radiation has been used to ablate a gold target in aqueous beta-cyclodextrin (CD) solutions to produce stable gold nanoparticle colloids with extremely small size (2 to 2.4 nm) and size dispersion (1 to 1.5 nm).