Study of the pO2-Sensitivity of the Dendrimeric and Free Forms of Pd-meso-tetra(4-carboxyphenyl)porphyrin, Incorporated or not in Chitosan-Based Nanoparticles

The concentration of oxygen and its rate of consumption are important factors in certain medical treatments, such as radiotherapy and photodynamic therapy (PDT). Measuring the tissue concentration of oxygen or its partial pressure (pO2) can be achieved by taking advantage of the oxygen-dependent luminescence lifetime of certain molecules, including metallo-porphyrin derivatives, due to the oxygen-dependent quenching of their triplet state. Unfortunately, most of these porphyrin derivatives are phototoxic due to the O21? produced in the pO2 measurement procedure. The aim of this work was to characterize new nanoparticle oxygen sensors, where the palladium-porhyrin molecule (Pd-meso-tetra(4-carboxyphenyl)porphyrin) or its dendrimer form, is incorporated into an oxygen permeable matrix of chitosan-based colloidal particles. It was hypothesized that the reactive O21? produced during the pO2 measurement would react inside the particle thus reducing its toxicity for the surrounding tissue, whereas the 3? ground state of O2, that is to be measured, would diffuse freely in the peptide. We observed that the incorporation of the porphyrin in the nanoparticles resulted in a reduction of the phosphorescence lifetime sensitivity to pO2 by about one order of magnitude. Our studies of these new sensors indicate that the oxygen concentration can be measured in aqueous solutions with a precision of ±20% for oxygen concentrations ranging between 0% and 25%

Vascular regrowth following photodynamic therapy in the chicken embryo chorioallantoic membrane

Photodynamic therapy (PDT) induces damage to the endothelium, which can lead to increased vascular permeability and, under intensive PDT conditions, even to platelet aggregation, vasoconstriction, and blood flow stasis. Eventually, ischemia, hypoxia, and inflammation can occur, resulting in angiogenesis. We studied the sequence of the vascular events after Visudyne®-PDT in the chicken chorioallantoic membrane (CAM) at day 11 of development. Using epi-fluorescence microscopy, we monitored the regrowth of capillaries in the PDT treated area. Immediately after irradiation, the treatment resulted in blood flow arrest. And 24h post PDT, sprouting of new blood vessels was observed at the edge of the PDT zone. Neovessels looping out from the edge of the PDT zone gave rise to specialized endothelial tip structures guiding the vessels towards the center of the treated area. At 48h almost all of the treated area was repopulated with functional but morphologically altered vasculature. These observations also showed reperfusion of some of the vessels that had been closed by the PDT treatment. CAM samples were immunohistochemically stained for Ki-67 showing proliferation of endothelial cells in the PDT area. Also, several markers of immature and angiogenic blood vessels, such as αVβ3-integrin, vimentin and galectin-1, were found to be enhanced in the PDT area, while the endothelial maturation marker intercellular adhesion molecule (ICAM)-1 was found to be suppressed. These results demonstrate that the new vascular bed is formed by both neo-angiogenesis and reperfusion of existing vessels. Both the quantitative real-time RT-PCR profile and the response to pharmacological treatment with Avastin®, an inhibitor of angiogenesis, suggest that angiogenesis occurs after PDT. The observed molecular profiling results and the kinetics of gene regulation may enable optimizing combination therapies involving PDT for treatment of cancer and other disease

Quantitative Diffuse Reflectance and Diffuse Transmittance Infrared Spectroscopy of Surface-Derivatized Silica Powders

Absolute diffuse reflectance and transmittance FT-IR spectra of optically thin layers of surface-derivatized silica powders are measured, using a photopyroelectric detector placed in direct contact with the sample. The role of inhomogeneities in the surface of the powder for quantitativediffuse reflectance and transmittance measurements is examined. It is found to be equally important and nonnegligible for both sampling methods. Diffuse transmittance is shown to be more sensitive to changes of the depth of the layer than diffuse reflectance. The effect of the pressure applied to the sample surface on the scatteringcoefficient of two types of silica powders of different morphologies is demonstrated. A new analytical procedure based on DRIm spectrometry is applied to the quantitative study of the influence of the chemical environment of a cyano functional group covalently linked to the silica surface on its molar extinction coefficient

Ozone LIDAR as an Analytical Tool in Effective Air Pollution Management: The Geneva 96 Campaign

The LIDAR (LIght Detection And Ranging) technique has developed into one of the practical high performance techniques for conducting air quality and meteorological measurements. DIfferential Absorption Lidar (DIAL) is used for measuring trace gases, including pollutants like ozone at low concentrations. Multiple wavelengths backscatter and depolarization measurements give information about particles in the atmosphere, and single wavelength lidar can be used for meteorological measurements like wind velocity and temperature. Range resolved in situ data obtained by lidar can play a significant role in our understanding of the air quality in the planetary boundary layer, particularly when applied in conjunction with air quality models. This is because DIAL can be used to measure concentrations in three dimensions in real time with a spatial resolution that corresponds well to that used in the model calculations. Thus one obtains an advantage when comparing with point measurements at or near ground level which are often perturbed by local emissions. A summary of the lidar principle is presented here, followed by different examples of vertical ozone profiles and time series obtained with a new optical layout of the EPFL-LPAS DIAL system using dual telescope detection. These data were obtained during the summer 96 field campaign in the Geneva area. Results are then compared with the mesoscale Eulerian model calculations performed in our laboratory. The overall results provide new insight into air pollution dynamics in the Geneva area and calculations are under way, using the model adjusted by the measurements, to optimize air pollution abatement strategies under certain atmospheric conditions in this part of Switzerland

Autofluorescence bronchoscopy: quantification of inter-patient variations of fluorescence intensity

Autofluorescence (AF) from bronchial tissue is increasingly used for the endoscopic detection of early bronchial neoplasia. Several imaging systems are commercially available, all detecting the absolute or relative AF intensity and/or spectral contrasts between normal tissue and early neoplastic lesions. These devices have a high sensitivity for flat neoplasia, but the specificity remains limited. Variations in the AF intensity between individuals (inter-patient variations) is considered one of the most limiting factors. In the clinical study presented here, we quantified those variations using a non-invasive optical reference positioned in situ during AF bronchoscopy. The inter-patient variations in intensity on the main carina were in the order of 25- 30%. The results of this study are quite useful for improving and defining the design of the optical features (dynamic range, physical sensitivity) of AF detection systems

Total VOC reactivity in the planetary boundary layer: 2. A new indicator for determining the sensitivity of the ozone production to VOC and NO

A new indicator is proposed for determining if tropospheric ozone production in a specifiacr eai s limitedb yV OC or NOx.T he indicato1r 9= r•ø•C/•oød•Xes cribeths e ratio of the lifetimes of OH against the losses by reacting with VOC and NOx. Whereas •oøx• c anb e obtainebdy c onventionmale asurementthse, n ewp umpa ndp robeO H approach which is described in part one of this publication makes it now possible to obtain also ß_ov •o c ßI ndicator values above a thresholdv alue of 0.2 __+50 % are representativeo f NOx-saturatedc onditionsw here an increaseo f NOx emissionsc auses lower ozone production.F or valuesb elow 0.01 the ozone productioni s very insensitivet o changeso f VOC emissionsT. he robustnesso f this indicator againsts everalp arameters sucha s temperature,h umidity,p hotolysisa, nd initial ozone concentrationsis tested in a box model and comparedt o the robustnesso f other earlier proposedi ndicators.I n contrast to earlier proposed indicators, this new one is not based on photochemically producedl ong-liveds peciesb ut describest he instantaneousr egime of an air parcel. Three-dimensionasl imulations howst hat this indicator is quite successfuiln estimatingt he impact of increasedo r reducede missionso n the ozone concentrationsfo r each location in the modeling area. This will make it a very helpful tool for developing ozone abatement strategies

Photodynamic drug delivery enhancement in tumours does not depend on leukocyte-endothelial interaction in a human mesothelioma xenograft model†

OBJECTIVES The pre-treatment of tumour neovessels by low-level photodynamic therapy (PDT) improves the distribution of concomitantly administered systemic chemotherapy. The mechanism by which PDT permeabilizes the tumour vessel wall is only partially known. We have recently shown that leukocyte-endothelial cell interaction is essential for photodynamic drug delivery to normal tissue. The present study investigates whether PDT enhances drug delivery in malignant mesothelioma and whether it involves comparable mechanisms of actions. METHODS Human mesothelioma xenografts (H-meso-1) were grown in the dorsal skinfold chambers of 28 nude mice. By intravital microscopy, the rolling and recruitment of leukocytes were assessed in tumour vessels following PDT (Visudyne® 400μg/kg, fluence rate 200mW/cm2and fluence 60J/cm2) using intravital microscopy. Likewise, the distribution of fluorescently labelled macromolecular dextran (FITC-dextran, MW 2000kDa) was determined after PDT. Study groups included no PDT, PDT, PDT plus a functionally blocking anti-pan-selectin antibody cocktail and PDT plus isotype control antibody. RESULTS PDT significantly enhanced the extravascular accumulation of FITC-dextran in mesothelioma xenografts, but not in normal tissue. PDT significantly increased leukocyte-endothelial cell interaction in tumour. While PDT-induced leukocyte recruitment was significantly blunted by the anti-pan-selectin antibodies in the tumour xenograft, this manipulation did not affect the PDT-induced extravasation of FITC-dextran. CONCLUSIONS Low-level PDT pre-treatment selectively enhances the uptake of systemically circulating macromolecular drugs in malignant mesothelioma, but not in normal tissue. Leukocyte-endothelial cell interaction is not required for PDT-induced drug delivery to malignant mesotheliom

Photobiomodulation Suppresses Alpha-Synuclein-Induced Toxicity in an AAV-Based Rat Genetic Model of Parkinson's Disease

Converging lines of evidence indicate that near-infrared light treatment, also known as photobiomodulation (PBM), may exert beneficial effects and protect against cellular toxicity and degeneration in several animal models of human pathologies, including neurodegenerative disorders. In the present study, we report that chronic PMB treatment mitigates dopaminergic loss induced by unilateral overexpression of human α-synuclein (α-syn) in the substantia nigra of an AAV-based rat genetic model of Parkinson's disease (PD). In this model, daily exposure of both sides of the rat's head to 808-nm near-infrared light for 28 consecutive days alleviated α-syn-induced motor impairment, as assessed using the cylinder test. This treatment also significantly reduced dopaminergic neuronal loss in the injected substantia nigra and preserved dopaminergic fibers in the ipsilateral striatum. These beneficial effects were sustained for at least 6 weeks after discontinuing the treatment. Together, our data point to PBM as a possible therapeutic strategy for the treatment of PD and other related synucleinopathies