Probing the Interaction Between a Surfactant-Cobalt(III) Complex and Bovine Serum Albumin

The mechanism of binding of the surfactant-cobalt(III) complex, cis-[Co(phen)2(C14H29NH2)Cl](ClO4)2⋅3H2O (phen = 1,10-phenanthroline, C14H29NH2 = tetradecylamine) with bovine serum albumin (BSA) was investigated by UV-vis absorption, circular dichroism (CD) and fluorescence spectroscopic techniques. The results of fluorescence titration revealed that the surfactant-cobalt(III) complex quenched the intrinsic fluorescence of BSA through a combination of static and dynamic quenching. The apparent binding constant (K a) and number of binding sites (n) were calculated below and above the critical micelle concentration (CMC). The thermodynamic parameters determined by the van't Hoff analysis of the constants (ΔH ∘=14.87 kJ⋅mol−1; ΔS ∘=152.88 J⋅mol−1⋅K−1 below the CMC and 25.70 kJ⋅mol−1 and 243.14 J⋅mol−1⋅K−1, respectively, above the CMC) clearly indicate that the binding is entropy-driven and enthalpically disfavored. Based on Förster's theory of non-radiation energy transfer, the binding distance, r, between donor (BSA) and the acceptor (surfactant-cobalt(III) complex) was evaluated. UV-vis, CD and synchronous fluorescence spectral results showed that the binding of the surfactant-cobalt(III) complex to BSA induced conformational changes in BS

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 system

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%

Study of the stability of the 5-aminolevulinic acid tyrosine ester in aqueous solution

Photodynamic therapy based on photoactivable porphyrins (PAPs) can treat various dermatological conditions. The side-effects as well as the non-selective or insufficient accumulation of PAPs in the targeted tissues limit performances. We studied the stability in solution at different temperatures (21 degrees C; 4 degrees C), different pH values (7.5; 2.0), and as a function of time of 5-aminolevulinic acid's Tyrosine-ester, a molecule presenting interesting properties to selectively produce PAPs in blood vessels after topical application. Solutions of this precursor can be kept up to 24 h at refrigerated temperatures and under acidic pH. At room temperature or physiological pH, they must be prepared minutes before their use

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

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

Near-Infrared 808 nm Light Boosts Complex IV-Dependent Respiration and Rescues a Parkinson-Related pink1 Model

Mitochondrial electron transport chain (ETC) defects are observed in Parkinson's disease (PD) patients and in PD fly- and mouse-models; however it remains to be tested if acute improvement of ETC function alleviates PD-relevant defects. We tested the hypothesis that 808 nm infrared light that effectively penetrates tissues rescues pink1 mutants. We show that irradiating isolated fly or mouse mitochondria with 808 nm light that is absorbed by ETC-Complex IV acutely improves Complex IV-dependent oxygen consumption and ATP production, a feature that is wavelength-specific. Irradiating Drosophila pink1 mutants using a single dose of 808 nm light results in a rescue of major systemic and mitochondrial defects. Time-course experiments indicate mitochondrial membrane potential defects are rescued prior to mitochondrial morphological defects, also in dopaminergic neurons, suggesting mitochondrial functional defects precede mitochondrial swelling. Thus, our data indicate that improvement of mitochondrial function using infrared light stimulation is a viable strategy to alleviate pink1-related defects