Relationship between the stability and surface tension of the tear film

FCT, QREN and FEDER/COMPETE through CFUM

Evaluation of optical properties of different types of contact lenses

The main objective of this work was to attain a deeper knowledge of contact lenses (CL) optical properties and to understand the influence of CL power on other properties which can affect the optical performance and compromise the ocular physiology.Fundação para a Ciência e a Tecnologia (FCT), QREN/FSE/COMPETE

Vesicle-micelle transition in aqueous mixtures of the cationic dioctadecyldimethylammonium and octadecyltrimethylammonium bromide surfactants

The vesicle-micelle transition in aqueous mixtures of dioctadecyldimethylammonium and octadecyltrimethylammonium bromide (DODAB and C18TAB) cationic surfactants, having respectively double and single chain, was investigated by differential scanning calorimetry (DSC), steady state fluorescence, dynamic light scattering (DLS) and surface tension. The experiments performed at constant up to 1.0 mM total surfactant concentration reveal that these homologue surfactants mix together to form either mixed vesicles and/or micelles, or both of these structures in equilibrium, depending on the relative amount of the surfactants. The main transition melting temperature Tm of the mixed DODAB-C18TAB vesicles is larger than that for the neat DODAB in water owing to the incorporation of C18TAB in the vesicle bilayer, however, little amount of C18TAB having a minor effect on the Tm of DODAB. The surface tension decreases sigmoidally with C18TAB concentration and the inflection point lies around xDODAB ≈ 0.4, indicating the onset of micelle formation owing to saturation of DODAB vesicles by C18TAB molecules and formation of vesicle structures. At low C18TAB concentrations When xDODAB > 0.5 C18TAB molecules are mainly solubilized by the vesicles bilayers, while at high C18TAB concentrations but when xDODAB < 0.25 micelles are dominant. Fluorescence data of the Nile Red probe incorporated in the system at different surfactant molar fractions indicate the formation of micelle and vesicle structures. These structures have apparent hydrodynamic radius RH of about 180 and 500-800 nm, respectively, as obtained by DLS measurements.Fundação para a Ciência e a Tecnologia (FCT

DODAB/Monoolein mixed cationic liposomes for gene delivery : investigation by DLS, DSC, fluorescence spectroscopy and phase scanning microscopy

FCT and FEDER for financial support to CFUM and also by funding through project PTDC/QUI/69795/2006 and PhD grant of J.P.N. Silva (SFRH/BD/46968/2009)

Inhibition of S. epidermidis adhesion to hydrogel contact lenses by anionic and nonionic surfactants

In this study the adhesion of S. epidermidis to the 4 FDA groups of hydrogel CL uncoated and coated with ½ CMC of an anionic (sodium cholate) and a non-ionic surfactant (octylglucoside) was assessed. The results revealed that cell adhesion to CL was highly dependent on surface hydrophobicity. Concerning the effect of surfactants, the non-ionic one was more effective in inhibiting microbial adhesion than the ionic surfactant. Octylglucoside promoted an inhibition in the extent of bacterial adhesion of about 62%, while sodium cholate caused a decrease in the number of cells adhered of about 43%. The effect of a commercial multipurpose care solution containing 1% of poloxamine was compared and the results indicate that adhesion inhibition was greater when 0.33% of octylglucoside was used. Octylglucoside is a natural surfactant, non-toxic, harmless to the eye, and due to its high efficiency in inhibiting microbial adhesion, as proved in this work, is recommended to be incorporated in CL care solutions

Two-way MANCOVA: an application to public health

The aim of this work is to use the MANCOVA model to study the influence of the phenotype of an enzyme - Acid phosphatase - and a genetic factor - Haptoglobin genotype - on two dependent variables - Activity of Acid Phosphatase (ACP1) and the Body Mass Index (BMI). Therefore it's used a general linear model, namely a multivariate analysis of covariance (Two-way MANCOVA). The covariate is the age of the subject. This covariate works as control variable for the independent factors, serving to reduce the error term in the model. The main results showed that only the ACP1 phenotype has a significant effect on the activity of ACP1 and the covariate has a significant effect in both dependent variables. The univariate analysis showed that ACP1 phenotype accounts for about 12.5% of the variability in the activity of ACP1. In respect to this covariate it can be seen that accounts for about 4.6% of the variability in the activity of ACP1 and 37.3% in the BMI

Alterações na transmitância UV-Visível induzidas pelo uso de lentes de contacto de silicone-hidrogel

Fundação para a Ciência e a Tecnologia (FCT) through Centro de Física da U

Interaction of DODAB with neutral phospholipids and cholesterol studied using fluorescence anisotropy

Liposomes composed of cationic lipids and neutral phospholipids have been used as vehicles for cellular delivery of DNA and drug delivery. The aim of this study is to get a better understanding of phospholipid–cationic lipid interactions that is essential for the development of this potential. We have studied the interaction between cationic lipid liposomes primarily composed of dioctadecyldimethylammonium bromide (DODAB) with two different phospholipids, dioleoyl phosphatidylethanolamine (DOPE) and soybean phosphatidylcholine (PC), as well as with cholesterol. The effect of these components on the liposome’s physical properties (microviscosity and polarity) was accessed by studying, both the steady-state and time-resolved, fluorescence anisotropy of the dye Nile Red. This information combined with analysis of the steady-state emission and fluorescence lifetime of Nile Red using the different lipids and cholesterol provided information concerning the polarity and hydration level changes in these vesicle systems along with organisational information

6th Iberian Meeting of Colloids and Interfaces - RIC16: book of abstracts

info:eu-repo/semantics/publishedVersio