Publications

Abstract Zinc oxide is widely used in the manufacture of a vast number of consumer goods and industrial applications. The employ of nano and sub-micrometer zinc oxide materials has recently been introduced as a more economic and more effective alternative to bulk zinc oxide. Furthermore zinc oxide is being used as antibacterial material since metal oxides are recognized as possessing antibacterial properties and are regarded as safe materials to human beings and animals. The present work aims to present our study on the antibacterial properties of zinc oxide particles prepared by a polyol thermal method. Spherical submicrometer ZnO particles were prepared and their antibacterial properties were tested in aqueous suspensions of E. coli bacteria. For ZnO concentrations higher than 50 ppm an inhibition of the growth rate of bacteria higher than 95 % is achieved.

Abstract Solid lipid nanoparticles (SLN) are colloidal drug and/or gene carriers developed from solid lipids and surfactants that are considered safe. Cationic SLN, usually used for formulating poorly water-soluble drugs and for gene delivery purposes, as positively charged particles may attach to cellular surfaces and be internalized more easily than negatively charged SLN, but they can also cause damage. The main aim of this work was to test a set of cationic SLN and investigate its influence on the amount of reactive oxygen species (ROS), on antioxidant enzymes activities and on possible oxidative damage to membrane lipids in HepG2 cells. The Dichlorofluorescein assay revealed great increase in ROS presence after cell exposure to SLN. While the exposure to SLN increased the activities of superoxide dismutase and glutathione peroxidase it decreased glutathione reductase activity. Although no significant increase in thiobarbituric reactive species was found, a decrease in sulfhydryl groups was detected. These results indicate that cationic SLN caused oxidative stress in HepG2 cells, but under reported exposure conditions HepG2 cells could attenuate the stress and thus the damage to cellular components was minimal.

Abstract The enthalpies of solution of alcohols were determined by calorimetry in HEPES and (HEPES + trehalose) at 298.15 K. The used methodology and experiment's design allowed us to extract from a single titration experiment the enthalpy of solution (Delta H-sol(m)), the limiting solubility of the alcohol in each aqueous media, and an estimation of the enthalpy of solution of water in the alcohol phase. From these values the changes in Gibbs energy (Delta(sol)G(m)) and in entropy (Delta S-sol(m)) of solution were derived. A decrease in solubility for 1-butanol and 1-pentanol in the crowded media (HEPES + trehalose) was observed which is driven by a significant decrease in the favorable enthalpy of solution. The partial molar heat capacity, C-p,2(infinity) in each media was determined in our heat capacity drop calorimeter, also at 298.15 K. A significant decrease of the partial molar heat capacity was observed for both alcohols in (HEPES + trehalose), which together with the obtained decrease in favorable Delta H-sol(m), is consistent with a decrease in hydrophobic solvation, as a result of a decrease in free solvent availability induced by the trehalose. Finally, we tentatively predict that in the aqueous media of the crowded solutions that characterize cells and biological fluids, solutes with low aqueous solubility will be more soluble, whereas the solubility of highly polar solutes will be reduced.

Abstract The development of new drugs always was time consuming and costly. With the development in experimental methods was possible to scan small-compounds libraries in order to find potentially suitable molecules. Nevertheless, these methods are able to so with a very low rate. Protein kinases are a class of enzymes involved in the great majority of cellular process. Due to its presence in many signal pathways, cell cycle and gene expression control mechanisms, this class is one of the major targets for pharmaceutical industries today. Aiming the reduction of time and costs in drug development computational tools started to be used, and commonly called Computer aided drug design (CADD). These methods can be separated in two different types of approaches, structure based (SBDD) and ligand based (LBDD). In order to use structure based methods, information about the 3D structure of the target is needed, normally obtained through x-ray crystallography or NMR. Ligand based methods are preferred when this information is not available. The focus of the present chapter is the structure based methods used in the computer drug discovery and design process targeting kinases. Starting with the visual and energetic analysis of the binding site, it is obtained enough information for the creation of a Pharmacophore model and the application of Virtual Screening process. The results of the screening can then be analysed through Molecular Docking process followed by Molecular Dynamics in order to better simulate the real binding conditions. The obtained complexes can be analysed using energy calculations, in order to better understand the binding process. Within the described procedures, computational tools originate a great amount of useful information since hit discovery from lead optimization. The data obtained can save time and reduce costs in the process of drug design and discovery in a large scale.

Abstract The raising level of awareness regarding the harmful effects of solar radiation has resulted in an increase in the production and use of sunscreens. These commercial products contain ultraviolet (UV) filters that absorb, reflect or scatter UV radiation (290-320 nm for UVB and 320-400 nm for UVA) therefore preventing sunburn, photo-aging and ultimately skin diseases such as skin cancer. A high screening efficiency can only be guaranteed if a UV filter has a high photo-stability. However, UV filters are known to undergo degradation upon exposure to sunlight and chemical substances used in water disinfection such as chlorine, leading to the formation of undesirable byproducts with properties different from the parent compounds. This chapter presents a comprehensive review on the computational studies performed so far on the structural, electronic, energetic and UV absorption properties of some of the most widely used UV-filters and their degradation products (UVFDP). Ab initio and density functional theory (DFT) methods have been used to obtain the molecular structure, energetics and other molecular properties of UVF-DP. UV-Vis absorption spectra and excited state properties have been calculated using the time dependent density functional theory (TD-DFT). The influence of different solvents in these properties has been studied using solution models. Transformation and degradation mechanisms have been established with the aid of computational methods and results indicate that these can be employed to assess the environmental fate of UV-filters.

Abstract In the present study we have developed lipid nanoparticle (LN) dispersions based on a multiple emulsion technique for encapsulation of hydrophilic drugs or/and proteins by a full factorial design. In order to increase ocular retention time and mucoadhesion by electrostatic attraction, a cationic lipid, namely cetyltrimethylammonium bromide (CTAB), was added in the lipid matrix of the optimal LN dispersion obtained from the factorial design. There are a limited number of studies reporting the ideal concentration of cationic agents in LN for drug delivery. This paper suggests that the choice of the concentration of a cationic agent is critical when formulating a safe and stable LN. CTAB was included in the lipid matrix of LN, testing four different concentrations (0.25%, 0.5%, 0.75%, or 1.0%wt) and how composition affects LN behavior regarding physical and chemical parameters, lipid crystallization and polymorphism, and stability of dispersion during storage. In order to develop a safe and compatible system for ocular delivery, CTAB-LN dispersions were exposed to Human retinoblastoma cell line Y-79. The toxicity testing of the CTAB-LN dispersions was a fundamental tool to find the best CTAB concentration for development of these cationic LN, which was found to be 0.5 wt% of CTAB.

Abstract Solid lipid nanoparticles (SLN) are a promising drug delivery system for oral administration of poorlywater soluble drugs because of their capacity to increase the solubility of drug molecules when loaded in their lipid matrices, with the resulting improvement of the drug bioavailability. In the present work, we have developed praziquantel (PZQ)-loaded SLN and explored the biological applications of this system for intestinal permeation of PZQQ. The effect in vitro on Schistosoma mansoni culture and the cytotoxicity in HepG2 line cell were also evaluated. The results showed a significant decrease in the intestinal absorption of PZQloaded in SLN compared to free PZQ, suggesting that the SLN matrix could act as reservoir system. In culture of S. mansoni, we observed that PZQ-loaded SLN were more effective than free PZQ, leading the death of the parasites in less time. The result was proportional to doses of PZQ (25 and 50 tig mL-1) and lipid concentration. Regarding cytotoxicity, the encapsulation of PZQinto SLN decreased the toxicity in HepG2 cells in comparison to the free PZQ. From the obtained results, PZQ-loaded SLN could be a new drug delivery system for the schistosomiasis treatment especially in marginalized communities, improving the therapeutic efficacy and reducing the toxic effects of PZQ. (C) 2014 Published by Elsevier B.V.

Abstract Insulin was used as model protein to developed innovative Solid Lipid Nanoparticles (SLNs) for the delivery of hydrophilic biotech drugs, with potential use in medicinal chemistry. SLNs were prepared by double emulsion with the purpose of promoting stability and enhancing the protein bioavailability. Softisan (R) 100 was selected as solid lipid matrix. The surfactants (Tween (R) 80, Span (R) 80 and Lipoid (R) S75) and insulin were chosen applying a 2(2) factorial design with triplicate of central point, evaluating the influence of dependents variables as polydispersity index (PI), mean particle size (z-AVE), zeta potential (ZP) and encapsulation efficiency (EE) by factorial design using the ANOVA test. Therefore, thermodynamic stability, polymorphism and matrix crystallinity were checked by Differential Scanning Calorimetry (DSC) and Wide Angle X-ray Diffraction (WAXD), whereas the effect of toxicity of SLNs was check in HepG2 and Caco-2 cells. Results showed a mean particle size (z-AVE) width between 294.6 nm and 627.0 nm, a PI in the range of 0.425-0.750, ZP about -3 mV, and the EE between 38.39% and 81.20%. After tempering the bulk lipid (mimicking the end process of production), the lipid showed amorphous characteristics, with a melting point of ca. 30 degrees C. The toxicity of SLNs was evaluated in two distinct cell lines (HEPG-2 and Caco-2), showing to be dependent on the concentration of particles in HEPG-2 cells, while no toxicity in was reported in Caco-2 cells. SLNs were stable for 24 h in in vitro human serum albumin (HSA) solution. The resulting SLNs fabricated by double emulsion may provide a promising approach for administration of protein therapeutics and antigens.

Abstract The encapsulation of epigallocatechin gallate (EGCG) in lipid nanoparticles (LNs) could be a suitable approach to avoid drug oxidation and epimerization, which are common processes that lead to low bioavailability of the drug limiting its therapeutic efficacy. The human health benefits of EGCG gained much interest in the pharmaceutical field, and so far there are no studies reporting its encapsulation in LNs. The purpose of this study has been the development of an innovative system for the ocular delivery of EGCG using LNs as carrier for the future treatment of several diseases, such as dry eye, age-related macular degeneration (AMD), glaucoma, diabetic retinopathy and macular oedema. LNs dispersions have been produced by multiple emulsion technique and previously optimized by a factorial design. In order to increase ocular retention time and mucoadhesion by electrostatic attraction, two distinct cationic lipids were used, namely, cetyltrimethylammonium bromide (CTAB) and dimethyldioctadecylammonium bromide (DDAB). EGCG has been successfully loaded in the LNs dispersions and the nanoparticles analysis over 30 days of storage time predicted a good physicochemical stability. The particles were found to be in the nanometer range (<300 nm) and all the evaluated parameters, namely pH, osmolarity and viscosity, were compatible to the ocular administration. The evaluation of the cationic lipid used was compared regarding physical and chemical parameters, lipid crystallization and polymorphism, and stability of dispersion during storage. The results show that different lipids lead to different characteristics mainly associated with the acyl chain composition, i.e. double lipid shows to have influence in the crystallization and stability. Despite the recorded differences between DTAB and DDAB, both cationic LNs seem to fit the parameters for ocular drug delivery.

Abstract The present work aimed at studying the interaction between insulin and SiNP surfaced with mucoadhesive polymers (chitosan, sodium alginate or polyethylene glycol) and the evaluation of their biocompatibility with HepG2 and Caco-2 cell lines, which mimic in vivo the target of insulin-loaded nanoparticles upon oral administration. Thus, a systematic physicochemical study of the surface-modified insulin-silica nanoparticles (Ins-SiNP) using mucoadhesive polymers has been described. The surfacing of nanoparticle involved the coating of silica nanoparticles (SiNP) with different mucoadhesive polymers, to achieve high contact between the systems and the gut mucosa to enhance the oral insulin bioavailability. SiNP were prepared by a modified Stoner method at room temperature via hydrolysis and condensation of tetraethyl orthosilicate (TEOS). Interaction between insulin and nanoparticles was assessed by differential scanning calorimetry (DSC), X-ray and Fourier-transform infrared (FTIR) studies. The high efficiency of nanoparticles' coating resulted in more stable system. FTIR spectra of insulin-loaded nanoparticles showed amide absorption bands which are characteristic of alpha-helix content. In general, all developed nanoparticles demonstrated high biocompatible, at the tested concentrations (50-500 mu g/mL), revealing no or low toxicity in the two human cancer cell lines (HepG2 and Caco-2). In conclusion, the developed insulin-loaded SiNP surfaced with mucoadhesive polymers demonstrated its added value for oral administration of proteins.