Thin films composed of Ag nanoclusters dispersed in TiO2: Influence of composition and thermal annealing on the microstructure and physical responses

Noble metal powders containing gold and silver have been used for many centuries, providing different colours in the windows of the medieval cathedrals and in ancient Roman glasses. Nowadays, the interest in nanocomposite materials containing noble nanoparticles embedded in dielectric matrices is related with their potential use for a wide range of advanced technological applications. They have been proposed for environmental and biological sensing, tailoring colour of functional coatings, or for surface enhanced Raman spectroscopy. Most of these applications rely on the so-called localised surface plasmon resonance absorption, which is governed by the type of the noble metal nanoparticles, their distribution, size and shape and as well as of the dielectric characteristics of the host matrix. The aim of this work is to study the influence of the composition and thermal annealing on the morphological and structural changes of thin films composed of Ag metal clusters embedded in a dielectric TiO2 matrix. Since changes in size, shape and distribution of the clusters are fundamental parameters for tailoring the properties of plasmonic materials, a set of films with different Ag concentrations was prepared. The optical properties and the thermal behaviour of the films were correlated with the structural and morphological changes promoted by annealing. The films were deposited by DC magnetron sputtering and in order to promote the clustering of the Ag nanoparticles the as-deposited samples were subjected to an in-air annealing protocol. It was demonstrated that the clustering of metallic Ag affects the optical response spectrum and the thermal behaviour of the films.

Degradação fotocatalítica de petróleo e seus derivados através da utilização de nanopartículas de dióxido de titânio puro e misturado com óxido de grafeno reduzido

Dissertação de mestrado integrado em Engenharia de Materiais

Delivery as nanoparticles reduces imatinib mesylate-induced cardiotoxicity and improves anticancer activity

Clinical effectiveness of imatinib mesylate in cancer treatment is compromised by its off-target cardiotoxicity. In the present study, we have developed physically stable imatinib mesylate-loaded poly(lactide-co-glycolide) nanoparticles (INPs) that could sustainably release the drug, and studied its efficacy by in vitro anticancer and in vivo cardiotoxicity assays. MTT (methylthiazolyldiphenyl-tetrazolium bromide) assay revealed that INPs are more cytotoxic to MCF-7 breast cancer cells compared to the equivalent concentration of free imatinib mesylate. Wistar rats orally administered with 50 mg/kg INPs for 28 days showed no significant cardiotoxicity or associated changes. Whereas, increased alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase levels, and reduced white blood cell, red blood cell, and hemoglobin content were observed in the animals administered with free drug. While the histological sections from hearts of animals that received INPs did not show any significant cardiotoxic symptoms, loss of normal architecture and increased cytoplasmic vacuolization were observed in the heart sections of animals administered with free imatinib mesylate. Based on these results, we conclude that nano-encapsulation of imatinib mesylate increases its efficacy against cancer cells, with almost no cardiotoxicity.

Preparação de suspensões aquosas de nanopartículas de carbono para deposição em superfícies

Dissertação de mestrado integrado em Engenharia de Materiais

Optimization of magnetoelectric composites based on electroactive polymers for energy harvesting and sensor application

Tese de Doutoramento em Engenharia de Materiais.

Semipermeable capsules wrapping a multifunctional and self-regulated co-culture microenvironment for osteogenic differentiation

A new concept of semipermeable reservoirs containing co-cultures of cells and supporting microparticles is presented, inspired by the multi-phenotypic cellular environment of bone. Based on the deconstruction of the â stem cell nicheâ , the developed capsules are designed to drive a self-regulated osteogenesis. PLLA microparticles functionalized with collagen I, and a co-culture of adipose stem (ASCs) and endothelial (ECs) cells are immobilized in spherical liquified capsules. The capsules are coated with multilayers of poly(L-lysine), alginate, and chitosan nano-assembled through layer-by-layer. Capsules encapsulating ASCs alone or in a co-culture with ECs are cultured in endothelial medium with or without osteogenic differentiation factors. Results show that osteogenesis is enhanced by the co-encapsulation, which occurs even in the absence of differentiation factors. These findings are supported by an increased ALP activity and matrix mineralization, osteopontin detection, and the up regulation of BMP-2, RUNX2 and BSP. The liquified co-capsules also act as a VEGF and BMP-2 cytokines release system. The proposed liquified capsules might be a valuable injectable self-regulated system for bone regeneration employing highly translational cell sources.

Closed hybrid hierarchical reservoirs based on the deconstruction of the cellular native microenvironment

The stem cell niche organization and dynamics provide valuable cues for the development of mimetic environments that could have potential to stimulate the regenerative process. We propose the use of biodegradable biomaterials to produce closed miniaturised structures able to encapsulate different cell types or bioactive molecules. In particular, capsules are fabricated using the so-called layer-by-layer technology, where the consecutive (nano-sized) layers are well stabilized by electrostatic interactions or other weak forces. Using alginate-based spherical templates containing cells or other elements (e.g. proteins, magnetic nanoparticles, microparticles) it is possible to produce liquefied capsules that may entrap the entire cargo under mild conditions. The inclusion of liquefied micropcapsules may be used to produce hierarchical compartmentalised systems for the delivery of bioactive agents. The presence of solid microparticles inside such capsules offers adequate surface area for adherent cell attachment increasing the biological performance of these hierarchical systems, while maintain both permeability and injectability. We demonstrated that the encapsulation of distinct cell types (including mesenchymal stem cells and endothelial cells) enhances the osteogenic capability of this system, that could be useful in bone tissue engineering applications.

Folate-targeted nanoparticles for rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is the most common inflammatory rheumatic disease, affecting almost 1% of the world population. Although the cause of RA remains unknown, the complex interaction between immune mediators (cytokines and effector cells) is responsible for the joint damage that begins at the synovial membrane. Activated macrophages are critical in the pathogenesis of RA and have been shown to specifically express a receptor for the vitamin folic acid (FA), folate receptor (FR). This particular receptor allows internalization of FA-coupled cargo. In this review we will address the potential of nanoparticles as an effective drug delivery system for therapies that will directly target activated macrophages. Special attention will be given to stealth degree of the nanoparticles as a strategy to avoid clearance by macrophages of the mononuclear phagocytic system (MPS). This review summarizes the application of FA-target nanoparticles as drug delivery systems for RA and proposes prospective future directions.

Zebrafish embryos as in vivo model for toxicity evaluation: screening of nanoparticle formulations DODAB:MO and DODAC:MO

Dissertação de mestrado em Molecular Genetics

Chemical functionalization in bionanoparticles

Dissertação de mestrado em Biofísica e Bionanossistemas

Bacterial cellulose-lactoferrin as an antimicrobial edible packaging

Bacterial cellulose (BC) films from two distinct sources (obtained by static culture with Gluconacetobacter xylinus ATCC 53582 (BC1) and from a commercial source (BC2)) were modified by bovine lactoferrin (bLF) adsorption. The functionalized films (BC+bLF) were assessed as edible antimicrobial packaging, for use in direct contact with highly perishable foods, specifically fresh sausage as a model of meat products. BC+bLF films and sausage casings were characterized regarding their water vapour permeability (WVP), mechanical properties, and bactericidal efficiency against two food pathogens, Escherichia coli and Staphylococcus aureus. Considering their edibility, an in vitro gastrointestinal tract model was used to study the changes occurring in the BC films during passage through the gastrointestinal tract. Moreover, the cytotoxicity of the BC films against 3T3 mouse embryo fibroblasts was evaluated. BC1 and BC2 showed equivalent density, WVP and maximum tensile strength. The percentage of bactericidal efficiency of BC1 and BC2 with adsorbed bLF (BC1+bLF and BC2+bLF, respectively) in the standalone films and in inoculated fresh sausages, was similar against E. coli (mean reduction 69 % in the films per se versus 94 % in the sausages) and S. aureus (mean reduction 97 % in the films per se versus 36 % in the case sausages). Moreover, the BC1+bLF and BC2+bLF films significantly hindered the specific growth rate of both bacteria. Finally, no relevant cytotoxicity against 3T3 fibroblasts was found for the films before and after the simulated digestion. BC films with adsorbed bLF may constitute an approach in the development of bio-based edible antimicrobial packaging systems.

Development of nanohydrogels as a vehicle for the release of bioactive compounds in food matrices

PhD in Chemical and Biological Engineering