Smart macroporous structures for the purification of viral particles

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Coupling electrokinetics and iron nanoparticles for the remediation of contaminated soils

Fundação para a Ciência e a Tecnologia - PTDC/AGR-­AAM/101643/2008 NanoDC ; SFRH/BD/76070/2011 ; FP7-­PEOPLE-­IRSES-­2010-­269289-­ ELECTROACROSS

Exploring the bioavailability of (poly)phenols from berries and their potential activities in humans

(Poly)phenols are the most widely distributed secondary metabolites, in plants, and, therefore, are regular constituents of human food products. The regular ingestion of (poly)phenol-containing foods has been associated with a reduced risk of acquiring chronic diseases and many studies are currently trying to corroborate this theory. However, the precise contribution of (poly)phenols to disease prevention is still unknown.(...)

Double-walled PLLA/PLGA particles for the sustained release of Meloxicam: preparation, characterisation and contolled release studies

There were two main objectives in this thesis investigation, first, the production, characterisation, in vitro degradation and release studies of double walled microspheres for drug release control. The second one, and the most challenging, was the production of double walled nanospheres, also for drug control delivery. The spheres were produced using two polymers, the Poly(L-lactide)Acid, PLLA, and the Poly(L-lactide-co-glycolic)Acid, PLGA.Afterwards, a model drug, Meloxicam, which is an antiinflammatory drug, was encapsulated into the particles. Micro and nanospheres were produced by the solvent extraction/evaporation method, where perfect spherical particles were obtained. By varying the polymers PLLA/PLGA mass ratio, different core and shell composition, as well as several shell and core thickness were observed. In the particles with a PLLA/PLGA mass ratio 1:1, the shell is composed by PLLA and the core by PLGA. It was also verified that the Meloxicam has a tendency to be distributed in the PLGA layer. Micro and nanoparticles were characterised in morphology, size, polymer cristalinity properties and drug distribution. Particles degradation studies was performed, where the particles in a PVA solution of pH 7,4 where placed in an incubator, during approximately 40 days, at 120rpm, and 37ºC, simulating, as much as possible, the human body environment. From these studies, the conclusion was that particles containing a PLGA shell and a PLLA core degrade more rapidly, due to the fact that PLLA is more hydrophobic than the PLGA. Concerning the drug release controlled results, done also for 40 and 50 days, they showed that the microspheres containing a shell of PLLA release more slowly than when the shell is composed of PLGA. This result was predictable, since the drug is solubilised in the PLGA polymer and so, in that case, the PLLA shell works like a barrier between the drug and the outer medium. Another positive aspect presented by this study is the lower initial burst effect, obtained when using double walled particles, which is one of the advantages of the same. In a second part of this investigation, the production of the nanospheres was the main goal, since it was not yet accomplished by other authors or investigators. After several studies, referring to the speed, time and type of agitation, as well as, the concentration and volume of the first aqueous solution of poly-vinyl-alcohol (PVA) during the process of solvent extraction/evaporation it was possible to obtain double walled nanospheres.(...)

Gold nanoparticles for plasmid delivery

Gene therapy presents an ideal strategy for the treatment of genetic as well as acquired diseases, such as cancer and typically involves the insertion of a functioning gene into cells to correct a cellular dysfunction or to provide a new cellular function. Gene delivery vectors are based in two models: viral and non-viral. Viral vectors have high transfection efficiency but their major barrier is immunogenicity. Since the non-viral vectors have no immunogenicity, these have been widely studied. Gold nanoparticles have been proposed as optimal delivery systems of genetic material, due their small size, high surface-to-volume ratio and the ability to be functionalized with multiple molecules. In the present work, an AuNP-based formulation was developed to deliver a plasmid in a colorectal cancer cell line, containing as reporter gene the gene encoding to EGFP. The delivery system resulted from the functionalization of 14 nm AuNP with a PEG layer (4300114 PEG chains/AuNP), which increases stability and biocompatibility of AuNPs; quaternary ammonium groups which provide positive charges that allow electrostatic binding of plasmid, which is considered the therapeutic agent to be transported into cells. The system developed was characterized by UV-vis spectroscopy, DLS, TEM and by electrophoretic mobility, yielding a formulation with 113.5 nm.Transfection efficiency of the formulation developed was evaluated through PCR and through EGFP expression by fluorescence microscopy and fluorescence spectroscopy. The internalization was observed 3h post transfection; however a low level of EGFP expression was achieved. After 24h of incubation, EGFP expression increases just 3 times compared to non-transfected cells. The commercial system (Lipofectamine) expressed EGFP 5 times more than the system developed AuNP@PEG@R4N+@pEGFP. This difference could be related to lower translocation to the nucleus.

Gold nanoparticles for the detection of DNA adducts as biomarkers of exposure to acrylamide

The main objective of this thesis was the development of a gold nanoparticle-based methodology for detection of DNA adducts as biomarkers, to try and overcome existing drawbacks in currently employed techniques. For this objective to be achieved, the experimental work was divided in three components: sample preparation, method of detection and development of a model for exposure to acrylamide. Different techniques were employed and combined for de-complexation and purification of DNA samples (including ultrasonic energy, nuclease digestion and chromatography), resulting in a complete protocol for sample treatment, prior to detection. The detection of alkylated nucleotides using gold nanoparticles was performed by two distinct methodologies: mass spectrometry and colorimetric detection. In mass spectrometry, gold nanoparticles were employed for laser desorption/ionisation instead of the organic matrix. Identification of nucleotides was possible by fingerprint, however no specific mass signals were denoted when using gold nanoparticles to analyse biological samples. An alternate method using the colorimetric properties of gold nanoparticles was employed for detection. This method inspired in the non-cross-linking assay allowed the identification of glycidamide-guanine adducts and DNA adducts generated in vitro. For the development of a model of exposure, two different aquatic organisms were studies: a goldfish and a mussel. Organisms were exposed to waterborne acrylamide, after which mortality was recorded and effect concentrations were estimated. In goldfish, both genotoxicity and metabolic alterations were assessed and revealed dose-effect relationships of acrylamide. Histopathological alterations were verified primarily in pancreatic cells, but also in hepatocytes. Mussels showed higher effect concentrations than goldfish. Biomarkers of oxidative stress, biotransformation and neurotoxicity were analysed after prolonged exposure, showing mild oxidative stress in mussel cells, and induction of enzymes involved in detoxification of oxygen radicals. A qualitative histopathological screening revealed gonadotoxicity in female mussels, which may present some risk to population equilibrium.

Engineering of metal oxide nanoparticles for application in electrochemical devices

The growing demand for materials and devices with new functionalities led to the increased inter-est in the field of nanomaterials and nanotechnologies. Nanoparticles, not only present a reduced size as well as high reactivity, which allows the development of electronic and electrochemical devices with exclusive properties, when compared with thin films. This dissertation aims to explore the development of several nanostructured metal oxides by sol-vothermal synthesis and its application in different electrochemical devices. Within this broad theme, this study has a specific number of objectives: a) research of the influence of the synthesis parameters to the structure and morphology of the nanoparticles; b) improvement of the perfor-mance of the electrochromic devices with the application of the nanoparticles as electrode; c) application of the nanoparticles as probes to sensing devices; and d) production of solution-pro-cessed transistors with a nanostructured metal oxide semiconductor. Regarding the results, several conclusions can be exposed. Solvothermal synthesis shows to be a very versatile method to control the growth and morphology of the nanoparticles. The electrochromic device performance is influenced by the different structures and morphologies of WO3 nanoparticles, mainly due to the surface area and conductivity of the materials. The dep-osition of the electrochromic layer by inkjet printing allows the patterning of the electrodes without wasting material and without any additional steps. Nanostructured WO3 probes were produced by electrodeposition and drop casting and applied as pH sensor and biosensor, respectively. The good performance and sensitivity of the devices is explained by the high number of electrochemical reactions occurring at the surface of the na-noparticles. GIZO nanoparticles were deposited by spin coating and used in electrolyte-gated transistors, which promotes a good interface between the semiconductor and the dielectric. The produced transistors work at low potential and with improved ON-OFF current ratio, up to 6 orders of mag-nitude. To summarize, the low temperatures used in the production of the devices are compatible with flexible substrates and additionally, the low cost of the techniques involved can be adapted for disposable devices.

Field-effect transistors based on Zinc oxide nanoparticles

This work reports the development of field-effect transistors (FETs), whose channel is based on zinc oxide (ZnO) nanoparticles (NPs). Using screen-printing as the primary deposition technique, different inks were developed, where the semiconducting ink is based on a ZnO NPs dispersion in ethyl cellulose (EC). These inks were used to print electrolyte-gated transistors (EGTs) in a staggered-top gate structure on glass substrates, using a lithium-based polymeric electrolyte. In another approach, FETs with a staggered-bottom gate structure on paper were developed using a sol-gel method to functionalize the paper’s surface with ZnO NPs, using zinc acetate dihydrate (ZnC4H6O4·2H2O) and sodium hydroxide (NaOH) as precursors. In this case, the paper itself was used as dielectric. The various layers of the two devices were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared spectroscopy (FTIR), thermogravimetric and differential scanning calorimetric analyses (TG-DSC). Electrochemical impedance spectroscopy (EIS) was used in order to evaluate the electric double-layer (EDL) formation, in the case of the EGTs. The ZnO NPs EGTs present electrical modulation for annealing temperatures equal or superior to 300 ºC and in terms of electrical properties they showed On/Off ratios in the order of 103, saturation mobilities (μSat) of 1.49x10-1 cm2(Vs)-1 and transconductance (gm) of 10-5 S. On the other hand, the ZnO NPs FETs on paper exhibited On/Off ratios in the order of 102, μSat of 4.83x10- 3 cm2(Vs)-1and gm around 10-8 S.

VO2 thin films and nanoparticles for energy-saving applications in architectural elements

Vanadium dioxide (VO2) is a promising material with large interest in construction industry and architecture, due to its thermochromic properties. This material may be used to create "smart" coatings that result in improvements in the buildings energy efficiency, by reducing heat exchanges and, consequently, the need for acclimatization. In this work, VO2 thin films and coatings were produced and tested in laboratory, to apply in architectural elements, such as glass, rooftop tiles and exterior paints. Thin films were produced by RF magnetron sputtering and VO2 nanoparticles were obtained through hydrothermal synthesis, aiming to create "smart" windows and tiles, respectively. These coatings have demonstrated the capability to modulate the transmittance of infrared radiation by around 20%. The VO2 nanoparticle coatings were successfully applied on ceramic tiles. The critical temperature was reduced to around 40ºC by tungsten doping. Ultimately, two identical house models were built, in order to test the VO2 coatings, in real atmospheric conditions during one of the hottest months of the year, in Portugal – August.