Cancer is a major health care problem with growing incidence, not only at a national level but also worldwide. Due to this urgency in reducing cancer prevalence, the scientific community has put forward a great attention in the search for novel anti-cancer treatments, particularly, in the development of nanocarriers capable to control and promote drug delivery to target cells. These drug delivery systems are capable to overcome the limitations presented by the conventional chemotherapeutic treatments. Among the various types of nanocarriers developed so far, mesoporous silica nanoparticles (MSNs) possess unique structural properties that make them highly suitable to encapsulate and deliver drugs to cancer cells. However, for these specialized nanocarriers to be applied in cancer therapies it is still of critical importance to control the time frame of drug release at the tumor microenvironment or inside cancer cells, in order to maximize the therapeutic effect and reduce unspecific cytotoxicity. One alternative to control drug release is to endow the nanocarriers with a pH responsive drug release that takes advantage of the naturally acidic tumor microenvironment and also of the acidic pH of lysosomes. In this thesis the development of dual drug loaded pH-responsive mesoporous silica nanoparticles (MSNs) with a calcium carbonate-based coating is presented as an effective alternative to deliver drugs to prostate cancer cells. This approach allowed the simultaneous co-encapsulation of a non-steroidal anti-inflammatory drug (Ibuprofen) and Doxorubicin (an anti-tumoral drug), with high efficiency. Furthermore, the idealized calcium carbonate coating successfully promoted a pH sensitive drug release from the MSNs matrix. The delivery systems proved to be capable of maintaining the drugs inside their mesoporous structure under physiological pH, and to prompt its release in acidic environments. The resulting dual loaded MSNs coated with calcium carbonate have spherical morphology and a mean size of 167 nm, presenting therefore, good characteristics to be applied as nanocarriers. Such, is supported by the cytotoxicity studies where the idealized MSNs produced a 93% higher anti-proliferative effect than the non-coated silica nanoparticles, being even more effective than the dual free drug administration, as well. Overall, the carbonate coating of MSNs showed to be a simple and cost-effective approach for cancer therapy, in particular for a pH-triggered drug delivery. Moreover, the versatile nature of these nanocarriers allows surface modifications that can improve the selectivity to target cells, allow imaging or even a combination of them both.

Nanocarriers with a pH responsive behavior are receiving an ever growing attention due to their potential for promoting on-demand drug release and thus increase the therapeutic effectiveness of anti-tumoral pharmaceutics. However, the majority of these systems require costly, time-consuming and complex chemical modifications of materials or drugs to synthesize nanoparticles with pH triggered release. Herein, the development of dual drug loaded pH-responsive mesoporous silica nanoparticles (MSNs) with a calcium carbonate-based coating is presented as an effective alternative. This innovative approach allowed the loading of a non-steroidal anti-inflammatory drug (Ibuprofen) and Doxorubicin, with high efficiency. The resulting dual drug loaded MSNs have spherical morphology and a mean size of 171 nm. Our results indicate that under acidic conditions the coating disassembles and the drugs are rapidly released, whereas at physiologic pH the release is slower and gradually increases with time. Furthermore, an improved cytotoxic effect was obtained for Doxorubicin–Ibuprofen MSNs coated with CaCO3 in comparison with non-coated particles. The cytotoxic effect of dual loaded carbonate coated particles, was similar to that of Doxorubicin + Ibuprofen free drug administration at 72 h, even with the delivery of a significantly lower amount of drug by MSNs-CaCO3. These results suggest that the carbonate coating of MSNs is a promising approach to create a pH-sensitive template for a delivery system with application in cancer therapy.

Compósitos de polipropileno e carbonato de cálcio em escala nanométrica foram preparados através de processamento em extrusora de rosca dupla co-rotacional. Metodologia estatística (projeto de experimentos) foi utilizada para avaliar o efeito das variáveis: teor de carbonato de cálcio, velocidade de rotação e configuração dos parafusos nas propriedades dos materiais obtidos. As propriedades mecânicas foram determinadas por meio de ensaios de tração (ASTM D 638), de resistência à flexão (ASTM D 790) e de resistência ao impacto (ASTM D 256). A processabilidade dos materiais foi avaliada através de determinações do índice de fluidez (ASTM D 1238). A microscopia eletrônica de varredura foi usada para avaliar a dispersão da carga na matriz e para obter informações sobre a adesão interfacial entre ambas. Os resultados obtidos demonstraram que o teor de carga adicionado ao polímero é a variável que exerce influência mais significativa sobre o módulo de flexão e que o teor de carga e a rotação dos parafusos são as variáveis que mais afetam as propriedades de impacto. O aumento da concentração das nanopartículas causou um aumento do módulo de flexão e da resistência ao impacto, enquanto que o aumento da velocidade de rotação dos parafusos provocou a redução das propriedades do impacto. A configuração do parafuso é a variável que tem um efeito mais significativo sobre a resistência mecânica do material. A utilização de um perfil de parafuso mais cisalhante promoveu a obtenção de valores mais altos de resistência à tração. A velocidade de rotação foi a variável mais significativa na determinação do módulo de Young. O aumento da velocidade de rotação associado à utilização da configuração do parafuso mais cisalhante da extrusora propicia um aumento do módulo de Young do polipropileno. Análise de microscopia eletrônica de varredura mostrou que não houve uma boa dispersão das nanopartículas na matriz polimérica e que, apesar de haver um revestimento das partículas com estearato de cálcio, há necessidade de se obter interações mais fortes entre a matriz polimérica e a carga inorgânica. A comparação entre os perfis de parafuso utilizados no processo de extrusão mostrou que materiais mais resistentes à flexão e ao impacto são obtidos a 350 rpm, utilizando a configuração de parafuso menos cisalhante. Há, entretanto, redução das propriedades de tração. Para obtenção de nanocompósitos de polipropileno e carbonato de cálcio, outras condições de processamento, e/ou outros procedimentos de revestimento das cargas devem ser testados de forma a promover melhor dispersão da carga e melhor interação entre carga e matriz.

The need to develop new dental luting agents in order to improve the success of treatments has greatly motivated research. OBJECTIVE: The aim of this study was to evaluate the diametral tensile strength (DTS) and film thickness (FT) of an experimental dental luting agent derived from castor oil (COP) with or without addition of different quantities of filler (calcium carbonate - CaCO3). MATERIAL AND METHODS: Eighty specimens were manufactured (DTS N=40; FT N=40) and divided into 4 groups: Pure COP; COP 10%; COP 50% and zinc phosphate (control). The cements were mixed according to the manufacturers' recommendations and submitted to the tests. The DTS test was performed in the MTS 810 testing machine (10 KN, 0.5 mm/min). For FT test, the cements were sandwiched between two glass plates (2 cm²) and a load of 15 kg was applied vertically on the top of the specimen for 10 min. The data were analyzed by means of one-way ANOVA and Tukey's test (α=0.05). RESULTS: The values of DTS (MPa) were: Pure COP- 10.94±1.30; COP 10%- 30.06±0.64; COP 50%- 29.87±0.27; zinc phosphate- 4.88±0.96. The values of FT (µm) were: Pure COP- 31.09±3.16; COP 10%- 17.05±4.83; COP 50%- 13.03±4.83; Zinc Phosphate- 20.00±0.12. One-way ANOVA showed statistically significant differences among the groups (DTS - p=1.01E-40; FT - p=2.4E-10). CONCLUSION: The experimental dental luting agent with 50% of filler showed the best diametral tensile strength and film thickness.

Calcium carbonate has many applications in different fields; its use in environment remediation is particularly considered, due to its non-toxicity and potentially high efficiency. The structure, morphology and surface features of calcium carbonate can greatly affect its performance. Hierarchical porosity, in particular, can be beneficial for several functional properties. In this study, we report the synthesis of biomorphic calcium carbonate using a sustainable template agent – waste cork powder. Pyrolysed cork powder was infiltrated by an appropriate calcium-containing salt and successively thermally treated. Selected precursors, different impregnation-solution concentrations and thermal conditions were tested. The resulting materials were characterised by XRD, Raman spectroscopy and SEM. Surface area and porosity features were studied by BET analysis, with a detailed study on the effect of synthesis on the mesoporosity of the materials, average sizes varying between 4−15 nm. The most valuable results were achieved with calcium acetate followed by pyrolysis performed for relatively short time period. This maintained the porous 3D honeycomb cork structure made of ∼20 μm hexagonal cells, while consisting of highly mesoporous single-phase CaCO3. Such samples showed the highest surface area ever reported for CaCO3 prepared using a plant-based template; moreover, it also exhibited a dual-scale hierarchical porosity as, in addition to micrometer scale cellular macroporosity, it contained a significant mesoporosity in the cell walls, with a very narrow range of 3.6–3.9 nm. These promising characteristics enable the potential employment of cork-derived CaCO3 for environment remediation.

Marine-derived food wastes mainly include seafood, fish and feed production resources. From the crustaceans traded annually, 6 to 8 million tonnes of valuable shrimp, lobster and/or crab shells waste are produced worldwide. In this systemic work, the researchers with complementary technical expertise, covering the fields of chemical engineering design, chemistry, materials, predictive environmental sciences and economy, worked together to develop a sustainable multiproduct pipeline for the biorefinery of unwanted by-products. All process bio-products from the shells waste were recovered, separated, and purified. Only harmless solvents, namely water, the protonating acetic acid under mild functional conditions and buffers, conjugated with solid–liquid extraction, centrifugation, and membrane ultrafiltration technologies were applied. Here, a success business model is shown after its standardised evaluation in terms of purification performance, economic impact, and life cycle assessment has been performed, driving this sector towards a sustainable ocean-based economy

CaCO3/cellulose nanocomposite materials were prepared by the controlled reaction of CaCl2 with dimethylcarbonate ((CH3)2CO3) in alkaline medium in the presence of cellulose fibers. The effect of several reaction parameters, such as reaction time, temperature, fiber mass fraction and extent of cellulose modification (carboxymethylation), on the final properties of the nanocomposites was investigated by ICP-AES, FT-IR, XRD, SEM, TGA, ToF-SIMS and XPS. The results showed that the hydrolysis conditions strongly influenced the quantity and morphology of CaCO3 particles deposited at the surface of cellulosic fibers. Under specific experimental conditions, the substrate promoted the selective control growth of CaCO3 at the surface of the fibers. The use of these CaCO3/cellulose nanocomposites as reinforcing materials in polyethylene (PE) based composites was also tested. Preliminary DMA studies showed a much higher mechanical performance for the composites with the CaCO3/cellulose fibers nanocomposites as compared to cellulose fibers.

The goal of this study is to find a practicable way to recycle cuttlebone waste in the production of lime. It was studied the behavior of calcium oxide obtained from the calcination of this waste at 900, 1000 and 1100 ºC and, after wet slaking, the produced lime was characterized. All the results were compared to calcium oxide or to hydrated lime obtained from commercial limestone. According to the slaking results, the waste and the limestone calcined at 1000 ºC achieved the R4 (around 13 min to reach 60 ºC) and R5 (60 ºC in 25 s) reactiv­ity class, respectively. Changing the calcination temperature to 900 or 1100 ºC did not promote an increase in the reactivity of the calcined waste. Although less reactive than the calcined limestone, the calcined cuttlebone can be transformed without significant constraint into building lime, since this construction material fulfills the relevant physic-chemical standard specifications.