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- Assessment and comparison of the properties of biodiesel synthesized from three different types of wet microalgal biomassPublication . Gangadhar, Katkam N.; Pereira, Hugo; Diogo, Herminio P.; Borges dos Santos, R. M.; Devi, B. L. A. Prabhavathi; Prasad, R. B. N.; Custódio, Luísa; Xavier Malcata, F.; Varela, João; Barreira, LuísaIn recent years, microalgae-based carbon-neutral biofuels (i.e., biodiesel) have gained considerable interest due to high growth rate and higher lipid productivity of microalgae during the whole year, delivering continuous biomass production as compared to vegetable-based feedstocks. Therefore, biodiesel was synthesized from three different microalgal species, namely Tetraselmis sp. (Chlorophyta) and Nannochloropsis oculata and Phaeodactylum tricornutum (Heterokontophyta), and the fuel properties of the biodiesel were analytically determined, unlike most studies which rely on estimates based on the lipid profile of the microalgae. These include density, kinematic viscosity, total and free glycerol, and high heating value (HHV), while cetane number (CN) and cold filter plugging point (CFPP) were estimated based on the fatty acid methyl ester profile of the biodiesel samples instead of the lipid profile of the microalgae. Most biodiesel properties abide by the ASTM D6751 and the EN 14214 specifications, although none of the biodiesel samples met the minimum CN or the maximum content of polyunsaturated fatty acids with a parts per thousand yen4 double bonds as required by the EN 14214 reference value. On the other hand, bomb calorimetric experiments revealed that the heat of combustion of all samples was on the upper limit expected for biodiesel fuels, actually being close to that of petrodiesel. Post-production processing may overcome the aforementioned limitations, enabling the production of biodiesel with high HHV obtained from lipids present in these microalgae.
- Influence of preparation procedures on the phenolic content, antioxidant and antidiabetic activities of green and black teasPublication . Almeida, Tânia Santos de; Araújo, Maria Eduarda Machado; Rodríguez, Lucía González; Júlio, Ana; Mendes, Beatriz Garcia; Borges dos Santos, R. M.; Simões, José Artur MartinhoThe influence of common tea preparation procedures (temperature, infusion time, consumption time interval and tea bag/loose-leaf) and the type of water used, on the total phenolic content (TPC), the radical scavenging activity and the alpha-glucosidase inhibitory activity were assessed. Higher TPC and antioxidant activity were obtained when using lower mineralized waters. Tea bags also evidenced higher antioxidant activity than loose-leaf samples. Under the same conditions (90 degrees C and five minutes of infusion time) green tea contains almost twice the quantity of polyphenols and the free radical scavenging ability of black tea. In the alpha-glucosidase assay all infusions were active (97-100 %). Furthermore, HPLC allowed to identify some of the polyphenols present in both teas and to monitor their composition change with time. After twenty-four hours, the antioxidant activity was maintained without significant changes, but a small decrease in enzyme inhibition was observed, although this activity was still very high.
- Development of a prototype of an aerosolization device for dry powders to improve in vitro cell-based assays in the context of lung deliveryPublication . Pontes, Jorge Filipe; Hermínio P., Diogo; Conceição, Eusébio; Musacchio, Flávia; Borges dos Santos, R. M.; Grenha, AnaThe lung has been, for the past years, subject of intense research for local and systemic drug delivery approaches. However, robust correlations between in vitro and in vivo results are often impaired, as in vitro experiments frequently have limitations mimicking lung conditions, especially when involving cell-based studies. This work proposes a 3D-printed device for aerosolization of dry powders over cells in culture, thus better resembling the conditions of aerosolization occurring in vivo. The proposed device comprises two parts, the weighing head, and the main body. Dry powders are weighed in the weighing head, which is then sealed to the main body. Next, compressed air is injected into the device, dragging the powder onto a plate, which fits the bottom of the main body. The plate is a suitable surface for cell culture. Dry powders (polysaccharide-based microparticles) were tested using the device, leading to an aerosolization yield up to 51%, which was observed to depend on the tested dry powder. The dry powder deposition profile is currently being evaluated using a Quartz-Crystal Microbalance, which replaces the plate at the bottom of the device’s main body. These experiments entail a more precise determination of the mass of aerosolized powders by analysing the differences in the vibration frequencies of a quartz crystal, thus allowing to assess the deposition profile. Although preliminary, the results show that the developed device may comprise an affordable solution for in vitro testing of dry powders when aerosolization over a surface is required.
- Development of a dry powder insufflation device with application in in vitro cell-based assays in the context of respiratory deliveryPublication . Pontes, Jorge Filipe; Diogo, Hermínio P.; Conceição, Eusébio; Almeida, Maria P.; Borges dos Santos, Rui M.; Grenha, AnaResearch on pharmaceutical dry powders has been increasing worldwide, along with increased therapeutic strategies for an application through the pulmonary or the nasal routes. In vitro methodologies and tests that mimic the respiratory environment and the process of inhalation itself are, thus, essential. The literature frequently reports cell-based in vitro assays that involve testing the dry powders in suspension. This experimental setting is not adequate, as both the lung and the nasal cavity are devoid of abundant liquid. However, devices that permit powder insufflation over cells in culture are either scarce or technically complex and expensive, which is not feasible in early stages of research. In this context, this work proposes the development of a device that allows the delivery of dry powders onto cell surfaces, thus simulating inhalation more appropriately. Subsequently, a quartz crystal microbalance (QCM) was used to establish a technique enabling the determination of dry powder deposition profiles. Additionally, the determination of the viability of respiratory cells (A549) after the insufflation of a dry powder using the developed device was performed. In all, a prototype for dry powder insufflation was designed and developed, using 3D printing methods for its production. It allowed the homogenous dispersion of the insufflated powders over a petri dish and a QCM crystal, and a more detailed study on how dry powders disperse over the supports. The device, already protected by a patent, still requires further improvement, especially regarding the method for powder weighing and the efficiency of the insufflation process, which is being addressed. The impact of insufflation of air and of locust bean gum (LBG)-based microparticles revealed absence of cytotoxic effect, as cell viability roughly above 70 % was always determined.