Inês J. Seabra

Cotton gauze bandage: a support for protease immobilization for use in biomedical applications

Neste trabalho foi efetuada a imobilizacao de tripsina numa gaze esterilizada de algodao. Foram determinadas as condicoes otimas de imobilizacao: foi estudada a influencia do pH, concentracao e volume da solucao de tripsina usada na imobilizacao na hidrolise da N-benzoil-DL-arginina p-nitroanilida. As propriedades cataliticas, os parâmetros cineticos e as condicoes de estabilidade das enzimas livre e imobilizada foram comparadas. Os resultados mostraram que o pH e a temperatura otimos para a tripsina imobilizada foram 9.5 e 55 oC, respectivamente, maiores que os correspondentes da forma livre (7,5 e 45 oC). A 37 oC e a pH 7,0 (aproximadamente as condicoes fisiologicas) Km (constante de Michaelis) foi 3,98 µmol/mL e Vmax (velocidade maxima de reaccao) foi 0,719 µmol/(min mg) para a tripsina imobilizada; para a tripsina livre os valores correspondentes foram 2,46 µmol/mL e 2,89 µmol/(min mg). A quantidade de enzima imobilizada foi de 6 mg/g (base seca). Apos 30 dias nao se verificou libertacao de tripsina do suporte. O bom desempenho da tripsina imobilizada na gaze esterilizada de algodao comprova a sua potencial utilizacao como agente anti-inflamatorio no tratamento de lesoes cutâneas.

Supercritical solvent impregnation of natural bioactive compounds in N-carboxybutyl chitosan membranes for the development of topical wound healing applications

Supercritical Solvent Impregnation (SSI) was used to load topical membrane-type wound dressing biomaterials with natural based bioactive compounds namelly quercetin as an antiinflammatory and thymol as anaesthetic and skin permeation enhancer. The biodegradable and biocompatible membranes where prepared as film- and foam-like structures of N-carboxybutylchitosan and agarose to study the influence of morphological structure on the fluid handling capacities of the materials. Results show that SSI is a feasible and advantageous process that permits to ‘tune’ the relative loaded amounts of the bioactive substances by changing the operational conditions. The process also promotes the size reduction of quercetin particles with a significant improvement in its solubility in aqueous solutions and consequently in its bioavailability. The prepared materials present a sustained delivery for quercetin and adequate fluid handling capacities that are in the typical and desired ranges for commercial wound dressings.

Adsorbent Derived from Pinus pinaster Tannin for Cationic Surfactant Removal

Abstract Pinus tannin gel (PTG) has proven to be an effective adsorbent for removing various cationic pollutants including heavy metals, dyes, and surfactants. The form of obtaining these condensed tannins from Pinus pinaster bark was conventional aqueous extraction using 5.0% ethanol as additive. The present study focused on the removal of the surfactant hexadecyltrimethylammonium bromide (CTAB) from aqueous solutions using PTG. Kinetic studies showed that the Lagergren, Ho, and Elovich models all adequately explained the kinetics of CTAB adsorption onto PTG, with r2 correlation coefficients of around 0.98. The influences of pH and temperature were found not to be critical, and the CTAB-PTG system was modeled theoretically according to the Langmuir hypothesis using linear, nonlinear, and multiparametric forms, obtaining the values of the activation energies and such system constants as k l .

CHAPTER 7:Recent Trends and Perspectives for the Extraction of Natural Products

In this chapter we present and discuss the most recent trends and perspectives on the extraction of natural products. This was made considering: (i) the natural‐origin extracts/target compounds that are currently being more studied and extracted (as well as in their potential applications); (ii) the most recently extracted vegetable raw materials that can be explored as sources for the envisaged target compounds; (iii) the current and most promising strategies regarding the extraction methodologies that are expected to be further developed and employed on the extraction of natural products; and (iv) the novel/alternative solvents, solvent mixtures and extraction additives that could be beneficially used in the above referred extraction methodologies. To accomplish this task, we performed a literature search (covering the period between 2000 and 2011) and used several specific search descriptors in order to verify the above referred trends in the extraction of natural products. Results showed that, in recent years, there has been a clear renewed/increased interest in the extraction of natural products and in their advantageous applications, namely as food supplements, phytomedicines, nutraceuticals, cosmetics and natural pesticides. The most used natural‐origin raw materials to obtain these natural products were terrestrial plant‐origin raw materials. In addition, there was a greater interest in the extraction from plant residues/wastes, from marine organisms and from microorganisms. In terms of the most employed natural products extraction methods, supercritical fluid extraction methods seemed to keep the interest of researchers, while other methods, such as ultrasound, microwave, pressurized‐liquid, sorptive and combined/hyphenated extraction techniques, have gained more attention in recent years. Finally, a recent interest was also observed in using novel extraction solvents (or solvent mixtures) that may improve process safety and sustainability, and/or that may improve extraction yields, selectivities and stabilities of the target compounds. Moreover, it is expected that the observed trends will be maintained in the near future as they were mostly motivated by recent consumer demands and by safety, environmental and regulatory issues.