Novel alginate-chitosan aerogel fibres for potential wound healing applications.

Aerogels produced from marine polymers, such as chitosan and alginate, are of interest for wound healing applications due to their attractive properties. These properties can be the aerogel's high porosity along with the antimicrobial activity of chitosan or the capacity to provide a moist environment of alginate. The aim of this work was to develop a new route towards hybrid alginate-chitosan aerogel fibres and to evaluate their potential for wound healing applications. The influence of chitosan molecular weight and its content on the fibres characteristics was evaluated. To produce the fibres, the formation of polyelectrolyte complex hydrogels of both polymers was performed by the emulsion-gelation method. Hydrogels were converted in alcogels through a solvent exchange followed by drying with supercritical CO2. Resulting aerogels were observed to be light-weight, fluffy mesoporous fibres with a specific surface area of 162-302 m2/g and specific pore volume of 1.41-2.49 cm3/g. Biocompatibility of the fibres was evaluated, and the result showed that they were non-cytotoxic. Bioactivity of the fibres regarding the ability to close a wound on an in vitro scale and antibacterial activity were also evaluated. Aerogel fibres presented percentages of recovered scratch area of about 75%, higher than the untreated control (~50%) and a clear antibacterial activity against Staphylococcus aureus and Klebsiella pneumoniae. The obtained results suggest that these alginate-chitosan aerogel fibres could be good candidates for wound healing applications.

Microwave and ultrasound pre-treatments to enhance anthocyanins extraction from different wine lees.

Wine lees are rich in anthocyanins (AC), natural colorants with health promoting properties. The extraction kinetics of AC from different wine lees in conventional solid-liquid extraction were studied for the first time. The influence of parameters such as temperature, solid-liquid ratio (RS-L) and type of solvent (hydro-alcoholic mixtures) was also studied. Furthermore, microwaves (MW) and ultrasounds (US) were used as pre-treatments (a prior step to the conventional extraction) in order to increase AC yield. Maximum extraction yield (2.78 mgMALVIDIN-EQUIVALENTS/gDRY-LEES) was achieved after 15 min at 25 °C, with a RS-L of 1/10 (g/mL) and with a 50%vol. ethanol mixture. When MW were used AC extraction yield was doubled (6.20 mgMALVIDIN-EQUIVALENTS/gDRY-LEES) and the required time to achieve a constant yield was reduced (from 15 min to 90 s). Meanwhile, US only shortened extraction time in less proportion (from 15 to 5 min). Putative identification of main extract compounds was performed by LC/MS-MS.

Phenolic characterization of aging wine lees: Correlation with antioxidant activities.

Aging wine lees are water-wastes produced during the wine aging inside wood barrels that can be considered as alternative sources of bioactive compounds. Phenolic characterization and antioxidant activity (AA) measurements of wines lees solid-liquid extracts have been undertaken on a dry extract (DE) basis. Solvents with different polarities (water, methanol, ethanol, two hydroalcoholic mixtures and acetone) were used. Total phenolic (TPC) and total flavonoid contents (TFC) were determined. The mixture of 75:25(v/v) EtOH:H2O showed the highest values with 254 mgGAE/gDE and 146 mgCATE/gDE respectively. HORAC, HOSC and FRAP were used to determine the AA of the extracts being also highest for the mixture of 75:25(v/v) EtOH:H2O (4690 µmolCAE/gDE, 4527 µmolTE/gDE and 2197 µmolTE/gDE, respectively). For ORAC method, methanol extract showed the best value with 2771 µmolTE/gDE. Correlations between TPC, TFC, phenolic compounds and AA were determined. Most relevant compounds contributing to AA were identified using data from mass spectrometry, being mainly anthocyanins.

Alginate-based hybrid aerogel microparticles for mucosal drug delivery.

The application of biopolymer aerogels as drug delivery systems (DDS) has gained increased interest during the last decade since these structures have large surface area and accessible pores allowing for high drug loadings. Being biocompatible, biodegradable and presenting low toxicity, polysaccharide-based aerogels are an attractive carrier to be applied in pharmaceutical industry. Moreover, some polysaccharides (e.g. alginate and chitosan) present mucoadhesive properties, an important feature for mucosal drug delivery. This feature allows to extend the contact of DDS with biological membranes, thereby increasing the absorption of drugs through the mucosa. Alginate-based hybrid aerogels in the form of microparticles (<50µm) were investigated in this work as carriers for mucosal administration of drugs. Low methoxyl pectin and κ-carrageenan were co-gelled with alginate and further dried with supercritical CO2 (sc-CO2). Spherical mesoporous aerogel microparticles were obtained for alginate, hybrid alginate/pectin and alginate/κ-carrageenan aerogels, presenting high specific surface area (370-548m(2)g(-1)) and mucoadhesive properties. The microparticles were loaded with ketoprofen via adsorption from its solution in sc-CO2, and with quercetin via supercritical anti-solvent precipitation. Loading of ketoprofen was in the range between 17 and 22wt% whereas quercetin demonstrated loadings of 3.1-5.4wt%. Both the drugs were present in amorphous state. Loading procedure allowed the preservation of antioxidant activity of quercetin. Release of both drugs from alginate/κ-carrageenan aerogel was slightly faster compared to alginate/pectin. The results indicate that alginate-based aerogel microparticles can be viewed as promising matrices for mucosal drug delivery applications.

Supercritical fluid precipitation of ketoprofen in novel structured lipid carriers for enhanced mucosal delivery--a comparison with solid lipid particles.

Structured lipid carriers based on mixture of solid lipids with liquid lipids are the second generation of solid lipid particles, offering the advantage of improved drug loading capacity and higher storage stability. In this study, structured lipid carriers were successfully prepared for the first time by precipitation from gas saturated solutions. Glyceryl monooleate (GMO), a liquid glycerolipid, was selected in this work to be incorporated into three solid glycerolipids with hydrophilic-lipophilic balance (HLB) ranging from 1 to 13, namely Gelucire 43/01™, Geleol™ and Gelucire 50/13™. In general, microparticles with a irregular porous morphology and a wide particle size distribution were obtained. The HLB of the individual glycerolipids might be a relevant parameter to take into account during the processing of solid:liquid lipid blends. As expected, the addition of a liquid lipid into a solid lipid matrix led to increased stability of the lipid carriers, with no significant modifications in their melting enthalpy after 6 months of storage. Additionally, Gelucire 43/01™:GMO particles were produced with different mass ratios and loaded with ketoprofen. The drug loading capacity of the structured lipid carriers increased as the GMO content in the particles increased, achieving a maximum encapsulation efficiency of 97% for the 3:1 mass ratio. Moreover, structured lipid carriers presented an immediate release of ketoprofen from its matrix with higher permeation through a mucous-membrane model, while solid lipid particles present a controlled release of the drug with less permeation capacity.

Development of multicore hybrid particles for drug delivery through the precipitation of CO2 saturated emulsions.

Hybrid lipid-polymer particles are gaining increasing interest to be applied as drug delivery systems due to their greater stability in biological fluids and enhanced cellular uptake of drugs. However, a major drawback is the fact that these particles are usually produced through techniques that use organic solvents. This work studies the possibility of producing for the first time hybrid particles composed by lipid multicores enveloped in a polymeric layer through Particles from Gas Saturated Solutions (PGSS(®)), without using organic solvents. An oil-in-water emulsion, composed by Gelucire 43/01™ (GEL) as the discontinuous phase and by an aqueous polyethylene glycol 4000 (PEG) solution as the continuous phase, was successfully precipitated by PGSS(®). Operating conditions that ensured the stability of the CO2 saturated emulsion were previously evaluated. The resulting PEG-GEL particles present a spherical-like morphology constituted by several lipid cores encapsulated into a polymeric shell. The applicability of these structured particles to be used as drug delivery system (DDS) was studied by using ketoprofen, a nonsteroidal anti-inflammatory drug (NSAID), as model drug. The particles provided an initial burst release of the drug due to the progressive dissolution of the external layer of PEG, followed by a controlled release of the NSAID from the GEL cores.