Loading...
24 results
Search Results
Now showing 1 - 10 of 24
- Risperidone release from solid lipid nanoparticles (SLN): validated HPLC method and modelling kinetic profilePublication . Silva, Ana Catarina; Lopes, Carla Martins; Fonseca, J.; Soares, M.E.; Santos, D.; Souto, Eliana B.; Ferreira, D.A simple reverse-phase (RP) high performance liquid chromatography (HPLC) method was developed and validated, according to the International Harmonisation Guidelines (ICH), for the determination of risperidone (RISP) from solid lipid nanoparticles (SLN). Chromatographic runs were performed on a RP-C18 column, using an isocratic mobile phase of methanol, acetate buffer (0.05 M; pH 4.6) and triethylamine (60:40:0.02, v/v/v). The flow rate was 1 ml/min, the run time was 10 min and the RISP absorbance was measured at 280 nm, using UV detection. A linear response was obtained for a RISP concentration range of 0.25 - 10.00 g/ml (R2 = 0.9996), with a detection and quantification limits of 0.011 and 0.034 g/ml, respectively. The method was shown to be specific, precise at the intra-day (RSD < 0.796%) and inter-day (RSD < 0.331%) levels, and accurate with recoveries between 86.86 - 100.3% (RSD < 0.613%). Method robustness was observed as well. The suitability of the method for RISP quantifications was assessed by the determination of encapsulation parameters (encapsulation efficiency and drug loading) and by studying the RISP release profile from SLN. Kinetic models (zero order, Higuchi, Korsmeyer-Peppas and Baker-Lonsdale) were used to fit the obtained release profile and to predict the in vivo performance of RISP-loaded SLN. A combined pattern of diffusion and erosion release mechanism (anomalous non-Fickian transport) was found for the RISP-loaded SLN, which shows the ability of the system for controlled drug release.
- Novos sistemas terapêuticos nanotecnológicosPublication . Marques, Inês; Lopes, Carla Martins; Souto, Eliana B.A Nanotecnologia é uma nova ciência que emergiu nos últimos anos em várias áreas de aplicação, incluindo a da actividade farmacêutica, em particular na concepção de novas formas farmacêuticas. Com efeito, a produção de novas formas farmacêuticas constituídas por nanocristais de fármacos tem vindo a adquirir cada vez mais interesse por parte da comunidade científica. A principal vantagem da utilização de nanocristais de fármacos está directamente relacionada com a facilidade inerente ao processo de produção. O objectivo final consiste na produção de uma suspensão de partículas de fármaco com dimensões inferiores a 1 μm, que seja física e quimicamente estável, garantindo a viabilidade tecnológica e terapêutica para um determinado fármaco. Nanotechnology is a novel science which has emerged in the latest years in several fields, including the pharmaceutical sciences in particular in the development of novel drug delivery systems. Among the scientific community, the production of drug nanocrystals as novel delivery systems has being gathering attention. The main advantage of drug nanocrystals includes production facilities available. The final aim of this technology is to produce a physicochemically stable suspension to warrantee technological and therapeutic feasibility for a particular drug.
- Cancer nanopharmaceuticals: physicochemical characterization and in vitro/in vivo applicationsPublication . Zielińska, Aleksandra; Szalata, Marlena; Gorczyński, Adam; Karczewski, Jacek; Eder, Piotr; Severino, Patrícia; Cabeda, JM; Souto, Eliana B.; Słomski, RyszardPhysicochemical, pharmacokinetic, and biopharmaceutical characterization tools play a key role in the assessment of nanopharmaceuticals’ potential imaging analysis and for site-specific delivery of anti-cancers to neoplastic cells/tissues. If diagnostic tools and therapeutic approaches are combined in one single nanoparticle, a new platform called nanotheragnostics is generated. Several analytical technologies allow us to characterize nanopharmaceuticals and nanoparticles and their properties so that they can be properly used in cancer therapy. This paper describes the role of multifunctional nanoparticles in cancer diagnosis and treatment, describing how nanotheragnostics can be useful in modern chemotherapy, and finally, the challenges associated with the commercialization of nanoparticles for cancer therapy.
- Novel carriers for sunscreen formulationsPublication . Doktorovova, Slavomira; Marques, Cecília; Barbosa, Catarina; Lopes, Carla Martins; Souto, Eliana B.Sunscreens are cosmetic products for convenient and safe delivery of solar filters. These are used to prevent the skin damage caused by sunlight exposure. Due to photo-instability and potential adverse effects of some of these filters, novel application forms are demanded. Lipid based colloidal carriers commonly named as lipospheres provide the advantage of sufficient protection of the solar filters, their delivery to upper skin layer only, and controlled release. Being composed of biocompatible and biodegradable materials similar to those existing in the stratum corneum, they are generally well tolerated. This review gives an overview of novel approaches to sunscreen formulations.
- Effect of polymer viscosity on physicochemical properties and ocular tolerance of FB-loaded PLGA nanospheresPublication . Araújo, J.; Vega, E.; Lopes, Carla Martins; Egea, M.A.; Garcia, M.L.; Souto, Eliana B.Poly(lactide-co-glycolide) acid (PLGA) nanospheres incorporating flurbiprofen (FB) were produced by the solvent displacement technique, for ocular applications aiming to avoid/minimize inflammation induced by surgical trauma. In this work, a PLGA of low viscosity has been tested and the results obtained were compared with those previously reported by Vega et al. The physicochemical properties of the developed formulations were evaluated by measuring particle size, zeta potential and FB entrapment efficiency, showing no significant differences. Release studies demonstrated that the formulation produced with PLGA of higher viscosity revealed a slower drug release rate. Stability analysis, for a period of 75 days, was performed using three complementary methods: (i) turbidity experiments using a Turbiscan optical analyzer, (ii) particle size measurements, and (iii) zeta potential analysis. The results revealed long-term physicochemical stability suitability for ophthalmic use, being independent from the polymer viscosity. The ocular tolerance was assessed by an alternative in vitro method to animal experimentation, the HETCAM. For all developed formulations no ocular irritancy has been detected.
- Cationic solid lipid nanoparticles (cSLN): structure, stability and DNA binding capacity correlation studiesPublication . Doktorovova, S.; Shegokar, R.; Rakovsky, E.; Gonzalez-Mira, E.; Lopes, Carla Martins; Silva, A.M.; Martins-Lopes, P.; Muller, R.H.; Souto, Eliana B.Cationic solid lipid nanoparticles (cSLN) are promising lipid nanocarriers for intracellular gene delivery based on well-known and widely accepted materials. cSLN containing single-chained cationic lipid cetyltrimethylammonium bromide were produced by high pressure homogenization and characterized in terms of(a) particle size distribution by photon correlation spectroscopy (PCS) and laser diffractometry (LD), (b) thermal behaviour using differential scanning calorimetry (DSC) and (c) the presence of various polymorphic phases was confirmed by X-ray diffraction (WAXD). SLN composed of Imwitor 900PTM (IMW) showed different pDNA stability and binding capacity in comparison to those of Compritol 888 ATOTM (COM). IMW-SLN, having z-ave = 138–157 nm and d(0.5) = 0.15–0.158 m could maintain this size for 14 days at room temperature. COM-SLN had z-ave = 334 nm and d(0.5) = 0.42 m on the day of production and could maintain similar size during 90 days. IMW-SLN revealed improved pDNA binding capacity. We attempted to explain these differences by differentinteractions between the solid lipid and the tested cationic lipid.
- Preparation, characterization and biocompatibility studies on risperidone-loaded solid lipid nanoparticles (SLN): High pressure homogenization versus ultrasoundPublication . Silva, Ana Catarina; González-Mira, E.; García, M.L.; Egea, M.A.; Fonseca, J.; Silva, R.; Santos, D.; Souto, Eliana B.; Ferreira, D.The suitability of solid lipid nanoparticles (SLN) for the encapsulation of risperidone (RISP), an antipsychotic lipophilic drug, was assessed for oral administration. The hot high pressure homogenization (HPH) and the ultrasound (US) technique were used as production methods for SLN. All the studies on the SLN formulations were done in parallel, in order to compare the results and conclude about the advantages and limitations of both techniques. The particle sizes were in the nanometer range for all prepared SLN formulations and the zeta potential absolute values were high, predicting good long-term stability. Optical analyses demonstrated the achievement of stable colloidal dispersions. Physicochemical characterization of dispersions and bulk lipids, performed by differential scanning calorimetry (DSC) and X-ray assays, support prediction of occurrence of drug incorporation in the SLN and good long term stability of the systems. The toxicity of SLN with Caco-2 cells and the existence of contaminations derived from the production equipments were assessed by the (4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide (MTT) assay. The results showed 90% of cell viability after SLN exposure, with no significant differences within all prepared formulations (p > 0.05). From this study, we conclude that SLN can be considered as efficient carriers for RISP encapsulation. Moreover, HPH and US revealed to be both effective methods for SLN production.
- Glucagon-like peptide 1: biochemistry, secretion and main physiological effectsPublication . Silva, Amélia M.; Lopes, Carla Martins; Misler, Stanley; Cooper, Gregory D.; Andreani, Tatiana; Souto, Eliana B.O “Glucagon-like peptide 1” (GLP-1), hormona produzida nas células-L intestinais por processamento diferencial do proglucagon, é libertado após ingestão de alimentos. Efeitos de GLP- 1 observam-se, essencialmente, a nível gastrintestinal e pancreático resultando da sua acção directa, ligação ao receptor nas células alvo, ou indirecta, por regulação parácrina. Pelo seu papel na regulação da ingestão de alimentos e na secreção de insulina induzida por glicose, agonistas do receptor de GLP-1 são alvo de estudos para a terapia da obesidade e diabetes. The peptide hormone Glucagon-like peptide 1 (GLP-1), produced in the intestinal L-cells by differential processing of proglucagon, is secreted in response to meal intake. GLP-1 affects various systems, the gastrointestinal and pancreatic systems being the best studied, either by direct binding to the GLP-1 receptor, at the target-cells surface, or indirectly as a result of paracrine regulation. Because of GLP-1’s roles, in augmenting glucose-induced insulin secretion and modulating food intake, currently GLP-1 receptor agonists are being studied for diabetes and obesity therapy.
- The role of lipids in drug absorption throught the GITPublication . Doktorovova, Slavomira; Morsy, Tarek; Balcão, Victor; Souto, Eliana B.Os vectores lipídicos apresentam inúmeras vantagens para a administração oral de substâncias farmacológicas, p.ex. são compostos por moléculas lipídicas semelhantes àquelas que figuram nos tecidos humanos, tornando-se biocompatíveis, biotoleráveis e biodegradáveis. São exemplos as tradicionais emulsões O/A, as suspensões de nanopartículas lipídicas (SLNs e NLC s) e, recentemente, as SolEmuls®, que permitem localizar fármacos fracamente solúveis em ambas as fases das emulsões, na camada interfacial de lecitina. Este artigo aborda o papel dos lípidos no aumento da absorção e da biodisponibilidade de fármacos administrados oralmente. Lipid carriers show several advantages for oral delivery of pharmacologically active drugs, e.g. are composed of lipid molecules similar to those in human tissues, becoming therefore biocompatible, biotolerable and biodegradable. Examples include traditional o/w emulsions, suspensions of lipid nanoparticles (SLNs and NLC s) and, recently, the SolEmuls®, which allows localizing poorly soluble drug molecules both in oil and aqueous phases, in the interfacial layer of lecithin. This paper reports on the role of lipids in enhancing both drug absorption and bioavailability when administered orally.
- Estado da arte na prestação de cuidados e tratamento da diabetes mellitusPublication . Ramalho, Sancho Miguel Balsa; Souto, Eliana B.; Lopes, Carla MartinsA Diabetes Mellitus é um dos maiores problemas mundiais de Saúde Pública. A Diabetes é uma desordem metabólica de etiologia múltipla, caracterizada por uma hiperglicemia crónica com distúrbios no metabolismo dos hidratos de carbono, lípidos e proteínas, resultantes de deficiências na secreção ou acção da insulina, ou de ambas. O plano de tratamento pode incluir várias estratégias: consciencialização e educação para a adesão à terapêutica, implementação de plano alimentar e recomendações nutricionais, prática de exercício físico, administração de agentes antidiabéticos, insulina e gestão das complicações associadas.
- «
- 1 (current)
- 2
- 3
- »