Helena Ferreira

Effect of ultrasound parameters for unilamellar liposome preparation.

In this study, it was investigated the effects of ultrasound, namely power input, distance from ultrasound tip to base of reactor and treatment time, in the formation of liposomes. Results indicate a dependence on cavitation events that are a function of power input, and consequently dependent on the position of the probe within the reaction vessel and the wave behaviour. Short treatment times are required to achieve nanosized vesicles in anti-nodal (lambda/4; 19mm) reactor geometries. In this wave point the cavitation phenomenon is more pronounced when compared with the nodal point (lambda/2; 38mm). Therefore, the consideration of the above parameters is vital if dependable and repeatable results are to be achieved.

Sonoproduction of Liposomes and Protein Particles as Templates for Delivery Purposes

The development of nano and micro delivery systems (DS), so small in size, is growing in importance, such as in drug targeting. In an era where nano is the new trend, micro and nano materials are in the forefront of progress. These systems can be produced by a diversity of methods. However, the use of high-intensity ultrasound offers an easy and versatile tool for nano- and microstructured materials that are often unavailable by conventional methods. Similarly to the synthesis methods that can be used, several starting materials can be applied to produce particulate systems. In this review, the recent strategic development of DS is discussed with emphasis on liposomes and polymer-based, specially protein-based, nanomedicine platforms for drug delivery. Among the variety of applications that materials in the particulate form can have, the control release of drugs is probably the most prominent one, as these have been in the forefront line of interest for biomedical applications. The basic concepts of sonochemical process pertaining to DS are summarized as well as the role of sonochemical procedure to their preparation. The different applications of these systems wrap up this review.

Insights on the mechanism of formation of protein microspheres in a biphasic system

Microspheres of bovine serum albumin (BSA) and silk fibroin are produced by applying ultrasound in a biphasic system consisting of an aqueous protein solution and an organic solvent. The protein microspheres are dispersed in an aqueous media where the protein remains at the interface covering the organic solvent. This only occurs when high shear forces are applied that induce changes to force the protein to the interface. Fourier transform infrared results indicate a large increase in the content of the β-sheet during the formation of silk fibroin microspheres. Molecular dynamics simulations show a clear adaption on the 3D structure of BSA when stabilized at the interface, without major changes in secondary structure. Further studies demonstrate that high water content, oil solvents, and larger peptides with separated and clear hydrophobic and hydrophilic areas lead to more stable and smaller spheres. This is the first time that these results are presented. We also present herein the rationale to produce tailored protein microspheres with a controlled size, controlled charge, and increased stability.

Protein microspheres as suitable devices for piroxicam release

Bovine serum albumin-piroxicam (BSA-piroxicam) and human serum albumin-piroxicam (HSA-piroxicam) microspheres were sonochemically prepared and characterized. The use of polyvinyl alcohol (PVA) lead to an improvement of formulation characteristics, including smaller size, lower polydispersity index (PDl), higher entrapment efficiency and higher stability. The release kinetics of these proteinaceous microspheres was determined in presence of protease, indicating an anomalous drug transport mechanism (diffusion and polymer degradation). In presence of higher protease concentration, BSA microspheres exhibit Case II transport, leading to zero order release (protein degradation). These proteinaceous devices did not show cytotoxicity against human skin fibroblasts in vitro, for range concentrations below to 300 mg L(-1), greatly supporting their potential application in the treatment of inflammatory diseases.

Incorporation of peptides in phospholipid aggregates using ultrasound

This study presents the highlights of ultrasonic effects on peptides incorporated on phospholipid aggregates (liposomes). These liposomes or vesicles are known as transport agents in skin drug delivery and for hair treatment. They might be a good model to deliver larger peptides into hair to restore fibre strength after hair coloration, modelling, permanent wave and/or straightening. The preparation of liposomes 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) with peptides (LLLLK LLLLK LLLLK LLLLK; LLLLL LCLCL LLKAK AK) was made by the thin film hydration method. The LUVs (uni-lamellar vesicles) were obtained by sonication, applying different experimental conditions, such as depth (mm) and power intensity (%). Photon-correlation spectroscopy (PCS) and electronic microscopy (EM) results confirmed that the incorporation of these peptides, with different sequence of amino acids, presented differences on the diameter, zeta-potential of membrane surface and shape of liposomes. The liposomes that included peptide LLLLK LLLLK LLLLK LLLLK present an increased in zeta-potential values after using ultrasound and an amorphous aspect. Conversely, the liposomes that incorporated the peptide LLLLL LCLCL LLKAK AK presented a define shape (rod shape) and the potential surface of liposome did not change significantly by the use of ultrasound.

Deformable Liposomes for the Transdermal Delivery of Piroxicam

Deformable Liposomes for the Transdermal Delivery of Piroxicam nAbstract nObjective: Deformable liposomes have been used to improve drugs transdermal delivery. These vesicular systems were employed to deliver piroxicam through the skin as a mean to treat inflammatory diseases and avoid undesired side-effects. nMethods: Deformable liposomes, composed by egg-yolk phosphatidylcholine, sodium cholate and α-tocopherol, were prepared by the thin film hydration method followed by extrusion. Piroxicam was included into the lipid bilayer or in the aqueous phase using inclusion complexes of piroxicam with β-cyclodextrin. After characterization, it was evaluated their in vitro permeation using Franz diffusion cells with polysulfone membranes or pig skin. nResults: The entrapment of piroxicam in the aqueous compartment, through the use of β-cyclodextrin inclusion complexes, enabled higher entrapment efficiency (63.27% more than when entrapped in the lipid bilayer). The optimized deformable liposomes population were homogeneous (PDI < 0.1) in terms of size (108.93 ± 3.74 nm) and presented a spherical shape. Size stability studies demonstrated that the vesicles were stable along two months of storage. In vitro permeation studies using Franz diffusion cells and polysulfone membranes showed that the vesicles own enough deformability to pass through pores smaller than their own size in a percentage ≈ 45%. Furthermore, a constancy of their diameter and morphology was verified after pores passage. In the experiments performed with pig skin, the permeation of the deformable liposomes incorporating piroxicam β-cyclodextrin complexes decrease considerably. After 24 h of diffusion, only 1.1-3.2 % of the initial population reached the liquid receptor as result of the presence of the stratum corneum which is the main barrier of the skin. Nevertheless, the histological studies demonstrated that deformable liposomes were uniformly distributed on the skin structure and thus were able to achieve a percutaneous permeation of their content. nConclusion: The results support the possibility to use this formulation on the topical treatment of inflammatory conditions.

Sonochemical Proteinaceous Microspheres for Wound Healing

In this work, we report a novel approach using proteinaceous microspheres of bovine serum albumin (BSA), human serum albumin (HSA) and silk fibroin (SF) containing different organic solvents, namely n-dodecane, mineral oil and vegetable oil, to reduce the activity of human neutrophil elastase (HNE) found in high levels on chronic wounds. The ability of these devices to inhibit HNE was evaluated using porcine pancreatic elastase (PPE) solution as a model of wound exudates. The results obtained indicated that the level of PPE activity can be tuned by changing the organic solvent present on different protein microspheres, thus showing an innovative way of controlling the elastase-antielastase imbalance found in chronic wounds. Furthermore, these proteinaceous microspheres were shown to be important carriers of elastase inhibitors causing no cytotoxicity in human skin fibroblasts in vitro, making them suitable for biomedical applications, such as chronic wounds.

Universality in the stock exchange market

We consider the α re-scaled Standard & Poors 100 (SP100) daily index positive returns and negative returns ( that we call, after normalization, the α positive fluctuations and α negative fluctuations, respectively. We use the Kolmogorov–Smirnov statistical test as a method to find the values of α that optimize the data collapse of the histogram of the α fluctuations with the truncated Bramwell–Holdsworth–Pinton (BHP) probability density function (pdf) and the truncated generalized log-normal pdf f LN that best approximates the truncated BHP pdf. The optimal parameters we found are , , and . Using the optimal α′s, we compute analytical approximations of the probability distributions of the normalized positive and negative SP100 index daily returns r(t). Since the BHP pdf appears in several other dissimilar phenomena, our result reveals a universal feature of the stock exchange markets.

Universality in nonlinear prediction of complex systems

We exploit ideas of nonlinear dynamics and statistical physics in a complex nondeterministic dynamical setting using the Ruelle-Takens embedding. We present some new insights on the quality of the prediction in the laminar regime and we exhibit the data collapse of the predicted relative first difference fluctuations to the universal Bramwell–Hodsworth–Pinton distribution. Hence, the nearest neighbour method of prediction acts as a filter that does not eliminate the randomness, but exhibits its universal character.

Wound-healing evaluation of entrapped active agents into protein microspheres over cellulosic gauzes

The use of active ingredients in wound management have evolved alongside the pharmaceutical agents and dressings used to deliver them. However, the development of gauzes, dressings with specific properties, still remains a challenge for several medical applications. A new methodology for the controlled release of active components for the healing of burn wounds is proposed herein. Cotton and non-woven bandages have been cationised to promote the attachment of protein microspheres. The active agents, piroxicam and vegetable oil, were entrapped into the microspheres using ultrasound energy. Active agents were released from the microspheres by a change in pH. Wound healing was assessed through the use of standardised burn wounds induced by a cautery in human full-thickness skin equivalents (EpidermFT). The best re-epithelialisation and fastest wound closure was observed in wounds treated with proteinaceous microspheres attached to gauzes, after six days of healing, in comparison with commercial collagen dressing and other controls. Furthermore, the ability of these materials to reduce the inflammation process, together with healing improvement, makes these biomaterials suitable for wound-dressing applications.