Maria Helena Andrade Santana

Current State-of-Art and New Trends on Lipid Nanoparticles (SLN and NLC) for Oral Drug Delivery

Lipids and lipid nanoparticles are extensively employed as oral-delivery systems for drugs and other active ingredients. These have been exploited for many features in the field of pharmaceutical technology. Lipids usually enhance drug absorption in the gastrointestinal tract (GIT), and when formulated as nanoparticles, these molecules improve mucosal adhesion due to small particle size and increasing their GIT residence time. In addition, lipid nanoparticles may also protect the loaded drugs from chemical and enzymatic degradation and gradually release drug molecules from the lipid matrix into blood, resulting in improved therapeutic profiles compared to free drug. Therefore, due to their physiological and biodegradable properties, lipid molecules may decrease adverse side effects and chronic toxicity of the drug-delivery systems when compared to other of polymeric nature. This paper highlights the importance of lipid nanoparticles to modify the release profile and the pharmacokinetic parameters of drugs when administrated through oral route.

THE EFFECT OF SOME PROCESSING CONDITIONS ON THE CHARACTERISTICS OF BIODEGRADABLE MICROSPHERES OBTAINED BY AN EMULSION SOLVENT EVAPORATION PROCESS

Abstract - Unloaded microspheres were prepared from polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHB-HV) polymers using an oil-in-water emulsion solvent evaporation method. The study was conducted to evaluate how the polymer and some process parameters affect properties of the final microspheres such as particle size, superficial area, zeta potential, surface morphology and microsphere degradation. The variables included surfactant concentration in the emulsion water phase and solvent composition. From the results, it was found that the parameters affecting microsphere size the most were surfactant concentration in the emulsion water phase and solvent composition. Properties such as zeta potential, surface area and surface morphology remained pratically unchanged over the range of the processing conditions studied here. Keywords : microencapsulation, poly-hydroxybutirate-hydroxyvalerate, emulsification/evaporation. INTRODUCTION Polymers and copolymers of lactic and glycolic acids are the most commonly used to develop drug delivery systems due to their safe and authorized use applications in humans (Chulia et al., 1994). However, other biodegradable polymers have been studied to increase the number of biodegradable materials available for pharmaceutical and medical applications. One of these, the polyhydroxyalkanoates (PHAs) comprise a large family of bacterial storage polyesters. Their chemical structure (Figure 1) is very similar to the highly popular synthetic biodegradable polymers, the polylactides (PLA) and their copolymers with glycolides, poly(lactide-co-glycolide) (PLGA), but they generally degrade at a much slower rate (Amass et al., 1998). Poly-3-hydroxybutyrate (PHB) and its copolymers with hydroxyvalerate (PHB-HV) are the most widely used members of this biopolymer group (Amass et al., 1998). They are produced biosynthetically by bacteria from natural raw materials and indeed can be readily broken down by microorganisms under different conditions. The polymers accumulate in discrete, membrane-bound granules in the bacterial cell, from which they can be extracted directly by organic solvents such as chloroform or by membrane-rupturing techniques such as mechanical, chemical and enzymatic disruption of cell walls.

Polymorphism, crystallinity and hydrophilic-lipophilic balance of stearic acid and stearic acid-capric/caprylic triglyceride matrices for production of stable nanoparticles.

There is an increasing interest in lipid nanoparticles because of their suitability for several administration routes. Thus, it becomes even more relevant the physicochemical characterization of lipid materials with respect to their polymorphism, lipid miscibility and stability, as well as the assessment of the effect of surfactant on the type and structure of these nanoparticles. This work focuses on the physicochemical characterization of lipid matrices composed of pure stearic acid or of mixtures of stearic acid-capric/caprylic triglycerides, for drug delivery. The lipids were analyzed by Differential Scanning Calorimetry (DSC), Wide Angle X-ray Diffraction (WAXD), Polarized Light Microscopy (PLM) and hydrophilic-lipophilic balance (HLB) in combination with selected surfactants to determine the best solid-to-liquid ratio. Based on the results obtained by DSC and WAXD, the selected qualitative and quantitative composition contributed for the production of stable nanoparticles, since the melting and the tempering processes provided important information on the thermodynamic stability of solid lipid matrices. The best HLB value obtained for stearic acid-capric/caprylic triglycerides was 13.8, achieved after combining these lipids with accepted surfactants (trioleate sorbitan and polysorbate 80 in the ratio of 10:90). The proposed combinations were shown useful to obtain a stable emulsion to be used as intermediate form for the production of lipid nanoparticles.

Spray-dried chitosan microspheres cross-linked with d, l-glyceraldehyde as a potential drug delivery system: preparation and characterization

Chitosan microspheres of a small particle size and with good sphericity were prepared by a spray-drying method followed by treatment with a cross-linking agent. Owing to restrictions on the use of cross-linked chitosan microspheres in the pharmaceutical field, d,l-glyceraldehyde, a biocompatible reatant was used. The parameters studied affecting extent of cross-linking were cross-linking time and concentration of the cross-linking agent. Glutaraldehyde, the aldehyde most frequently employed as chemical cross-linking agent for proteins, was also used as a control. The cross-linked spray-dried chitosan microspheres were analyzed with respect to their morphological aspects, particle size, zeta potential and water uptake capacity. It was found that an increase either in d,l-glyceraldehyde concentration or in duration of cross-linking caused a decrease in both the swelling capacity and the zeta potential of the chitosan microspheres. Compared to glutaraldehyde, d,l-glyceraldehyde appears to be a good cross-linking agent for chitosan microspheres with the advantage that it is nontoxic.

Encapsulation of mepivacaine prolongs the analgesia provided by sciatic nerve blockade in mice.

PurposeLiposomal formulations of local anesthetics (LA) are able to control drug-delivery in biological systems, prolonging their anesthetic effect. This study aimed to prepare, characterize and evaluatein vivo drug-delivery systems, composed of large unilamellar liposomes (LUV), for bupivacaine (BVC) and mepivacaine (MVC).MethodsBVC and MVC hydrochloride were encapsulated into LUV (0.4 μm) composed of egg phosphatidylcholine, cholesterol and α-tocopherol (4:3:0.07 molar ratio) to final concentrations of 0.125, 0.25, 0.5% for BVC and 0.5, 1, 2% for MVC. Motor function and antinociceptive effects were evaluated by sciatic nerve blockade induced by liposomal and plain formulations in mice.ResultsLiposomal formulations modified neither the intensity nor the duration of motor blockade compared to plain solutions. Concerning sensory blockade, liposomal BVC (BVCLUV) showed no advantage relatively to the plain BVC injection while liposomal MVC (MVCLUV) improved both the intensity (1.4–1.6 times) and the duration of sensory blockade (1.3–1.7 times) in comparison to its plain solution (P < 0.001) suggesting an increased lipid solubility, availability and controlled-release of the drug at the site of injection.ConclusionMVCLUV provided a LA effect comparable to that of BVC. We propose MVCLUV drug delivery as a potentially new therapeutic option for the treatment of acute pain since the formulation enhances the duration of sensory blockade at lower concentrations than those of plain MVC.RésuméObjectifDes préparations liposomales d’anesthésiques locaux (AL) peuvent contrôler l’administration de médicaments dans les systèmes biologiques, prolongeant leur effet anesthésique. Notre objectif était de préparer, caractériser et évaluer des systèmes d’administration de médicaments in vivo, composés de gros liposomes unilamellaires (GLU), pour la bupivacaïne (BVC) et la mépivacaïne (MVC).MéthodeLe chlorhydrate de BVC et de MVC a été mis en capsules dans des GLU (0,4 μm) composés de lécithine d’œuf, de cholestérol et de α-tocophérol (concentration molaire 4:3:0,07) pour obtenir des concentrations finales de 0,125, 0,25, 0,5 % pour la BVC et 0,5, 1, 2 % pour la MVC. La fonction motrice et les effets antinociceptifs ont été évalués par le blocage du nerf sciatique induit par des préparations liposomales et des préparations simples chez des souris.RésultatsLes préparations liposomales, comparées aux préparations simples, n’ont pas modifié l’intensité ni la duré du bloc moteur. Quant au bloc sensitif, la BVC liposomale (BVCLUV) n’a pas présenté d’avantage par rapport à l’injection de BVC simple tandis que la MVC liposomale (MVCLUV) a amélioré l’intensité (1,4–1,6 fois) et la duré du bloc sensitif (1,3–1,7 fois) comparée à la solution simple (P < 0,001). Ce qui laisse croire à une meilleure solubilité lipidique, à une disponibilité accrue et à une meilleure administration du médicament à libération contrôlée au site de l’injection.ConclusionLa MVCLUV fournit un effet AL comparable à celui de la BVC. Nous proposons l’administration de MVCLUV comme un nouveau choix possible de traitement de la douleur aiguë, puisque la préparation augmente la durée du bloc sensitif à des concentrations plus faibles que celles de la MVC simple.

Humic acids: Structural properties and multiple functionalities for novel technological developments.

Humic acids (HAs) are macromolecules that comprise humic substances (HS), which are organic matter distributed in terrestrial soil, natural water, and sediment. HAs differ from the other HS fractions (fulvic acid and humins) in that they are soluble in alkaline media, partially soluble in water, and insoluble in acidic media. Due to their amphiphilic character, HAs form micelle-like structures in neutral to acidic conditions, which are useful in agriculture, pollution remediation, medicine and pharmaceuticals. HAs have undefined compositions that vary according to the origin, process of obtainment, and functional groups present in their structures, such as quinones, phenols, and carboxylic acids. Quinones are responsible for the formation of reactive oxygen species (ROS) in HAs, which are useful for wound healing and have fungicidal/bactericidal properties. Phenols and carboxylic acids deprotonate in neutral and alkaline media and are responsible for various other functions, such as the antioxidant and anti-inflammatory properties of HAs. In particular, the presence of phenolic groups in HAs provides antioxidant properties due to their free radical scavenging capacity. This paper describes the main multifunctionalities of HAs associated with their structures and properties, focusing on human health applications, and we note perspectives that may lead to novel technological developments. To the best of our knowledge, this is the first review to address this topic from this approach.

Retinyl palmitate flexible polymeric nanocapsules: characterization and permeation studies.

Polymeric nanocapsules with elastic characteristics were prepared by the pre-formed polymer interfacial deposition method. The system consists of an oily core of retinyl palmitate with Span 60 and a polymeric wall of poly(D,L-lactide) (PLA). A narrow size distribution (215 nm, P.D.I. 0.10) was showed by dynamic light scattering (DLS) analyses. Particle deformability was observed by transmission electron microscopy (TEM) images and permeation of the particles through two superposed membranes of smaller pore diameters. Permeation studies were achieved using plastic surgery abdominal human skin by Franz diffusion cell. Retinyl palmitate permeates into deep skin layers. Besides, a PLA fluorescent derivative conjugated with Nile blue dye by an amide covalent bound was additionally obtained. Permeation profile of the nanocapsules with the fluorescent polymer was evaluated by confocal laser scanning microscopy (CLSM). The CLSM showed that nanocapsules were distributed uniformly, suggesting that the permeation mechanism through skin is intercellular. Thus, the use of these nanocapsules may be a feasible strategy to enhance the permeation of actives into the skin when delivery to deep layers is aimed.

Relevant Aspects of Centrifugation Step in the Preparation of Platelet-Rich Plasma

Introduction. Platelet-Rich Plasma (PRP) is rich in growth factors, playing important role in tissue healing. The wide variation of reported protocols for preparation of PRP leads to variable compositions, which induce different biological responses and prevent results comparison. This study aims to highlight relevant aspects of the centrifugation step to obtain reproducible results and overall quality. Material and Methods. Samples of blood were collected from 20 healthy donors that have signed free informed consent. Two centrifugation steps (spins) were analyzed for the influence of centrifugal acceleration, time, processed volume, and platelet gradient. The Pure Platelet-Rich Plasma (P-PRP) was characterized as platelet concentration, integrity, and viability (sP-selectin measurement). Results. Lower centrifugal accelerations favour platelet separation. The processing of 3.5 mL of blood at 100 ×g for 10 min (1st spin), 400 ×g for 10 min (2nd spin), withdrawing 2/3 of remnant plasma, promoted high platelet recovery (70–80%) and concentration (5x) maintaining platelet integrity and viability. The recovery of platelets was reduced for a larger WB volume (8.5 mL) processed. Conclusion. Centrifugal acceleration, time, WB processed volume, and minimization of the platelet gradient before sampling are relevant aspects to ensure reproducible compositions within the autologous nature of PRP.

Optimizing SLN and NLC by 2(2) full factorial design: effect of homogenization technique.

Solid lipid nanoparticles (SLN) and nanostructured lipid carrier (NLC) have been employed in pharmaceutics and biomedical formulations. The present study focuses on the optimization of the production process of SLN and NLC by High Shear Homogenization (HSH) and High Pressure Homogenization (HPH). To build up the surface response charts, a 2(2) full factorial design based on 2 independent variables was used to obtain an optimized formulation. The effects of the production process on the mean particle size, polydispersity index (PI) and zeta potential (ZP) were investigated. Optimized SLN were produced applying 20,000 rpm HSH and 500 bar HPH pressure and NLC process 15,000 rpm HSH and 700 bar HPH pressure, respectively. This factorial design study has proven to be a useful tool in optimizing SLN (~100 nm) and NLC (~300 nm) formulations. The present results highlight the benefit of applying statistical designs in the preparation of lipid nanoparticles.

The synergy between structural stability and DNA-binding controls the antibody production in EPC/DOTAP/DOPE liposomes and DOTAP/DOPE lipoplexes

We present a comparative study of the physico-chemical properties, in vitro cytotoxicity and in vivo antibody production of surface-complexed DNA in EPC/DOTAP/DOPE (50/25/25% molar) liposomes and DOTAP/DOPE (50/50% molar) lipoplexes. The study aims to correlate the biological behavior and structural properties of the lipid carriers. We used DNA-hsp65, whose naked action as a gene vaccine against tuberculosis has already been demonstrated. Additionally, surface-complexed DNA-hsp65 in EPC/DOTAP/DOPE (50/25/25% molar) liposomes was effective as a single-dose tuberculosis vaccine. The results obtained showed that the EPC inclusion stabilized the DOTAP/DOPE structure, producing higher melting temperature and lower zeta potential despite a close mean hydrodynamic diameter. Resemblances in morphologies were identified in both structures, although a higher fraction of loaded DNA was not electrostatically bound in EPC/DOTAP/DOPE. EPC also induced a striking reduction in cytotoxicity, similar to naked DNA-hsp65. The proper immune response lead to a polarized antibody production of the IgG2a isotype, even for the cytotoxic DOTAP/DOPE. However, the antibody production was detected at 15 and 30 days for DOTAP/DOPE and EPC/DOTAP/DOPE, respectively. Therefore, the in vivo antibody production neither correlates with the in vitro cytotoxicity, nor with the structural stability alone. The synergistic effect of the structural stability and DNA electrostatic binding upon the surface of structures account for the immunological effects. By adjusting the composition to generate proper packing and cationic lipid/DNA interaction, we allow for the optimization of liposome formulations for required immunization or gene therapy. In a specific manner, our results contribute to studies on the tuberculosis therapy and vaccination.