Josep R. Ticó

Impact of physical parameters on particle size and reaction yield when using the ionic gelation method to obtain cationic polymeric chitosan-tripolyphosphate nanoparticles

Ionic gelation is the most frequently used method to obtain chitosan-tripolyphosphate nanoparticles due to its simplicity and because it does not generate waste solvents in the samples prepared. This paper presents a study of the physical factors involved in this method for obtaining nanoparticles in order to determine which of them significantly influences the particle size of polymeric nanoparticles made from low-molecular-weight chitosan, without any additional chemical treatment, with the aim of standardising and optimising the method conditions, in addition to establishing the reaction yield. The results indicate that stirring speed during ionic gelation reaction is decisive for the size of the nanoparticles obtained. Furthermore, it thus follows that the stirring speed during ionic gelation significantly affects reaction yield, and therefore, by manipulating this parameter a greater proportion of nanoparticles of a given size range can be obtained.

Application of the SeDeM Diagram and a new mathematical equation in the design of direct compression tablet formulation.

Application of the new SeDeM Method is proposed for the study of the galenic properties of excipients in terms of the applicability of direct-compression technology. Through experimental studies of the parameters of the SeDeM Method and their subsequent mathematical treatment and graphical expression (SeDeM Diagram), six different DC diluents were analysed to determine whether they were suitable for direct compression (DC). Based on the properties of these diluents, a mathematical equation was established to identify the best DC diluent and the optimum amount to be used when defining a suitable formula for direct compression, depending on the SeDeM properties of the active pharmaceutical ingredient (API) to be used. The results obtained confirm that the SeDeM Method is an appropriate system, effective tool for determining a viable formulation for tablets prepared by direct compression, and can thus be used as the basis for the relevant pharmaceutical development.

DNA delivery via cationic solid lipid nanoparticles (SLNs)

In recent years the use of solid lipid nanoparticles (SLNs) as transport systems for the delivery of drugs and biomolecules has become particularly important. The use of cationic SLNs developed by the technique of microemulsion, which are complexed with DNA in order to study their application as non-viral vectors in gene therapy, is reported. The nanoparticles are characterized by scanning electron microscopy and transmission electron microscopy (SEM and TEM), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). Furthermore, the process of lyophilization of the samples and their stability was studied. The nanoparticles obtained presented a particle size of 340 nm with a positive surface charge of 44 mV and the capability of forming lipoplexes with DNA plasmids was stated.

Optimization of parameters of the SeDeM Diagram Expert System: Hausner index (IH) and relative humidity (%RH)

As a methodology for characterizing substances in relation to their viability in direct compression, the SeDeM Diagram Expert System may be considered an open system in terms of the number of parameters applied and the optimization of these parameters. With the experience acquired from applying the SeDeM Diagram, in this study, we propose optimizing the parameters corresponding to the Hausner index (IH) and relative humidity (%HR) in order to simplify the mathematical calculation, so that it provides reliable data that can be extrapolated. The proposed optimization does not involve a conceptual change in the parameters considered nor a significant change in the results obtained compared with the previous calculation methodology initially established for the SeDeM Diagram Expert System, which means that the conclusions obtained by applying this method are equivalent.

A new optimized formulation of cationic solid lipid nanoparticles intended for gene delivery: Development, characterization and DNA binding efficiency of TCERG1 expression plasmid

Solid lipid nanoparticles (SLNs) are being considered as a new approach for therapeutics for many known diseases. In addition to drug delivery, their use as non-viral vectors for gene delivery can be achieved by the inclusion of cationic lipids, which provide a positive surface potential that favours binding to the DNA backbone. This work is based on the idea that the optimization of the components is required as the first step in simplifying the qualitative and quantitative composition of SLNs as much as possible without affecting the essential properties that define SLNs as optimal non-viral vectors for gene delivery. We selected the best lipids and surfactants in terms of particle size and zeta potential and characterized the properties of the resulting nanoparticles using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The SLNs had a particle size of approximately 120 nm and a positive surface charge of 42 mV. In addition, we analysed the main physicochemical characteristics of the bulk components of the nanoparticles using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and mass spectrometry (MS). The suitability of the optimized SLNs for DNA binding was evaluated after the lyophilisation process using a carboxyl-terminal region of the TCERG1 gene, a human factor that has been implicated in several diseases. We show that the SLNs presented high efficiency in the binding of DNA, and importantly, they presented no toxicity when assayed in an in vivo system.

Characterization of alginate beads loaded with ibuprofen lysine salt and optimization of the preparation method.

The parameters influencing alginate ionotropic gelation and the production of alginate beads loaded with hydrosoluble ibuprofen lysine salt (IBU-L) were studied, as well as the optimization of the method for its attainment. A three-factor and three-level factorial design (3(3)) was carried out to determine the influence of three experimental variables: polymer concentration, CaCl2 concentration, and curing time on the dependent variables drug load and encapsulation efficiency. The effect of the pH used in the preparation bath was also evaluated. Concentrations of CaCl2 and pH of gelling bath were seen to affect bead formation and stability as well as their ability to properly entrap the drug. In this work, IBU-L was used as a model of a non-steroidal anti-inflammatory drug with good solubility in alginate solutions. IBU-L was successfully encapsulated in alginate beads obtained by the ionotropic gelation method. The obtained alginate matrixes are able to modify the release of the entrapped IBU-L and this occurs in a pH-sensitive way that can be correlated with the swelling behaviour of the alginate-produced beads. Morphological characteristics were evaluated by means of scanning electron microscopy.

Chitosan nanoparticles as non-viral gene delivery systems: Determination of loading efficiency

Chitosan has been studied for use in particle delivery systems for therapeutic purposes, since one of its most important applications is as a non-viral vector in gene therapy. Due to its positive charge, it is capable of forming DNA complexes (polyplexes) obtained through several methods and with the property of protecting nucleic acids. Two methods for obtaining the nanoparticles of chitosan-nucleic acids are reported in this study: simple complexation (of depolymerized chitosan or of different chitosan salts with plasmid) and ionic gelation (by adsorption of plasmid in the nanoparticles or by encapsulation of plasmid into nanoparticles). The determination of the loading efficiency of chitosan nanoparticles with the plasmid is carried out by electrophoretic mobility of the samples on agarose gel. Furthermore, the nanoparticles have been characterized according to their morphology, size and surface charge using AFM, TEM, laser diffraction and dynamic light scattering techniques. The polyplexes obtained have been found to be spherical and nanometric in size (between 100-230nm) with a zeta potential between 37 and 48mV. Positive results have been obtained by agarose gel electrophoresis for all studied cases: a concentration of between 20 and 30μg/mL of chitosan salts is required while for the remaining chitosan samples studied, 100% loading efficiency does not occur until a concentration equal to 100μg/mL (regardless of previous depolymerisation and the method performed). Chitosan-plasmid nanocapsules have been obtained at the polymer concentrations worked with (between 0.025 and 0.2%).

New classification of directly compressible (DC) excipients in function of the SeDeM Diagarm Expert System

As a methodology for characterizing substances with regard to its viability in direct compression, the SeDeM Diagram Expert System may be considered a new tool in terms of the number of parameters applied and its optimization. The paper is based on the experimental SeDeM characterization study of 51 directly compressible (DC) excipients. After selecting the parameters, and comparing the corresponding results, the choices available within the SeDeM Expert System could be expanded. Through applied variants, the maximum and optimal values of the DC diluent excipient were precisely defined and the mathematical limits of the parameters, functions and parametric indices that define the level of direct compressibility were established. These studies have allowed us to propose a new classification of excipients CD based on its rheological and compressibility capability, resulting in a periodic table of CD excipients. It has been determined that the best excipient for direct compression should have an index of good compression (IGC) of 8.832.

Development and validation of a new RP-HPLC method for the simultaneous determination of hydroquinone, kojic acid, octinoxate, avobenzone, BHA and BHT in skin-whitening cream

A new and simple reverse phase high performance liquid chromatography method was developed for the simultaneous determination of the major compounds of skin-whitening pharmaceutical cream, i.e., two active pharmaceutical ingredients: hydroquinone and kojic acid, two sunscreens: octinoxate and avobenzone and two antioxidants: butylated hydroxyanisole and butylated hydroxytoluene. Separation was achieved on a Zorbax SB-Phenyl (250 × 4.6 mm; 5 μm) column, using a mobile phase consisting of water with 0.1% acetic acid and acetonitrile, in a dual-mode gradient for 14 minutes. The column was maintained at 40 °C and detection was carried out at 230 nm by using a diode-array detector. The extraction procedure was studied by a design of experiments demonstrating its suitability. The structure of an additional unknown peak eluting in all chromatograms in the same proportion was identified by HPLC/MS as the keto tautomer of avobenzone. The method developed was successfully validated in accordance with ICH guidelines with regard to selectivity, linearity, accuracy, precision and robustness. Selectivity was found to be satisfactory. The linear regression analysis data for all compounds showed a good linear relationship with r2 > 0.999 in the concentration range from 50% to 120% of the label claimed for each compound. The percentage RSD for precision and accuracy of the method was found to be less than 2% for all compounds. The proposed method was applied for the determination of six major compounds in skin-whitening cream prototypes developed during the formulation development stage.

Improved formulation of cationic solid lipid nanoparticles displays cellular uptake and biological activity of nucleic acids

Non-viral delivery using cationic solid lipid nanoparticles (SLNs) represents a useful strategy to introduce large DNA and RNA molecules to target cells. A careful selection of components and their amounts is critical to improve transfection efficiency. In this work, a selected and optimized formulation of SLNs was used to efficiently transfect circular DNA and linear RNA molecules into cells. We characterized the main physicochemical characteristics and binding capabilities of these SLNs and show that they deliver DNA and RNA molecules into cells where they display full bioactivity at nontoxic concentrations using fluorescence- and luminescence-based methodologies. Hence, we established a novel and simple SLN formulation as a powerful tool for future therapeutic use.