Study of the protective capacity of a β-cyclodextrin polymer with chlorogenic acid (coffee antioxidant)

This study focuses on coffee as a source of antioxidants, hence, protecting from the damage caused by free radicals; which has been demonstrated to have a protective action in numerous diseases. This capacity is attributed to its phenolic compounds among which chlorogenic acid stands out, together with caffeic acid. Besides, cyclodextrins are well known for their capacity of forming inclusion complexes where the host molecule is located in the interior cavity, allowing the transport and storage of it. My experimental project is focused on the synthesis and characterization of a protective polymeric system formed by β-cyclodextrin, which is then going to be loaded with chlorogenic acid. This inclusion complex as well as the β-cyclodextrin polymer and chlorogenic acid themselves, have been studied through preliminary studies of stability, using principally UV and FTIR spectroscopies as well as thermogravimetric calorimetry, which showed that the polymer prevents the acid from degrading through time, when maintained either at dark or in direct sunlight. The protective effect has been determined through scavenging capacity measurements analyzing the variation in the activity of chlorogenic acid as well as its change when the acid is introduced into β-cyclodextrin. For this, it has first been studied the change in absorbance using a mixture of 2,2-diphenil- 1-picrylhydrazyl (DPPH) and chlorogenic acid at different concentrations; leading to the already known fact that, at higher concentrations, the antioxidant capacity increases. Furthermore, the controlled release of the antioxidant from the cavities of the β- cyclodextrin in the polymeric matrices has been studied through Sotax Dissolution tests and applying mathematical models. This data leads to the conclusion that the CD-chlorogenic acid inclusion complex helps to maintain the integrity and scavenging activity of the bioactive compound especially when the chlorogenic acid is measured over time

Estudio de la actividad antimicrobiana de films compuestos por nanopartículas de TiO2 para uso alimentario

Actualmente, hay un gran interés en la industria alimentaria por dotar los films con los que se envasa la comida, de características que mejoren los servicios suministrados por los films convencionales. El objetivo es aumentar la estabilidad de los alimentos y reducir su pérdida. Una de las estrategias empleadas es el uso de la nanotecnología en la creación de envases activos, equipando a la matriz polimérica de nanopartículas que tienen actividad antimicrobiana, con el propósito de aumentar la calidad y seguridad del alimento que protegen. Las nanopartículas de TiO2 (NP) destacan entre las nanopartículas por su poder fotocatalítico con el que ejerce su actividad antimicrobiana. Este trabajo consiste en la derivatización de estas nanopartículas con β-ciclodextrina (βCD) y la inclusión del conservante alimentario ácido sórbico (SA) en su cavidad, para ser implementadas en una matriz polimérica hidrosoluble. En este caso se ha empleado el alcohol polivinílico (PVA) como matriz polimérica, con el propósito de crear films con una superficie activa y estudiar su actividad antimicrobiana en la bacteria Gram negativa Escherichia coli y en la bacteria Gram positiva Staphylococcus aureus. Tras este estudio, se concluye que los films que contienen nanopartículas de TiO2 tienen mayor actividad antimicrobiana que aquellos que no las contienen. Por el análisis estadístico se concluye que la presencia de ácido sórbico no parece suponer una mejora significativa. No obstante, en los ensayos en disolución se observa que el ácido sórbico libre tiene un gran poder antimicrobiano, probablemente, en el caso de los films el conservante queda atrapado en la matriz polimérica y por eso su acción antimicrobiana queda mermada.Nowadays, the food processing industry has a great interest in supplying food-packaging films with properties that provide better services than those provided by conventional films. The aim is to increase food stability and to reduce its waste. One of the main strategies applied is the use of nanotechnology in the creation of active packages, equipping the polymer matrix of nanoparticles that possess antimicrobial activity, with the purpose of increasing the quality and safety of the food they protect. Of all the nanoparticles, the nanoparticles of TiO2 (NP) standout due to their photocatalytic activity with which they exert their antimicrobial activity. This research project entails the derivatization of these nanoparticles with β-cyclodextrin (βCD) and the inclusion of food preservative, sorbic acid (SA), in its cavity, for its implementation in a hydrosoluble polymer matrix. In this case, polyvinyl alcohol (PVA) has been utilized as the polymer matrix, with the goal of creating films with an active surface and to study their antimicrobial activity in the Gram-negative bacteria Escherichia coli and in the Gram-positive bacteria Staphylococcus aureus. Followed this project, it is concluded that the films containing nanoparticles of TiO2 have a greater antimicrobial activity than those without nanoparticles. With the statistical analysis it is concluded that the presence of sorbic acid does not seem to significantly increase the antimicrobial activity. However, in the experiments in solution it was observed that the free sorbic acid has a prominent antimicrobial activity, probably, in the case of the films the preservative is trapped in the polymer matrix, depleting its antimicrobial activity

Síntesis y caracterización de polímeros de ciclodextrina. Aplicación a la liberación de fármacos

Cyclodextrins (CD) are cyclic oligosaccharides which have been widely employed for pharmaceutical applications. CD based hydrogels have been synthesized by the crosslinking reaction with epichlorohydrin using αCD, ßCD, γCD, and 50:50 mixtures of α/ßCD and ß/γCD, at different synthesis temperatures. These gels have been characterized by measuring their swelling capacity, mechanical behavior, thermal properties and pore size distribution. The hydrogels synthesized at higher temperatures present a higher swelling capacity, due to the self-polymerization of epichlorohydrin, yielding a more expanded reticular structure with pores of higher diameter. Mechanical assays show that a lower synthesis temperature leads to stronger and harder polymers, according with a lower swelling capacity. Polymers containing different CD types and synthesized at the same temperature present similar reticular structures. In order to investigate the sorption capacity of these hydrogels toward different solutes, five model molecules have been selected: phenol, 3-nitrophenol, 4-nitrophenol, 1-naphthol, and the antiinflamatory drug diflunisal. The amounts sorbed have been related to the different affinities of CDs to the solutes. Drug delivery of two antiinflammatory (naproxen and nabumetone) and two antifungal drugs (naftifine and terbinafine) from ßCD polymer discs has been investigated. Drug release kinetics were carried out at physiological conditions of pH and temperature, and kinetic and diffusion constants were calculated. The drug release followed a simple Fickian diffusion mechanism for all the model drugs. Also, diffusion coefficients were calculated according to the simplified Higuchi model. Naproxen was also used to perform release assays from polymers containing different CDs. The βCD polymer showed the highest amount of drug loaded and the lowest one corresponds to the polymer containing αCD, in agreement with the affinities for naproxen of the corresponding cyclodextrins. It can be inferred that a simple Fickian diffusion mechanism occurs, except for the mixed polymers at pH 1.2 (anomalous transport) and in the case αCDP at pH 7.0 (burst phenomenon). Furthermore, the diffusion and relaxation contributions have been determined for the mixed polymers in order to achieve progress in the design of new polymer matrices according to the structure of the selected drugs

Sistemas de cloranfenicol y polivinilpirrolidona para aplicación tópica

En este trabajo se han preparado sistemas conteniendo el antibiótico cloranfenicol (CAP) y el polímero polivinilpirrolidona (PVP) para su aplicación tópica. Se han obtenido y caracterizado dispersiones sólidas por el método del cosolvente y fibras poliméricas del sistema fármaco-polímero empleando la técnica de hilado por soplado en solución (SBS). Se ha estudiado la existencia de interacciones entre CAP y PVP, tanto en disolución mediante espectroscopía UVVis y de fluorescencia, como en estado sólido mediante espectroscopía infrarroja (FTIR-ATR), difracción de rayos X (DRX) y calorimetría diferencial de barrido (DSC). A partir de las dispersiones sólidas en polvo y de las fibras poliméricas comprimidas en discos, se han estudiado las cinéticas de liberación del cloranfenicol y los datos experimentales se han ajustado a modelos matemáticos concretos. Una vez obtenidos los parámetros cinéticos ha sido posible determinar el mecanismo de liberación del fármaco. Se concluye que la presencia del polímero en las dispersiones sólidas y la presión aplicada al preparar los discos de fibras influyen en la liberación del principio activo, consiguiendo una liberación más controlada. Esto permitiría reducir la frecuencia adecuada para cambiar el apósito preparado con fibras y fármaco, disminuyendo así el riesgo de sobreinfección en la herida

Preparation and characterization of polymer composite materials based on PLA/TiO2 for antibacterial packaging

Polymer composite materials based on polylactic acid (PLA) filled with titanium dioxide (TiO2) nanoparticles were prepared. The aim of this work was to investigate the antibacterial action of TiO2 against a strain of E. coli (DH5) to obtain information on their potential uses in food and agro-alimentary industry. PLA/TiO2 systems were prepared by a two-step process: Solvent casting followed by a hot-pressing step. Characterization was done as a function of particle size (21 nm and <100 nm) and particle content (0%, 1%, 5%, 10%, and 20%, wt %). Structural characterization carried out by X-ray diffraction (XRD) and Fourier Transformed Infrared spectroscopy (FTIR) did not reveal significant changes in polymer structure due to the presence of TiO2 nanoparticles. Thermal characterization indicated that thermal transitions, measured by differential scanning calorimetry (DSC), did not vary, irrespective of size or content, whereas thermogravimetric analysis (TGA) revealed a slight increase in the temperature of degradation with particle content. Bacterial growth and biofilm formation on the surface of the composites against DH5 Escherichia coli was studied. Results suggested that the presence of TiO2 nanoparticles decreases the amount of extracellular polymeric substance (EPS) and limits bacterial growth

In-vitro release from reverse poloxamine/α-cyclodextrin matrices. Modelling and comparison of dissolution profiles

ABSTRACT: Gels obtained by complexation of octablock star PEO/PPO copolymers (Tetronic 90R4) with α-CD were evaluated as matrices for drug release. Both molecules are biocompatible so they can be potentially applied to drug delivery systems. Two different types of matrices of Tetronic 90R4 and α-CD were evaluated: gels and tablets. These gels are capable to gelifying in-situ and show sustained erosion kinetics in aqueous media. Tablets were prepared by freeze drying and comprising the gels. Using these two different matrices the release of two model molecules, L-Tryptophan (Trp), and a protein, bovine serum albumin (BSA), was evaluated. The release profiles of these molecules from gels and tablets prove that they are suitable for sustained delivery. Mathematical models were applied to the release curves from tablets in order to elucidate the drug delivery mechanism. Good correlations were found for the fittings of the release curves to different equations. The results point that the release of Trp from different tablets is always governed by Fickian diffusion while the release of BSA is governed by a combination of diffusion and tablet erosion

Drug release properties of diflunisal from layer-by-layer self-assembled kappa-carrageenan/chitosan nanocapsules: effect of deposited layers

Engineering of multifunctional drug nanocarriers combining stability and good release properties remains a great challenge. In this work, natural polymers kappa-carrageenan (kappa-CAR) and chitosan (CS) were deposited onto olive oil nanoemulsion droplets (NE) via layer-by-layer (LbL) self-assembly to study the release mechanisms of the anti-inflammatory diflunisal (DF) as a lipophilic drug model. The nano-systems were characterized by dynamic light scattering (DLS), zeta potential (zeta-potential) measurements, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (XEDS) and Fourier transform infrared spectroscopy (FTIR) to confirm the NE-coating with polymer layers. In addition, kinetic release studies of DF were developed by the dialysis diffusion bag technique. Mathematical models were applied to investigate the release mechanisms. The results showed that stable and suitably sized nanocapsules (similar to 300 nm) were formed. Also, the consecutive adsorption of polyelectrolytes by charge reversal was evidenced. More interestingly, the drug release mechanism varied depending on the number of layers deposited. The nanosized systems containing up to two layers showed anomalous transport and first order kinetics. Formulations with three and four layers exhibited Case II transport releasing diflunisal with zero order kinetics

Trehalose-based siamese twin amphiphiles with tunable self-assembling, DNA nanocomplexing and gene delivery properties

An original family of multivalent vectors encompassing gemini and facial amphiphilicity, namely cationic Siamese twin surfactants, has been prepared fromthe disaccharide trehalose; molecular engineering lets us modulate the self-assembling properties and the topology of the nanocomplexes with plasmid DNA for efficient gene delivery in vitro and in vivo

Lipid and polymeric nanocapsules

In recent years, innovative drug nanocarriers have been developed to enhance stability, bioavailability, and provide sustained release. In this chapter, systems based on natural macromolecules, lipids, or polymeric/polyelectrolyte nanocapsules and their principal chemical and functional characteristics are described. Nano-vesicular systems are especially relevant in different fields. Particularly, a promising potential is offered by systems based on colloidal nanocapsules, that exhibit a typical core-shell structure in which the drug can be confined into the cavity or in the polymeric coating that surrounds it. Both the cavity and the active substance can be lipophilic or hydrophilic and in solid or liquid form depending on the materials and methods used, making these nanocapsules attractive carriers for drug delivery. In addition, a compilation of different methods and materials employed in the preparation of these nanosystems and a recent review of applications of lipid and polymeric nanocapsules have been made, focussing on the encapsulation of drugs

Antibacterial and degradable properties of beta-cyclodextrin-TiO2 cellulose acetate and polylactic acid bionanocomposites for food packaging

Polylactic acid (PLA) and cellulose acetate (CA) as biodegradable polymers are being highly exploited in the development of innovative materials across several industrial sectors. PLA and CA composite films with TiO2 nanoparticles (NPs) and beta-cyclodextrin grafted TiO2 NPs were prepared. Thermo- and photo-degradation studies were performed on PLA and CA films and noticed that higher amount of TiO2 induce greater color variations, structure modifications and weight losses. It has been observed 9.3 % and 5.1 % maximum weight loss for 5 % TiO2 CA and PLA matrices, respectively. beta CD-modified TiO2 NPs increased the photo-degradation of the plain polymers to a lesser extent than TiO2 NPs. Benzoic acid (BA) and sorbic acid (SA) were incorporated to beta CD-TiO2 NPs and the antibacterial activity of PLA and CA composite films was studied by inactivation of Escherichia coli and Staphylococcus aureus. CA film filled with 5 % TiO2 NPs presented the highest antibacterial activity and achieved 71 % inhibition of E. coli and 88 % inhibition of S. aureus. CA composite films showed potential to be used as antimicrobial food packaging