Ezequiel Delgado

Use of Agave tequilana-lignin and zinc oxide nanoparticles for skin photoprotection

The use of sunscreens is essential for preventing skin damage and the potential appearance of skin cancer in humans. Inorganic active components such as zinc oxide (ZnO) have been used commonly in sunscreens due to their ability to block UVA radiation. This ultraviolet (UV) protection might be enhanced to cover the UVB and UVC bands when combined with other components such as titanium dioxide (TiO2). In this work we evaluate the photoprotection properties of organic nanoparticles made from lignin in combination with ZnO nanoparticles as active ingredients for sunscreens. Lignin nanoparticles were synthesized from Agave tequilana lignin. Two different pulping methods were used for dissolving lignin from agave bagasse. ZnO nanoparticles were synthesized by the precipitation method. All nanoparticles were characterized by SEM, UV-Vis and FT-IR spectroscopy. Nanoparticles were mixed with a neutral vehicle in different concentrations and in-vitro sun protection factor (SPF) values were calculated. Different sizes of spherical lignin nanoparticles were obtained from the spent liquors of two different pulping methods. ZnO nanoparticles resulted with a flake shape. The mixture of all components gave SPF values in a range between 4 and 13. Lignin nanoparticles showed absorption in the UVB and UVC regions which can enhance the SPF value of sunscreens composed only of zinc oxide nanoparticles. Lignin nanoparticles have the added advantage of being of organic nature and its brown color can be used to match the skin tone of the person using it.

Lysine-Grafted MCM-41 Silica as an Antibacterial Biomaterial

This paper proposes a facile strategy for the zwitterionization of bioceramics that is based on the direct incorporation of l-lysine amino acid via the ε-amino group onto mesoporous MCM-41 materials. Fourier transform infrared (FTIR) studies of lysine-grafted MCM-41 (MCM-LYS) simultaneously showed bands at 3080 and 1540 cm−1 and bands at 1625 and 1415 cm−1 corresponding to -NH3+/COO− pairs, which demonstrate the incorporation of the amino acid on the material surface keeping its zwitterionic character. Both elemental and thermogravimetric analyses showed that the amount of grafted lysine was 8 wt. % based on the bioceramic total weight. Moreover, MCM-LYS exhibited a reduction of adhesion of S. aureus and E. coli bacteria in 33% and 50%, respectively at physiological pH, as compared with pristine MCM-41. Biofilm studies onto surfaces showed that lysine functionalization elicited a reduction of the area covered by S. aureus biofilm from 42% to only 5% (88%). This research shows a simple and effective approach to chemically modify bioceramics using single amino acids that provides zwitterionic functionality, which is useful to develop new biomaterials that are able to resist bacterial adhesion.

Coacervated liposoluble fructan-based host–guest microspheres as unique drug delivery materials

A fundamental requirement in drug delivery design is the development of robust, target-specific, biocompatible, and pharmocokinetically-active cargo carriers. The use of natural polysaccharides for drug delivery has been a subject of long standing interest because they display many of the necessary aforementioned attributes. Herein, the current research details a new approach to a drug release system composed of microspheres derived from unique acetylated Agave tequilana Weber var. Azul fructans. The driving force and novelty behind this approach is that these fructans are liposoluble while still being able to be metabolized by bifidobacteria (lower GI, native colon bacteria). Modification of fructan solubility through acetylation supported the preparation of microspheres by precipitation–coacervation, thus providing a new synthetic approach for polysaccharides-based cargo carriers to facilitate the encapsulation of liposoluble cargo molecules such as ibuprofen. It was found that the enzymatic activity of B. animalis, a representative bacteria found in the human colon, was reduced, albeit, but not at the expense of providing a very compellingly favorable drug release profile.

Polyelectrolyte Complexation versus Ionotropic Gelation for Chitosan-Based Hydrogels with Carboxymethylcellulose, Carboxymethyl Starch, and Alginic Acid

The preparation of gels by charge interaction methods has been extensively studied, but it is not yet clear how these methods influence gel characteristics. The objective of this work was to study differences in morphology and surface charge of hydrogels prepared by ionotropic gelation, polyelectrolyte complexation, and a combination of both methods. Thus, the anionic charge was provided by carboxymethylcellulose (CMC), carboxymethylated starch (CMS), and alginic acid (AA); calcium chloride (CaCl2) and chitosan (CS) were used for the ionotropic gelation and polyelectrolyte complexation, respectively. Those materials are commercially available, have low toxicity, and are widely used in the area. These compounds interact through physical crosslinks, which are affected by physical changes of the medium. Our results showed that these two methods produced changes in the morphology of the hydrogels. CMC gels exhibited larger pores in the presence of CaCl2. In polyelectrolyte complexation, CMS produced an increased agglomeration of particles, while the addition of CaCl2 to AA generated dispersed particles of size in the order of millimeters. Mixing both ionotropic gelation and polyelectrolyte complexation methods yielded gels of varied charge (568 mV for CMC, 502 mV for CMS, and 1713 mV for AA). FTIR spectra of the hydrogels showed interactions between the different polymeric compounds, being the greatest changes between 1250 and 1600 cm−1, due possibly to the replacement of Na by Ca at crosslinking points. Therefore, the method of gel preparation employed had a major influence on the size and pore distribution, parameters which in turn influence encapsulation and drug delivery in these systems.

Rheological characterization of new thermosensitive hydrogels formed by chitosan, glycerophosphate, and phosphorylated β-cyclodextrin

A novel thermosensitive hydrogel consisting of phosphorylated β-cyclodextrin (βCD-PH), β-cyclodextrin (βCD) and chitosan was prepared by embedding βCD and βCD-PH, into the well-studied chitosan/αβ-glycerophosphate system (CS/αβGP). The relevance of this work is the use of βCD-PH to partially substitute αβGP as the gelling agent. The role of βCD and βCD-PH on the rheological properties of hydrogels, gelation time, and gelation temperature were investigated. The gelation time for all the samples (CS/αβGP, CS/αβGP/βCD, and CS/αβGP/βCD-PH) was less than a minute at 37 °C, which is suitable for biomedical applications. The gelation temperature for hydrogel CS/αβGP/βCD-PH increased linearly with the addition of βCD-PH within the interval 31.8-37.3 °C, at ratios CS:βCD-PH of 1:0.5, 1:1, 1:1.5 and 1:2 (w/w). The hydrogel thus obtained has potential applications in dual drug delivery (hydrophilic and hydrophobic).

Spruce xylan/HEMA-SBA15 hybrid hydrogels as a potential scaffold for fibroblast growth and attachment

A hybrid hydrogel (GHC-SBA15) based on spruce xylan (HC), 2-hydroxyethyl methacrylate (HEMA), and mesoporous silica (SBA15) was prepared with the intended use of fibroblast attachment and growth. Xylan was functionalized with acryloyl chloride to introduce vinyl groups and was crosslinked by radical polymerization with HEMA in presence of SBA15. Infrared spectroscopy and nuclear magnetic resonance confirmed the copolymerization of HEMA with xylan. Up to 20 wt.% addition, SBA15 was homogenously incorporated in the structured hydrogel network as observed by SEM. Moreover, nitrogen adsorption-desorption, small angle X-ray scattering and transmission electron microscopy indicated that the mesoporous SBA15 framework was maintained and that the hybrid hydrogel was a physical mixture of SBA15 with the copolymer HC/HEMA. Rheological analysis revealed that addition of 20% w/w SBA15 into hydrogel enhanced significantly the mechanical properties. In addition, we demonstrate that fibroblast L929 cells grew and spread on GHC-SBA15. Cell viability was within the expected range.