Héctor Javier Rendón Contreras

Adhesion between Cellulosic Fibers in Paper

The function of water in the adhesion between wet cellulose fibers both in the assembly of papers and the establishment of the properties is discussed. The contributions of friction and hydrogen bonds are reviewed, together with the new concept of interfiber ordered water structure created by the hydrophilic surfaces of the fibers. Procedures for the enhancement of interfiber adhesion are summarized in terms of the accessibility, the stereotopochemistry and the enthalpies of the interacting moieties on contiguous surfaces.

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.