Evaluating Non-Conventional Chitosan Sources for Controlled Release of Risperidone.

In this work, two chitosan samples from cuttlebone and squid pen are produced and characterized. We studied the formation of thermoresponsive hydrogels with ß-glycerol phosphate and found proper formulations that form the hydrogels at 37 °C. Gel formation depended on the chitosan source being possible to produce the thermoresponsive hydrogels at chitosan concentration of 1% with cuttlebone chitosan but 1.5% was needed for squid pen. For the first time, these non-commercial chitosan sources have been used in combination with ß-glycerol phosphate to prepare risperidone formulations for controlled drug delivery. Three types of formulations for risperidone-controlled release have been developed, in-situ gelling formulations, hydrogels and xerogels. The release profiles show that in-situ gelling formulations and particularly hydrogels allow an extended control release of risperidone while xerogels are not appropriate formulations for this end since risperidone was completely released in 48 h.

Chitosan: An Overview of Its Properties and Applications.

Chitosan has garnered much interest due to its properties and possible applications. Every year the number of publications and patents based on this polymer increase. Chitosan exhibits poor solubility in neutral and basic media, limiting its use in such conditions. Another serious obstacle is directly related to its natural origin. Chitosan is not a single polymer with a defined structure but a family of molecules with differences in their composition, size, and monomer distribution. These properties have a fundamental effect on the biological and technological performance of the polymer. Moreover, some of the biological properties claimed are discrete. In this review, we discuss how chitosan chemistry can solve the problems related to its poor solubility and can boost the polymer properties. We focus on some of the main biological properties of chitosan and the relationship with the physicochemical properties of the polymer. Then, we review two polymer applications related to green processes: the use of chitosan in the green synthesis of metallic nanoparticles and its use as support for biocatalysts. Finally, we briefly describe how making use of the technological properties of chitosan makes it possible to develop a variety of systems for drug delivery.

Solvatochromism in urea/water and urea-derivative/water solutions.

This work reports the experimental measurements of solvent acidity (SA), basicity (SB), and solvent dipolarity and polarizability (SPP) for water solutions with urea (U) and its molecular derivatives, monomethyl-urea (MU), 1,3-dimethyl-urea (DMU) and tetramethyl-urea (TMU). These solvatochromic parameters are applied to understanding the variation of indexes of refraction and densities and other physico-chemical properties reported for these solutions. These properties are well correlated to the SA, SB, and SPP solvent parameters of these solutions. As a result, from the characterization of the physico-chemical properties, one can infer that urea and its molecular derivatives are mainly modifiers in the structure of liquid water. The solvatochromic parameters indicate the possible existence of different mechanisms in the denaturation process of proteins in these urea/water solutions.

Interactions of 2,2,2-trifluoroethanol with aqueous micelles of Triton X-100.

The effect of 2,2,2-trifluoroethanol (TFE) on micellar properties of Triton X-100 (TX-100) in aqueous solutions was investigated by cloud point (CP), viscosity, surface tension, and fluorescence techniques. The critical micelle concentration (CMC) values of the corresponding mixtures were obtained by the pyrene 1:3 ratio method and by surface tension data using the pendant drop technique. All the techniques provided about the same values for the CMC. Up to 0.83 M TFE increased the CMC by 30%. The small increase in the CMC is consistent with a slight increase in the solubility of the TX-100. Fluorescence measurements indicate that the TFE decreased the aggregation number by about 30%. The CP decrease and the intrinsic viscosity increase with TFE concentration are consistent with a preferential interaction of TFE with TX-100 micelles. TFE molecules form hydrophobic domains in the micellar layer palisade because they hydrogen bond with the oxyethylene group in TX-100. The intrinsic viscosity data are consistent with an increase in micelle hydrodynamic radius owing to the presence of TFE.