Adley F. Rubira

Silver sulfadiazine loaded chitosan/chondroitin sulfate films for a potential wound dressing application

Silver sulfadiazine (AgSD) loaded chitosan/chondroitin sulfate (CHI/CS) films were formed to be applied as a potential wound dressing material. The liquid uptake capacity of both, CHI/CS and CHI/CS/AgSD, films exhibited a pH-dependent behavior. Tensile tests showed that the amount of CS used to form the films and the further incorporation of AgSD affect the mechanical properties of the films. In vitro AgSD-release assays showed that the CHI/CS mass ratio influences the AgSD release rate. All the investigated CHI/CS/AgSD films sustain the AgSD release up to 96h at physiological pH. Antibacterial activity and cell viability assays showed that all the CHI/CS/AgSD films have activity against Pseudomonas aeruginosa and Staphylococcus aureus but they were not toxic to Vero cells. The results presented in this work indicate that the CHI/CS/AgSD exhibits potential to be applied as a wound dressing material.

Starch-based microspheres for sustained-release of curcumin: Preparation and cytotoxic effect on tumor cells

Curcumin (CUR) has been proved to be highly cytotoxic against different tumor cell lines. However, its poor solubility in aqueous medium and fast degradation in physiological pH are the common drawbacks preventing its efficient practical use. Herein, we report the development of original microspheres based on the biopolymer starch crosslinked with N,N-methylenebisacrylamide (MBA) to be applied as an efficient delivering system for CUR. The starch-based microspheres showed high loading efficiency even in loading solution with different CUR concentrations. In vitro release assays data showed that the CUR release is governed by anomalous transport (n=0.73) and it is pH-dependent. Cytotoxicity assays showed that starch microspheres could improve the cytotoxicity of CUR toward Caco-2 and HCT-116 tumor cell lines up to 40 times than that found for pure CUR. This behavior was attributed to the slowly and sustained release of CUR from the microspheres.

Synthesis and characterization of pectin derivative with antitumor property against Caco-2 colon cancer cells

New pectin derivative (Pec-MA) was obtained in specific reaction conditions. The presence of maleoyl groups in Pec-MA structure was confirmed by (1)H NMR and FTIR spectroscopy. The substitution degree of Pec-MA (DS=24%) was determined by (1)H NMR. The properties of Pec-MA were investigated through WAXS, TGA/DTG, SEM and zeta potential techniques. The Pec-MA presented amorphous characteristics and higher-thermal stability compared to raw pectin (Pec). In addition, considerable morphological differences between Pec-MA and Pec were observed by SEM. The cytotoxic effect on the Caco-2 cells showed that the Pec-MA significantly inhibited the growth of colon cancer cells whereas the Pec-MA does not show any cytotoxic effect on the VERO healthy cells. This result opens new perspectives for the manufacture of biomaterials based on Pec with anti-tumor properties.

Synthesis of a microhydrogel composite from cellulose nanowhiskers and starch for drug delivery.

This work describes the preparation of a microhydrogel composite from cellulose nanowhiskers (CNW) and starch in an ultrasound assisted-emulsion. CNW, which showed rod-like morphology, was obtained by acid hydrolysis of cane-based cellulose. The introduction of vinyl bonds to both CNW and starch enabled us to create the microhydrogel composite in which CNW played a role as a covalent cross-linker. Furthermore, CNW may act as an emulsifying agent for emulsion, improving both sphericity and homogeneity of the microparticles. The drug release was regulated in response to changes in the CNW amounts. The modeling of the release kinetics indicated that the drug release is driven by an anomalous mechanism and that the addition of CNW to starch microparticles led to differences in that mechanism. The release rate became ca. 2.9 times slower when CNW is added. When combined with starch, CNW played a role as a retardant factor for drug release.

Synthesis and controlled curcumin supramolecular complex release from pH-sensitive modified gum-arabic-based hydrogels

Curcumin (CUR) is a polyphenolic compound including a beta-diketone moiety, which is associated with numerous pharmacological activities, but applications are limited due to its low water solubility. Thus, in this work some inclusion complexes of CUR with alpha-cyclodextrin (α-CD) and beta-cyclodextrin (β-CD) were prepared using different host : guest proportions to improve drug solubilization in biological fluids. The formation of these complexes was confirmed by 1H NMR and thermogravimetric analysis. The stoichiometries of the CUR/α-CD and CUR/β-CD complexes were 1 : 1 and 1 : 2 and the association constants were 344 mol−1 L and 7.2 × 107 mol−2 L2 for α-CD and β-CD, respectively. The major stability of the CUR/β-CD complex is justified by an inclusion of the aromatic ring inside the CD cavity, whilst in the case of α-CD-complexes the interactions occur via H-bridges, showing the latter complexes’ slow exchange on the NMR time-scale. Even so, the solubility of curcumin complexes is clearly controlled by the solubility of CDs, showing the highest solubility for CUR/α-CD complexes. Hydrogels of modified gum arabic containing CUR/α-CD (1 : 4) were obtained and used for controlled release of CUR in simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The kinetics of release was pH-responsive and the percentage of CUR released was ca. 97% in SIF and 6.7% in SGF. For the toxicity studies on undifferentiated Caco-2 cells, IC50s of 63.4 ± 14.4 μg mL−1 and 85.2 ± 14.9 μg mL−1 for CUR and CUR/α-CD (1 : 4), respectively, were obtained. The toxicity of these samples on differentiated Caco-2 cells was lower than on undifferentiated cells. Additionally, the CUR incorporated into hydrogels showed no toxic effects on differentiated and undifferentiated Caco-2 cells, indicating the pharmaceutical potential of three-dimensional matrices of GAm for controlled release of CUR complexed with cyclodextrin.

Recentes Avanços no Design de Hidrogéis de Chitina e Derivados de Chitina e seu Impacto sobre Meio Ambiente e Agricultura: Uma Revisão

Our purpose is to show and discuss the most relevant data on the synthesis approach and the characterization of hydrogels based on chitin and chitin-derivatives, such as chitosan, as well as their applications in several materials technologies. The current and future relevance of materials based on chitin, chitosan and derivatives have been verified by the impressive number of scientific and technological publications (both papers and patents) that appears day-by-day. This review is divided into four Sections. Section 1 reports some basic concepts of hydrogels. Section 2 deals with properties of chitin, and gelation chemistries. Applications in environment and agriculture are described in Section 3. Future trends and perspectives are considered in Section 4.

Solid-state polymerization of EDTA and ethylenediamine as one-step approach to monodisperse hyperbranched polyamides

Hyperbranched polyamides (HBPAs), a special class of polymers with extended use in colloidal systems, is synthesized by an innovative method taking advantage of the ordered aggregation of positive and negative molecular ions in solid-state. This novel and facile procedure introduces a one-step approach to convert ethylenediaminetetraacetic acid (EDTA) and ethylenediamine (EDA) in macromolecules with ordered framework. EDTA and EDA are converted in negative and positive molecular ions through acid–base reaction. Then, Coulomb interaction among the charged molecules are used to drive the aggregation of the ions during the precipitation induced by casting process. The solid material composed by the molecular ions are subjected to thermal treatment to promote amide formation reaction in solid-state. The synthesis condition is evaluated to understand the macromolecule growth. Solid-state reaction products are chemically characterized by FTIR and 1H and 13C NMR. Molecular weight is determined by gel permeation chromatography (GPC) and the particles diameter in solution and charges are measured by dynamic light scattering (DLS) and zeta potential, respectively, at different pH values. The results attested the synthesis of hyperbranched polyamides with features similar to polyamide dendrimers. Surprisingly, the method enables the synthesis of macromolecules with very low dispersity index (DPI), that in some cases can be as low as 1.1.

Chapter 7:Outstanding Features of Starch-based Hydrogel Nanocomposites

Starch-based hydrogel nanocomposites are a very important issue in both academic and industrial fields owing to their availability, renewable sources, chemical structure and potential applications in several technologies. In the light of this, the incorporation of submicron- or nano-sized materials into starch-based hydrogel formulations has been explored as a very attractive strategy to improve properties and applications. This chapter is devoted to recent aspects of the development of starch-based hydrogel nanocomposites focused on the formulation of functional materials with enhanced properties for more suitable applications in different fields. The main aspects discussed are those based on structure–property relationships and also specific functionalities for a given application. Further comprehensive studies will broaden the understanding of structure–property relationships. Some future trends are highlighted – breakthroughs are necessary for improving the boundaries of knowledge of the materials science field.