Síntese e Caracterização de Hidrogéis Baseados em Goma Xantana e Quitosana para a Liberação Controlada de Vitamina B12.

Abstract

This work contemplates the synthesis and characterization of hydrogels based on natural polysaccharides Xanthan Gum XG) and Chitosan (CTS). Prior to the synthesis of the hydrogels, the native polysaccharides were chemically modified with glycidyl methacrylate (GMA) to introduce vinyl groups in the structure of the XG and CTS, to enable the chemical crosslinking reaction with N'N'-dimethylacrylamide (DMA), which results in the formation of chemical hydrogels. The chemical modification was characterized by analysis of absorbance spectroscopy in the infrared region with Fourier transform (FTIR). For the synthesis of chemical hydrogels, different proportions of polysaccharides and the DMA spacer were used. After the synthesis of the hydrogels, the swelling mechanism in distilled water was studied, thus selecting the formulations XGA3, XGA4, XGA5, XGA6, CTSA3, CTSA4 and CTSA5, which showed lower fragility and lower degree of crosslinking for swelling tests in 1.2 and 6.8 buffer solutions, to investigate whether the synthesized materials showed pH-responsive behavior. It was observed that the hydrogels based on XG with the formulation XGA3 and XGA6 obtained higher results in the degree of swelling (SW) in a pH 6.8 solution (approximately 13 g g-1 and 15.3 g g-1 , respectively) than at pH 1.2 (SW of 10 g g-1 and 13 g g-1 ), due to the ionization of the carboxyl groups (-COO- ) present in the polysaccharide structure. The hydrogels based on CTS showed the opposite behavior, obtaining higher SW values in a buffer solution of pH 1.2 (3.44 g g-1 for CTSA4 and 3.49 g g-1 for CTSA5) than in pH 6.8 (2.98 g g-1 and 2.80 g g-1 ), as it has amine groups (-NH2) in its structure. In this way, it was possible to conclude that the hydrogels produced had the potential to be used as drug delivery devices. Due to the better results obtained, the hydrogels based on XG followed the assays of controlled release of vitamin B12 (VB12) in a simulated gastrointestinal system. Thus, the hydrogels of formulation XGA5 (50.0 mg of XGm and 0.20 mL of DMA) and XGA6 (50.0 mg of XGm and 0.25 mL of DMA) were loaded with VB12 by swelling in solution at the concentration of 100 µg mL-1 and, once dry, the release tests were performed by swelling in a buffered system at pHs 1.2 and 6.8, with the determination of VB12 released at defined time intervals, up to a total of 10 am From the asays, it was observed that the hydrogel of formulation XGA6 presented favorable characteristics for application as a vehicle for controlled release of VB12 in the intestine, since it obtained a higher percentage of cumulative release at pH 6.8 (approximately 17%) than in pH 1.2 (approximately 13%) and a more controlled release in solution 6.8, in order to release smaller amounts of the drug per time interval.