Síntese e caracterização de estruturas porosas de quitosana pela técnica de separação de fase para aplicações biomédicas

Abstract

The purpose of this research was to prepare and characterize porous hydrogels to biomedical applications. The studied system is based on the polymeric blend poly(vinyl alcohol)/Chitisan (PVA/Ch) developed by pH the induced phase separation. The PVA/Ch hydrogels were characterized by scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle, and equilibrium swelling measurements. The water sorption kinetics in the PVA/Ch membranes were used to determinate the diffusion coefficient and transport properties in according to Fick’s law. Contact angle data were evaluated for the determination of surface free energy (gc) of the PVA/Ch membranes. The biocompatible properties were evaluated by “in vitro” test as albumin (HSA) and fibrinogen (HSFb) adsorption. The cell viability (citotoxicity) was studied using colony supression assay (CHO-K, cell) method. Nitrofurazone, a topical antibiotic, was incorporated in the PVA/Ch membranes and drug permeation experiment was performed in phosphate buffer solution (PBS) in pH range of pH 2.0 - 9.0, respectively. A dependence was observed between the surface free energy (gc) and PVA membrane compositions. The water diffusion coefficients at pH 7.4 increased with increasing PVA content on the blends indicating that the water molecules still possess a high degree of trasnlational mobility and are not tightly bound in the PVA/Ch blend structure. The membranes swelling behaviors responded rapidly to the change in the enviromental pH condition due to the ionic nature of Ch. The results of nitrofurazone permeation demonstrate that with a PVA/Ch system, in vitro, a near zero-order release of the drug is observed. It appears that the mechanism of drug release may be due to diffusion through the swollen PVA/Ch membranes in the PBS solution. The diminution on the HSFb adsorption and increased adsorption of HSA for PVA/Ch membranes as well as xv the existance of a certain range of surface free energies for an improved biocompatibility, hints that it must due to the surface composition, molecular mobility of the hydrogel chains and interaction of the plasma proteins with water in PVA/Ch hydrogels. The results suggest that the PVA/Ch membranes will can be used as wound dressings in the treatment of skin ulcerations in burned or patients with restrincted mobility.