Resumo:
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
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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.
