Desenvolvimento e caracterização de membranas quitosana/silicatos em camadas para uso como suporte enzimático na construção de um biossensor de uréia.

Abstract

In this study the bentonite Argel 35, supplied for Bentonit União Nordeste, was purified seeking elimination of organic matter and used in the preparation of chitosan/purified bentonite membrane with mass ratios of 1/1, 5/1 and 10/1. For comparison chitosan/montmorillonite (Cloisite® Na+) membranes were prepared with the same mass ratios, the montmorillonite supplied for Southem Clay Products. The membrane of chitosan/purified bentonite and chitosan/montmorillonite were prepared by the solution intercalation process and characterized by infrared spectroscopy, x-ray diffraction, scanning electron microscopy, tensile properties, thermal analysis (thermogravimetric analysis and differential scanning calorimetry), contact angle measurements and the adsorption behavior of enzyme urease in the membranes was studied by means of spectrophotometry at 280 nm. The results indicate that the morphology, thermal stability, hydrophilicity and tensile properties such as tensile strength, elastic modulus and elongation at break are affected by the type of silicate and chitosan/silicate ratio. Bionanocomposites chitosan/silicate with mass ratio of 1/1, 5/1 and 10/1 indicate the formation of an ordered intercalated, disordered intercalated and exfoliated structures, respectively and the degree of the hidrophilicity and thermal stability decreasing in this order. Regarding the mechanical properties, the values of the tensile strength and of the elastic modulus of the chitosan/silicate membranes were more pronounced than the chitosan membranes and the elongation decreased. The evaluation of the adsorption of the enzyme urease at the chitosan/silicate membranes with mass ratio of 5/1 showed favored in pH 7.2 phosphate buffer solution at 25 °C. Since the nanocomposites prepared with purified bentonite showed similar behavior to that prepared with montmorillonite CloisiteÒ, this may be employed in urea biosensor in the preparation of chitosan/silicate membranes for application as support for immobilization of urease by adsorption.