Caracterização de hidrogéis semi-interpenetrantes de alginato e quitosana reticulados com cloreto de cálcio ou glutaraldeído: estudo do efeito das condições de preparo em suas propriedades mecânicas e físico-químicas

Abstract

The objectives of this work are the preparation and the mechanical and physical-chemical characterization of alginate and chitosan semi-interpenetrating hydrogels, to be applied in various areas of biomedicine. The combination of these polymers resulted in stable hydrogels that are capable to alter its viscosity and degree of swelling depending on the pH, pressure and temperature value. Three systems were prepared: the first, named A, alginate hydrogel was coated with chitosan and physically crosslinked with calcium chloride; the second, named Q, was chitosan coated with alginate and chemically crosslinked with glutaraldehyde; and the third, named MIX, was a mixture of alginate and chitosan (50% by volume) chemically crosslinked with glutaraldehyde. The choice of these systems was based on the application of these materials, which is the controlled release of drugs or tissues, proteins, cells and enzymes immobilization. The chosen variables were the porosity, the degree of swelling, the resistance to the environmental (pH and temperature), mechanical strength, and viscosity. It was noticed that, among the three systems, the sample A had high porosity, resistance to the acid regions, degradation at temperatures above 73° C, low mechanical strength, (796 ± 2) gf, and high degree of swelling in PBS, (9 ± 2) x 102%. This sample can be applied in acidic regions, such as the stomach, and used to immobilize and deliver proteins and other macromolecules in the body. The sample Q, in other hand, had smaller pores, resistance to basic pH, low mechanical strength of (1.2 ± 0.2) x 103gf and degree of swelling (9 ± 1) x 102%. The most important characteristic of this system was the thixotropy. So, the hydrogel Q can be applied in regions such as the intestine, skin or the human eye and it is useful for controlled release drug systems. The hydrogel MIX showed similar characteristics to the hydrogel Q, however, as it had a lamellar structure and higher degree of swelling (1.2 ± 0.2) x 103%, it can be used for immobilization of small tissues and cells to be released in regions of the basic pH, such as skin, bone, or intestine. Thus, from these results, it has become a promising field for studies in biomedicine and pharmacology.