Hidrogéis de pnipaam-co-aam como sistemas carreadores de produtos bioativos de interesse farmacêutico : Pnipaam-co-aam hydrogels as carrier systems of bioactive products of pharmaceutical interest

Hydrogels are polymer compounds with three-dimensional configuration that have the ability to absorb large amounts of water. Biological use can be found for hydrogels in dressings, contact lenses, and controlled release of drugs. Poly (N-isopropylacrylamide) (PNIPAAm) hydrogels are thermoresponsive and stable. Bromelain is the set of proteases obtained mainly from pineapple. It can act in processes of cicatrization and selective debridement of burns, besides having anti-inflammatory and fibrinolytic activities. Thus, the junction of the PNIPAAm hydrogel with an active substance such as bromelain can point to an application in wound healing. This work evaluated the possibility of such association from the development and characterization of the hydrogel, as evidenced in chapter II of this work. The results show that the behavior of bromelain incorporated to the hydrogel indicates considerable action and maintenance of its activity in the tests to which the system was exposed, which implies the possibility of therapeutic use for this. Abstract: Hydrogels are polymeric compounds with tridimensional structure that are able to load water and other substances. Such characteristic makes hydrogels suitable for innumerous applications in biomedical fields. For almost 60 years hydrogels have been studied and progress have been made in topical use. Natural and synthetic polymers have been applied to develop smart hydrogels that respond to physiological stimuli while releases drugs and bioactives. In view of this, this paper approaches the use of important materials in hydrogel’s synthesis as highlights the main sites affected by topical disorders and routes for therapeutic controlled release. Abstract: Hydrogels are materials known for decades, with applications in wound healing, contact lenses, biosensor and tissue engineer. Thermosensitive materials, such as PNIPAAm are considered for the development of hydrogels for controlled release, especially for topical use. Bromelain is a set of proteases found in plants of the Bromeliceae family, being that pineapples represent the main source of these enzymes. In burns, bromelain acts by hydrolyzing the devitalized tissue, both in vivo and i n vitro , which increases the healing capacity. Therefore, the combination of such hydrogels and bromelain could point to a topical application of interest. For this work, NIPAAm and AAm were co-polymerized and the hydrogel synthesized taken to swelling tests for 24 hours. The best formulation, was loaded with bromelain solutions. Pineapple residues were processed and precipitated with ethanol for posterior freeze-drying and use. After loading which was nearly 30%, the hydrogel discs were dryed and immersed in phosphate buffer pH 7.0 for release. The amount of protein and enzymatic activity were measured from the buffer after 60, 90 and 180 minutes and after 48 and 96 hours. Fourier transform infrared (FTIR) was performed to determine the specific chemical groups of the purified bromelain and the hydrogels, pure and containing bromelain. Micrographs of the hydrogels both pure and loaded with bromelain showed the appearance of the polymeric chains and how the loading clearly appears. The hydrogels were also submitted to mucoadhesion tests in order to assure the material’s retention, spread and bioavailability. Rheology and resistance experiments were applied to verify the samples’ physical behavior in face of stress. Cell viability assay showed percentage of death at 50% after 48h. In that sense, the characterization performed in these tests points to the possibility of association of thermosensitive hydrogels and a bioactive product, such as bromelain,