Técnica de revestimento de stents metálicos com biopolímero: desenvolvimento de metodologia.

Abstract

Stents are tubular and expandable endoprostheses that can be coated with biodegradable polymeric matrices in order to create a coating that can act passively, serving as a barrier between the metal surface and the biological tissue; or actively, directly interfering in the biological processes of recovery after implantation. Thus, chitosan, as a biocompatible and biodegradable biopolymer, presents itself as a promising biomaterial for this type of application. In this work, a research was carried out to develop a technique for coating stents from chitosan. For this, commercial stent samples were submitted to four coating techniques: dip coating, spin coating, spray coating and layer-by-layer, evaluating the behavior of different chitosan concentrations (0.1, 0.5 and 1% m/v), besides the association of sodium alginate in the layer-by-layer application. A rheology test was carried out in the polymeric solutions to evaluate and quantify the differences in viscosity between the used solutions, so that solutions with viscosities much high above the found average, were discarded. From the micrographies of Optical Microscopy and Scanning Electron Microscopy, it was possible to verify that dip coating and layer-by-layer techniques enabled the deposition of polymeric coating on the stents surface. The degree of swelling and compressive strength tests were also performed and corroborated the feasibility of the adopted coating techniques. Thus, it was possible to conclude that the best coating condition was obtained from chitosan solution with 0.5% chitosan and the dip coating technique. The micrographs of Optical Microscopy and Scanning Electron Microscopy for this test condition evidenced the presence of homogeneous and uniform coating on the stents surface.