Low-temperature plasma treatments in the design of polypropylene surgical meshes for hernia repair

Abstract

One of the new trends in textile biomaterials research is to deliver active compounds locally in the surgical site from the medical device. One way to manage post-operatory infections associated with mesh implants in abdominal hernia repair surgery can be the loading of antibiotics to the surgical textile meshes. In a novel approach to design an advanced drug-delivery systems based on surgical meshes, low-temperature plasma processes have been used to tailor the surface properties of polypropylene meshes to obtain high loading of ampicillin, maintaining the biological adhesion and the antibacterial activity of the current surgical meshes [1]. Plasma treatment of polymer fibers has been commonly employed to tailor surface adhesion and wetting properties by changing the surface chemical composition [2-3]. Appropriate selection of the plasma source enables the introduction of diverse functional groups on the target surface to improve wettability, biocompatibility or to allow subsequent covalent immobilization or physical adsorption of various molecules such as dyestuffs, pharmaceutical or cosmetic active principles [4-5]. Plasma can also be used for the deposition of polymer thin coatings by the so-called plasma polymerization process [6]. By modifying the process parameters of the plasma and the precursor molecule, different kinds of biocompatible coatings can be produced, from cell-adhesive to antifouling coatings. In this work, low-temperature plasma processes have been used to tailor the surface properties of polypropylene meshes, in a novel approach, to obtain high loadings of ampicillin, maintaining the biological adhesion and the antibacterial activity of the current surgical meshes [1]. As a first-step in the design of the antibiotic-loaded surgical mesh, plasma functionalization of the polymer surface with polar oxygen groups was used to modify the polypropylene fiber surface at a nanometric level. Surface wettability was improved and the availability of chemical bonds (C-O, C=O) increased. This was employed for the subsequent attachment of ampicillin allowing increasing its loading as function of the plasma treatment time. The chemical and morphological changes produced on the surface of polypropylene fibers lead to a 3-fold improvement of the ampicillin loading in the meshes after only 3.5 s of plasma treatment. However, this plasma treatment and the subsequent loading of the ampicillin in the polypropylene fibers were related with lower fibroblast adhesion, altered morphology and enhanced chemotaxis. Thus, plasma polymerization was used as dry method to create a thin coating of polyethylene glycol with the aim of keeping the high antibiotic loadings obtained with plasma functionalization and to maintain essentially unchanged fibroblast properties such as chemotaxis or adhesion with respect to untreated meshes, fulfilling the requirement of biocompatible device for the finished antibiotic-loaded mesh. Beyond the added value brought by the loading of an antibiotic to the mesh for its release directly to the surgical site, the use of plasma processes in the design of biomaterials brings an original approach to control simultaneously physic-chemical properties and regarding the treatment of the mesh without the use of any other chemicals for the binding of the active principle with the fiber.