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WPD. Chemical functionalisation and biomedical applications

Surfaces play a vital role in biology and medicine with most biological reactions occurring at surfaces and interfaces. Therefore, the purpose of this workpackage consists of applying the surface functionalisation techniques considered in WP.B-C to develop materials with specific biomedical applications.

This WPD will deal with the antibacterial functionalisation for biomaterials used in prostheses in orthopaedic surgery. Bacterial adhesion on implant surfaces is a major reason for implant sequelae and can eventually lead to implant removal. This septic failure of prostheses introduces severe consequences not only for the patients in terms of quality of life, but also for the society, that faces very high economic expenditures. However, the bacterial adhesion process is a complex series of physical and chemical interactions between the substratum and microbes and, despite the intensive studies, the “in vivo” process is still not totally clarified.

FUNCOAT pretends to study the functionalisation of surfaces for creating mechanisms to protect implants against infection during the implantation process of prostheses in orthopaedic surgery: Two strategies are considered in this project: the development of antibacterial coatings (D1) that prevent the growth of bacteria and/or lead to their killing when adsorbed on their surface, and the surface modification to change the chemical properties (D2).

Other topic considered is related with the coating for biomaterial in total hip and knee replacements in order to increase the survival of the implanted joints, which is around 90 % after 15 years implantation. The current trends in this field involve two lines: new crosslinking ultra high molecular weight polyethylene (UHMWPE) based on vitamin E and sequential irradiation-annealing, and new ceramic-ceramic or metal-metal joint pairs.

Bio-tribocorrosion is known to involve the interaction between mechanical wear processes and electrochemical and/or chemical corrosion process and leads to a material loss rate[28]. These synergetic effects of wear and corrosion are of great relevance and will also be considered in this WP.

D1.
Enhanced bio-activity on biomaterials:
This activity deals with the modification of the surface energy of the materials, particularly polymers (UHMWPE), to improve their bio-activity. For this purpose, we primarily propose the use of cold plasmas treatments, since these processes are currently used in industry and in healthcare environments. Ion Implantation shows up here as a very recent alternative technique to achieve doublefunctional surfaces: harder materials in combination to improved cell-proliferation capabilities.
D2.
Antibacterial functionalisation of surfaces:
A critical point for the development of implants is to prevent the infections that may occur during and after the implantation surgery. For this purpose local applications of antibacterial treatments present a clear advantage with regard to the extensive use of antibiotics or other treatments. FUNCOAT pretends the development of antibacterial coatings that prevent the growth of bacteria and/or lead to their killing when adsorbed on their surface.
D3.
Hard coatings for implants:
Other activity in WP.D is the development of multifunctional coatings that simultaneously present different properties. We will focus again on DLC coating due to their properties of hardness, wear resistance and good behaviour to friction in addition to the biocompatibility, chemical inertness and the possibility to dope with other elements with antibacterial or antiseptic behaviour, such are described in D2.
D4.
Tribocorrosion characterization in biological fluids:
This activity focuses on the evaluation of the chemomechanical mechanisms of bio-tribocorrosion of DLC coatings on polyethylene and metallic parts under conditions as close as possible to the synovial fluid at body temperature. Electrochemical methods will be used for the study of tribocorrosion reactions. In this activity, ion release to the surroundings will be also studied by ICP-MS analysis techniques.

The internal relationship between the activities/tasks with themselves and with other Work Packages is described in the following picture.

Diagrama WPD