Innovative procedures for advanced surface properties of medical stainless steel

As a result of exceptional mechanical properties, surgical-grade stainless steel (SS316) has been a primary SS alloy recommended for medical devices, such as coronary stents, hip-implant stems and spinal-disc replacements, and also for a variety of surgical tools such as scalpels and forceps, as well as operating tables. In fact, studies estimated that SS alloys established nearly 60% of the surgical implants used in the United States, while app. 85 % of surgical instruments are made of SS. However, SS316 as a biomaterial still lacks of desired biological response; i.) it does not exhibit any inherent antibacterial activity and has even a tendency of evoking a local inflammation, and moreover ii.) it can cause allergic and toxic reactions due to leakage of harmful alloy-constituents. Besides, there has been a dramatic increase in the emergence of multidrug resistant bacteria due to misuse and/or overuse of antibiotics, which cause drastic escalation of life threatening medical device associated infections, It is expected that by 2050 infections by resistant bacteria could be responsible for more deaths per year than those due to all combined cancer forms. The concept of the proposed project follows an urgent global need of development of innovative surface modification routes that would allow the fabrication of next-generation SS316. Within the project, surface finishing procedures in order to improve antibacterial activity and biocompatibility of SS316, in terms of corrosion resistance and mammalian cell response, will be performed. This will be achieved by unique combination of electrochemical anodization and non-thermal plasma treatment. Novel approach will alter SS316 surface characteristics, specifically nano topography, chemistry and wettability, which significantly influence biological response, but at the same time it will retain its inherent mechanical properties. Moreover, stable surface oxide layer induced by plasma treatment will prevent release of toxic/allergic elements into the human body. Additionally, advanced surface modification will allow direct drug loading on the surface of SS316 without the use of toxic polymer matrixes, which will present a breakthrough in the field of tissue engineering. Such surface modification treatment will be applicable for the design of not only medical devices, but also other hospital settings made from various metal alloys. The project is conceptualized as three-year research on: i.) Optimization of surface finishing methods for formation and characterization of nano-patterned SS316 with the unique combination of electrochemical anodization and non-thermal plasma treatment; ii.) Characterization of surface properties (wettability, morphology, surface chemistry, etc.) of novel SS316; iii.) Evaluation of antibacterial performance of novel SS316; iv.) Evaluation of biocompatibility of novel SS316; corrosion resistance, hemocompatibility and cytocompatibility. The proposed research project carries strong innovation character and includes high potential for bringing the breakthrough in the field of surface finishing procedures for biomaterials. The collaboration within the project will combine long lasting expertise of Department of Surface Engineering and Optoelectronics of JSI in plasma treatment with strong competences of the Groups of University of Ljubljana and Biomaterials group at the Advanced Materials Department of JSI in formation of nano-structures and investigations of interactions between materials and bacteria/cells. The collaboration will provide important new knowledge in the development of advanced stainless steel and its application as medical devices/implants and valuable new expertise which will be effectively used for creation of new consortia, planning and application of further national and international research projects.