S. A. Esenwein, C. Krueger, S. Bensch, J. Hauser, BG Trauma Center Bergmannsheil - University Hospital, Bochum, Germany; H. Halfmann, Ruhr-University of Bochum, Bochum, Germany
Introduction: Low pressure plasma treatment is an upcoming new method for surface modification. Treatment of metal implants performed with a plasma reactor leads to a change in surface free energy (SFE). A change of SFE should also influence the protein adhesion pattern, and thus it could lead to a change of biocompatibility because the pattern of adhered proteins is a decisive factor, if and how cells can grow on implant surfaces. Thus, in this study the influence of low-pressure plasma treatment on wettability and biocompatibility of different alloys used in numerous implants and medical devices was examined.
Methods: Coins of stainless steel X2CrNiMo18-15-3 and titanium alloys Ti6Al4V and Ti6Al7Nb were treated with different plasma process parameters. The following settings and plasma parameters were used: different gas mixtures (Ar, Ar/H2, Ar/O2, Ar/N2), operating pressures (5 Pa, 10 Pa, 20 Pa), different powers (500 W, 1000 W) and different treatment times (15s, 60s, 600s). Afterwards their wettability was measured with drop shape analysis. SFE calculations were performed based on the Neumann and the Owens-Wendt-Raabe method to analyze surface-surface interactions.
Results: The contact angle for water on all materials decreased from over 70° to less than 10° after 15 seconds of treatment, SFE raises from about 40 mN/m to 70 mN/m. No influence of pressure, power, gas mixture and treatment time on the absolute level of SFE can be stated in our parameter range. The effect is temporary, after treatment wettability returns to its former value within days. The changed adhesion of proteins could be demonstrated by collagen-I deposition on polished stainless steel implants.
Conclusions: Low pressure plasma treatment is a new method to increase wettability and biocompatibility for metal implant materials. It seems to be a useful procedure for deposition of proteins, drugs or growth factors on the implants’ surfaces.
Summary: Treatment of metal implants performed with a plasma reactor leads to a change in surface free energy (SFE). A change of SFE should also influence the protein adhesion pattern, and thus it could lead to a change of biocompatibility because the pattern of adhered proteins is a decisive factor, if and how cells can grow on implant surfaces. Thus, in this study the influence of low-pressure plasma treatment on wettability and biocompatibility of different alloys used in numerous implants and medical devices was examined. Test devices of different alloys (X2CrNiMo18-15-3, Ti6Al4V, Ti6Al7Nb) as used as implant materials were treated with different plasma process parameters. After this process their wettability was measured with drop shape analysis. SFE calculations were performed to analyze surface-surface interactions. The plasma treatment related changes of SFE values at different alloys is time dependent. The half-life periods of the increased SFEs were found to be between 30 and 37 hours. The changed adhesion of proteins could be demonstrated by collagen-I deposition on polished stainless steel implants. Low pressure plasma treatment is a new method to increase wettability and biocompatibility for metal implant materials. It seems to be a useful procedure for deposition of proteins, drugs or growth factors on the implants’ surfaces.
