Surface modification of metal implant materials by low-pressure plasma treatment

Background: Plasma treatment leads to a significant change of surface free energy of medical implant materials. These changes strongly influence protein and cell adhesion on the material surface. The aim of the study was to quantify the plasma-induced surface changes and to analyse whether the change of treatment parameters, such as pressure, gas mixture, energy and treatment time, influences the surface free energy of the implant materials. To improve the biocompatibility of the surfaces, polyamino acid coating experiments were performed. Materials and methods: Three different metal implant materials (X2CrNiMo18-15-3, Ti6Al4V, Ti6Al7Nb) were treated with a double-inductively coupled low-pressure plasma. The influence of treatment parameter variation on the surface free energy was evaluated by drop shape analysis. The plasma treated and non-treated materials were incubated in collagen I solution. Afterwards, the coatings were analysed by electron microscopy in terms of structure and adhesion. Results: Drop shape analysis revealed that plasma treatment leads to a significant increase of surface free energy in all groups. Long plasma treatment times and low treatment pressures lead to a significant (p < 0.05) extension of the detectable surface free energy increase. Coating experiments showed that only on plasma-treated samples solid and adherent collagen layers could be achieved.