Improvement Of Surface Bioactivity And Osteoblast Compatibility On PTFE Membrane By Plasma Immersion Ion Implantation

Polytetrafluoroethylene (PTFE) has been widely used in clinical medicine including facial reconstructive where it is used in facial augmentation surgery, guided tissue regeneration(GTR) and guided bone regeneration (GBR), etc. The general biocompatibility of the material is good. However, this material does not have functional groups to interact with outside cellular environment and is classified as bio-inert.(For example: PTFE neither supports osteoblast growth or induces calcium phosphate growth in simulated body fluid).Observing the interface of bioactive material with bone, it is well noted that a biologically active apatite layer is necessary on the material surface to act as boning interface.So,the surrounding bones can come into direct contact with the surface apatite and then produce bioactive apatite and collagen on this surface to form tight chemical bondings.The hydroxyapatite(HA) layer is very important for the bioactivity of the material. In this respect, surface modification is a desirable approach to improve the biocompatibility and bioactivity of PTFE while retaining the favorable bulk properties. In this work, O2 or Ar plasma immersion ion implantation (PIII) is conducted to modify the PTFE surface and to improve the surface bioactivity and osteo-compatibility.Method:Gaseous O2 or Ar was introduced to form the plasma in the PIII experiments and treat PTFE surface. The surface chemical states were determined by Attenuated Total Refraction Fourier transform infrared (ATR-FTIR) spectroscopy.The surface hydrophilicity was assessed by contact angle measurements using distilled water .The surfaces of specimen were observed by scanning electron microscopy (SEM). After different culturing times, the seeded osteoblast samples were observed by SEM and viewed and photographed with a fluorescence microscope after stained with 4,6-diamidino-2-phenylindole dihydrochloride hydrate (DAPI). All the samples were soaked in a simulated body fluid (SBF) for 14 and 28 days to investigate their bioactivity. After the immersion test, the specimens were characterized by FTIR and SEM spectroscopy.Results:1. In the SEM examination, there are many sharp rods on O2-PIII, Ar-PIII substrates compared to untreated ones. O2-PIII and Ar-PIII substrates display a more rugged topography than untreated ones. The surface measured contact angles using water as the media are that all the treatments increase the surface hydrophobicity of PTFE. In addition, after O2-PIII, Ar-PIII modification, C–O and C=O groups are formed on the PTFE substrates.2. The SEM views of various specimens were examinated after soaking in SBF for 14 and 28 days. Some scattered and clustered particles are formed on the O2-PIII and Ar-PIII samples after 14 days but no particles emerge on the untreated ones. When the immersion time is prolonged to 28 days, the number of particles on the plasma-treated specimens is clearly increased but no particles can be observed on the untreaed ones. The energy dispersive X-ray spectroscopy (EDS) spectra revealed that the formed particles contain calcium, phosphorus and oxygen. ATR-FTIR spectroscopy was also used to analysis the chemical structure of the particles. The EDS and ATR-FTIR results both indicate that carbonate-containing hydroxyapatite is formed on the O2-PIII and Ar-PIII samples after soaking in SBF for 14 and 28 days.3. The result of cell culture experiments displayed an enhanced osteoblasts adhesion and proliferation on the O2-PIII, Ar-PIII surfaces, and better cell proliferation was found on the O2-PIII surface. However, the distinction of cell proliferation between O2-PIII and Ar-PIII is not obvious.4. After 6-h culture,on the untreated surface the osteoblasts exhibited few adhesion with small amount of fillopodia and lamellipodia. On the Ar-PIII surfaces, the osteoblasts with more lamellipodia from the cells showed a better cell attachment but not covered the surface at all. On the O2-PIII surfaces, osteoblasts formed more than one layer net-like structure. It seemed that the osteoblasts spread better than Ar-PIII surfaces.5. After incubating for 1, 3 and 5-d, the quantity of the osteoblasts on the O2-PIII and Ar-PIII PTFE samples are larger than untreaed PTFE respectively. In particular, the O2-PIII treated samples exhibited better biocompatibility trend compared to Ar-PIII.Conclusions:Both O2-PIII and Ar-PIII processes can enhance surface roughness, decrease surface hydrophobicity of PTFE, and produce C–O and C=O groups into the surface, which do not exist on initial PTFE. In addition, both O2-PIII and Ar-PIII can transform the bio-inert PTFE surface into a bioactive one. The differences in surface topography and surface chemistry are believed to be the causes of the altered bioactivity. It also finds that osteoblast adhesion, spread and proliferation are enhanced by plasma treatment, and O2-PIII is more effective than Ar-PIII. Both O2-PIII and Ar-PIII treatment can improve osteoblast compatibility and bioactivity.