The effect of amorphous carbon films deposited on polyethylene terephthalate on blood compatibility

Acetylene (C₂H₂) plasma immersion ion implantation and deposition (PIII-D) was performed on polyethylene terephthalate (PET) at different bias voltages from -5KV to -15KV. The surface structure of the treated PET is determined by Rutherford backscattering spectrometry (RBS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results show the formation of thin hydrogenated amorphous carbon (a-C:H) films with different structures and chemical bonds on the PET surface. Atomic force microscopy (AFM) shows that the reduced average surface roughness (R _a) decreases from 33.1 nm to 11.4 nm by depositing the amorphous carbon film. The wettability of the films is investigated by contact angle measurement. After C₂H₂ PIII-D, the surface energy increases from 43.3 mN/m to 47.1 mN/m and the ratio of polar component γ_p to dispersive component γd increases from 0.06 to 0.35. Platelet adhesion and coagulation factor experiments are conducted to examine the blood compatibility in vitro. Scanning electron microscopy (SEM) and optical microscopy reveal that the amounts of adhered, aggregated and morphologically changed platelets are reduced on all amorphous carbon films. The number of platelet adhered on the amorphous carbon film deposited under -10 KV is reduced by almost 75% compared to the amount of platelets on the untreated film. The thrombin time (TT), prothrombin time (PT) and activated partial thromboplastin time (aPTT) of the modified PET are longer than those of the untreated PET. Our result thus shows that the amorphous carbon film deposited on the PET surface by C₂H₂ PIII-D improves platelet adhesion and activation. A possible reason for the good hemocompatibility is that the amorphous carbon coating minimizes its interactions with plasma protein and slightly changes the conformation of adsorbed plasma proteins.