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Title: Haemocompatibility of doped diamond-like carbon (DLC) thin films synthesized by plasma treated method
Other Titles: Deng li zi ti chu li fang fa yu xue xiang rong xing de yuan su shan za lei jin gang shi bo mo yan jiu
Authors: Kwok, Chung Hang (郭仲恒)
Department: Dept. of Physics and Materials Science
Degree: Doctor of Philosophy
Issue Date: 2006
Publisher: City University of Hong Kong
Subjects: Biomedical materials
Diamond thin films
Diamonds, Artificial
Ion implantation
Plasma (Ionized gases)
Notes: 175 leaves : ill. ; 30 cm.
CityU Call Number: TP873.5.D5 K86 2006
Includes bibliographical references.
Thesis (Ph.D.)--City University of Hong Kong and the University of Sydney, Australia, 2006
Type: Thesis
Abstract: Diamond-like carbon (DLC) has superior physical and chemical properties and has been widely used in the optics, magnetic media, and semiconductor industry for many decades. In the biomedical field, it is a potential surface coating material for cardiovascular implants, for instance, artificial heart valves, stents, etc. due to its good mechanical features. The haemocompatibility, however, of DLC is still not adequate for real medical applications and should be improved. Doping DLC with different elements is a possible solution. Plasma treated method is one of the effective and reliable approaches of surface modification. Plasma immersion ion implantation and deposition (PIII-D) as well as filtered pulsed cathodic vacuum arc (FCVA) were adopted in my research. In my experiments, carbon plasma was produced by radio frequency (r.f.) and arc method from gas (i.e. acetylene) and solid (graphite) source respectively. By altering the experimental parameters such as gas flow rate, inlet ratio, and substrate bias voltage, etc., different DLC thin films were fabricated. Furthermore, intentional element doping of the thin films was introduced by using various novel methods, for instance, external evaporation source, dual or co-axial target, for purpose of providing a mixed carbon - element plasma for film deposition. Primarily, my research aims at enhancing the haemocompatibility of DLC using the plasma treated method. DLC thin films doped with different biologically friendly elements including phosphorus, calcium, sodium, iron, and silver were synthesized via PIII-D or FCVA method. The blood compatibility of the films was evaluated by using the in-vitro platelet adhesion test. The quantity and morphology of the adhered platelets were measured with a low number of adhered and activated platelets indicating a good haemocompatibility of the material. To study the phenomena and mechanisms leading to good results in the platelet adhesion test, the films were characterized by various techniques including scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), transmission election microscopy (TEM), electron energy loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Raman spectroscopy, and contact angle test. Experimental results show that the doped DLC films have better haemocompatiblity than traditional DLC and low-temperature isotropic pyrolytic carbon (LTIC). It is believed that the interfacial energy between the materials and proteins (albumin and fibrinogen) is the major factor. When the doped DLC thin films have optimum interfacial energy, which favors the absorption of albumin (platelet adhesion inhibiting protein) but not the fibrinogen (platelet adhesion activating protein) and less conformational change of fibrinogen, coagulation and activation of platelets will be suppressed. Moreover, a low medium (water) - material interfacial tension (γ SL ≈ 1-3 dyn/cm) also provides a mechanically stable interface as well as long-term compatibility with blood, which causes good blood compatibility. In conclusion, a series of DLC thin films doped with phosphorus, calcium, sodium, iron, and silver were synthesized by PIII-D and FCVA methods. The haemocompatibility behavior of doped DLC thin films was analyzed in terms of wettability or interfacial energy of the materials. The work suggests that doped DLC has superior compatibility with blood and is a potential biomaterial for bloodcontacting devices in biomedical engineering applications.
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