Research On The Surface Modified Medical Carbon/Carbon Composites And Their Biomedical Applications

Carbon/carbon composites is a developed material in material science. It has been studied for30yearsas a medical implant. With good biological compatibility, chemical stability, good mechanicalproperties and elastic modulus similar to human bones, carbon/carbon composites have good prospectfor application. But so far, they have not being actually clinically used. This dissertation mainlystudies carbon/carbon composites preparation, biological compatibility, surface modification，theimprovement of wear resistance，the preparation of individual artificial bone and the effect on thedosage in radiotherapy.In this dissertation, according to the present situation that carbon/carbon composites has shortcomingsfor the use in the field of medicine such as the impurities or even high content of toxic elements, wepropose that the high temperature (2800-3200℃) processing time be extended to reducecarbon/carbon composite material impurity (toxicity) content. Research on biological safety has beencarried out according to the National Standards for Medical Equipment of the People’s Republic ofChina. We believe that the carbon/carbon composite material which is processed at2800-3200℃for12h is in line with the national standards of medical devices. We studied the effects on osteoblastgrowth with carbon/carbon composite by different preparation processes, and analyzed the cell growthfactors.We also studied adhesion characteristics of osteoblastic cells on carbon/carbon compositesurface, discussed and explained adhesion mechanism.Pyrolytic carbon structure distribution of medical carbon/carbon composites surface modified bygradient chemical vapor deposition（CVD）can improve the surface wear resistance and obtain thetechniques for preparing medical carbon/carbon composite coating by gradient CVD was obtained.This technique can solve the problem of easy abrasion of medical carbon/carbon composite. Also themechanism of friction resistance by gradient CVD was explored by scanning electron microscope(SEM), X ray diffraction (XRD), friction test machine.A novel technology of plasma pre-treatment was developed for preparation of hydroxyapatite coatingon carbon/carbon composite by plasma spraying.This technique provides improved adhesive coating.By scanning electron microscope (SEM), X ray diffraction (XRD), infrared spectroscopy(FT-IR) and scratch test analysis, we found active groups and pyrolytic carbon defects removed oncarbon/carbon composite surface after plasma pretreatment. These factors are beneficial for theimprovement of the bond strength of the coatings.The research of biological properties was carried out in vivo and in vitro. New apatite layer can bedeposited on the hydroxyapatite coatings in vivo and in vitro. These new apatite coating can inducenew bone formation. In vitro, the growth of osteoblasts on the surface of the coating is good. Animalexperiment proved that hydroxyapatite coatings can induce the rapid growth of new bone tissue.At thesame time, systematic research has been done about the bone tissue repair at the interface of coatingusing scanning electron microscope (SEM) and pathological sections. From the routine bloodexamination and biochemical examination analysis, we found that hydroxyapatite coating andcarbon/carbon composite material have good biological safetyWe studied the prospect of the carbon/carbon composite implants in radiation therapy. Compared withmetal implants, the carbon/carbon composite implants have incomparable superiority in radiotherapyfor the treatment of various steps. With Monte Carlo simulation, we analyzed in detail the incidentsurface dose and the exit surface dose of implant. We also study the dose effect of implants in theactual plan design. The mechanical properties of carbon/carbon composite implants after absorbingdifferent radiation therapy dose were tested.That radiation therapy dose does not have impact onmechanical properties of carbon/carbon composites.Therefore, they are more suitable to patients inneed of radiotherapy.It is found that carbon plates will neither increase the incident surface dose, norlead to the sharp decrease of exit surface dose (the effect of a second build-up). Carbon fiberorthopedic implants have a good prospect for radiotherapy patients because they have minimalperturbation effects on the radiotherapy dose distribution.Finally, a novel method that can rapidly prepare individual artificial bone of carbon/carbon compositewas developed.The DICOM format of the skeletal model is converted to non-uniform rational B-spineformat that can be identified by mechanical processing software. Individual artificial bone contourwas sketched with the help of visual operation effect. Individual artificial bone of carbon/carboncomposite was prepared through the CNC Machining Center.