| Background:Owing to excellent biocompatibility, calcium phosphate (CaP) has been widely used as bone substitute, scaffold for drug delivery and growth factor, and matrix for bone tissue engineering. When used as bone substitute, CaP implants are able to form the chemical bonding between implants and biological bone. The interface between implants and biological bone exhibits the continuity in chemical composition and mechanical properties which result in the function continuity.The mechanism of CaP bioactivity is widely accepted as: The Ca++ and PCV'dissolve from the surface CaP implant under influence of body fluid, subsequently deposits as the bone-like apatite layer on the surface of the CaP implant. This layer maybe selectively adsorb the special proteins from blood, such as vitronectin and fibronectin, and promotes the osteoblast adhesion, proliferation, and simulates the secretion of collagen fiber secreted by osteoblast and mineralization of collagen fiber, at last results in the formation of bone tissue on the surface of CaP implants. The key factor for CaP bioactivity is formation of bone-like layer on the surface of Ca-P implants.During the mechanism mentioned above, the proteins take part in and adjust the each steps, but the interaction between CaP and proteins is not fully understood.Up to now there are many debates and controversial answers about following questions:(1) What are the roles of proteins in the above process?(2) What are the effects of CaP properties, such as chemical composition, on the characteristics of bone-like layers in the biological environments?(3) What is the difference of the bone-like apatite layers formed in simulated body fluid without proteins in vitro and the biological environments?(4) How to characterize correctly the characteristics of bone-like layer, such as structure, chemical composition?Objectives:In this study, the main attention was concentrated to the interaction of proteins and CaP ceramics (hydroxyapatite (HA), tricalcium phosphate (TCP)) in vitro (immersed the samples into fetal calf serum) and in vivo (implanted the diffusion chamber enclosed the test ceramics samples into animals). We designed a series of experiments to investigate:1. The behaviors and characterization of proteins adsorbed on the surface of HA and TCP in vivo and in vitro;2. The process and mechanism of proteins adsorption on the surface on CaP;3. The effects of proteins on the formation and characteristics of bone-like apatite layers formed on surface of HA and TCP in vivo and in vitro.4. The mechanism of bone-like apatite layer formation in vitro and in vivo;5. New characterization method of XPS for crystal structure of bone-like apatite layer.IV6. The implantation of porous HA/TCP ceramics adsorbed the bovine bone morphogenetic proteins in the spine fusion and the interface phenomena between bone/ImplantResults:1. The Chemical composition significantly influence the adsorption behavior of protein:XPS and PAGE results indicated that in vitro there was no significant difference for protein adsorption on the surface of HA and TCP in the quantity and type of proteins. In the vivo the quantity of adsorbed proteins on TCP surface was more then HA, and the HA did not show the ability to adsorb the proteins with low molecular weight, but TCP can adsorbed he proteins with low molecular weight on its surface. The overall amount of proteins adsorbed on both HA and TCP in vivo was more than in vitro. This results maybe indicate that in vivo TCP implants are able to adsorb the growth factors owing to almost all of growth factors are proteins with low molecular weight, and TCP is better delivery scaffold matrix of growth factors than HA.This thesis first postulated the process and mechanism of charged protein adsorption on the surface of CaP with negative zeta-potentials according to the surface charge distribution on protein surface and conformation adjustment of proteins during the adsorption process.The process of proteins adso...
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