Preparation And Characterization Of Calcium Phosphate/Collagen Composite Coatings On Ti Substrate

Titanium and its alloy are used as orthopedic and dental implants in the medical field because of their attributes of strength, stiffness, toughness, biocompatibility and corrosion resistance. Bone is mainly a collagen fibril/calcium phosphate composite with small amounts of non-collagen proteins and water. In vivo tests have proven that such a composite is bioactive and biodegradable to a certain extent, hence it enhances new bone growth. That is because collagen could improve the attachment of cells to the material, which makes the surface richer of growth factor and cells. If collagen could be attached to the bone replacement metal, the bioactive environment will shorten the recovering period.Based on the knowledge of electrical deposition, we design to prepare a calcium phosphate and collagen composite coating on titanium substrate. Get detail facts through experiment and give a useable deposition model which could be helpful in the future research.Through this research, deposition time, pH value of the electro late, temperature of the water bath are all affect a lot in the deposition process.Biomimetic mineralized collagen and calcium phosphate composite coating has been reported recent years by electrolytic deposition. And also the collagen physically absorbed on the surface of the calcium phosphate layer. However, most of their research only mentioned partially of the principium related to their results. Only part of the phenomena had reasonable explanations.After taking all of the facts and principium of the other groups into consideration, and compared with our experiment process, parameters and results, we set up a more comprehensive electrolytic chemical deposition theory of calcium phosphate/collagen composite coating. The deposition model could be departed as four parts, firstly, precipitation of calcium phosphate at cathode at the beginning of the electrolytic process accompanied with collagen fibril self-assemble at its isoelectric point, secondly, precipitation of calcium phosphate on the specific point of collagen fibril during its self-assembly process make the collagen mineralized, thirdly, with the reaction goes on, the isoelectric point of the collagen moves toward the cathode, leads to the collagen's transfer, collagen becomes closer to the Ti substrate, at the end, collagen was attached to the substrate by the chemical force of calcium phosphate growth. The deposition coating forms.Following the guidance of this model, we obtain a mechanically robust calcium phosphate/collagen coating, in which collagen fibrils density decreases while calcium phosphate gradually increases from the surface of the coating to the titanium substrate consistently and uniformly. The thickness of each layer, i.e. mineralized collagen and pure calcium phosphate, has been characterized. The morphology, phase, and microstructure of the composite coating were investigated and briefly discussed.