Study On Biological Properties Of Porous Anodic Alumina Loaded Inorganic Bioactive Particles

Porous anodic alumina（PAA）is formed on the surface of pure aluminum by the method of electrochemical oxidation,which has highly regular nano-pores that the size of them can be precisely controlled.In particular.PAA has excellent chemical stability and good biocompatibility,and the nano-pore structure is similar to the microstructure of bone tissue.Therefore,PAA has been extensively studied in the field of surface coating of biomaterials.In addition,the nano-porous structure of PAA provides ample space for further loading of bioactive substances so as to endow the PAA with special biological properties.Copper（Cu）and Zinc（Zn）are widely used in the field of biological materials due to their broad spectrum bactericidal effect.Recent study has found that the introduction of the appropriate amount of Cu into biological ceramic material could promote the adhesion,proliferation and functional expression of osteoblasts.On the other hand,Zn could stimulate bone formation through the activating of protein synthesis and the improving of activity of ATP,and it could also promote the calcium deposition of mesenchymal stem cells.In addition,CaO-SiO₂ system has been recognized as the basis for many third generation tissue regeneration materials presently in development.CaO-SiO₂ system has excellent bioactivity and biodegradability,where it can rapidly induce the bone-like apatite deposition and promote the bone cell proliferation and differentiation.We attempt to structure ternary mulriple CaO-SiO₂-Cu O by introducing appropriate Cu into CaO-SiO₂,and expect to endue it with better biological properties.Firstly,Cu and Zn was loaded respectively into the pores of PAA（termed Cu/PAA and Zn/PAA）with pore sizes of 75nm（PAA75）by alternating current deposition technology.Besides,sol-gel derived amorphous CaO-SiO₂-Cu O materials were filled into 200 nm large aperture of PAA（PAA200）nano-pores（termed CaO-SiO₂-Cu O/PAA）by a facile ultrasonic-assisted sol-dipping strategy.The surface microstructure and chemical property were characterized by field emission scanning electron microscopy（FESEM）,energy dispersive X-ray spectrometer（EDS）,X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.The ability of the CaO-SiO₂-Cu O/PAA to form apatite was evaluated by soaking them in simulated body fluid（SBF）in vitro.The surface microstructure and chemical properties after soaking in SBF were characterized by FESEM.The release of ions into the SBF was also measured by ICP-OES.The antibacterial properties of the samples were tested against Escherichia coli（E.coli）andStaphylococcus aureus（S.aureus）.The osteoblasts in new born rats were inoculated on the surface of specimens to evaluate the attachment and proliferation of the samples.In addition,the ionic concentration in the DMEM which cultured with Cu（5s,10s）/PAA and Zn（2s,5s）/PAA were measured by ICP-OES.The conclusions are as follows:Cu（5s,10s）/PAA and Zn（2s,5s,10s）/PAA were prepared by controlling the deposition time of the alternating current deposition.FESEM show that Cu and Zn was loaded into the PAA channel without altering the nano-porous structure.XRD indicated that the crystal form of Cu and Zn in the PAA channel is fcc structure.XPS showed that the main valence state of Cu on the Cu/PAA was +2 and 0,and the same result apare to Zn/PAA.The antibacterial test revealed that antibacterial rate of Cu（10s）/PAA to E.coli and S.aureus were 82%±11% and 89%±4% after 1d culture.The antibacterial rates of Zn（10s）/PAA to E.coli and S.aureus were 95%±1% and92%±5% after 1d culture,respectively.With the prolong of culture time,the inhibition rate of Cu（10s）/PAA and Zn（10s）/PAA were decreased.In addition,the cellular compatibility in vitro shows that the OD value of r OB on Cu（5s）/PAA and Zn（2s）/PAA was dramatically higher than that in blank control（p<0.01）.CaO-SiO₂-Cu O bioactive sol with different viscosity were loaded into nano-pores of PAA200 by a sol-gel method with ultrasound assisted impregnation.FESEM show that the sol is uniformly distributed in the porous structure of PAA,and the sol with viscosity about 0.02 pa s has the best filling effect.XPS showed that the main form of Cu was +2.In vitro SBF experiments revealed that the CaO-SiO₂-Cu O/PAA dramatically enhanced the apatite-forming ability of PAA in SBF and Ca,Si and Cu ions were released from the samples in a sustained and slow manner.E.coli and S.aureus growth were reduced on the surface of CaO-SiO₂-Cu O/PAA（by 87%±3% and 89%±2%,respectively）compared to PAA controls after 24 hours of culture.In addition,The result of proliferation of newborn rats osteoblasts showed that CaO-SiO₂-Cu O/PAA demonstrated great potential for promoting the proliferation of osteoblasts.In summary,this study demonstrated that the Cu/PAA,Zn/PAA and CaO-SiO₂-Cu O/PAA samples possess excellent antibacterial activity and good compatibility to osteoblasts,and CaO-SiO₂-Cu O/PAA possess good apatite-forming ability,causing them to be a promising coating candidate for numerous implant materials and hard tissue repair materials for orthopedic.