| Titanium is a bioinert material commonly used as a load-bearing bone replacement in clinical practice,which needs to be modified to endow it with bioactivities.After implantation,titanium metal cannot change its interactions with the host actively with the dynamic changing environment due to the fixed biological properties.Therefore,it is of practical significance to regulate the bioactivity of titanium metal to match the repair process by external stimulations.Previous studies show that surface characteristics,such as morphology and electric potential,is one of the important factors that influence cell behaviors.However,the effects of surface morphology combined with dynamic potential on cell behaviors are still unclear.Therefore,this work aims to study the problem,and the details are listed as follows:(1)The surface design of titanium with tunable bioactivity.Since titania has good bioactivity of titania,titanium dioxide nanotube(TNT)arrays are constructed on one side of the titanium sheet by anodic oxidation.The effects of diameter and crystal form of TNT on cell behaviors are investigated.Considering the strong penetration and convenient operation of magnetic field,terbium-dysprosium-iron alloy(Terfenol-D)particles are compounded with polyvinylidene fluoride trifluoroethylene P(VDF-TrFe)to prepare a magnetoelectric composite(MEC).The MEC film is casted on the other side of titanium surface to avoid covering TNT.When magnetic field is applied,the Terfenol-D particles deform due to the magnetostrictive effect,and then the load is transferred to the P(VDF-TrFe)matrix,correspondingly a potential is generated on P(VDF-TrFe)surface by the piezoelectric effect,finally opposite charges are built on TNT through electrical conduction.The adhesion,proliferation,and differentiation behaviors of cells cultured on the surface of TNT are then studied by adjusting the strength of the magnetic field.(2)Preparation and characterization of titanium dioxide nanotubes and P(VDFTrFe)/Terfenol-D magnetoelectric composite films.TNT on one side of titanium sheet is prepared by electrolysis in a electrolyte containing 0.3 M ammonium fluoride and 75% glycerol at 30 V for 2 h to 10 h,and then heat-treated at 500? for 3 h.The characterization and test results show that the optimized electrolysis time is 6 h,which obtains a hydrophilic TNT surface with a diameter of 50-60 nm and an anatase phase structure.The P(VDF-TrFe)/Terfenol-D magnetoelectric composite(MEC)film on the other side of titanium is prepared by melt casting method.The film is heated at 210°C for 1 hour,and then heated at 145°C to 95°C for 4 hours.P(VDF-TrFe)is polarized at 1 KV to 5 KV for 1 min to 1 h.The optimized conditions are heating MEC at 135°C for 4 h and polarization at 4 KV for 5 minutes,which balances the bioactivity,piezoelectricity,and polarization.The characterization and test results reveal that the ball milled Terfenol-D particles with a diameter of about 10 ?m are homogeneously dispersed in the P(VDF-TrFe)matrix;ball milling eliminates the hysteresis effect of TerfenolD particles;Terfenol-D particles increase the Curie transition temperature of P(VDF-TrFe)about 10? and enhances the crystallinity of the ? ferroelectric phase;the piezoelectricity remains stable after being immersed in simulated body fluid for one month;when the magnetic field frequency is 750 Hz,the magnetoelectric coupling coefficient is stable at about 7.45 m V/oe.(3)Studies of surface potential effect on cell behaviors by applying different magnetic fields on titanium dioxide nanotubes.A static magnetic field with a strength of 0-2200 oe is constructed on the culture plate using a neodymium-iron-boron magnet.The adhesion,proliferation,and osteogenic differentiation behaviors of mouse bone marrow mesenchymal stem cells(m BMSCs)on the surface of titanium dioxide nanotubes are evaluated.Bovine serum albumin is used as the model protein to analyze the effect of magnetic field on its adsorption behavior on the surface of titanium dioxide nanotubes.The results indicate that magnetic field,Terfenol-D and P(VDF-TrFe)are noncytotoxic.With the increase of magnetic field strength,the presence of surface potential promotes the spreading,proliferation,and osteogenic differentiation of m BMSs C on the surface of titanium dioxide nanotubes.The adsorption experiment implies that magnetic field induced positive potential improves the adsorption of negatively charged proteins on the surface of titanium dioxide nanotubes,and hence enhances the bioactivity of titanium.In summary,magnetic field is employed to generate a dynamic potential on titanium surface,which can regulate cell adhesion,proliferation,and differentiation behavior.As a result,the bioactivity of titanium could be regulated externally.Therefore,this work sheds a light on precise and personalized treatment of bone repair. |
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