Preliminary Study On The Construction And Function Of Mg/Zn-MOF74 Coating On Titanium Surface

Medical titanium and titanium alloys were widely used in hard tissue replacement in clinical orthopedics and dentistry,mainly due to their excellent mechanical properties and biocompatibility.Studies have shown that bacterial infection is one of the main causes of implant failure.Invasive bacteria not only directly adhere to the implant surface,interfere with the biological functions of bone formation related cells,but also activate the host immune system,stimulate inflammatory macrophages and inhibit bone formation.Therefore,the preparation of multifunctional?antibacterial,anti-inflammatory,bone-promoting?titanium implants is the key to adress these issues.In this study,we synthesized an organic framework material?Mg/Zn-MOF74?mixed with Mg and Zn on the surface of alkali-heat treated titanium?AT?via solvothermal method,which endowing titanium materials with antibacterial,anti-inflammatory and accelerating bone-formation biological functions.Furthermore,we evaluated its biological responses in vitro and in vivo.The main research contents and conclusions are listed as follows:1.Synthesis and characterization of Mg/Zn-MOF74 coating on titanium surfaceAn organic framework material?Mg/Zn-MOF74?mixed with Mg and Zn was synthesized on the surface of alkali-heat treated titanium?AT?via a solvothermal method.The results of SEM,EDS,water contact angle and XRD showed that the Mg/Zn-MOF74 composite coating was successfully constructed on the surface of AT.Through coating stability test,we confirmed that pure magnesium coating?AT-Mg?had the weakest stability.As increasing the zinc content in the coating,the coating stability gradually increased.In addition,we also detected the release of DHTA,Zn²⁺and Mg²⁺using nano-drop and atomic absorption methods.The results showed that the Mg/Zn-MOF74 coating was easily degraded under the condition of pH 6.5.Under the condition of pH 7.4,the release rate of DHTA and Zn²⁺significantly decreased with the increase of zinc ions,while the release rate of Mg²⁺only slightly increased.2.Cytocompatibility and anti-inflammatory evaluation of Mg/Zn-MOF74 coating on titanium surface in vitroIn this study,the effects of Mg/Zn-MOF74 coating on osteoblasts'adhesion,proliferation and differentiation were firstly investigated at the cellular and molecular levels.FDA fluorescence staining showed that all MOF74 modified samples had excellent cytocompatibility,mainly due to the pre-immersion of samples into PBS for 3days,which resulted in full degradation of MOF74 coating.The results of CCK-8,ALP,mineralization,collagen secretion and osteogenic gene expression?ALP,COLI,OPN and OCN?further demonstrated that the coating promoted osteoblast proliferation and differentiation.In addition,macrophage FDA staining,activity assy and inflammatory factor expression results indicated that the Mg/Zn-MOF74 composite coating had an early anti-inflammatory effect.Finally,experiments on the effects of DHTA,Mg²⁺and Zn²⁺on osteoblasts demonstrated that moderate DHTA could significantly increase the activity of osteoblasts;osteoblasts were highly sensitive to Zn²⁺.0.005?M Zn²⁺could effectively promoted the proliferation of osteoblasts.Unlike DHTA and Zn²⁺,the addition of Mg²⁺?within 10?M?increased the viability of osteoblasts,and its effect increased with increasing concentration.3.Antibacterial evaluation of Mg/Zn-MOF74 coating on titanium surface in vitroThe antibacterial properties of the MOF74 surface coating was evaluated with S.aureus and Escherichia coli.The anti-adhesion SEM test showed that the surface modified titanium material significantly could reduce the adhesion of the two bacteria,and effectively inhibit the bacteria proliferation,reflecting a short-term antibacterial function.The results of inhibition rate via coating plate method showed that AT-Mg,AT-Mg/Zn3 and AT-Mg/Zn5 samples had higher antibacterial rate.When increasing culture time,the inhibition rates of different samples slightly decreased,however,the overall trend didn't change significantly.In addition,the growth inhibition tests of DHTA,Mg²⁺and Zn²⁺on bacteria showed that DHTA and Zn²⁺could significantly inhibited the growth of S.aureus and Escherichia coli.Its inhibition effect increased with the increase of concentration.The addition of Mg²⁺had no any antibacterial properties.4.Biological evaluation of Mg/Zn-MOF74 coating on titanium surface in vivoIn this study,we employed coating plate method,HE staining,and Micro-CT experiments further confirmed that the AT-Mg/Zn3 implant had the highest inhibition rate?more than 90%?among three groups of samples.Meanwhile,AT-Mg/Zn3 sample diaplyed significant impact for promoting new bone formation in vivo.5.Study on composite functional coatings of Mg-MOF74 and Sr-HA on titanium surfaceBy employing SEM,EDS,water contact angle and XRD characterization,we confirmed that a composite coating of Mg-MOF74 and Sr-HA had been successfully constructed on pure Ti surface.In vitro bacterial adhesion,spin coating plates,FDA staining and CCK-8 experiments verified that Sr-HA-MOF74 coating had excellent ability to kill Staphylococcus aureus,Escherichia coli and Saos-2 osteosarcoma cells at an early stage.Meanwhile,cellular activity assay,collagen secrection,mineralization,and ALP experiments demonstrated that the coating promoted proliferation and differentiation of osteoblasts.