| In recent years,cases of bone implant repair due to congenital defects,sports and traffic accidents have increased sharply,and the demand for bone materials with excellent performance has been increasing.As we all know,autogenous bone is the standard for bone transplantation,but its source is limited and it is easy to cause necrosis at the supply site.Compared with autogenous bone,allogenic bone has a wide range of sources.However,there are still many problems such as slow integration and remodeling,immune rejection,and disease transmission.Therefore,the search for safe and effective artificial bone implant material is the goal pursued by researchers.The ideal artificial bone implant material should be able to simulate the composition and structure of natural bone,promote the repair of bone defect sites,and provide a long-term good physiological environment in the body.However,the current artificial bone implant materials have problems such as insufficient bionic degree,low surface biological activity,and mechanical property mismatch due to agglomeration and poor compatibility of the two-phase interface.Therefore,the self-made nano lamellar hydroxyapatite(LHAp)bioceramic material is similar in structure and composition to bone mineral minerals.It has the characteristics of high biomimetic degree and excellent biological activity,but still has the problems of high brittleness and difficult processing.Based on this,in this paper,biodegradable polylactic acid(PLA,extrusion grade 3052 D and injection molding grade 4032D)and polyether ether ketone(PEEK,medical grade 450G)with strength/modulus matching human bone were selected as the matrix of LHAp.Two different biomedical composites for bone implantation were prepared by melt compound,in order to obtain bone implant material with high interface binding ability,uniform dispersion of LHAp,high surface bioactivity,and a high degree of bionics.(1)In this paper,the direct melt intercalation method was used to strip LHAp into nanoplate hydroxyapatite(np-HAp).After that,the structure bionic np-HAp/PLA nanocomposites were prepared by extrusion and injection molding processes that are easy to mass produce.The mechanical properties test and thermogravimetric analysis(TGA)were used to study the effect of np-HAp content on the mechanical properties and thermal stability of the composites.The biocompatibility and in vitro bioactivity of np-HAp/PLA composites were evaluated by in vitro biological behavior test.The study found that,compared with PLA,the compression yield strength and decomposition temperature of np-HAp/PLA composites were increased by 29.9%(p < 0.05)and 17.5%,respectively.More importantly,np-HAp significantly improved cell adhesion and proliferation ability.Compared with other shapes of HAp,np-HAp has larger surface area and more exposed active sites,making the composites have more excellent in vitro biological activitie,so it is expected to become a new type of load-bearing bone implant material.(2)In order to further improve the interface bonding strength between np-HAp and PLA,LHAp was surface modified with silane coupling agent(SC)and stearic acid(SA),respectively.After that,modified np-HAp/PLA composites(SC-np-HAp/PLA and SA-np-HAp/PLA)were prepared by extrusion,injection molding and hot pressing.The compression performance test and TGA were used to study the influence of modifier on the mechanical properties and thermal stability of composites.The hydrolysis resistance of the modified np-HAp/PLA composite was analyzed by an in vitro biodegradation experiment.The study found that,compared with the compressive yield strength of np-HAp/PLA composite(about 84.7 MPa),SC-np-HAp/PLA composite increased by 9.4%,while SA-np-HAp/PLA composite decreased by 11.4%.TGA results show that SC-np-HAp/PLA composite are improved by 7.4%,compared to np-HAp/PLA composite initial decomposition temperature(353.3 ?),while SA-np-HAp/PLA composite is increased by 5.6%.In addition,the results of in vitro degradation experiments show that the weight loss rate of SC-np-HAp/PLA composite is only 22.7%;while SA-np-HAp/PLA composite is as high as 44.5%.In the biological enzyme degradation experiment,it was found that the surface of the four samples degraded by proteinase K formed a petal-like three-dimensional structure.The composites exposed a large amount of np-HAp,among which,the SC-np-HAp/PLA composite was observed to be the most exposed.SC and a large number of active functional groups of np-HAp form a strong hydrogen bond,thereby enhancing the binding ability of np-HAp and PLA two-phase interface.However,SA is only physically adsorbed on the surface of np-HAp,and is easily released to the PLA matrix during processing.Therefore,np-HAp modified by SC has better interface binding ability with PLA matrix,which will provide a reference for the preparation of bone implant material.(3)In order to provide patients with bone defects with long-term stable implant materials,LHAp,graphene oxide(GO)and PEEK(medical grade 450G)are melt-composited,and np-HAp/GO/PEEK composites have been obtained.After that,the obtained composite material was subjected to laser surface treatment with three parameters,and pit structures with different diameters were constructed on the surface.X-ray diffraction(XRD)and fourier transform infrared spectroscopy(FTIR)were used to analyze the crystal structure and chemical structure of the structured surface of np-HAp/GO/PEEK composites,respectively.The tensile properties,hydrophilicity and crystallinity of the laser-treated np-HAp/GO/PEEK composites were investigated through mechanical properties and differential scanning calorimetry(DSC)tests.The cell adhesion and proliferation ability of the structured surface of the material was evaluated by in vitro biological behavior test.The study found that laser treatment will not destroy the crystal forms of np-HAp,GO and PEEK,but will change the nature of the functional groups on the surface of np-HAp/GO/PEEK composites.The different diameter pit structures on the surface of np-HAp/GO/PEEK composite can significantly improve the cell compatibility.In particular,the porous array of pits with a diameter of 400 ?m obviously promotes the adhesion and proliferation of mouse embryonic osteoblast precursor cells(MC3T3-E1),which provides a new way to improve the surface biological activity of bone implant composite.It is worth mentioning that although laser treatment changes the flatness of the composite surface,the effect of this treatment on the tensile properties,hydrophilicity,and crystallinity of the material is very limited(less than 2%).In this paper,the biomedical composites(np-HAp/PLA ? SC-np-HAp/PLA,and np-HAp/GO/PEEK)studied have good mechanical properties and thermal stability,which can meet the requirements of bearing bones and in vitro sterilization.At the same time,the three materials have high surface biological activity and have significant advantages in stimulating bone induction and bone conduction ability.Therefore,they will provide key materials for bone implants,and provide theoretical and technical basis for the design and development of bone implant materials. |
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