Study On Surface Modification Of Polyetheretherketone (PEEK) To Improve Its Antibacterial Property,Hydrophilicity And Cell Adhesion Ability

Polyetheretherketone?PEEK?is an attractive implant material in biomedical field due to its non-toxicity,non-sensitization,abrasion resistance,easy processing and forming,and similar mechanical properties to bone.Therefore,PEEK had been officially approved as an implant biomaterial by the Food and Drug Administration of the United States in the late1990s.However,the original PEEK has poor hydrophilicity and belongs to bio-inert material,which is not conducive to cell adhesion,so its osteointegration performance is not ideal.And for implant materials,good antimicrobial properties are also indispensable.Therefore,how to improve the antimicrobial,hydrophilic and cell adhesion of PEEK by simple and efficient methods to be used for implant materials has been a research hot spot in the field of modified PEEK.It is well known that modification of PEEK using the wet chemical method can effectively improve its hydrophilicity and cell compatibility.In this study,the surface modification of PEEK powder and sheet materials using wet chemical methods and the resulting change of biocompatibility will be explored.The main contents and results of this study are as follows:?1?The effects of mixed acids of nitric acid and concentrated sulfuric acid with different volume ratios on the surface morphology of PEEK sheets were investigated systematically and quantitatively.Porous PEEK(SNPEEK_?1/1?)was obtained using mixed acids of nitric acid and concentrated sulfuric acid with a volume ratio of 1:1.On the basis of this,the ethylenediamine was grafted its surface to achieve amination.The modified PEEK with both surface structure and chemical state was prepared and desighnated as SNPEEK_?1/1?-NH₂.The structure and properties of PEEK before and after modification were characterized by Scanning Electron Microscopy?SEM?,Energy Dispersive Spectroscopy?EDS?,X-ray Photoelectron Spectroscopy?XPS?and Water Contact Angle?WCA?.The results showed that SNPEEK_?1/1?had a multi-level structure of micron pit-nanopore,containing nitro group and a little amount of S,but its wettability was not greatly improved.SNPEEK_?1/1?-NH₂also had a multi-stage structure of micron pit-nano pore,nitro group and has been successfully aminated.In addition,it had good wettability and contained almost no S.?2?For PEEK powder,firstly,sulfonation treatment was carried out with concentrated sulfuric acid.On the basis of this,it reacted with sulfoxide chloride to obtain aromatic sulfonyl chloride,which was then reacted with ethylenediamine,spermine and GRGD,respectively,to achieve amination and named as SPEEK36-EDA,SPEEK36-Sp and SPEEK36-GRGD,respectively,which had been characterized by Fourier Transform Infrared Spectroscopy?FTIR?,XPS and WCA.The results demonstrated that the SPEEK36-EDA,SPEEK36-Sp and SPEEK36-GRGD had been successfully aminated and had good wettability.?3?For in vitro biocompatibility study of powder PEEK before and after modification,the proliferation and adhesion of human umbilical vein endothelial cells?HUVEC?cultured in blank group,original PEEK group,SPEEK36-EDA and SPEEK36-Sp group for 1 day and3 days were investigated by using MTT method,fluorescence microscope and SEM.The results showed that the modified SPEEK36-EDA had good cell compatibility,no cytotoxicity and was beneficial to cell proliferation and adhesion.In contrast,SPEEK36-Sp showed poor cell compatibility.?4?The antimicrobial ability and the in vitro and in vivo biocompatibility of PEEK before and after modification were studied.The results of antimicrobial experiments showed that SNPEEK_?1/1?-NH₂ had better antimicrobial activity than the original PEEK,which was attributed to the grafted nitro group.In the study of in vitro biocompatibility,MTT and SEM results showed that the modified SNPEEK_?1/1?and SNPEEK_?1/1?-NH₂ had good cell compatibility,no cytotoxicity and beneficial to cell adhesion;In the study of in vivo biocompatibility,New Zealand white rabbit model was established.The original PEEK,SNPEEK_?1/1?and SNPEEK_?1/1?-NH₂ implants were implanted into the femur of the right hind limb for one month.The osseointegration of implants was investigated by general observation,push-out test and hard tissue section analysis.The results showed that the wound healing of the original PEEK implants was poor.However,the modified SNPEEK_?1/1?and SNPEEK_?1/1?-NH₂ implants bonded well with the surrounding bone tissue,and the wound were free of swelling and inflammation,and the implants were stable and free of loosening.In the push-out test,the femur of the right hind limb of New Zealand white rabbits without implants were used as the natural bone.Bone binding force was measured by two methods to evaluate the binding effect of modified PEEK with surrounding bone tissues,The values for natural bone were 51.15N and 246.69N,repectively.The maximum push force for SNPEEK_?1/1?was 177.17N while it was 322.45N for SNPEEK_?1/1?-NH₂.The results of hard tissue sections showed that there were no inflammatory responses at the implant sites in each group.Compared with the original PEEK,modification for SNPEEK_?1/1?was beneficial to promote the repair of bone defects.The most significant change was investigated in SNPEEK_?1/1?-NH₂ group.The defect areas in SNPEEK_?1/1?-NH₂ group had been filled with new tissue,and the new bone tissue was closely bound to the surrounding host bone without significant difference,,indicating that the amination modification after the formation of pores greatly promoted the repair of bone defects.