Photothermal Antibacterial And Osteogenic Properties Of Carbon Fiber Reinforced Polyetheretherketone Surface Modified Materials

The ideal bone implant material needs to have multiple functions such as biocompatibility,non-cytotoxicity,and bone tissue regeneration.In order to meet this challenge,based on our previous work,we have developed a PEEK composite material reinforced with long carbon fiber（40 mm）that is formed by three-dimensional pinhole molding of CFPEEK preforms.The composite material has excellent mechanical properties and has broad application prospects in orthopedic internal fixation and implant materials.However,the biological inertness of CFPEEK limits its biological applications.To further improve the bioactivity of the composite,SCFPEEK-PDA-Ti₃C₂T_x（SCP-PDA-Ti）was prepared in this study by surface modification of long carbon fiber-reinforced polyetheretherketone with two-dimensional titanium carbide（MXene）nanosheets and polydopamine（PDA）.We constructed new composites consisting of Ti₃C₂T_x nanosheets,PDA and bioinert sulfonated carbon fiber reinforced polyetheretherketone（SCFPEEK）and endowed the bioinert material with a bimodal therapeutic function:photothermal antimicrobial healing ability and osteogenesis promotion ability.Four Ti₃C₂T_x nanosheet concentrations of 1.5 mg/ml,2.0 mg/ml,2.5mg/ml and 3.0 mg/ml were set to investigate the effects of different concentrations of Ti₃C₂T_x nanosheets on the osteogenesis-promoting ability and photothermal antibacterial ability of the composites.For the modified material we performed the following tests:1.Basic characterization of materials:Firstly,we examined whether the Ti₃C₂T_xnanosheets were etched successfully by TEM and XRD,and then we examined the surface elements,surface morphology,hydrophilic properties and in vitro bioactivity of the surface modified composites by XPS,SEM,water contact angle test and in vitro mineralization experiments.2.Antibacterial ability of the materials:The thermal images of the materials under NIR laser irradiation for 10 min were firstly recorded by Testo 869 thermal imager and organized into a temperature increases curve and temperature rising and cooling cycles curves,then the bacterial plate counting method was selected to detect the photothermal antibacterial ability of each group of materials.3.Material cell experiment:Use rBMSCs to conduct cell experiments on each group of materials,and the materials were examined for cell proliferation capacity,cytotoxicity,cell adhesion and growth,alkaline phosphatase activity,mineralization capacity and osteogenic genes by CCK-8 test,live/dead cell staining observation,SEM,CLSM,ALP quantitative and qualitative tests,ARS quantitative and qualitative tests and RT-PCR analysis expression.4.Material animal experiment:8-week-old SD rats were selected to make defects in the skull and implanted with materials for 4 weeks and 8 weeks to conduct animal experiments.The osteogenic differentiation ability of each group of materials in vivo were evaluated by Micro-CT test of rat skulls,H＆E staining,Masson staining and VG staining of hard tissue sections.Experimental results:1.TEM and XRD test results showed that Ti₃C₂T_x nanochips were successfully etched;the XPS spectra showed that the surface modification of CFPEEK was successful;the SEM images showed that the surface of the modified material became rougher than that of CFPEEK;the water contact angle test found that the hydrophilicity of CFPEEK after being modified by PDA and Ti3C2Tx nanosheets was enhanced;in vitro mineralization experiment results showed that the surface modification of PDA/Ti₃C₂T_x was beneficial to the deposition of hydroxyapatite,and the higher the concentration of Ti₃C₂T_x nanosheets was the more apatite is deposited.2.By recording the temperature of the material within 10 minutes under NIR laser irradiation,it was found that the temperature of SCP-PDA-Ti（2.5）and SCP-PDA-Ti（3.0）reaching 52°C or higher is sufficient to kill bacteria.Temperature rising and cooling cycles curves showed that SCFPEEK-PDA-Ti₃C₂T_x material had thermal stability;the relative viability results of the bacteria obtained by the plate counting method showed that the SCP-PDA-Ti（2.5）and SCP-PDA-Ti（3.0）two groups of surface modification materials had 100%antibacterial rates against E.coli and S.aureus.However,the temperature of SCP-PDA-Ti（3.0）almost reached 60°C after light exposure,which is harmful to cells,so SCP-PDA-Ti（2.5）is the optimal group.3.CCK-8 results showed that SCFPEEK-PDA-Ti₃C₂T_x surface modification material was beneficial to cell proliferation,and the higher the concentration of Ti₃C₂T_xnanosheets,the better the proliferation effect;fluorescence microscope observation of live/dead cell staining results found that all materials were not cytotoxic;SEM and CLSM results showed that the surface cells of the material modified with Ti₃C₂T_xnanosheets had better cell growth,adhesion,and more pseudopodia;ALP staining results showed that the color of SCFPEEK-PDA-Ti₃C₂T_x surface modified material was darker than that of the unmodified material,and the two groups of SCP-PDA-Ti（2.5）and SCP-PDA-Ti（3.0）had the darkest color.The quantitative test of ALP and the staining result had the similar trend,that was the ALP activity of the material after the modification of Ti₃C₂T_x nanosheets increased and the higher the concentration of Ti₃C₂T_x nanosheets,the higher the ALP activity.The staining results and quantitative analysis results of ARS were similar with the trends of ALP results.RT-PCR detected the expression of four bone formation-related genes BMP-2,Runx2,ALP and COL-1.After statistical analysis,it was found that the osteogenic gene expression of the material after the modification of Ti₃C₂T_x nanosheets was better.The results of ALP,ARS and RT-PCR indicated that the surface-modified SCFPEEK-PDA-Ti₃C₂T_xmaterial had a good ability to promote osteogenic differentiation in vitro.4.Micro-CT test and hard tissue section staining results of animal experiments showed that SCP-PDA-Ti（2.5）surface modification material had better bone formation ability in vivo and had no adverse effects on animals.Conclusion:Through the above test,it can be obtained that the SCP-PDA-Ti（2.5）surface modification material has 100%photothermal antibacterial ability and no damage to cells in terms of antibacterial.It has good bone formation ability in vitro and in vivo.Considering the overall economic benefits,SCP-PDA-Ti（2.5）is the best group of surface modification materials.Above all,Ti₃C₂T_x MXene-modified CFPEEK composites not only exhibit excellent mechanical strength,but also posse the bimodal therapeutic effect,which has a potential in orthopedic internal fixation and implant materials.This surface modification process offers a new development idea for the application of CFPEEK as an orthopedic implant.