Study On The Properties Of PCL/nHA/PEG Bone Scaffold Prepared By 3D Printing Technology

Purpose:Artificial bone scaffold,as a promising new material for bone defect repair,has once again become a research hotspot with the promotion of 3D printing technology.FDM(fused deposition manufacturing)technology is one of the 3D printing technologies,which has unique advantages in the rapid,accurate and personalized design of the internal structure and shape of printed products.It has been shown that PCL/HA bone scaffold materials prepared by FDM technique using polycaprolactone(PCL)and hydroxyapatite(HA)have good biocompatibility,but due to the high-temperature preparation process of FDM technique and the hydrophobicity of PCL material itself,there are still problems such as poor hydrophilicity,too smooth surface,unfavorable cell adhesion and slow degradation of PCL/HA bone scaffold,which need to be further optimized to improve their properties as bone tissue engineering scaffolds.In this paper,to address the above clinical problems,we prepared a bionic PCL/nHA/PEG bone scaffold with multi-scale porous structure using PCL and nano-hydroxyapatite(nHA)as the main components of the bone scaffold and polyethylene glycol(PEG)with good hydrophilic and hydrolytic ability as the modifier using FDM technology.We compared the PCL/nHA/PEG bone scaffold with the PCL/nHA bone scaffold and evaluated its improvement in morphology,physicochemical properties,degradation,cytocompatibility and osteogenic properties to provide a theoretical basis for the preparation and performance improvement of 3D printed bone tissue engineering scaffolds,with the aim of preparing a bone grafting material that better meets the requirements of bone tissue engineering scaffolds for future clinical treatment.Method:1.A 10 mm×10 mm×6 mm(length×width×height)porous cube scaffold was prepared by the FDM 3D printer with its own software Bio Maker V2.The scaffold was composed of Zig-Zag alignment pattern alternating along 0°/90°direction.A nozzle with an inner diameter of 0.4 mm is selected,the printing temperature is100°C,the line spacing and layer height are set according to the experimental design,the extrusion speed is 0.2 mm~3/s,the printing speed is 1.5 mm/s,and the printing platform is not set to temperature.2.The composite particles for FDM printing were prepared by melt blending PCL and nHA in the mass ratios of 9:1,8:2 and 7:3,respectively,and the line spacing of the scaffolds was divided into three groups:1.2 mm,1.0 mm and 0.8 mm,respectively,and orthogonal analysis was performed on the mass ratios of the composites and the line spacing of the scaffolds to prepare nine different groups of scaffolds.Then,the scaffolds were tested and evaluated for their morphological structure,mechanical properties and porosity,and the scaffolds with high porosity were optimized to meet the mechanical properties of the scaffolds.3.Based on the previous experiments,the PCL/nHA scaffolds with the best nHA content and porosity were modified by adding different weight ratios of PEG to the scaffolds.The PCL/nHA/PEG scaffolds with optimal PEG content were optimized by structural analysis,physical phase analysis,mechanical properties,porosity,water absorption,hydrophilicity,degradation stability,biocompatibility,bioactivity and biocompatibility assessment of each group of scaffolds,in preparation for subsequent animal experiments,with the aim of becoming bone tissue engineering scaffold materials for clinical applications.Results:PCL/nHA scaffolds were successfully prepared by FDM technique.When PCL:nHA=8:2 and the line spacing of the scaffolds was 0.8 mm,the nHA particles were uniformly distributed on the surface and profile of the scaffolds.The elastic modulus of the scaffold was 69.14±3.83 MPa,the compressive strength was6.37±0.63 MPa,and the porosity was 24.78±1.55%.The PCL/nHA/PEG scaffold with PEG addition was creamy white in color,with the same morphology as the sample without PEG addition,uniform pore size and interconnected pores.x-ray diffraction spectroscopy(XRD)characterization showed that the composite scaffold material consisted of PCL,nHA and PEG,and the printing process did not lead to any change in the components.Scanning electron microscopy(SEM)was used to observe the morphology of the scaffolds,and all groups of scaffolds had good structural morphology and interconnected pore channels.Further analysis of the SEM images of the scaffolds by Image J software revealed that the diameter of the extruded filaments and the layer height of the scaffolds gradually decreased with increasing PEG content,while the pore size gradually increased,but the pore sizes of all bone scaffolds were in the range of 100μm-400μm,which met the requirements of the bone scaffold material for the pore size.With the increase of PEG content from 0 wt%to 30 wt%,the elastic modulus and compressive strength of PCL/nHA/PEG scaffolds decreased from 69.14±3.83 MPa and 6.37±0.63 MPa to 43.02±1.76 MPa and 3.69±0.09 MPa,respectively.The porosity and water absorption rate increased from 24.78±1.55%and23.58±1.40%to 39.28±0.88%and 43.18±0.48%,with increases of 58.51%and49.90%,respectively.Due to the fast hydrolysis rate of PEG,when the bone scaffold was degraded for 7 days,sponge-like multi-scale porous structures were formed on the surface of the bone scaffold using the hydrolytic pore-forming effect of PEG,leading to further increase in the porosity and water absorption rate of the bone scaffold.Live-dead cell staining assay and CCK-8 results showed that both PCL/nHA/PEG bone scaffold and PCL/nHA bone scaffold had good biosafety,but the former had more cells growing on the surface and flatter morphology.The multi-scale microporous structure formed by the rapid hydrolysis of PEG in the liquid environment promoted the deposition of apatite-like bone layer on the scaffold surface in the simulated humoral environment.Conclusion:The PCL/nHA/PEG scaffold prepared by FDM technology has the maximum porosity in accordance with the mechanical property requirements when PCL:nHA=8:2,the line spacing is 0.8 mm,and the PEG content is 20 wt%,and has a spongy bone trabecular structure with multi-scale micropores compared with PCL/nHA scaffold,which exhibits better hydrophilicity,degradation rate,in vitro mineralization ability and cell adhesion morphology.It is the potential candidate for bone substitute materials.Innovation points:The novelties of this experiment are:(1)Preparation of PCL/nHA/PEG bone scaffolds using FDM technique.(2)Construction of spongy multi-scale porous structures similar to cancellous bone for bone scaffolds using hydrolysis of PEG in a liquid environment.