Biomimetic Structures Design And Mechanical Property Control Of Laser Additive Manufactured Scaffolds For Bone

Addressing critical-size bone defects is a pivotal area of focus within bone tissue engineering,garnering significant attention.Presently,the primary treatment modality involves surgical repair of bone defects.Given the limitations of autografts,allografts,and xenografts in addressing critical-size bone defects,bone tissue engineering scaffolds have emerged as a novel option for addressing critical-size bone defects.Nonetheless,challenges persist with bone scaffolds,including structural uniformity,elastic modulus mismatch between host and implant,inadequate bone ingrowth,and postoperative failure,constraining their development and clinical utilization.To address these challenges,this study adopts the natural cancellous bone’s(NCanb)structural form as a model,simulating the high-porosity random porous structure of bone trabecular structure.Leveraging laser additive manufacturing(laser powder bed fusion,L-PBF)technology,Niti alloy materials are utilized to develop a tissue engineering biomimetic bone scaffolds design and preparation process that integrates bionic design,mechanical property control,and high-precision complex structure scaffolds additive manufacturing technology.A bionic trabecular bone scaffolds(Bio S),with porosity and elastic modulus aligned with natural cancellous bone,was prepared while ensuring mechanical load-bearing.This study conducts an indepth analysis of the inherent relationship between the scaffold’s structural design parameters and its mechanical properties,investigates local reinforcement strategies,discusses design criteria for scaffolds with adjustable mechanical properties,and assesses the performance of gradient bionic trabecular bone scaffolds for repairing various bone defects.The primary research findings and conclusions of this study are summarized as follows:(1)Analyzing the structural properties of natural trabecular bone,structural features are extracted and used to design bionic trabecular bone scaffolds with varying porosity and trabecular diameter.These designs are then subjected to pressure tests,finite element(FE)simulations,computational fluid dynamics,and other analyses to evaluate their bone-promoting ability and mechanical load-bearing capacity compared to conventional clinical scaffolds.The results indicate that Bio S-85-90 and Bio S-80-50 exhibit mechanical properties comparable to natural bone trabeculae,effectively mitigating the common "stress shielding" issue associated with traditional implants.Computational fluid dynamics analysis reveals that high fluid shear stress regions within the bionic trabecular bone scaffold facilitate the transmission of mechanical stimulation signals to osteoblasts adhering to the scaffold surface,promoting their growth and differentiation.Notably,the Bio S-80 scaffold demonstrates superior osteoinductive properties across the X,Y,and Z axes,exhibiting significant efficacy in bone repair;(2)The slime mold algorithm(SMA)was developed,drawing inspiration from the foraging behavior of slime molds in nature.Finite element simulations are employed to replicate the near-service stress environment experienced by bone defect repair scaffolds at key stress-bearing regions,identifying weaknesses in the mechanical properties of the simulated bone trabecular scaffold.Leveraging the 3D SMA algorithm,local reinforcement was implemented to strengthen weak areas in the mechanical properties of the simulated trabecular scaffold.Subsequently,a locally reinforced simulated trabecular scaffold(Bio S-SMA)was fabricated.Its reinforcing effects were examined through pressure tests and computational fluid dynamics analyses,among other methods.The results indicate the successful construction of a locally reinforced trabecular bone-like scaffold suitable for repairing bone defects in the primary stressbearing region,without altering the scaffold’s porosity or trabecular diameter.The elastic modulus of the reinforced trabecular bone-like scaffold remains within the natural bone’s elastic modulus range,while exhibiting enhanced mechanical properties,dependable service performance,and favorable bone growth effects.This scaffold represents a more reliable and effective solution for bone defect repair in bone tissue engineering;(3)To address challenges such as elastic modulus mismatch,difficulties in adjusting mechanical properties,and the absence of personalized design in traditional bone scaffolds for repairing bone defects,a bionic trabecular bone scaffold with freely adjustable mechanical properties was developed.A comprehensive investigation into the mechanical property variances among various shapes of trabecular bone structures,optimization of the bionic trabecular bone structure,and exploration of the regulatory mechanism of design parameters such as radius(R)and smoothing parameter(S)on the mechanical characteristics of the bionic trabecular bone scaffold were conducted.A mathematical model was developed to control the mechanical properties of the bionic trabecular bone scaffold.Additionally,an investigation into its parameter optimization scheme for bone defect repair in various stress-bearing regions was conducted.The results show that the rod-plate(RPT)trabecular bone structure has the best mechanical properties,and this was used as a template to design an RPT-like trabecular bone scaffold.Through manipulation of design parameters,the mechanical properties of the simulated bone trabecular scaffold can be efficiently controlled.For instance,multiobjective optimization was conducted using hip joint implants as a case study to attain the maximum compression resistance within the porosity and elastic modulus constraints of natural bone;(4)Drawing inspiration from the gradient structure of natural trabecular bone,a design and manufacturing process for a bionic trabeculae bone gradient structure scaffolds was developed.The influence of gradient-parameter design on the mechanical properties of the scaffold was thoroughly analyzed,addressing technical challenges associated with mimics,simplifying,optimizing,and applying natural trabecular bone gradients.Leveraging the synergy of bionic structure design and density gradient regulation,a bionic trabeculae bone gradient structure scaffold was fabricated.Subsequently,a corresponding implant with a similar gradient structure was designed,and its suitability and biological properties for bone repair across various defect modes were evaluated for compatibility.Findings indicate that the maximum elastic modulus of the scaffold designed with a bionic trabeculae bone gradient structure does not surpass 800 MPa,aligning with the elastic modulus limit range of cancellous bone.The bionic trabeculae bone gradient structure implant demonstrates superior performance across various bone defect models.The scaffold exhibits favorable bone repair effects and effectively mitigates the "stress shielding" issue commonly associated with bone scaffolds.Biocompatibility experiments demonstrate that the bionic trabeculae bone gradient structure scaffold possesses excellent biocompatibility,rendering it an ideal scaffold for bone repair.