Page 466 - IJB-10-6

International Journal of Bioprinting Stress prediction in 3D-printed scaffolds

of bone defects are pressing needs. Although organ the scaffold, 23–28 providing important references for the
transplantation is an effective treatment for bone repair, design and optimization of bone repair scaffolds. Currently,
2
the challenge of insufficient donor supply remains. Bone FEA often uses theoretically designed scaffold structures
3,4
tissue engineering offers hope for repairing bone defects as models. However, there are deviations between the
and has garnered significant attention in the field of bone actual structure of the 3D printed scaffold and the design
regeneration. Bone tissue engineering scaffolds provide structure, leading to the distortion of the FEA model, low
5,6
a temporary environment for cell adhesion, proliferation, prediction accuracy, and lack of application value. 29–31
and differentiation, gradually degrading as new bone tissue
forms, ultimately facilitating bone tissue regeneration. The To address these issues, this work proposes an effective
7
mechanical properties of bone implants are crucial factors method for predicting the mechanical properties and
influencing implant stability and success. There is an stress distribution within printed scaffolds, which is more
urgent need to develop bone scaffolds that integrate both accurate compared to traditional FEA. This study combined
biological and mechanical properties. optical coherence tomography (P-OCT), micro-computed
tomography (CT), and FEA to evaluate and monitor the
In clinical settings, artificial bone scaffolds may deformation of HAP scaffolds in different states during
fracture after a period of implantation, leading to repair the preparation process (after printing, sintering, and
failures or even bone necrosis. This issue is closely related drying). It also investigated the impact of different states
to the mechanical strength and stress distribution of and micropore morphologies (90°, 60°, 45°) on the stress
the implanted scaffolds. When the elastic modulus of distribution within the HAP scaffolds. This method can
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an implant significantly exceeds that of natural bone effectively predict the stress distribution of the scaffold
or when stress concentrations occur, the mechanical after sintering immediately after printing, shortening
balance between the implant and the surrounding bone the experimental cycle and improving the success rate of
tissue can be disrupted, leading to implant loosening and clinical applications.
premature fracture. Additionally, localized stress within
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the scaffold that exceeds that of the surrounding material 2. Methods
may result in stress-induced fractures. One of the urgent
problems to be solved is how to optimize and accurately 2.1. Printing ink preparation
predict the mechanical properties of scaffolds during their The printing ink was prepared by mixing HAP powder
construction process, avoiding stress concentration while with organics. Briefly, 5.2 mL of deionized water
ensuring their biocompatibility. (Mingshan, China) was mixed with 0.16 g of ammonium
polyacrylate powder (Mingshan, China) and 0.2 g of
Hydroxyapatite (HAP), the main component of sodium alginate powder (Regenovo Biotechnology Co.,
natural bone, is an ideal material for bone repair. It can Ltd., China). This mixture was subjected to agitation for
be fabricated into bone repair scaffolds with different 5 min in a mixer (Thinky, Japan). Subsequently, 7 g of
properties through techniques such as freeze-drying or HAP powder (Macklin, China) was added and stirred
biological 3D printing. 10–14 Among these, 3D printing thoroughly. The final uniformly mixed ink was loaded into
technology allows for customized design for patients a printing cartridge, which was then sealed and stored in a
and precise control over the shape of the scaffolds, thus refrigerator at 4°C for preservation.
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widely used in bone tissue engineering. Researchers
16
have optimized the mechanical properties of scaffolds 2.2. Scaffold design and fabrication
and regulated the stress distribution within scaffolds, by After ink preparation, 3D printing was conducted using
altering their macroscopic morphologies. 17,18 Controlling Bio-Architect-PX (Regenovo Biotechnology Co., Ltd.,
the surface morphology and pore geometry of scaffolds China). Three different printing angles (90°, 60°, 45°) of
provides great potential for manipulating the mechanical HAP scaffolds were designed in this study, with a porosity
behavior of 3D-printed scaffolds. Although a large amount of 60% (Figure 1). A needle with an inner diameter of
of work has been reported in the biomedical field, 19–22 0.41 mm was selected, with a printing speed of 8 mm/s
there is still a lack of understanding regarding how these and air pressure set at 0.2 MPa. The model parameters of
structures affect the stress distribution within the scaffold the printing scaffolds are listed in Table 1. After printing,
under mechanical compressive loads. the scaffolds were crosslinked in a 5% (w/v) calcium
Finite element analysis (FEA) can analyze the chloride solution and then transferred to a −80°C ultralow
mechanical behavior of various complex structures by temperature freezer overnight. Finally, the scaffolds were
simulating their mechanical behavior under loading dried in a freeze-dryer (Christ, Germany). The dried
conditions, predicting mechanical properties such as scaffolds were sintered at 1100°C in a box-type resistance
modulus and strength, as well as stress distribution within furnace to achieve the final state.

Volume 10 Issue 6 (2024) 458 doi: 10.36922/ijb.4460