查看更多>>摘要：? 2022Biodegradable Zn-Li alloys exhibit superior mechanical performance and favorable osteogenic capability for load-bearing bone devices. Additive manufacturing (AM) endows freedom for the fabrication of bone implants of personalized structure to satisfy patient-specific needs. In this paper, AM of Zn-Li alloys was attempted for the first-time using laser powder bed fusion (LPBF), and the fabricated samples exhibited good fusion quality and high dimensional accuracy. The processing optimization, mechanical properties, in vitro corrosion behavior and cytocompatibility were investigated by using Zn-0.7Li bulk and porous samples. The ultimate tensile strength and elastic modulus of bulk samples respectively reached 416.5 MPa and 83.3 GPa, and both were the highest among various additively manufactured Zn alloys reported so far. Porous samples achieved compressive strength (18.2 MPa) and elastic modulus (298.0 MPa), which were comparable to those of cancellous bone. Porous samples exhibited a higher corrosion rate and alleviated the problem of slow degradation of Zn-Li alloys. Nevertheless, osteoblastic cells showed a more spreading and healthier morphology when adhering to the porous samples compared to the bulk samples, thus a better cytocompatibility was confirmed. This work shows tremendous potential to precisely design and modulate biodegradable Zn alloys to fulfill clinical needs by using AM technology. Statement of significance: This paper firstly studied processing optimization during laser powder bed fusion of Zn-Li alloy. Bulk and porous Zn-0.7Li samples in customized design were obtained with high formation quality. The tensile strength of bulk samples reached 416.5 MPa, while the compressive strength and modulus of porous samples reduced to 18.2 MPa and 298.0 MPa, comparable to those of bone. The weight loss of porous samples was roughly 5 times that of bulk samples; osteoblastic cells showed a more spreading and healthier morphology at porous samples, indicating improved biodegradation rate and cytocompatibility. This work shows tremendous potential to precisely design and modulate biodegradable Zn alloy porous scaffolds to fulfill clinical needs by using additive manufacturing technology.
查看更多>>摘要：? 2022The existing biodegradable magnesium alloy stent (BMgS) structure is prone to problems, such as insufficient support capacity and early fracture at areas of concentrated stress. Herein, a stent structural design, which reduced the cross section of the traditional sin-wave stent by nearly 30% and introduces a regular arc structure in the middle of the support ring. The influence of the dual-parameter design of bending radius (r) and ring length (L) on plastic deformation, expansion and compression resistance performances are discussed. The non-dominated sorting genetic algorithm II (NSGA-II) was used to search for the optimal solution. It was found that the introduction of parameter r effectively improved the plastic deformation and expansion performance, and the reduction of L improved stent compression resistance. Finally, an optimized stent configuration was obtained. In vitro mechanical tests, including balloon inflation, radial strength and flexibility, verified the simulation results. The radial strength for the optimised stent increases by approximately 40% compared with that for the sinusoidal stent. Microarea X-ray diffraction result shows that the circumferential residual stress for the optimised stent decreases by half compared with that for the sinusoidal stent, thus effectively reducing the stress concentration phenomenon. Statement of significance: Despite current progress in BMgS research, the optimal design of the structure is limited. We present a new type of structurally designed stent. The performance of this stent was analysed by a finite element method and experimentally verified. The structural design positively influenced stent performance.
查看更多>>摘要：? 2022 Acta Materialia Inc.Evaporation of phosphate species during thermal treatment (> 400°C) of calcium phosphates leads to the formation of an alkaline layer on their surface. The aim of this study was to evaluate the hypothe- sis that the biological response of thermally treated calcium phosphates is modified by the presence of such an alkaline layer on their surface. For this purpose, 0.125–0.180 mm α- and β-tricalcium phosphate (TCP) granules were obtained by crushing and size classification, with some being subjected to thermal treatment at 500°C. The four types of granules (α-TCP, β-TCP, α-TCP-500°C, and β-TCP-500°C) were implanted subcutaneously and orthotopically in rats. Sham operations served as control. Subcutaneously, α-TCP and β-TCP induced significantly more multinucleated giant cells (MNGCs) than calcined granules. Most of the induced MNGCs were TRAP-negative, CD-68 positive and cathepsin K- negative, reflecting a typical indication of a reaction with a foreign body. The vessel density was signifi- cantly higher in the α-TCP and β-TCP groups than it was in the α-TCP-500°C and β-TCP-500°C groups. In the femur model, β-TCP-500°C induced significantly more new bone formation than that induced by β-TCP. The granule size was also significantly larger in the β-TCP-500°C group, making it more resistant to degradation than β-TCP. The MNGC density was higher in the α-TCP and β-TCP groups than in the α-TCP-500°C and β-TCP-500°C groups, including cathepsin-positive, CD-68 positive, TRAP-positive and TRAP-negative MNGCs. In conclusion, this study confirms that the biological response of calcium phosphates was affected by the presence of an alkaline layer on their surface. Thermally-treated α-TCP and β-TCP granules produced significantly fewer MNGCs and were significantly less degraded than non-thermally-treated α-TCP and β-TCP granules. Thermally treating α-TCP and β-TCP granules shifts the reaction from a foreign body re- action towards a physiological reaction by downregulating the number of induced MNGCs and enhancing degradation resistance. Statement of significance: Changes of biomaterials surface (polymers, ceramics, metals) is a key to modulate the bioma- terial induced inflammatory pattern and thereby have a direct influence on the regenerative capacity. This is the reason why the effect of thermal treatment of α- and β-tricalcium phos- phate granules at 500°C was studied. To the best of our knowledge, this is the first article fo- cusing on modulating the cellular reaction by thermal treatment of α- and β-tricalcium phos- phate granules. We believe that the manuscript will provide important insights understanding the direct influence of the biomaterials physicochemical characteristics on the cellular reaction and the regenerative pattern in vivo.
查看更多>>摘要：? 2021 Acta Materialia Inc.The authors regret to report that two errors were discovered in Figs. 2 and 7. The representative images for VECM with HE staining presently shown in Fig. 2c is incorrect due to errors at the time of figure assembly. The representative images for cells seeded onto VECM under dynamic culture conditions in Fig. 7a are also incorrect. In order to better display that cells could penetrate deeper into the matrix under dynamic culture conditions when compared to those under static culture condition, we corrected the Dynamic Culture image in Fig 7a. The corrected versions of Figs. 2 and 7 are provided below. Although these corrections do not alter any findings and conclusions of this work, the authors sincerely apologize for any inconvenience and confusion caused.
查看更多>>摘要：? 2022 Acta Materialia Inc.The authors regret to report that the affiliation for author Dewen Liu was published incorrectly. The correct affiliation is as follows: Artemisinin Research Center, Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing 100700, China. The authors apologise for any inconvenience caused.
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