Exploring the interconnectivity of biomimetic hierarchical porous Mg scaffolds for bone tissue engineering:Effects of pore size distribution on mechanical properties,degradation behavior and cell migration ability

Interconnectivity is the key characteristic of bone tissue engineering scaffold modulating cell migration,blood vessels invasion and transport of nutrient and waste.However,efforts and understanding of the interconnectivity of porous Mg is limited due to the diverse architectures of pore struts and pore size distribution of Mg scaffold systems.In this work,biomimetic hierarchical porous Mg scaffolds with tailored interconnectivity as well as pore size distribution were prepared by template replication of infiltration casting.Mg scaffold with better interconnectivity showed lower mechanical strength.Enlarging interconnected pores would enhance the interconnectivity of the whole scaffold and reduce the change of ion concentration,pH value and osmolality of the degradation microenvironment due to the lower specific surface area.Nevertheless,the degradation rates of five tested Mg scaffolds were no different because of the same geometry of strut unit.Direct cell culture and evaluation of cell density at both sides of four typical Mg scaffolds indicated that cell migration through hierarchical porous Mg scaffolds could be enhanced by not only bigger interconnected pore size but also larger main pore size.In summary,design of interconnectivity in terms of pore size distribution could regulate mechanical strength,microenvironment in cell culture condition and cell migration potential,and beyond that it shows great potential for personalized therapy which could facilitate the regeneration process.

Design and Preparation of Bone Tissue Engineering Scaffolds with Porous Controllable Structure

A novel method of designing and preparing bone tissue engineering scaffolds with controllable porous structure of both macro channels and micro pores was proposed. The CAD software UG NX3.0 was used to design the macro channels＇ shape, size and distribution. By integrating rapid prototyping and traditional porogen technique, the macro channels and micro pores were formed respectively. The size, shape and quantity of micro pores were controlled by porogen particulates. The sintered β-TCP porous scaffolds possessed connective macro channels of approximately 500 μm and micro pores of 200-400 μm. The porosity and connectivity of micro pores became higher with the increase of porogen ratio, while the mechanical properties weakened. The average porosity and compressive strength offl-TCP scaffolds prepared with porogen ratio of 60wt% were 78.12% and 0.2983 MPa, respectively. The cells＇ adhesion ratio of scaffolds was 67.43%. The ALP activity, OCN content and cells micro morphology indicated that cells grew and proliferated well on the scaffolds.

Fabrication of Highly Anisotropic and Interconnected Porous Scaffolds to Promote Preosteoblast Proliferation for Bone Tissue Engineering

Mimicking the complex structure of natural bone remains a challenge for bone tissue scaffolds.In this study,a novel processing strategy was developed to prepare the bone-like scaffolds that are featured by highly oriented and fully interconnected pores.This type of biomimetic scaffolds was evolved from solid phase stretching of immiscible polycaprolactone(PCL)/poly(ethylene oxide)(PEO)blends with cocontinuous structure and the pore morphology was inherited from selective extraction of water soluble PEO phase.The pore anisotropy was readily tuned by varying the stretching strain without loss of interconnectivity.Significant promotion in preosteoblast proliferation,alkaline phosphatase activity and osteogenic gene expression was observed in the oriented porous scaffolds compared to the isotropic porous counterpart.The oriented architecture provided a topographical cue for aligned growth of preosteoblasts,which activated the Wnt/β-catenin signaling pathway.The proposed strategy enriches the toolbox for the scaffold design and fabrication for bone tissue engineering.

Fabrication of Porous Scaffolds Using NaHCO_3 Particulates as the Porogen Material

A new method of fabricating porous polymer scaffolds was developed, using sodium hydrogen carbonate particulates as the porogen to foam. The pore structure of polymer scaffolds can easily be manipulated by controlling the size and weight fraction of sodium hydrogen carbonate particulates. The scaffolds are highly porous with a porosity greater than 90% and with a larger pore size ranging from 100-400μm, and are well distributed with the interconnected and open pore wall structure which is necessary for tissue engineering. We investigated the effect of the porosity of scaffolds, the pore size of scaffolds and material of polymer on the mechanical properties of scaffolds. The scaffolds fabricated by the method have more big pores than those by the convenient method of salt leaching.

Biomaterial–Related Cell Microenvironment in Tissue Engineering and Regenerative Medicine

An appropriate cell microenvironment is key to tissue engineering and regenerative medicine.Revealing the factors that influence the cell microenvironment is a fundamental research topic in the fields of cell biology,biomaterials,tissue engineering,and regenerative medicine.The cell microenvironment consists of not only its surrounding cells and soluble factors,but also its extracellular matrix(ECM)or nearby external biomaterials in tissue engineering and regeneration.This review focuses on six aspects of bioma-terial-related cell microenvironments:①chemical composition of materials,②material dimensions and architecture,③material-controlled cell geometry,④effects of material charges on cells,⑤matrix stiff-ness and biomechanical microenvironment,and⑥surface modification of materials.The present chal-lenges in tissue engineering are also mentioned,and eight perspectives are predicted.

Morphological Evaluation of PLA/Soybean Oil Epoxidized Acrylate Three-Dimensional Scaffold in Bone Tissue Engineering

Tissue engineering’s main goal is to regenerate or replace tissues or organs that have been destroyed by disease,injury,or congenital disabilities.Tissue engineering now uses artificial supporting structures called scaffolds to restore damaged tissues and organs.These are utilized to attach the right cells and then grow them.Rapid prototyping appears to be the most promising technology due to its high level of precision and control.Bone tissue replacement“scaffolding”is a common theme discussed in this article.The fused deposition technique was used to construct our scaffold,and a polymer called polylactic acids and soybean oil resin were used to construct our samples.The samples were then divided into two groups;the first group was left without immersion in the simulated body fluid and served as a control for comparison.The second group was immersed in the simulated body fluid.The results of the Field Emission Scanning Electron Microscope(FESEM),Energy Dispersive X-ray Spectroscopy(EDX)and X-ray diffraction(XRD)were utilized to interpret the surface attachment to ions,elements,and compounds,giving us a new perspective on scaffold architecture.In this study,an innovative method has been used to print therapeutic scaffold that combines fused deposition three-dimensional printing with ultraviolet curing to create a high-quality biodegradable polymeric scaffold.Finally,the results demonstrate that adding soybean oil resin to the PLA increased ion attachment to the surface while also attracting tricalcium phosphate formation on the surface of the scaffold,which is highly promising in bone tissue replacement.In conclusion,the soybean oil resin,which is new in the field of bone tissue engineering,shows magnificent characteristics and is a good replacement biopolymer that replaces many ceramic and polymeric materials used in this field that have poor morphological characteristics.

Rapid Prototyping Technology of Tissue Engineering Scaffold

In the modern medicine field, the transplant of organ and tissue is a big problem due to serious shortage of donor organ. Artificial organ and tissue is one of solutions. With the development of science, various tissue manufacture techniques emerged. Hereinto, due to its versatility both in materials and structure, rapid prototyping technology has become one of the important methods for tissue engineering scaffold fabrication in this field.

Protein-spatiotemporal partition releasing gradient porous scaffolds and anti-inflammatory and antioxidant regulation remodel tissue engineered anisotropic meniscus

Meniscus is a wedge-shaped fibrocartilaginous tissue,playing important roles in maintaining joint stability and function.Meniscus injuries are difficult to heal and frequently progress into structural breakdown,which then leads to osteoarthritis.Regeneration of heterogeneous tissue engineering meniscus(TEM)continues to be a scientific and translational challenge.The morphology,tissue architecture,mechanical strength,and functional applications of the cultivated TEMs have not been able to meet clinical needs,which may due to the negligent attention on the importance of microenvironment in vitro and in vivo.Herein,we combined the 3D(three-dimensional)-printed gradient porous scaffolds,spatiotemporal partition release of growth factors,and anti-inflammatory and anti-oxidant microenvironment regulation of Ac2-26 peptide to prepare a versatile meniscus composite scaffold with heterogeneous bionic structures,excellent biomechanical properties and anti-inflammatory and anti-oxidant effects.By observing the results of cell activity and differentiation,and biomechanics under anti-inflammatory and anti-oxidant microenvironments in vitro,we explored the effects of anti-inflammatory and anti-oxidant microenvironments on construction of regional and functional heterogeneous TEM via the growth process regulation,with a view to cultivating a high-quality of TEM from bench to bedside.

Novel 3D printed shape-memory PLLA-TMC/GA-TMC scaffolds for bone tissue engineering with the improved mechanical properties and degradability

The biodegradable substitution materials for bone tissue engineering have been a research hotspot.As is known to all,the biodegradability,biocompatibility,mechanical properties and plasticity of the substitution materials are the important indicators for the application of implantation materials.In this article,we reported a novel binary substitution material by blending the poly(lactic-acid)-co-(trimethylenecarbonate)and poly(glycolic-acid)-co-(trimethylene-carbonate),which are both biodegradable polymers with the same segment of flexible trimethylene-carbonate in order to accelerate the degradation rate of poly(lactic-acid)-co-(trimethylene carbonate)substrate and improve its mechanical properties.Besides,we further fabricate the porous poly(lactic-acid)-co-(trimethylene-carbonate)/poly(glycolic-acid)-co-(trimethylene-carbonate)scaffolds with uniform microstructure by the 3D extrusion printing technology in a mild printing condition.The physicochemical properties of the poly(lactic-acid)-co-(trimethylenecarbonate)/poly(glycolic-acid)-co-(trimethylene-carbonate)and the 3D printing scaffolds were investigated by universal tensile dynamometer,fourier transform infrared reflection(FTIR),scanning electron microscope(SEM)and differential scanning calorimeter(DSC).Meanwhile,the degradability of the PLLATMC/GA-TMC was performed in vitro degradation assays.Compared with PLLA-TMC group,PLLA-TMC/GATMC groups maintained the decreasing Tg,higher degradation rate and initial mechanical performance.Furthermore,the PLLA-TMC/GA-TMC 3D printing scaffolds provided shape-memory ability at 37℃.In summary,the PLLA-TMC/GA-TMC can be regarded as an alternative substitution material for bone tissue engineering.

Evaluating and Modeling the Mechanical Properties of the Prepared PLGA/nano-BCP Composite Scaffolds for Bone Tissue Engineering

In this paper, preparation of nano-biphasic calcium phosphate （nBCP）, mechanical behavior and load-bearing of poly （lactide-co-glycolide） （PLGA） and PLGA/nBCP are presented. The nBCP with composition of 63/37 （w/w） HA/-TCP （hydroxyapatite/fl-tricalcium phosphate） was produced by heating of bovine bone at 700℃. Composite scaffolds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinforcement material. All scaffolds were prepared by thermally induced solid-liquid phase separation （TIPS） at -60~C under 4 Pa （0.04 mbar） vacuum. The results of elastic modulus testing were adjusted with Ishai-Cohen and Narkis models for rigid polymeric matrix and compared to each other. PLGA/nBCP scaffolds with 30 wt% nBCP showed the highest value of yield strength among the scaffolds. In addition, it was found that by increasing the nBCP in scaffolds to 50 wt%, the modulus of elasticity was highly enhanced. However, the optimum value of yield strength was obtained at 30 wt% nBCP, and the agglomeration of reinforcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of matrix has the significant role in elastic modulus of scaffolds, as also the size of the filler particles in the matrix.

PARTICLE-COLLISION AND POROGEN-LEACHING TECHNIQUE TO FABRICATE POLYMERIC POROUS SCAFFOLDS WITH MICROSCALE ROUGHNESS OF INTERIOR SURFACES

A facile technique is herein reported to fabricate three-dimensional （3D） polymeric porous scaffolds with interior surfaces of a topographic microstructure favorable for cell adhesion. As demonstration, a well-known biodegradable polymer poly（lactide-co-glycolide） （PLGA） was employed as matrix. Under the porogen-leaching strategy, the large and soft porogens of paraffin were modified by colliding with small and hard salt particles, which generated micropits on the surfaces of paraffin spheres. The eventual PLGA scaffolds after leaching the modified porogens had thus interior surfaces of microscale roughness imprinted by those micropits. The microrough scaffolds were confirmed to benefit adhesion of bone marrow stromal cells （BMSCs） of rats and meanwhile not to hamper the proliferation and osteogenic differentiation of the cells. The insight and technique might be helpful for biomaterial designing in tissue engineering and regenerative medicine.

Synthetic biodegradable functional polymers for tissue engineering:a brief review

Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly(glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix(ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.

Long-term morphological evaluation of porous poly-DL-lactic acid for soft tissue augmentation

Soft tissues are important for aesthetic considerations in implant therapy. The purpose of this study was to investigate soft tissue augmentation by using porous poly-DL-lactic acid (PDLLA)shaped as a tablet, with a diameter of5.0 mmand a height of2.0 mm. Porous PDLLA was implanted between the periosteal and epithelial tissues in 25 rats that were sacrificed at 1, 2, 4, 12, and 24 weeks. The average height of the PDLLA scaffolds at approximately 24 weeks was 1.85 ±0.08 mm, and the molecular weight decreased with time. Sinusoidal capillaries at 1 week, connective tissues at 4 weeks, and necrotic tissues at 24 weeks were observed more than other periods. At 24 weeks, the connective tissue surviving in the pores was confirmed to contain blood vessels;therefore, blood vessels are considered to be critical for the survival of soft tissue in scaffold pores. In this study, PDLLA was found to be useful for soft tissue augmentation in the long term. Although the molecular weight of PDLLA decreased with time, the height of the PDLLA scaffolds was preserved. The connective tissue surviving in the pores of the scaffolds at 24 weeks were associated with blood vessels. Further studies are necessary to investigate the optimal scaffold shape and surface characteristics to improve the penetration of blood vessels.

Fabrication of a Mood vessel scaffold with a combined polymer for tissue enginerring

Objective To investigate the possibility to fabricate a blood vessel scaffold with a combined polymer for tissue engineering. Methods A blood vessel scaffold was designed with a combined polymer composed of rabbit vascular smooth muscle cells ( VSMCs), collagen and a non-spinning fabric mesh of polyglycolic acid(PGA). VSMQ were implanted into collagen gel and their growth was observed. The mixed solution of VSMQ and collagen was dropped into the tubular scaffold, followed by 7-day culturing. Results VSMQ formed many prominences after culturing in gelatinous collagen for 3 - 4 hours. With cells extending, some cells became shuttle-or spindle-shaped. After VSMQ-collagen complex was implanted into the PGA mesh, most of VSMCs remained in the pore of PGA mesh with the formation of gelation. VSMCs could adhere to and grow on the PGA fiber. Conclusion The non-spinning PGA porous biodegradable material coated with collagen is a good carrier for VSMCs to adhere and grow. 5 refs,3 figs.

Study of Tissue Engineered Dental Implants of human alveolar Bone-Evaluations on their osteogenic activities invitro

The development of the activated cellular bony implant, in light of the principle on tissue engineering, has brought about a new era to the fields of dental maxillofacial implantation. The present study separated the osteoblast like cells from human alveolar bone and seeded them into 3 types of biodegradable scaffold to form the complexes and then evaluated their osteogenic activities in vitro, in order to acquire experimental data that are essential to future clinical practice of this new type of therapeutical procedure in oral and maxillofacial surgery. Material and methods: Human alveolar bone origin cells were separated from alveolar bone around the third impacted teeth of 3 patients by enzyme digestion and went on cultures with α MEM containing β glycerophosphate and Dexamethasone at 5% CO2 ,37℃ for 21 28 days. Confirmed osteoblasts like cells were then seeded onto 3 types of degradable biomaterials of polyglycolic acid scaffold, collagen sponge, and L lactic acid/ε caprolactone to form cell matrices complexes. The 3 types of complex were continued to culture for 21 28 days in vitro at the same conditions with the single layer cultured cells. The cell proliferation, morphological changes, ALPase activity and mineral nodules formation on scaffolds were measured and observed at 3 days intervals to evaluate the affinities & the osteogenic activities of the human alveolar osteoblast like cells in the 3 different complexes. Result and discussion: The results indicated that the cultured human alveolar bone origin cells from 3 patients could successfully express the osteoblasts phenotype in single layered culturing in vitro after stimulated by β glycerophosphate and Dexamethasone. It has been shown that the cultured osteoblast like cells seeded on PGAS matrix had the highest attachmental, proliferative and osteogenic activities, suggesting a good bio affinity between the human alveolar osteoblast like cells and the PGAS matrix. The statistical analysis (ANOVA) showed that there were significant differences between PGAS osteoblasts complex and CLGS or LACT complexes on osteogenic activities. (P<0.05). It was also noticed that cultured human alveolar osteoblasts seeded in biodegradable materials had a delayed peak period on cell proliferation and PLAase production ,suggesting the osteoblasts seeded on scaffolds need a period of time to adjust themselves before they can normally proliferate and expres their phenotypes. Conclusion: PGAS osteoblasts complex is worth to be further developed into a tissue engineered cellular artificial bony implant for reconstructing the oral maxillofacial bony defects in a more effective way in the future.

可降解生物医用多孔Zn基支架研究进展

目前,治疗创伤、先天畸形、肿瘤组织切除等原因造成的大段骨缺损仍是骨科手术面临的主要挑战。利用骨组织工程支架代替自体骨移植在缺损部位进行骨重建为解决该问题带来新的方案。鉴于理想骨组织工程支架应具备良好生物相容性、适宜生物降解性、与骨组织相匹配的力学性能以及抗菌性等特征,多孔Zn基支架可能成为理想骨组织工程支架的最佳候选者。然而,近些年的研究发现目前开发的多孔Zn基支架存在力学性能差、体外浸泡及植入体内初期降解速率相对较快导致过量Zn 2+释放、高浓度Zn 2+能够抑菌杀菌但也会使Zn基支架细胞毒性增强进而导致支架植入体内后出现骨整合延迟等问题。鉴于此,近些年关于多孔Zn基支架的研究主要聚焦于改善支架力学性能、调控支架降解速率,同时赋予支架抑菌杀菌性能和良好生物相容性等方面。研究者们主要采取了对多孔Zn支架进行合金化处理、控制孔隙率、控制孔隙形貌和尺寸等手段来提高多孔Zn基支架的力学性能,同时实现对多孔Zn基支架降解速率的调控。此外,也有研究者利用电偶腐蚀原理调控多孔支架的降解速率。由于多孔Zn基支架降解过程中释放的Zn 2+严重影响支架的抑菌杀菌性能和生物相容性,且抑菌杀菌性能和良好生物相容性对Zn 2+浓度需求恰好相反,故目前对于同时赋予支架抑菌杀菌性能和良好生物相容性的有效手段仍在探索研究中。本文归纳了可降解多孔Zn基骨组织工程支架在制备方法、力学性能、生物降解性能、抑菌杀菌性能和生物相容性等方面的研究进展,分析了多孔Zn基骨组织工程支架面临的问题并展望了其前景,以期为制备力学性能优异、降解速率适宜可控并同时具备抑菌杀菌性能和良好生物相容性的多孔Zn基骨组织工程支架提供参考。

Integrated gradient tissue-engineered osteochondral scaffolds:Challenges,current efforts and future perspectives

The osteochondral defect repair has been most extensively studied due to the rising demand for new therapies to diseases such as osteoarthritis.Tissue engineering has been proposed as a promising strategy to meet the demand of simultaneous regeneration of both cartilage and subchondral bone by constructing integrated gradient tissue-engineered osteochondral scaffold(IGTEOS).This review brought forward the main challenges of establishing a satisfactory IGTEOS from the perspectives of the complexity of physiology and microenvironment of osteochondral tissue,and the limitations of obtaining the desired and required scaffold.Then,we comprehensively discussed and summarized the current tissue-engineered efforts to resolve the above challenges,including architecture strategies,fabrication techniques and in vitro/in vivo evaluation methods of the IGTEOS.Especially,we highlighted the advantages and limitations of various fabrication techniques of IGTEOS,and common cases of IGTEOS application.Finally,based on the above challenges and current research progress,we analyzed in details the future perspectives of tissue-engineered osteochondral construct,so as to achieve the perfect reconstruction of the cartilaginous and osseous layers of osteochondral tissue simultaneously.This comprehensive and instructive review could provide deep insights into our current understanding of IGTEOS.

碳纳米管在组织工程修复中的作用与优势

背景:近来年,碳纳米管材料因其独特的结构及材料特性而备受关注,将其作为组织工程材料在组织修复中的研究逐渐深入,在动物体内已取得良好的修复效果。目的:综述碳纳米管作为组织工程材料的特性及碳纳米管用于组织工程修复中的研究进展。方法:应用计算机检索万方医学网、中国知网、维普、Web of Science和PubMed数据库中的相关文献,中文检索词为“碳纳米管、复合材料、组织工程、组织修复”,英文检索词为“carbon nanotubes,composite materials,tissue engineering,tissue repair”,最终纳入75篇文献进行归纳总结。结果与结论:①碳纳米管主要分为由单层管状石墨烯形成的单壁碳纳米管和由多个同心管状石墨烯层组成的多壁碳纳米管,通过修饰改性碳纳米管以及调节浓度使含有碳纳米管的复合支架材料获得更好导电性、机械性能、生物相容性及生物降解性。②通过促进蛋白质吸附、调控电信号转导通路及机械转导信号通路可以促进细胞增殖、分化、黏附等行为及提高细胞活性,从而促进骨重塑及整合、改善神经及心肌功能、加速缺损修复促进组织再生,且在体内无不良反应。③目前的研究表明碳纳米管复合材料能够完全修复临界大块骨缺损,达到自体移植相似的神经修复效果及使得受损心肌的生理心肌传导速度完全恢复。因此,碳纳米管作为新型生物材料在组织工程修复领域中具有巨大的潜力。④碳纳米管在组织修复领域的相关研究尚处于体外实验或动物实验水平,基于碳纳米管的复合材料要从实验研究走向临床实践还需要克服很多困难,如碳纳米管的毒理学评价、有效性评价等需后续研究进一步完善,而碳纳米管的直径、长度、纯度及复合材料的制备方法等参数与组织修复相关通路的联系需要进一步研究。