Macro/microporous silk fibroin scaffolds with potential for articular cartilage and meniscus tissue engineering applications

This study describes the developmental physicochemical properties of silk fibroin scaffolds derived from high-concentration aqueous silk fibroin solutions. The silk fibroin scaffolds were prepared with different initial concentrations (8, 10, 12 and 16%, in wt.%) and obtained by combining the salt-leaching and freeze-drying methodologies. The results indicated that the antiparallel β-pleated sheet (silk-II) conformation was present in the silk fibroin scaffolds. All the scaffolds possessed a macro/microporous structure. Homogeneous porosity distribution was achieved in all the groups of samples. As the silk fibroin concentration increased from 8 to 16%, the mean porosity decreased from 90.8 ± 0.9 to 79.8 ± 0.3% and the mean interconnectivity decreased from 97.4 ± 0.5 to 92.3 ± 1.3%. The mechanical properties of the scaffolds exhibited concentration dependence. The dry state compressive modulus increased from 0.81 ± 0.29 to 15.14 ± 1.70 MPa and the wet state dynamic storage modulus increased by around 20- to 30-fold at each testing frequency when the silk fibroin concentration increased from 8 to 16%. The water uptake ratio decreased with increasing silk fibroin concentration. The scaffolds present favorable stability as their structure integrity, morphology and mechanical properties were maintained after in vitro degradation for 30 days. Based on these results, the scaffolds developed in this study are proposed to be suitable for use in meniscus and cartilage tissue-engineered scaffolding.     

Printability of calcium phosphate powders for three-dimensional printing of tissue engineering scaffolds

Three-dimensional printing (3DP) is a versatile method to produce scaffolds for tissue engineering. In 3DP the solid is created by the reaction of a liquid selectively sprayed onto a powder bed. Despite the importance of the powder properties, there has to date been a relatively poor understanding of the relation between the powder properties and the printing outcome. This article aims at improving this understanding by looking at the link between key powder parameters (particle size, flowability, roughness, wettability) and printing accuracy. These powder parameters are determined as key factors with a predictive value for the final 3DP outcome. Promising results can be expected for mean particle size in the range of 20-35 μm, compaction rate in the range of 1.3-1.4, flowability in the range of 5-7 and powder bed surface roughness of 10-25 μm. Finally, possible steps and strategies in pushing the physical limits concerning improved quality in 3DP are addressed and discussed.     

纳米材料组织工程支架在女性生殖系统再生中的应用研究

生殖系统的健康与女性生殖能力和生活质量密切相关。近年来女性生殖系统相关疾病发病率日渐升高并呈现年轻化趋势,对女性生殖健康带来诸多不利影响,亟需发展有效的治疗方法。通过组织工程技术引导组织再生,从而实现器官功能的恢复,为相关疾病的治疗提供了新途径。本文对近年来基于纳米结构和生物材料的组织工程支架构建以及组织工程技术在卵巢早衰、卵泡体外培养、子宫宫腔黏连、子宫缺损修复、盆腔器官脱垂等疾病治疗中的应用研究进行回顾总结和综合评述。     

Angiogenic growth factor release system for in vivo tissue engineering: a trial of bone marrow transplantation into ischemic myocardium

For successful in vivo tissue engineering, a growth factor release system will be useful. We adopted autologous bone marrow transplantation as an angiogenic growth factor release system. Bone marrow transplanted into a synthetic vascular prosthesis produced continuous synthesis of angiogenic growth factors, resulting in rapid neointima formation on the prosthesis after implantation. We expected a similar angiogenic phenomenon to occur if bone marrow was transplanted into ischemic myocardium. Bone marrow was transplanted into ischemic myocardium created in dogs. Marrow cells continued synthesis of angiogenic growth factors, which were effective in protecting the capillary network from ischemia, but not myocytes. Autologous bone marrow was injected intramuscularly into ischemic myocardium created in the left ventricular wall of dogs. Control operations were performed without bone marrow. On days 3 and 7, marrow cells survived, and their adjacent cells and the surrounding extracellular matrix were immunohistochemically bFGF reactive. At 3 weeks, no marrow cells were identified. Myocytes disappeared, but the capillary blood vessel networks remained. With some exceptions, these capillaries did not contain blood cell components. In the controls, scar tissue with a very small number of capillaries was formed. In conclusion, marrow cells survived for a short period of time after transplantation, and continued synthesis of angiogenic growth factors, which were effective in protecting endothelial cells from ischemia, but not myocytes. Therefore, the results also suggest that there are limitations in the treatment of ischemic myocardium using angiogenic growth factors alone.