Critical Role of Silicon in Directing the Bio-inspired Mineralization of Gelatin in the Presence of Hydroxyapatite

Significant progress has been made on understanding the critical role of organic components in directing the collagen mineralization.We hypothesize that the inorganic trace elements might also play important role in the mineralization of collagenous matrix.To this aim,we systematically compared the in-vitro biomineralization behaviors of gelatin,gelatin-HA and gelatin-SiHA electrospun membranes.The results indicated that the presence of Si ions played a striking influence on the nucleation behaviors and mineralized structures.The gelatin-SiHA samples demonstrated more homogeneous nucleation within the gelatin fiber and growth along the fiber direction,in comparison with the heterogeneous nucleation and growth of spherulitic clusters on top of the nanofiber surface,i.e.extrafibrillar mineralization.The likely shift of the nucleation mode to the intrafibrillar mineralization in the presence of Si ions led to good alignment of apatite c-axis with the long axis of the nanofiber,resulting in a mineralization process and microstructure that were closer to those in natural bone.Cellular response analysis indicated that Si incorporation improved the MSC attachment and cytoskeleton organization.Such findings might have important implication in both understanding the complex mechanisms involved in collagen mineralization and optimal designing of advanced bio-inspired materials with potential superior mechanical and biological properties.     

用于骨病治疗的酶抑制剂药物研发进展

近年来研究发现,多种骨病都伴随钙化异常发生,该钙化异常与组织非特异性碱性磷酸酶等生物酶的功能异常密切相关,破解这些酶的致病机理,研发能减缓异常钙化进程的相关酶抑制剂作为传统抗炎药物的重要补充,已成为该领域研究人员的关注热点,本文将针对过度钙化型骨病,对于其形成机理及药物研发的相关进展进行介绍。     

Evaluating the biodegradability of Gelatin/Siloxane/Hydroxyapatite (GS-Hyd) complex in vivo and its ability for adhesion and proliferation of rat bone marrow mesenchymal stem cells

Recent studies have shown that the use of biomaterials and new biodegradable scaffolds for repair or regeneration of damaged tissues is of vital importance. Scaffolds used in tissue engineering should be biodegradable materials with three-dimensional structures which guide the growth and differentiation of the cells. They also tune physical, chemical and biological properties for efficient supplying of the cells to the selected tissues and have proper porosity along with minimal toxic effects. In this manner, the study of these characteristics is a giant stride towards scaffold design. In this study, Gelatin/Siloxane/Hydroxyapatite (GS-Hyd) scaffold was synthesized and its morphology, in vivo biodegradability, cytotoxic effects and ability for cell adhesion were investigated using mesenchymal stem cells (MSCs). The cells were treated with different volumes of the scaffold suspension for evaluation of its cytotoxic effects. The MSCs were also seeded on scaffolds and cultured for 2 weeks to evaluate the ability of the scaffold in promoting of cell adhesion and growth. To check the biodegradability of the scaffold in vivo, scaffolds were placed in the rat body for 21 days in three different positions of thigh muscle, testicle, and liver and they were analyzed by scanning electron microscopy (SEM) and weight changes. According to the results of the viability of this study, no cytotoxic effects of GS-Hyd scaffold was found on the cells and MSCs could adhere on the scaffold with expanding their elongations and forming colonies. The rate of degradation as assessed by weight loss was significant within each group along with significant differences between different tissues at the same time point. SEM micrographs also indicated the obvious morphological changes on the surface of the particles and diameter of the pores through different stages of implantation. The greatest amount of degradation happened to the scaffold particles implanted into the muscle, followed by testicle and liver, respectively.     

Bifunctional bisphosphonate derivatives and platinum complexes with high affinity for bone hydroxyapatite

A series of ethylenediamine/1,3-propanediamine derivatives containing bifunctional bisphosphonate substituents and their corresponding dichloroplatinum(II) complexes have been synthesized and characterized by elemental analysis, ¹H NMR, ¹³C NMR, ³¹P NMR, and HRMS spectra. Based on WST-8 assay with CCK-8, in general, the newly synthesized dichloroplatinum complexes 1–6 showed higher in vitro antitumor activity than platinum-free compounds L1–L6 against three tumor cell lines (especially osteosarcoma MG-63). According to hydroxyapatite binding experiment, complexes 2, 3, and 6 showed much higher affinity (K′ = 3.7, 4.0, and 3.0, respectively) for bone hydroxyapatite than cisplatin (K′ < 0.1), comparable to zoledronate (K′ = 2.8). It can be found that representative complex 2 with high cytotoxicity and in vitro antiproliferative activity against osteosarcoma cell line, as well as promising hydroxyapatite binding ability has been screened as a potential bone-targeting antitumor agent for subsequent in vivo study. In addition, flow cytometry experiment was applied to investigate the mode of action of representative complex 2.     

Ultrastructure of ceramic-bone interface using hydroxyapatite and beta-tricalcium phosphate ceramics and replacement mechanism of beta-tricalcium phosphate in bone

Hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) are useful for grafting and augmentation of bone tissue. Observation by transmission electron microscopy (TEM) was done to investigate the ultrastructures at the interfaces between the biomaterials and the adjacent tissue, and osteogenesis around the biomaterials in the present study. HA and beta-TCP ceramics were used in disk forms which had macropores and micropores, and were implanted between the parietal bone and the cranial periosteum of rats. Specimens were prepared for observation at 4 and 8 weeks postoperatively. The microscopic results indicated that an intervening layer was present on the surface of HA, whereas it was not present on the surface of beta-TCP. A characteristic fibrillar structure was observed in the intervening layer between HA and bone under decalcification by HCl. In beta-TCP, in reticular structures observed close to the bone tissue by optical microscopy, calcification and sparse collagen fibers were interspersed among the granules of beta-TCP. In addition, close to the interface between beta-TCP and bone, many osteocytes with numerous processes were present. Some processes were elongated towards the interface. These results revealed the difference in the ultrastructures of the interfaces between HA and beta-TCP, and the dissolution mechanism of beta-TCP in bone.     

Regulation of fructosyltransferase activity by carbohydrates, in solution and immobilized on hydroxyapatite surfaces

We tested the effect of several carbohydrates on the activity of cell-free fructosyltransferases (FTF) in solution and immobilized onto hydroxyapatite (HA) and found an inhibitory dose-dependent effect of glucose on FTF activity, both on the surface and in solution. Glucose at 160 mM inhibits FTF activity by 75% both on HA and in solution. Fructose at 160 mM inhibited FTF activity by 25% in solution and by 15% on HA. Levan inhibited FTF activity by 30% in solution, while dextrans and inulin had a limited effect on FTF activity. Circular dichroism and infrared analysis demonstrated no major changes in the chemical structure of fructans synthesized by cell-free FTF on HA and in solution, in the presence or absence of glucose. However, as verified by size-exclusion chromatography, glucose inhibited the synthesis of high molecular-weight fructans. The results indicate that glucose, a byproduct of the FTF enzymatic reaction, is the main carbohydrate affecting FTF activity. Selective inhibition of high molecular-weight fructan production by glucose, may indicate that two mechanisms are involved in the synthesis of fructans, both in solution and on the surface.     

羟基磷灰石水泥的体外生物学安全性试验

羟基磷灰石水泥(HAC)是新型的羟基磷灰石类人工骨材料。1991年得到美国食品与药物管理局(FDA)的批准,在临床试用,用于颅骨缺损的填充治疗。华东理工大学最近研制出类似的HAC。我们用它的生理盐水浸出液对其进行了生物学安全性试验,包括细胞培养毒性试验、全身注射毒性试验、Ames试验、微核试验及UDS试验。结果表明HAC的浸出液对培养细胞的生长无抑制作用,对体细胞的遗传物质(染色体、DNA)无致突变作用。上述结果提示我们,HAC用于人体是安全的。     

Silk fibroin/hydroxyapatite composites for bone tissue engineering

Silk fibroin (SF) is a natural fibrous polymer with strong potential for many biomedical applications. SF has attracted interest in the field of bone tissue engineering due to its extraordinary characteristics in terms of elasticity, flexibility, biocompatibility and biodegradability. However, low osteogenic capacity has limited applications for SF in the orthopedic arena unless suitably functionalized. Hydroxyapatite (HAp) is a well-established bioceramic with biocompatibility and appropriate for constructing orthopedic and dental substitutes. However, HAp ceramics tend to be brittle which can restrict applications in the repair of load-bearing tissues such as bones. Therefore, blending SF and HAp combines the useful properties of both materials as bone constructs for tissue engineering, the subject of this review.     

AZ31B镁合金植入小鼠的生物相容性考察

目的 评价羟基磷灰石(hydroxyapatite, HAP)涂层的AZ31B镁合金（HAP/AZ31B）作为植入材料的生物安全性。方法 采用恒电压阴极电沉积法制备表面HAP涂层的HAP/AZ31B材料;判定生物材料的致突变及毒性作用;检测材料表面的腐蚀状况并进行能谱分析。结果 HAP/AZ31B材料无致突变作用,对动物组织未产生严重的炎症反应;经HAP涂层后的AZ31B材料腐蚀较慢,微核出现率为4.4‰,溶血率为0.25%。结论HAP/AZ31B表现出较好的生物安全性和相容性,有可能成为新型可降解骨支架材料。