Biomimetic Route to Calcium Phosphate Coated Polymeric Nanoparticles: Influence of Different Functional Groups and pH

The controlled synthesis of organic–inorganic hybrid particles with selective morphology using polymeric nanoparticles as templates offers an effective biomimetic route to design composite materials with interesting properties for various potential applications. In this study, the formation of hybrid particles via the bio‐inspired mineralization of calcium phosphate (CaP) on the surface of different surface‐functionalized polymeric nanoparticles is reported. The versatile miniemulsion polymerization is used to prepare different surface functionalized nanoparticles with covalently bound carboxylic acid and phosphonic acid surface‐functionalities. Functional comonomers with varying hydrophilicity like acrylic acid (AA), vinylphosphonic acid (VPA), and vinylbenzylphosphonic acid (VBPA) are employed for the copolymerization with styrene. The influence of different functional groups at different pH on the crystal phase and morphology of the calcium phosphate phase in the hybrid nanoparticles is analyzed in detail by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron as well as X‐ray diffraction (ED and XRD) techniques. The calcium ion binding affinity of different surface functional groups at varying loading conditions is studied using calcium ion selective electrode to shed light on the mineralization kinetics as well as on the interfacial chemistry involved between the complexing ions and the functional groups on the particle surface. The CaP/polymer hybrid particles with well‐defined crystal phases and morphologies offering varying surface topographies are interesting candidates for cell adhesion and proliferation studies for potential tissue engineering applications. They could be used as bone fillers, building blocks for the nucleation, and the growth of new bone material or implant coatings to reduce the immune response.

     

Hypoxia promotes mineralization of human dental pulp cells

Introduction

Dental pulp can be exposed to hypoxic conditions in case of trauma or inflammation. Dental pulp cells (DPCs) have mineralization potential, which plays a key role in pulp repair and reparative dentinogenesis process. Little information is available about DPC mineralization in hypoxic condition. The purpose of this study was to assess the influence of hypoxia on DPC mineralization to pave the way for a better understanding of dental pulp regeneration and reparative dentin formation.

Methods

Human DPCs were obtained by using tissue explant technique in vitro and cultured in normoxia (20% O₂) or hypoxia (5% O₂). Cell viability was investigated by methyl-thiazol-tetrazolium assay. Cell mineralization was assessed by von Kossa staining and alizarin red S staining. Important mineral genes such as osteocalcin (OCN), dentin matrix acidic phosphoprotein-1 (DMP-1), bone sialoprotein (BSP), and dentin sialophosphoprotein (DSPP) were determined by real-time polymerase chain reaction.

Results

Cell viability of DPCs increased more in hypoxia than in normoxia from day 3 to day 5. Von Kossa staining and alizarin red S staining showed DPCs in hypoxia had higher mineralization activity than in normoxia. Expression of mRNAs for OCN, DMP-1, BSP, and DSPP was greater in hypoxia than in normoxia.

Conclusions

These results imply that hypoxia promotes DPC mineralization.     

热敏脂质体介导的仿生矿化胶原凝胶的基础研究

目的:通过模拟基质小泡介导的矿化过程,合成一种类似于天然骨结构和成分的羟基磷灰石/胶原复合材料.方法:利用薄膜-超声法分别制备载Ca2+和Pi脂质体,描述其基本特征.并观察在早期釉质龋模型上的应用.最后,合成脂质体/胶原前驱液,加热到37℃形成矿化胶原凝胶,应用扫描电镜,能谱仪来观察冻干矿化胶原凝胶的特征.结果:合成了小直径亚稳定的脂质体;复合材料的成分类似于天然骨.结论:利用脂质体包封盐溶液,模拟基质小泡;在体温条件下与酸性胶原溶液反应形成胶原凝胶.但是胶原凝胶机械性能及生物相容性尚需进一步研究.     

Atypical presentation of pseudoxanthoma elasticum with abdominal cutis laxa: Evidence for a spectrum of ectopic calcification disorders?

A patient is presented with severe cutis laxa of the abdomen. Molecular investigations, including sequencing of the fibulin-5 and elastin gene, failed to endorse the diagnosis of inherited cutis laxa. Ultrasonographical discovery of renal calcifications during his general work-up suggested a possible diagnosis of pseudo-xanthoma elasticum (PXE). A discrete yellowish reticular pattern in the anterior neck region was detected upon careful clinical examination. Clinically, the patient presented characteristics of both classic PXE (retinopathy, renal calcifications) and the PXE-like syndrome (cutis laxa beyond the flexural areas). Skin biopsy and ophthalmological examination confirmed the diagnosis of PXE. In addition, ultrastructural evaluation revealed calcium deposits in the periphery of elastic fibers, a typical observation in the PXE-like syndrome. Immunohistochemical experiments and ELISA tests for various inhibitors of calcification displayed results which were partly reminiscent of both PXE and the PXE-like syndrome. Molecular analysis revealed not only two ABCC6 mutations (related to PXE), but also a gain of function SNP in the GGCX gene, in which loss-of-function mutations cause the PXE-like syndrome. We conclude that the patients phenotype and--to a further extent--the PXE-like syndrome, are part of a spectrum of ectopic calcification disorders which are clinically and/or pathogenetically related to PXE. The molecular findings in this patient are however insufficient to explain the entire phenotype and suggest a role for multiple genetic factors in soft tissue mineralization.     

Pulsed low intensity ultrasound enhances mineralisation in preosteoblast cells

Pulsed low intensity ultrasound has been shown to be highly efficacious in the treatment of nonunion fractures and in the acceleration of fresh fracture healing. MC3T3-E1 subclone 14 cells were cultured for up to 25 days either with or without a daily treatment with low intensity pulsed ultrasound. It was determined that, on day 10 there was a dramatic increase in alkaline phosphatase and MMP-13 mRNA levels detected in ultrasound-treated cultures compared with untreated controls. The activity of alkaline phosphatase was significantly increased at days 6, 8 and 10. On day 10, the amount of mineralisation within cultures, assessed using alizarin red staining, was significantly increased in ultrasound-treated cultures compared with untreated controls. These results suggest that one of the mechanisms that low intensity pulsed ultrasound has on fracture repair is to enhance the process of endochondral ossification where the soft callus is converted to mineralised hard callus.     

富血小板血浆对犬骨髓间充质细胞矿化能力的影响

目的研究富血小板血浆(platelet-rich plasma,PRP)对犬骨髓间充质细胞(marrow stromal cells,MSCs)碱性磷酸酶(alka-line phosphatase,ALP)及矿化结节形成能力的影响。方法将不同浓度(10%、20%、30%)的PRP及重组人骨形成蛋白(rhBMP-2)加入体外培养的第3代MSCs中,对照组为无血清培养液,检测其对细胞ALP活性的影响;将第3代的MSCs在体外进行培养,实验组加入矿化液和PRP(10%或30%),对照组只加矿化液。4周后用茜素红及Von-Kossa染色检测矿化结节的形成。结果10%PRP和rhBMP-2能显著提高MSCs的ALP活性,其中10%PRP对体外矿化结节的形成,亦有一定程度的促进作用。结论PRP有促进MSCs向成骨细胞方向转化的趋势。     

Spatial Distribution Characteristics of Microbial Mineralization in Saturated Sand Centrifuge Shaking Table Test

Calcium carbonate induced by microorganisms can quickly fill and cement sand particles, thereby effectively reducing the potential for the liquefaction of sand. This process could represent a new green approach to the liquefaction treatment of saturated sand and has good prospects for application. However, owing to the diversity of microbial activities and the heterogenous spatiotemporal distribution of bacterial nutrient seepage in sandy soil foundations, the resultant complex distribution of calcium carbonate deposition in a sandy soil foundation can lead to differences in solidification strength and improvement effect. To understand the influence of earthquake action on the liquefaction resistance of saturated sand treated by microorganisms, and to evaluate the effect of microbial technology on sand liquefaction prevention under dynamic load, this study simulated the dynamic stress conditions of saturated sand under shear waves, using the world′s first centrifuge shaking table (R500B), which realizes horizontal and vertical two-way vibration. On the basis of spatial heterogeneity of microbial mineralization after centrifuge shaking table tests, the effect of microbial strengthening on liquefied sand was analyzed, and the spatial distribution of calcium carbonate mineralization was examined. The results showed that the distribution of microorganisms in the solidified soil exhibited obvious spatial heterogeneity with a significant edge effect. Although microbial mineralization effectively improved the liquefaction resistance of saturated sand, a sudden change in the process of calcium carbonate deposition altered the cementation of the sand with depth. Moreover, the curing strength had obvious complexity and uncertainty that directly affected the shear stiffness of the soil under dynamic load, and this constitutes one of the reasons for the degradation of shear stiffness of sand during liquefaction. The derived conclusions could be used as a reference for engineering applications of microbial treatment of a liquefiable sandy soil foundation.     

磷灰石-多孔纤维素复合物与成骨细胞相容性的研究

目的制备磷灰石- 多孔纤维素复合物,评价该复合物的细胞相容性。方法通过化学修饰将磷酸根接枝于天然多孔纤维素玉米芯表面,经预矿化处理后,在模拟体液中进行仿生矿化,X线衍射检测磷灰石- 多孔纤维素复合物表面磷灰石微晶的形成,扫描电镜（SEM）观察复合物表面形貌。体外分离培养扩增乳鼠颅盖骨成骨细胞,经传代培养作为种子细胞接种于复合物表面进行培养。采用MTT和碱性磷酸酶（ALP）活性检测及SEM观察细胞在复合物表面生长、增殖与分化情况。结果仿生矿化后玉米芯表面形成了磷灰石晶体。成骨细胞在磷灰石- 多孔纤维素复合物表面吸附、铺展,具有较好的增殖及合成ALP的能力。结论磷灰石- 多孔纤维素复合物与成骨细胞具有良好的相容性,在仿生构建骨再生材料方面具有潜在的价值。     

促矿化液对大鼠成骨细胞增殖分化的影响

目的比较大鼠成骨细胞在矿化条件与非矿化条件下增殖和分化的过程,评价促矿化液对其生理功能的影响,明确促矿化液加入细胞培养环境的适宜时间。方法取SD大鼠头盖骨做成骨细胞原代培养,将增殖稳定后的第4代细胞分别在矿化条件和非矿化条件下培养,检测其形态、碱性磷酸酶活性、细胞周期等。结果大鼠成骨细胞增殖基本稳定后促矿化液组与无促矿化液组细胞分裂增殖指数相似,但前者碱性磷酸酶活性明显较高且持久。结论成骨细胞增殖基本稳定后加入促矿化液对细胞增殖无影响,但可明显促进细胞矿化功能,是加入促矿化液诱导细胞矿化功能的较好时机。