The bioelectrical properties of bone tissue

Understanding the bioelectrical properties of bone tissue is key to developing new treatment strategies for bone diseases and injuries,as well as improving the design and fabrication of scaffold implants for bone tissue engineering.The bioelectrical properties of bone tissue can be attributed to the interaction of its various cell lineages(osteocyte,osteoblast and osteoclast)with the surrounding extracellular matrix,in the presence of various biomechanical stimuli arising from routine physical activities;and is best described as a combination and overlap of dielectric,piezoelectric,pyroelectric and ferroelectric properties,together with streaming potential and electro-osmosis.There is close interdependence and interaction of the various electroactive and electrosensitive components of bone tissue,including cell membrane potential,voltage-gated ion channels,intracellular signaling pathways,and cell surface receptors,together with various matrix components such as collagen,hydroxyapatite,proteoglycans and glycosaminoglycans.It is the remarkably complex web of interactive cross-talk between the organic and non-organic components of bone that define its electrophysiological properties,which in turn exerts a profound influence on its metabolism,homeostasis and regeneration in health and disease.This has spurred increasing interest in application of electroactive scaffolds in bone tissue engineering,to recapitulate the natural electrophysiological microenvironment of healthy bone tissue to facilitate bone defect repair.

Research on Career Identity in China:A Literature Review

Career identity is one of the important topics to study the psychological problems of employees,especially after the outbreak of CoV-19.Being a populous country in the world,China has a large number of employees from all walks of life,and its research on career identity has attracted more and more attention.Thus,this study aims to sort out the history,characteristics,and trends of the research on career identity in China through a literature review,which can help more scholars pay attention to China’s career identity research.In this study,Citespace is used to statistically analyze the selected literature from China’s National Knowledge Infrastructure(CNKI)and Web of Science(WOS).The results show that:(1)The historical evolution of career identity research in China can be divided into three stages:germination,development and maturity.(2)From the perspective of cooperation between authors and institutions,researchers tend to do independent research,mainly focusing on the research in the field of psychology.(3)From the key words,career identity and employability are the main high-frequency words.(4)From the cluster analysis,the research focuses mainly include social support,teachers’career identity,influencing factors,and job involvement.(5)From the emergent analysis,it can be seen that the research on roles and differences between urban and rural areas is weakening,and the research on factors such as job satisfaction is gradually strengthening as the frontier theme.Finally,according to the existing analysis results,this study predicts the future trend of career identity in China and thinks that it will extend from the fields of concept explanation,interdisciplinary research,scientific research tools,and so on.

Extrapolating neurogenesis of mesenchymal stem/stromal cells on electroactive and electroconductive scaffolds to dental and oral-derived stem cells

The high neurogenic potential of dental and oral-derived stem cells due to their embryonic neural crest origin,coupled with their ready accessibility and easy isolation from clinical waste,make these ideal cell sources for neuroregeneration therapy.Nevertheless,these cells also have high propensity to differentiate into the osteo-odontogenic lineage.One strategy to enhance neurogenesis of these cells may be to recapitulate the natural physiological electrical microenvironment of neural tissues via electroactive or electroconductive tissue engineering scaffolds.Nevertheless,to date,there had been hardly any such studies on these cells.Most relevant scientific information comes from neurogenesis of other mesenchymal stem/stromal cell lineages(particularly bone marrow and adipose tissue)cultured on electroactive and electroconductive scaffolds,which will therefore be the focus of this review.Although there are larger number of similar studies on neural cell lines(i.e.PC12),neural stem/progenitor cells,and pluripotent stem cells,the scientific data from such studies are much less relevant and less translatable to dental and oral-derived stem cells,which are of the mesenchymal lineage.Much extrapolation work is needed to validate that electroactive and electroconductive scaffolds can indeed promote neurogenesis of dental and oral-derived stem cells,which would thus facilitate clinical applications in neuroregeneration therapy.

Enrichment,expansion,and identification of stem-like cells from hepatic carcinoma HepG2 cells

Objective:To establish a method for enriching,culturing and identifying stem-like subpopulation from human hepatic carcinoma cells,and to explore its biological properties.Methods:HepG2cells were cultured in cancer stem cell(CSC)medium to form spheroids.The stem-like HepG2cells obtained from tumor spheroids were then expanded.Flow cytometry was used to detect the expression of CD90 and CD133on the surface of stem-like HepG2 cells.The in vitro colony forming ability and in vivo tumorigenicity were detected by clone formation assay and tumorigenesis assay.Results:HepG2cells could grow in suspension and form spheroids in CSC medium.The stem-like cells had the ability of self-renewal and proliferation.The expression of CD90and CD133on the surface of these stem-like cells were higher than those of parental HepG2cells(P<0.01).The colony formation ability of stem-like cells was higher than that of parental HepG2cells.When injected with 1×106 cells,stemlike cells could form tumors earlier than parental cells in nude mice.The stem-like cells’tumorigenesis rate was higher and the tumor size was larger than those of parental HepG2cells(P<0.01).Conclusion:The suspension sphere culture method could enrich stem-like cells from HepG2cells.The obtained stem-like cells possessed the properties of self-renewal in vitro and tumorigenicity in vivo.

Investigation of the first quasi-rectangular metro tunnel constructed by the 0-θ method

Quasi-rectangular shield tunneling is a cutting-edge trenchless method for constructing metro tunnels with double tubes,owing to its advantages in saving underground space and reducing ground disturbance.However,the conventional quasi-rectangular shield tunneling method is not applicable when constructing a tunnel without a center pillar,such as a scissor crossover section of a metro line.Therefore,the O-0 tunneling method,which combines the quasirectangular shield and pipe jacking methods,was investigated in this study to solve the aforementioned construction challenges.This study presents a case study of the Sijiqing Station of the Hangzhou Metro Line 9 in China,in which the O-0 method was first proposed and applied.Key techniques such as switching between two types of tunneling modes and the tunneling process control in complex construction environments were investigated.The results demonstrated that the O-0 method can address the technical challenges presented by the post-transition line with a high curvature and a scissors crossover line.In addition,the adoption of the 0-0 method ensured that the transformation between shield tunneling and pipe jacking was safe and efficient.The ground settlement monitoring results demonstrated that the disturbance to the surrounding environment can be limited to a safe level.This case study contributes to the construction technology for a metro tunnel containing both post-transition lines with a small turning radius and a scissors crossover line.A practical construction experience and theoretical guidance were provided in this study,which are of significance for both the industry and academia.

Electrical charge on ferroelectric nanocomposite membranes enhances SHED neural differentiation

Stem cells from human exfoliated deciduous teeth(SHED)uniquely exhibit high proliferative and neurogenic potential.Charged biomaterials have been demonstrated to promote neural differentiation of stem cells,but the dose-response effect of electrical stimuli from these materials on neural differentiation of SHED remains to be elucidated.Here,by utilizing different annealing temperatures prior to corona poling treatment,BaTiO_(3)/P(VDF-TrFE)ferroelectric nanocomposite membranes with varying charge polarization intensity(d_(33)≈0,4,12 and 19 pC N^(-1))were fabricated.Enhanced expression of neural markers,increased cell elongation and more prominent neurite outgrowths were observed with increasing surface charge of the nanocomposite membrane indicating a dose-response effect of surface electrical charge on SHED neural differentiation.Further investigations of the underlying molecular mechanisms revealed that intracellular calcium influx,focal adhesion formation,FAK-ERK mechanosensing pathway and neurogenic-related ErbB signaling pathway were implicated in the enhancement of SHED neural differentiation by surface electrical charge.Hence,this study confirms the dose-response effect of biomaterial surface charge on SHED neural differentiation and provides preliminary insights into the molecular mechanisms and signaling pathways involved.

基于循证构建肠内营养护理质量敏感指标体系

目的构建住院成人患者肠内营养护理质量敏感指标体系,为监测临床肠内营养护理质量提供科学、客观及量化的依据。方法运用约翰霍普金斯循证护理方法进行证据综合,为构建肠内营养护理质量敏感指标体系奠定基础;采取小组讨论法获取符合具体实践的指标内容,初步拟订肠内营养护理质量敏感指标及其计算公式和资料收集方法;再通过2轮专家函询,改进并确立肠内营养护理质量敏感指标体系。结果最终构建了包含3项一级指标、6项二级指标、17项三级指标在内的肠内营养护理质量敏感指标体系;2轮函询专家积极系数为92%与100%,权威系数为0.915与0.925,协调系数为0.124～0.242。结论构建的肠内营养护理质量敏感指标体系科学、实用,有利于肠内营养护理质量的改进。

角膜塑形镜控制青少年近视有效性及安全性的Meta分析

目的:就角膜塑形镜对青少年近视患者的有效性及安全性进行Meta分析。方法:循证医学研究。以2017年1月前发表的角膜塑形镜控制儿童近视进展有效性和安全性的临床资料为目标,检索Medline及中国知网、万方数据库。通过Stata11.0对文献进行Meta分析。计算1年和2年时间的眼轴长度改变的加权均数差(WMD)和不良反应发生率的比值比(OR及95%CI),并按研究类型、种族、测量仪器等因素进行亚组分析。结果:共纳入14项研究,病例共2563例,其中塑形镜组1339例,框架镜组1224例。Meta分析结果显示:2年观察中,塑形镜组和框架镜组眼轴的变化量有显著差异,WMD=-0.361,95%CI:-0.604~0.118,1年观察中,塑形镜组和框架镜组眼轴的变化量有显著差异,WMD=-0.356,95%CI:-0.610^-0.102。随访1年后塑形镜组近视控制率为66.6%,随访2年后为51.3%[近视控制率=(塑形镜组眼轴变化量-框架镜组眼轴变化量)/框架镜组眼轴变化量]。2年随访时间内,塑形镜组和框架镜组不良反应发生率的OR=6.408,95%CI:2.460~16.688。结论:角膜塑形镜是一个有效且相对安全的控制儿童近视进展的方法。

石墨烯/金属-有机框架复合材料制备及其应用

金属-有机框架(Metal-Organic Frameworks,MOFs)是由金属离子与有机配体通过配位键连接而成的高度有序多孔网络框架。MOFs具有比表面积大、孔径可调、结构多样等特性,在材料、环境以及生物医药等领域的应用具有潜在的优势。但是,MOFs存在易水解、稳定性较低、导电性差以及不易加工等缺点,与其他材料复合是改善其性能的有效途径之一。石墨烯具有突出的化学稳定性、良好的导电性、光学特性和力学特性等性能。石墨烯与MOFs的复合可有效提高和改善MOFs光电性能、稳定性以及可回收利用性。本综述介绍了原位生长法、界面生长法和共混成型法等石墨烯/MOFs复合材料的制备方法。进一步论述了其在气体分离与存储、水体净化、化学传感器和催化剂领域的应用。最后,对石墨烯/MOFs复合材料制备技术的开发及其潜在应用进行了总结和展望。

Restoration of electrical microenvironment enhances bone regeneration under diabetic conditions by modulating macrophage polarization

Macrophage-mediated inflammation compromises bone repair in diabetic patients.Electrical signaling cues are known to regulate macrophage functions.However,the biological effects of electrical microenvironment from charged biomaterials on the immune response for regulating osteogenesis under diabetic conditions remain to be elucidated.Herein the endogeneous electrical microenvironment of native bone tissue was recapitulated by fabricating a ferroelectric BaTiO_(3)/poly(vinylidene fluoridetrifluoroethylene)(BTO/P(VDF-TrFE))nanocomposite membrane.In vitro,the polarized BaTiO_(3)/poly(vinylidene fluoridetrifluoroethylene)(BTO/P(VDF-TrFE))nanocomposite membranes inhibited high glucose-induced M1-type inflammation,by effecting changes in cell morphology,M1 marker expression and pro-inflammatory cytokine secretion in macrophages.This led to enhanced osteogenic differentiation of human bone marrow mesenchymal stem cells(BM-MSCs).In vivo,the biomimetic electrical microenvironment recapitulated by the polarized nanocomposite membranes switched macrophage phenotype from the pro-inflammatory(M1)into the pro-healing(M2)phenotype,which in turn enhanced bone regeneration in rats with type 2 diabetes mellitus.Mechanistic studies revealed that the biomimetic electrical microenvironment attenuated pro-inflammatory M1 macrophage polarization under hyperglycemic conditions by suppressing expression of AKT2 and IRF5 within the PI3K-AKT signaling pathway,thereby inducing favorable osteo-immunomodulatory effects.Our study thus provides fundamental insights into the biological effects of restoring the electrical microenvironment conducive for osteogenesis under DM conditions,and offers an effective strategy to design functionalized biomaterials for bone regeneration therapy in diabetic patients.

Matrix stiffness modulates tip cell formation through the p-PXN-Rac1-YAP signaling axis

Endothelial tip cell outgrowth of blood-vessel sprouts marks the initiation of angiogenesis which is critical in physiological and pathophysiological procedures.However,how mechanical characteristics of extracellular matrix(ECM)modulates tip cell formation has been largely neglected.In this study,we found enhanced CD31 expression in the stiffening outer layer of hepatocellular carcinoma than in surrounding soft tissues.Stiffened matrix promoted sprouting from endothelial cell(EC)spheroids and upregulated expressions of tip cell-enriched genes in vitro.Moreover,tip cells showed increased cellular stiffness,more actin cytoskeleton organization and enhanced YAP nuclear transfer than stalk and phalanx ECs.We further uncovered that substrate stiffness regulates FAK and Paxillin phosphorylation in focal adhesion of ECs promoting Rac1 transition from inactive to active state.YAP is subsequently activated and translocated into nucleus,leading to increased tip cell specification.p-Paxillin can also loosen the intercellular connection which also facilitates tip cell specification.Collectively our present study shows that matrix stiffness modulates tip cell formation through p-PXN-Rac1-YAP signaling axis,shedding light on the role of mechanotransduction in tip cell formation.This is of special significance in biomaterial design and treatment of some pathological situations.

Dielectric and Ferroelectric Properties of BaTiO_3 Nanofibers Prepared via Electrospinning

BaTiO3 nanofibers of about 400 nm in diameter were synthesized via electrospinning.The evolution of the morphology and phase composition of the BaTiO3 nanofibers was studied by scanning electron microscopy and X-ray diffraction within the annealing temperature of 750-1050 ℃.Higher annealing temperature led to rougher surface and better crystallization of the BaTiO3 nanofibers.Below 1050 ℃,the BaTiO3 nanofibers maintained its large aspect ratios and could still be regarded as individual nanofiber.The dielectric permittivities of the BaTiO3 nanofibers（εr 820） were calculated with the MG equation by considering the porous bulk specimens as composites of BaTiO3 nanofibers and air.The ferroelectric properties of the BaTiO3nanofibers were measured by using a ferroelectric analyzer coupled with an atomic force microscope.P-E loop measured for the BaTiO3 nanofiber exhibits small hysteresis.

Efficacy of a mineralized collagen bone-grafting material for peri-implant bone defect reconstruction in mini pigs

The mechanism of the mineralization process induced by natural mineralized collagen(MC)has been investigated for decades.The purpose of this study was to investigate the efficacy of selfassembled MC for peri-implant bone defect reconstruction in a mini pig.A standardized peri-implant bone defect model was created using 14 mini pig mandibles.Two materials were evaluated,i.e.a mixture of hydroxyapatite and collagen(Type A,TA),and self-assembled MC(Type B,TB).Bio-Oss(BO)and untreated(blank control,BC)groups were used as controls.After 3-and 6-month healing periods,the mini pigs were sacrificed for histomorphometric and microcomputed tomography analysis.After 3 months of healing,the average alveolar ridge height was 3.2761.57mm for group TA,3.28±2.02mm for group TB and 3.37±1.09mm for group BO,while group BC showed the lowest height of 2.68±0.47mm.After 6 months of healing,the average alveolar ridge height was 2.64±1.13mm for group TA,4.31±1.80mm for group TB and 3.8761.38mm for group BO,while group BC showed the lowest height of 2.48±1.80mm.The experimental groups and control group showed similar bone volume density,bone complexity and histological reaction.The self-assembled MC(Type B)stimulated new bone formation in the reconstruction of deficient alveolar ridges around the dental implant;it also displayed excellent clinical operability compared with bone grafts without collagen.

Comparative study on foundation treatment methods of immersed tunnels in China

Based on engineering practices of four typical traffic immersed tunnels built in China,this paper details the features of the four dominant foundation treatment methods for immersed tunnel construction:pile foundation,sand flow foundation,grouting foundation,and gravel bedding foundation.Subsoil stress time-history of different method are specified first,plus a summary of settlement assessment method for foundation quality control.Further,a comprehensive comparison of settlement and cost of these four foundation treatment methods is conducted to highlights the specific merits,disadvantages and conditions encountered in each foundation treatment method,based on real projects information.The findings of this article could henceforth be applied to foundation treatment work in immersed tube tunnel construction.

Ant colonization increased total mercury but reduced methylmercury contents in boreal mires, Northeast China

Soil macroinvertebrates as ecosystem engineers play significant, but largely ignored, roles in affecting mercury(Hg) cycle by altering soil physical-chemical properties. Ant is likely expanded into boreal mires with climate warming, however, its impacts on Hg cycle remained poorly understood. We compared total Hg(THg) and methylmercury(Me Hg) contents in soils from antmounds( Lasius flavus) and the nearby ambient in a boreal mire in Northeast China. The present work seeks to unravel factors that controlling Me Hg levels in case of ant appearance or absence. The average THg was 179 μg/kg in the ant mound and was 106.1 μg/kg in nearby soils, respectively. The average Me Hg was 10.9 μg/kg in the ant mound and was 12.9 μg/kg in nearby soils, respectively. The ratios of Me Hg to THg(%Me Hg) were 7.61% in ant mounds and 16.75% in nearby soils, respectively. Ant colonization caused THg enrichment and Me Hg depletion, and this change was obvious in the 10-20 cm depth soil layer where ants mainly inhabited. Spectrometry characteristics of soil dissolved organic matter(DOM) exert a stronger control than microorganisms on Me Hg variation in soils. A structural equation model revealed that the molecular weight of DOM inhibited Me Hg irrespective of ant presence or absence, while humification conducive to Me Hg significantly in ant mound soils. Microorganisms mainly affected Hg methylation by altering the molecular weight and humification of DOM. We propose that the effects of ant colonization on Me Hg rested on DOM feature variations caused by microorganisms in boreal mires.

Viscoelastic modeling of the stress relaxation behavior for the bionic extracellular matrix polymer scaffold

Viscoelasticity of the extracellular matrix(ECM)plays a critical part in controlling cell behavior.However,the structure-related viscoelasticity of the synthetic ECM and its mechanism are rarely reported.Due to its high tissue similarity,synthetic ECM with structural anisotropy and viscoelasticity holds a great promise for structure and function correlation studies.Here,we reported a series of synthetic composite hydrogel-based ECM with different levels of anisotropic orientation and viscoelastic properties through recently developed post-treatment procedures(the confined pre-strain stretching and drying procedure,the soaking salt solution procedure,and the synergetic sequences of two procedures).Further,by establishing a multimode Maxwell viscoelastic mechanic model,the stress relaxation behavior of the bionic ECM with different levels of anisotropic orientation and viscoelastic properties was simulated successfully.The characteristic viscoelastic parameters of the bionic ECM could also be calculated exactly.This study presented a novel viscoelastic mechanic model for mimicking the key ECM features of the synthetic ECM with anisotropic structure and viscoelasticity properties.