Study of Cell Behaviors on Anodized TiO_2 Nanotube Arrays with Coexisting Multi-Size Diameters

It has been revealed that the different morphologies of anodized TiO_2 nanotubes, especially nanotube diameters, triggered different cell behaviors. However, the influence of TiO_2 nanotubes with coexisting multi-size diameters on cell behaviors is seldom reported. In this work, coexisting four-diameter TiO_2 nanotube samples, namely,one single substrate with the integration of four different nanotube diameters(60, 150, 250, and 350 nm), were prepared by repeated anodization. The boundaries between two different diameter regions show well-organized structure without obvious difference in height. The adhesion behaviors of MC3T3-E1 cells on the coexisting fourdiameter TiO_2 nanotube arrays were investigated. The results exhibit a significant difference of cell density between smaller diameters(60 and 150 nm) and larger diameters(250 and 350 nm) within 24 h incubation with the coexistence of different diameters, which is totally different from that on the single-diameter TiO_2 nanotube arrays. The coexistence of four different diameters does not change greatly the cell morphologies compared with the singlediameter nanotubes. The findings in this work are expected to offer further understanding of the interaction between cells and materials.

Modeling and simulation of an anatomy teaching system

Specimen observation and dissection have been regarded as the best approach to teach anatomy,but due to the severe lack of anatomical specimens in recent years,the quality of anatomy teaching has been seriously affected.In order to disseminate anatomical knowledge effectively under such circumstances,this study discusses three key factors(modeling,perception,and interaction)involved in constructing virtual anatomy teaching systems in detail.To ensure the authenticity,integrity,and accuracy of modeling,detailed three-dimensional(3D)digital anatomical models are constructed using multi-scale data,such as the Chinese Visible Human dataset,clinical imaging data,tissue sections,and other sources.The anatomical knowledge ontology is built according to the needs of the particular teaching purposes.Various kinds of anatomical knowledge and 3D digital anatomical models are organically combined to construct virtual anatomy teaching system by means of virtual reality equipment and technology.The perception of knowledge is realized by the Yi Chuang Digital Human Anatomy Teaching System that we have created.The virtual interaction mode,which is similar to actual anatomical specimen observation and dissection,can enhance the transmissibility of anatomical knowledge.This virtual anatomy teaching system captures the three key factors.It can provide realistic and reusable teaching resources,expand the new medical education model,and effectively improve the quality of anatomy teaching.

NEW NON-NATURALLY REDUCTIVE EINSTEIN METRICS ON Sp(n)

In this paper, we consider a class of left invariant Riemannian metrics on Sp(n),which is invariant under the adjoint action of the subgroup Sp(n-3) × Sp(1) × Sp(1) × Sp(1).Based on the related formulae in the literature, we show that the existence of Einstein metrics is equivalent to the existence of solutions of some homogeneous Einstein equations. Then we use a technique of the Gr?bner basis to get a sufficient condition for the existence, and show that this method will lead to new non-naturally reductive metrics.

Left-Invariant Minimal Unit Vector Fields on the Solvable Lie Group

Bozek(1980)has introduced a class of solvable Lie groups Gn with arbitrary odd dimension to construct irreducible generalized symmetric Riemannian space such that the identity component of its full isometry group is solvable.In this article,the authors provide the set of all left-invariant minimal unit vector fields on the solvable Lie group Gn,and give the relationships between the minimal unit vector fields and the geodesic vector fields,the strongly normal unit vectors respectively.

生物可降解镁植入物——骨肿瘤患者的潜在支架

骨癌患者切除术后可能发生复发和转移.传统的金属支架可以对骨缺损部位提供力学支撑,但无法有效清除复发的肿瘤细胞.本文中,我们介绍了一种可以抑制骨肉瘤生长的生物可降解镁丝植入物.简而言之,镁丝释放镁离子激活锌指蛋白Snail1从胞浆到细胞核的转运,通过下游的miRNA-181d-5p/TIMP3和miRNA-181c-5p/NLK两条平行的抗肿瘤信号通路诱导骨肉瘤细胞凋亡,抑制骨肉瘤细胞增殖.同时,镁丝释放出的氢气消除了细胞内过多的活性氧,从而抑制了骨肿瘤细胞的生长.裸鼠骨肉瘤细胞皮下荷瘤实验进一步证实镁丝能有效抑制肿瘤生长,延长荷瘤小鼠生存期.此外,镁丝对正常细胞和组织无毒性,揭示了镁植入物是骨肉瘤患者潜在的抗肿瘤支架材料.

Translational status of biomedical Mg devices in China

Magnesium(Mg)and its alloys as temporary medical implants with biodegradable and properly mechanical properties have been investigated for a long time.There are already three kinds of biodegradable Mg implants which are approved by Conformite Europeene(CE)or Korea Food and Drug Administration(KFDA),but not China Food and Drug Administration(CFDA,now it is National Medical Products Administration,NMPA).As we know,Chinese researchers,surgeons,and entrepreneurs have tried a lot to research and develop biodegradable Mg implants which might become other new approved implants for clinical applications.So in this review,we present the representative Mg implants of three categories,orthopedic implants,surgical implants,and intervention implants and provide an overview of current achievement in China from academic publications and Chinese patents.We would like to provide a systematic way to translate Mg and its alloy implants from experiment designs to clinical products.

Research of a novel biodegradable surgical staple made of high purity magnesium

Surgical staples made of pure titanium and titanium alloys are widely used in gastrointestinal anastomosis.However the Ti staple cannot be absorbed in human body and produce artifacts on computed tomography(CT)and other imaging examination,and cause the risk of incorrect diagnosis.The bioabsorbable staple made from polymers that can degrade in human body environment,is an alternative.In the present study,biodegradable high purity magnesium staples were developed for gastric anastomosis.U-shape staples with two different interior angles,namely original 90
and modified 100
,were designed.Finite element analysis(FEA)showed that the residual stress concentrated on the arc part when the original staple was closed to B-shape,while it concentrated on the feet for the modified staple after closure.The in vitro tests indicated that the arc part of the original staple ruptured firstly after 7 days immersion,whereas the modified one kept intact,demonstrating residual stress greatly affected the corrosion behavior of the HP-Mg staples.The in vivo implantation showed good biocompatibility of the modified Mg staples,without inflammatory reaction 9 weeks post-operation.The Mg staples kept good closure to the Anastomosis,no leaking and bleeding were found,and the staples exhibited no fracture or severe corrosion cracks during the degradation.

High-purity magnesium pin enhances bone consolidation in distraction osteogenesis via regulating Ptch protein activating Hedgehog-alternative Wnt signaling

Magnesium alloys are promising biomaterials for orthopedic implants because of their degradability,osteogenic effects,and biocompatibility.Magnesium has been proven to promote distraction osteogenesis.However,its mechanism of promoting distraction osteogenesis is not thoroughly studied.In this work,a high-purity magnesium pin developed and applied in rat femur distraction osteogenesis.Mechanical test,radiological and histological analysis suggested that high-purity magnesium pin can promote distraction osteogenesis and shorten the consolidation time.Further RNA sequencing investigation found that alternative Wnt signaling was activated.In further bioinformatics analysis,it was found that the Hedgehog pathway is the upstream signaling pathway of the alternative Wnt pathway.We found that Ptch protein is a potential target of magnesium and verified by molecular dynamics that magnesium ions can bind to Ptch protein.In conclusion,HP Mg implants have the potential to enhance bone consolidation in the DO application,and this process might be via regulating Ptch protein activating Hedgehog-alternative Wnt signaling.

A novel lean alloy of biodegradable Mg-2Zn with nanograins

Lean alloy(low alloyed)is beneficial for long-term sustainable development of metal materials.Creating a nanocrystalline microstructure is a desirable approach to improve biodegradability and mechanical properties of lean biomedical Mg alloy,but it is nearly impossible to realize.In the present study,the bulk nanocrystalline Mg alloy(average grain size:~70 nm)was successfully obtained by hot rolling process of a lean Mg-2wt.%Zn(Z2)alloy and both high strength((223 MPa(YS)and 260 MPa(UTS))and good corrosion resistance(corrosion rate in vivo:0.2 mm/year)could be achieved.The microstructure evolution during the rolling process was analyzed and discussed.Several factors including large strain,fine grains,strong basal texture,high temperature and Zn segregation conjointly provided the possibility for the activation of pyramidal<c+a>slip to produce nanocrystals.This finding could provide a new development direction and field of application for lean biomedical Mg alloys.

Hybrid zeolite-based ion-exchange and sulfur oxidizing denitrification for advanced slaughterhouse wastewater treatment

The discharge of slaughterhouse wastewater(SWW)is increasing and its wastewater has to be treated thoroughly to avoid the eutrophication.The hybrid zeolite-based ion-exchange and sulfur autotrophic denitrification(IX-AD)process was developed to advanced treat SWW after traditional secondary biological process.Compared with traditional sulfur oxidizing denitrification(SOD),this study found that IX-AD column showed:(1)stronger ability to resist NO_(3)^(-) pollution load,(2)lower SO_(4)^(2-) productivity,and(3)higher microbial diversity and richness.Liaoning zeolites addition guaranteed not only the standard discharge of NH_(4)^(+)-N,but also the denitrification performance and effluent TN.Especially,when the ahead secondary biological treatment process run at the ultra-high load,NO_(3)-N removal efficiency for IX-AD column was still~100%,whereas only 64.2%for control SOD column.The corresponding average effluent TN concentrations for IX-AD and SOD columns were 5.89 and 65.55 mg/L,respectively.Therefore,IX-AD is a promising technology for advanced SWW treatment and should be widely researched and popularized.

Site-Dependent Osseointegration of Biodegradable High-Purity Magnesium for Orthopedic Implants in Femoral Shaft and Femoral Condyle of New Zealand Rabbits

Magnesium （Mg） has been widely accepted as osteoconductive biomaterial, but osseointegration of Mg device at different implantation sites is still unclear. In the present study, high-purity magnesium （HP Mg） pins were implanted into femoral shaft and condyle of New Zealand rabbits concurrently. 2, 8, 12 and 16 weeks after surgery, rabbit femurs were harvested for micro-computed tomography （micro-CT） scanning and subsequent histological examinations. HP Mg pins were retrieved for scanning electron microscope and energy dispersive spectrum （SEM/EDS） analyses. HP Mg pins at both implantation sites performed stable corrosion with mineral deposition and bone incorporation on surface. However, difference in distribution of contact osteogenesis centers and biological properties of peri-implant bone tissues was detected between femoral shaft and femoral condyle. In femoral condyle, contact osteogenesis centers originated from both periosteum and cancellous bones and the whole HP Mg pin was encapsuled in trabecular bone at 16 weeks. Meanwhile, bone volume to total bone volume （BV/TV） and bone mineral density （BMD） of peri-implant bone tissues were above those of normal bone tissues. In femoral shaft, contact osteogenesis centers were only from periosteum and direct bone contact was confined in cortical bone, while BV/TV and BMD kept lower than normal. Furthermore, new formation of peri-implant bone tissues was more active in femoral condyle than in femoral shaft at 16 weeks. Therefore, although HP Mg performed good biocompatibility and corrosion behavior in vivo, its bioadaption of osseointegration at different implantations sites should be taken into consideration. Bone metaphysic was suitable for Mg devices where peri-implant bone tissues regenerated rapidly and the biological properties were close to normal bone tissues.

Comparative Study about Degradation of High-purity Magnesium Screw in Intact Femoral Intracondyle and in Fixation of Femoral Intracondylar Fracture

Bone screws encounter complex mechanical environment in fracture fixation of weight-bearing bone.In the present study, high-purity magnesium（HP Mg） screws were applied in fixation of rabbit femoral intracondylar fracture with 3 mm gap. In the control group, HP Mg screws of the same design were implanted at corresponding position of contralateral leg. At 4, 8 and 16 weeks after surgery, retrieved femurs went through micro-computed tomography（micro-CT） scanning and hard tissue processing. Under mechanical stress involved in fracture fixation, bending of screw bolt was observed at the portion exposed to facture gap at 4 weeks. Then local corrosion at the same portion was detected 16 weeks after surgery,which indicated the accumulation effect of mechanical stress on Mg corrosion. HP Mg screws in the fracture group had no significant difference with the control group in screw volume, surface area, surfaceto-volume ratio（S/V）. And peri-implant bone volume/tissues volume（BV/TV） and bone volume density（BMD） in the fracture group was comparable to that in the control group. Furthermore, histological analysis showed new formed bone tissues in fracture gap and fracture healing 16 weeks after surgery. Under mechanical stress, HP Mg screw suffered bolt bending and local corrosion at the portion exposed to fracture gap. But it had no influence on the integral corrosion behaviors, osseointegration of HP Mg screw and the fracture healing. Therefore, HP Mg screws possessed good potential in fracture fixation of weightbearing bones.

In vitro crevice corrosion of biodegradable magnesium in different solutions

Magnesium(Mg)is a promising biomedical metal because of its biodegradability.The crevice between tissue and Mg implant can not be neglected in some implantation sites due to inducing crevice corrosion of Mg.In this paper,a new single mold was designed to build the in vitro experimental setup and four kinds of solutions,i.e.the deionized water(DW),the 0.9 wt.%sodium chloride solution(NaCl),the phosphate buffer saline(PBS)and the modified simulated body fluid(m-SBF)were used to explore necessary factors of crevice corrosion in Mg.It was observed that crevice corrosion in Mg sheets would occur in NaCl and PBS solution under 0.2,0.5 and 0.8 mm crevice thickness.And it was found that there were two necessary factors,i.e.chloride ion and crevice dimension,in crevice corrosion.For the high-purity Mg cannulated screws,crevice corrosion could occur inside tunnel when immersed in PBS.