Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not...Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.展开更多
In the present work,seven Mg-Zn-Ag alloys with the nominal composition of Mg_(96-x)Zn_(x)Ag_(4)(x=17,20,23,26,29,32,35 in at.%)were prepared by induction melting and single-roller melt-spinning.The X-ray diffraction(X...In the present work,seven Mg-Zn-Ag alloys with the nominal composition of Mg_(96-x)Zn_(x)Ag_(4)(x=17,20,23,26,29,32,35 in at.%)were prepared by induction melting and single-roller melt-spinning.The X-ray diffraction(XRD)analyses indicate the metallic glasses with three composition of Mg_(73)Zn_(23)Ag_(4),Mg_(70)Zn_(26)Ag_(4),and Mg_(67)Zn_(29)Ag_(4)were obtained successfully.The differential scanning calorimetry(DSC)measurement was used to obtain the characteristic temperature of Mg-Zn-Ag metallic glasses for the glass-forming ability analysis.The maximum glass transition temperature(Trg)was found to be 0.525 with a composition close to Mg_(67)Zn_(29)Ag_(4),which results in the best glass-forming ability.Moreover,the immersion test in simulated body fluid(SBF)demonstrate the relative homogeneous corrosion behavior of the Mg-Zn-Ag metallic glasses.The corrosion rate of Mg-Zn-Ag metallic glasses in SBF solution decreases with the increase of Zn content.The sample Mg_(67)Zn_(29)Ag_(4)has the lowest corrosion rate of 0.19mm/yr,which could meet the clinical application requirement well.The in vitro cell experiments show that the Madin-Darby canine kidney(MDCK)cells cultured in sample Mg_(67)Zn_(29)Ag_(4)and its extraction medium have higher activity.However,the Mg-Zn-Ag metallic glasses exhibit obvious inhibitory effect on human rhabdomyosarcoma(RD)tumor cells.The present investigations on the glass-forming ability,corrosion behavior,cytocompatibility and tumor inhibition function of the Mg-Zn-Ag based metallic glass could reveal their biomedical application possibility.展开更多
In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion ...In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion behavior of the PEO coatings are investigated systematically.The results reveal that the introduction of NaF promotes the formation of MgF2 nanophases in the passivation layer on Mg alloy,decreasing the breakdown voltage and discharge voltage.As a result,the continuous arcing caused by high discharge voltage is alleviated.With the increasing of NaF content,the Zn content in the PEO coating is enhanced and the pore size in the coating is decreased correspondingly.Due to the high-content ZnO doping,the PEO coating protected AZ31B alloy demonstrates the better corrosion resistance.Compared with the bare AZ31B alloy,the high-content ZnO doped PEO coated sample shows an increased corrosion potential from-1.465 V to-1.008 V,a decreased corrosion current density from 3.043×10^(-5) A·cm^(-2) to 3.960×10^(-8) A·cm^(-2) and an increased charge transfer resistance from 1.213×10^(2) ohm·cm^(2) to 2.598×10^(5) ohm·cm^(2).Besides,the high-content ZnO doped PEO coated sample also has the excellent corrosion resistance in salt solution,exhibiting no obvious corrosion after more than 2000 h neutral salt spraying and 28 days’immersion testing.The improved corrosion resistance can be ascribed to the relative uniform distribution of ZnO in PEO coating which can transform to Zn(OH)2 and form a continuous protective layer along the corrosion interface.展开更多
Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples...Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.展开更多
Infections with multidrug-resistant(MDR)Gram-negative bacteria,such as MDR Escherichia coli(E.coli),remain a challenge due to the lack of safe antibiotics and high fatality rates under anti-infection therapies.This wo...Infections with multidrug-resistant(MDR)Gram-negative bacteria,such as MDR Escherichia coli(E.coli),remain a challenge due to the lack of safe antibiotics and high fatality rates under anti-infection therapies.This work presents a form of biomimetic intelligent catalysis inspired by the selective biocatalytic property of macrophages(MΦs),consisting of an intelligent controlling center(a living MΦ)and a Fenton reaction catalyst(Fe_(3)O_(4)@poly(lactic-co-glycolic acid)(PLGA)nanoparticles)for killing MDR E.coli without harming normal cells.The MΦ-Fe_(3)O_(4)@PLGA particles(i.e.,the intelligent catalysis particles)exhibit selective biocatalysis activity toward MDR E.coli by producing H_(2)O_(2) and lipid droplets(LDs).This process activates the lipid metabolism and glycan biosynthesis and metabolism pathways based on the result of RNA sequencing data analysis.The H_(2)O_(2) further reacts with Fe_(3)O_(4)@PLGA to form highly toxic hydroxyl radicals(·OH),while the LDs contain antimicrobial peptides and can target MDR E.coli.The highly toxicOH and antimicrobial peptides are shown to combat with MDR E.coli,such that the antibacterial efficiency of the MΦ-Fe_(3)O_(4)@PLGA particles against MDR E.coli is 99.29%±0.31%in vitro.More importantly,after several passages,the intelligent catalysis function of the MΦ-Fe_(3)O_(4)@PLGA particles is well maintained.Hence,the concept of biomimetic intelligent catalysts displays potential for treating diseases other than infections.展开更多
A new ternary compound,Mg_(11-x)Zn_(x)Sr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy(SEM),Energy-Dispersive Spectroscope(EDS),X-Ray Diffraction(XRD)and Transmission Electron Micr...A new ternary compound,Mg_(11-x)Zn_(x)Sr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy(SEM),Energy-Dispersive Spectroscope(EDS),X-Ray Diffraction(XRD)and Transmission Electron Microscopy(TEM).The XRD patterns were refined by the Rietveld refinement method and the results revealed that the crystallized Mg_(11-x)Zn_(x)Sr phase belonged to tetragonal I41/amd space group and had the Cd_(11)Ba prototype.The Mg atoms were successfully doped into Zn_(11)Sr crystal lattice by occupying Zn atomic sites.Moreover,the Rietveld refinement and computational results demonstrated a gradual decrease in the a-axis and c-axis lattice parameters with decreasing concentration levels of Mg coordination substitution in the lattice of Mg_(11-x)Zn_(x)Sr compound.The elastic constants and modulus of the Mg_(11-x)Zn_(x)Sr compounds calculated by first-principles calculations(FPC)indicated they were increased with the increasing of Zn content.The variation of hardness,D-band widths and the total density of states for Mg_(11-x)Zn_(x)Sr compounds with Zn content was discussed.展开更多
Cancer is a major threat to human life worldwide. Traditional cancer treatments, such as chemotherapy and surgery, have major limitations and can cause irreversible damage to normal tissues while killing the cancer ce...Cancer is a major threat to human life worldwide. Traditional cancer treatments, such as chemotherapy and surgery, have major limitations and can cause irreversible damage to normal tissues while killing the cancer cells. Magnesium(Mg) alloys are widely reported novel potential biomedical materials with acceptable mechanical properties and good osteogenic and angiogenic properties. In this review, we summarize the Mg alloys for antitumor applications, including pure Mg and Mg alloys(Mg-Ag, Mg-Gd, Mg-Li-Zn, Mg-Ca-Sr-Zn, et al.) fabricated by casting and extruding, selective laser melting methods. Mg alloys can exhibit antitumor effect on bone tumor, breast cancer, and liver tumor,etal. What's more, after tumor tissue is eliminated, Mg alloys prevent tumor recurrence, fill tissue defects and promote tissue regeneration.The antitumor effects of Mg alloys are mainly due to their degradation products. Overall, Mg alloys show great potential in tumor treatments due to the dual function of antitumor and tissue regeneration.展开更多
Magnesium-based biodegradable metals as cardiovascular stents have shown a lot of excellent performance, which have been used to treat coronary artery diseases. However, the excessive degradation rate, imperfect bioco...Magnesium-based biodegradable metals as cardiovascular stents have shown a lot of excellent performance, which have been used to treat coronary artery diseases. However, the excessive degradation rate, imperfect biocompatibility and delayed re-endothelialization still lead to a considerable challenge for its application. In this work, to overcome these shortcomings, a compound of catalyzing nitric oxide(NO) generation containing copper ions(Cu^(2+)) and hyaluronic acid(HA), an important component of the extracellular matrix, were covalently immobilized on a hydrofluoric acid(HF)-pretreated ZE21B alloy via amination layer for improving its corrosion resistance and endothelialization. Specifically,the Cu^(2+) chelated firmly with a cyclen 1,4,7,10-tetraazacyclododecane-N’, N’’, N’’’, N-tetraacetic acid(DOTA) could form a stability of hybrid coating, avoiding the explosion of Cu^(2+). The chelated Cu^(2+) enabled the catalytic generation of NO and promoted the adhesion and proliferation of endothelial cells(ECs) in vascular micro-environment. In this case, the synergistic effect of NO-generation and endothelial glycocalyx molecules of HA lead to efficient ECs promotion and smooth muscle cells(SMCs) inhibition. Meanwhile, the blood compatibility also had achieved a marked improvement. Moreover, the standard electrochemical measurements indicated that the functionalized ZE21B alloy had better anti-corrosion ability. In a conclusion, the dual-functional coating displays a great potential in the field of biodegradable magnesium-based implantable cardiovascular stents.展开更多
Venous sinus stent implantation is an emerging endovascular treatment technique effectively applied in diseases such as cerebral venous sinus thrombosis.However,arterial stents are commonly used in clinical practice f...Venous sinus stent implantation is an emerging endovascular treatment technique effectively applied in diseases such as cerebral venous sinus thrombosis.However,arterial stents are commonly used in clinical practice for venous sinus stent implantation,which is off-label and carries high risks and poor prognosis,highlighting the necessity of developing venous sinus-specific stents.This narrative review discusses the current situation and problems of venous sinus stent implantation and looks forward to the design focus and future development prospects of venous sinus-specific stents.展开更多
The sustained-release properties of the biodegradable nano-drug delivery systems were used to improve the residence time of the chemotherapeutic agent in the body. These drug delivery systems were widely used to deliv...The sustained-release properties of the biodegradable nano-drug delivery systems were used to improve the residence time of the chemotherapeutic agent in the body. These drug delivery systems were widely used to deliver chemotherapeutic drugs. The 5-fluorouracil loaded chitosan nanoparticles prepared in this paper have the above advantage. Here, we found that when the mass ratio of 5-fluorouracil and chitosan was 1:1, the maximum drug loading of nanoparticles was 20.13 ± 0.007%, the encapsulation efficiency was 44.28 ± 1.69%, the particle size was 283.9 ± 5.25 nm and the zeta potential was 45.3 ± 3.23 mV. The prepared nanoparticles had both burst-release and sustained-release phases in vitro release studies.In addition, the inhibitory effect of the prepared nanoparticles on gastric cancer SGC-7901 cells was similar to that of 5-fluorouracil injection, and the blank vector had no obvious inhibitory effect on SGC-7901 cells. In the pharmacokinetic study of rats in vivo, we found that AUC(0-t), MRT(0-t) and t1/2 z of nanoparticles were significantly increased in vivo compared with 5-fluorouracil solution, indicating that the prepared nanoparticles can play a role in sustained-release.展开更多
ZnS nanobelts with large aspect ratio are successfully synthesized on a large scale through thermally evaporating of ZnS powder with a trace of SnO_2 powder using gold coated Si wafer as the substrate at 1100°C.T...ZnS nanobelts with large aspect ratio are successfully synthesized on a large scale through thermally evaporating of ZnS powder with a trace of SnO_2 powder using gold coated Si wafer as the substrate at 1100°C.The results indicate that the as-obtained ZnS nanobelts are about 10 nm in thickness and hundreds of micrometers in length,and the aspect ratio reaches more than 104.Substrate dependent experiments are conducted to better study the growth mechanism of the ZnS nanobelts.Subsequently,optical properties of the as-synthesized ZnS nanobelts are also investigated by using a cathodoluminescence(CL) system,which shows the existence of a strong ultraviolet emission at 342 nm and two poor emission peaks at 522 nm and 683 nm at room temperature,respectively.展开更多
In the present work,the biomedical as-cast pure Mg,Mg–1 Ca and Mg–2 Sr alloys were processed with equal channel angular pressing(ECAP)technique to develop ultrafine microstructure within the materials,and their micr...In the present work,the biomedical as-cast pure Mg,Mg–1 Ca and Mg–2 Sr alloys were processed with equal channel angular pressing(ECAP)technique to develop ultrafine microstructure within the materials,and their microstructures,mechanical properties,degradation behavior,cytocompatibility in vitro and biocompatibility in vivo were studied comprehensively.Finer-gained microstructures and improved mechanical properties of these three materials after ECAP were confirmed compared to their as-cast counterparts.Moreover,after ECAP the degradation rate of pure Mg was increased while that of Mg–1 Ca or Mg–2 Sr alloys decreased compared to the ascast counterparts.Additionally,good in vitro cytocompatibility and in vivo biocompatibility of these three materials were revealed by cell cultural tests using osteoblastic MC3 T3-E1 and human mesenchymal stem cells(h MSC)and in vivo animal tests at the lateral epicondyle of SD-rats’femur.This study offers an alternative powerful avenue to achieve good comprehensive properties of magnesium-based biodegradable metals.It might also help to extend the applied range of magnesium-based biodegradable metals in orthopedic field.展开更多
A new species,Synanthedon elaeagnus sp.nov.feeding on Elaeagnus mollis,is described from Shanxi,China.This new species is similar to Synanthedon ulmicola Yang&Wang,1989 in general morphology,but it differs from th...A new species,Synanthedon elaeagnus sp.nov.feeding on Elaeagnus mollis,is described from Shanxi,China.This new species is similar to Synanthedon ulmicola Yang&Wang,1989 in general morphology,but it differs from this latter species by features of the forewing,female and male genitalia.Neighbor-joining and maximum likelihood analysis both recover Synanthedon elaeagnus sp.nov.as a well-supported monophyletic lineage with a high support value based on COI gene sequences.The key features of this new species are illustrated.展开更多
The effect of annealing temperature on the formation of the PtSi phase. distribution of silicides and the surface morphologies of silicides films is investigated by XPS. AFM. It is shown that the phase sequences of t...The effect of annealing temperature on the formation of the PtSi phase. distribution of silicides and the surface morphologies of silicides films is investigated by XPS. AFM. It is shown that the phase sequences of the films change from Pt-Pt2Si-PtSi-Si to Pt+Pt2Si+PtSi-PtSi-Si or Pt+Pt2Si+PtSi-PtSi-st with an increase of annealing temperature and the reason for the formation of mixed layers is discussed.展开更多
The nanohydroxyapatites (HAP) and its biological effects have been studied using ultraviolet absorption spectrum, X-ray diffraction (XRD) structure analysis, fluorescent and infrared spectrum of absorption and MTT met...The nanohydroxyapatites (HAP) and its biological effects have been studied using ultraviolet absorption spectrum, X-ray diffraction (XRD) structure analysis, fluorescent and infrared spectrum of absorption and MTT method. The nanohyd- roxyapatites are prepared and made by using Sol-gel method, in which the parameters of process and reaction are controlled as: PH 】9, Ca/P = 1.67, sintering temperature of 1100?C and sintering time 2 hours. The results of the study show that nanohydroxyapatites can absorb the amino acid molecules, the absorption is better for stronger acidity of amino acids. We also find that the nanohydroxyapatites and complex of nanoHAP+ nanoCrO2 can all restrain the proliferation of cells, but their toxiciteis are all first degree or minor, but the restrained effect of the latter is smaller than that of the former, although they can decrease the relative proliferation rate of cells. The nanohydroxyapatites can also change the molecular structure of human serum albumin.展开更多
The solidified microstructure of a Ni-Cu-Si cast alloy has been investigated, and a kind of banding structure was observed. The results showed that, the banding structure was composed of coarser particles which were N...The solidified microstructure of a Ni-Cu-Si cast alloy has been investigated, and a kind of banding structure was observed. The results showed that, the banding structure was composed of coarser particles which were Ni3Si type of precipitates and similar to the fine particles precipitate uniformly distributed within matrix of Ni solid solution, in both crystal structure and composition. The formation of bandings was resulted from cast thermal stress and dislocation walls. It was found that the cracks propagated along these bandings in tensile test. The banding structure can be depressed by reducing the cast thermal stress, which can improve the tensile ductility.展开更多
Detailed crystallographic analysis has been undertaken on the various combinations Of 24 martensite variants in the 18R martensite of a Cu-Zn-Al shape memory alloy. Based upon the calculated crystallographic data, the...Detailed crystallographic analysis has been undertaken on the various combinations Of 24 martensite variants in the 18R martensite of a Cu-Zn-Al shape memory alloy. Based upon the calculated crystallographic data, the interface energy of different twin interfaces was calculated using a lowangle-grain-interface model. For the variant/variant pairs in a self-accommodating group. the A/C type and A/B type interfaces have low interface energy, and A/D type interface is an intermediate one. In contrast, the intervariant interfaces that belong to different plate groups have high intrface energy. The calculated results are consiStent with the previous observations of the mobility of intervariant interfaces.展开更多
Magnesium alloys with unique biodegradable trait raise great interests among researchers.However,overquick degradation rate has become the biggest problem limiting the further application of biodegradable magnesium al...Magnesium alloys with unique biodegradable trait raise great interests among researchers.However,overquick degradation rate has become the biggest problem limiting the further application of biodegradable magnesium alloys1.Plasma ion implantation has been considered good and convinient sur-展开更多
Laser powder bed fusion(L-PBF)has been used to fabricate biodegradable Mg implants of WE43 alloy,but the degradation is too fast compared with the term bone reconstruction.Previous studies show that high temperature o...Laser powder bed fusion(L-PBF)has been used to fabricate biodegradable Mg implants of WE43 alloy,but the degradation is too fast compared with the term bone reconstruction.Previous studies show that high temperature oxidation(HTO)can successfully inhibit the degradation of WE43 alloy.In this work,the influence of HTO on L-PBF samples of WE43 alloy was investigated regarding tensile,compressive,and abrasive resistance,as well as in vitro cytotoxicity,cell proliferation,hemolysis,and osteogenesis.Compared with the as-built L-PBF samples,HTO increased grain size and grain texture,stabilized and coarsened precipitates,and caused discontinuous static recrystallization in the matrix.The oxide layer at the surface of the HTO samples improved surface roughness,hydrophilia,hardness,and abrasive resis-tance.The tensile strength decreased slightly from 292 to 265 MPa,while the elongation substantially increased from 10.97%to 16.58%after HTO.The in vitro cell viability,cell proliferation,hemolysis,and osteogenic effect were considerably enhanced due to the improvement of surface quality and the initial inhibition of excessive Mg^(2+)releasement.Overall,HTO is of great benefit to the surface performance,ductility,and biocompatibility of WE43 alloy fabricated by L-PBF for biodegradable applications.展开更多
Postoperative anatomical reconstruction and prevention of local recurrence after tumor resection are two vital clinical challenges in osteosarcoma treatment.A three-dimensional(3D)-printed porous Ti6Al4V scaffold(3DTi...Postoperative anatomical reconstruction and prevention of local recurrence after tumor resection are two vital clinical challenges in osteosarcoma treatment.A three-dimensional(3D)-printed porous Ti6Al4V scaffold(3DTi)is an ideal material for reconstructing critical bone defects with numerous advantages over traditional implants,including a lower elasticity modulus,stronger bone-implant interlock,and larger drug-loading space.Simvastatin is a multitarget drug with anti-tumor and osteogenic potential;however,its efficiency is unsatisfactory when delivered systematically.Here,simvastatin was loaded into a 3DTi using a thermosensitive poly(lactic-co-gly-colic)acid(PLGA)-polyethylene glycol(PEG)-PLGA hydrogel as a carrier to exert anti-osteosarcoma and oste-ogenic effects.Newly constructed simvastatin/hydrogel-loaded 3DTi(Sim-3DTi)was comprehensively appraised,and its newfound anti-osteosarcoma mechanism was explained.Specifically,in a bone defect model of rabbit condyles,Sim-3DTi exhibited enhanced osteogenesis,bone in-growth,and osseointegration compared with 3DTi alone,with greater bone morphogenetic protein 2 expression.In our nude mice model,simvastatin loading reduced tumor volume by 59%-77%without organic damage,implying good anti-osteosarcoma activity and biosafety.Furthermore,Sim-3DTi induced ferroptosis by upregulating transferrin and nicotinamide adenine dinucleotide phosphate oxidase 2 levels in osteosarcoma both in vivo and in vitro.Sim-3DTi is a promising osteogenic bone substitute for osteosarcoma-related bone defects,with a ferroptosis-mediated anti-osteosarcoma effect.展开更多
基金funded by the National Key Research and Development Program of China(2018YFE0104200)National Natural Science Foundation of China(51875310,52175274,82172065)Tsinghua Precision Medicine Foundation.
文摘Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.
基金National Key Research and Development Program of China(2018YFC1106702)Guangdong Basic and Applied Basic Research Foundation(2020A1515011301,2019A1515110067 and 2020A1515110055)+1 种基金Shenzhen Basic Research Project(JCYJ20210324120001003,JCYJ20200109144608205 and JCYJ20200109144604020)IER Foundation(HT-JDCXY-201902 and HT-JD-CXY-201907)for financial support.
文摘In the present work,seven Mg-Zn-Ag alloys with the nominal composition of Mg_(96-x)Zn_(x)Ag_(4)(x=17,20,23,26,29,32,35 in at.%)were prepared by induction melting and single-roller melt-spinning.The X-ray diffraction(XRD)analyses indicate the metallic glasses with three composition of Mg_(73)Zn_(23)Ag_(4),Mg_(70)Zn_(26)Ag_(4),and Mg_(67)Zn_(29)Ag_(4)were obtained successfully.The differential scanning calorimetry(DSC)measurement was used to obtain the characteristic temperature of Mg-Zn-Ag metallic glasses for the glass-forming ability analysis.The maximum glass transition temperature(Trg)was found to be 0.525 with a composition close to Mg_(67)Zn_(29)Ag_(4),which results in the best glass-forming ability.Moreover,the immersion test in simulated body fluid(SBF)demonstrate the relative homogeneous corrosion behavior of the Mg-Zn-Ag metallic glasses.The corrosion rate of Mg-Zn-Ag metallic glasses in SBF solution decreases with the increase of Zn content.The sample Mg_(67)Zn_(29)Ag_(4)has the lowest corrosion rate of 0.19mm/yr,which could meet the clinical application requirement well.The in vitro cell experiments show that the Madin-Darby canine kidney(MDCK)cells cultured in sample Mg_(67)Zn_(29)Ag_(4)and its extraction medium have higher activity.However,the Mg-Zn-Ag metallic glasses exhibit obvious inhibitory effect on human rhabdomyosarcoma(RD)tumor cells.The present investigations on the glass-forming ability,corrosion behavior,cytocompatibility and tumor inhibition function of the Mg-Zn-Ag based metallic glass could reveal their biomedical application possibility.
基金supported by the 2022 Shenzhen sustainable supporting funds for colleges and universities(20220810143642004)Shenzhen Basic Research Project(JCYJ20200109144608205 and JCYJ20210324120001003)+5 种基金Peking University Shenzhen Graduate School Research Startup Fund of Introducing Talent(No.1270110273)Shenzhen postdoctoral research fund project after outbound(No.2129933651)Shenzhen-Hong Kong Research and Development Fund(No.SGDX20201103095406024)City University of Hong Kong Strategic Research Grants(SRG)(Nos.7005264 and 7005505)Guangdong-Hong Kong Technology Cooperation Funding Scheme(TCFS)(No.GHP/085/18SZ)IER Foundation(IERF2020001 and IERF2019002).
文摘In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion behavior of the PEO coatings are investigated systematically.The results reveal that the introduction of NaF promotes the formation of MgF2 nanophases in the passivation layer on Mg alloy,decreasing the breakdown voltage and discharge voltage.As a result,the continuous arcing caused by high discharge voltage is alleviated.With the increasing of NaF content,the Zn content in the PEO coating is enhanced and the pore size in the coating is decreased correspondingly.Due to the high-content ZnO doping,the PEO coating protected AZ31B alloy demonstrates the better corrosion resistance.Compared with the bare AZ31B alloy,the high-content ZnO doped PEO coated sample shows an increased corrosion potential from-1.465 V to-1.008 V,a decreased corrosion current density from 3.043×10^(-5) A·cm^(-2) to 3.960×10^(-8) A·cm^(-2) and an increased charge transfer resistance from 1.213×10^(2) ohm·cm^(2) to 2.598×10^(5) ohm·cm^(2).Besides,the high-content ZnO doped PEO coated sample also has the excellent corrosion resistance in salt solution,exhibiting no obvious corrosion after more than 2000 h neutral salt spraying and 28 days’immersion testing.The improved corrosion resistance can be ascribed to the relative uniform distribution of ZnO in PEO coating which can transform to Zn(OH)2 and form a continuous protective layer along the corrosion interface.
基金funded by the National Key Research and Development Program of China (2018YFE0104200)National Natural Science Foundation of China (51875310, 52175274, 82172065)Tsinghua Precision Medicine Foundation
文摘Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.
基金supported by the China National Funds for Distinguished Young Scientists (51925104)the National Natural Science Foundation of China (NSFC) (51871162 and 52173251)+1 种基金NSFC-Guangdong Province Joint Program (U21A2084)the Central Guidance on Local Science and Technology Development Fund of Hebei Province (226Z1303G).
文摘Infections with multidrug-resistant(MDR)Gram-negative bacteria,such as MDR Escherichia coli(E.coli),remain a challenge due to the lack of safe antibiotics and high fatality rates under anti-infection therapies.This work presents a form of biomimetic intelligent catalysis inspired by the selective biocatalytic property of macrophages(MΦs),consisting of an intelligent controlling center(a living MΦ)and a Fenton reaction catalyst(Fe_(3)O_(4)@poly(lactic-co-glycolic acid)(PLGA)nanoparticles)for killing MDR E.coli without harming normal cells.The MΦ-Fe_(3)O_(4)@PLGA particles(i.e.,the intelligent catalysis particles)exhibit selective biocatalysis activity toward MDR E.coli by producing H_(2)O_(2) and lipid droplets(LDs).This process activates the lipid metabolism and glycan biosynthesis and metabolism pathways based on the result of RNA sequencing data analysis.The H_(2)O_(2) further reacts with Fe_(3)O_(4)@PLGA to form highly toxic hydroxyl radicals(·OH),while the LDs contain antimicrobial peptides and can target MDR E.coli.The highly toxicOH and antimicrobial peptides are shown to combat with MDR E.coli,such that the antibacterial efficiency of the MΦ-Fe_(3)O_(4)@PLGA particles against MDR E.coli is 99.29%±0.31%in vitro.More importantly,after several passages,the intelligent catalysis function of the MΦ-Fe_(3)O_(4)@PLGA particles is well maintained.Hence,the concept of biomimetic intelligent catalysts displays potential for treating diseases other than infections.
基金the National Key Research and Development Program of China(grant numbers 2018YFC1106702)the Natural Science Foundation of Guangdong Province,China(grant numbers 2020A1515011301,2018A0303100018 and 2018A030313950)+1 种基金Shenzhen Basic Research Project(grant numbers JCYJ20170815153143221,JCYJ20200109144608205 and JCYJ20170815153210359)IER Foundation(HT-JD-CXY-201902 and HT-JD-CXY201907)for financial support
文摘A new ternary compound,Mg_(11-x)Zn_(x)Sr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy(SEM),Energy-Dispersive Spectroscope(EDS),X-Ray Diffraction(XRD)and Transmission Electron Microscopy(TEM).The XRD patterns were refined by the Rietveld refinement method and the results revealed that the crystallized Mg_(11-x)Zn_(x)Sr phase belonged to tetragonal I41/amd space group and had the Cd_(11)Ba prototype.The Mg atoms were successfully doped into Zn_(11)Sr crystal lattice by occupying Zn atomic sites.Moreover,the Rietveld refinement and computational results demonstrated a gradual decrease in the a-axis and c-axis lattice parameters with decreasing concentration levels of Mg coordination substitution in the lattice of Mg_(11-x)Zn_(x)Sr compound.The elastic constants and modulus of the Mg_(11-x)Zn_(x)Sr compounds calculated by first-principles calculations(FPC)indicated they were increased with the increasing of Zn content.The variation of hardness,D-band widths and the total density of states for Mg_(11-x)Zn_(x)Sr compounds with Zn content was discussed.
基金supported by the National Key R&D Program of China [grant number 2021YFC2400700]the National Natural Science Foundation of China [grant numbers 82170929,81970908]the Beijing Natural Science Foundation [L222090,L222030]。
文摘Cancer is a major threat to human life worldwide. Traditional cancer treatments, such as chemotherapy and surgery, have major limitations and can cause irreversible damage to normal tissues while killing the cancer cells. Magnesium(Mg) alloys are widely reported novel potential biomedical materials with acceptable mechanical properties and good osteogenic and angiogenic properties. In this review, we summarize the Mg alloys for antitumor applications, including pure Mg and Mg alloys(Mg-Ag, Mg-Gd, Mg-Li-Zn, Mg-Ca-Sr-Zn, et al.) fabricated by casting and extruding, selective laser melting methods. Mg alloys can exhibit antitumor effect on bone tumor, breast cancer, and liver tumor,etal. What's more, after tumor tissue is eliminated, Mg alloys prevent tumor recurrence, fill tissue defects and promote tissue regeneration.The antitumor effects of Mg alloys are mainly due to their degradation products. Overall, Mg alloys show great potential in tumor treatments due to the dual function of antitumor and tissue regeneration.
基金supported by the National Key R&D Program of China (grant number 2021YFC2400700)National Natural Science Foundation of China (Nos.51871004 and U1804251)。
文摘Magnesium-based biodegradable metals as cardiovascular stents have shown a lot of excellent performance, which have been used to treat coronary artery diseases. However, the excessive degradation rate, imperfect biocompatibility and delayed re-endothelialization still lead to a considerable challenge for its application. In this work, to overcome these shortcomings, a compound of catalyzing nitric oxide(NO) generation containing copper ions(Cu^(2+)) and hyaluronic acid(HA), an important component of the extracellular matrix, were covalently immobilized on a hydrofluoric acid(HF)-pretreated ZE21B alloy via amination layer for improving its corrosion resistance and endothelialization. Specifically,the Cu^(2+) chelated firmly with a cyclen 1,4,7,10-tetraazacyclododecane-N’, N’’, N’’’, N-tetraacetic acid(DOTA) could form a stability of hybrid coating, avoiding the explosion of Cu^(2+). The chelated Cu^(2+) enabled the catalytic generation of NO and promoted the adhesion and proliferation of endothelial cells(ECs) in vascular micro-environment. In this case, the synergistic effect of NO-generation and endothelial glycocalyx molecules of HA lead to efficient ECs promotion and smooth muscle cells(SMCs) inhibition. Meanwhile, the blood compatibility also had achieved a marked improvement. Moreover, the standard electrochemical measurements indicated that the functionalized ZE21B alloy had better anti-corrosion ability. In a conclusion, the dual-functional coating displays a great potential in the field of biodegradable magnesium-based implantable cardiovascular stents.
基金funded by National Natural Science Foundation of China(82027802,82102220)Research Funding on Translational Medicine from Beijing Municipal Science and Technology Commission(Z221100007422023)+5 种基金Beijing Hospitals Authority Clinical Medicine Development of Special Funding Support(YGLX202325)Non-profit Central Research Institute Fund of Chinese Academy of Medical(2023-JKCS-09)Beijing Association for Science and Technology Youth Talent Support Program(BYESS2022081)Beijing Municipal Natural Science Foundation(7244510)Science and Technology Innovation Service Capacity Building Project of Beijing Municipal Education Commission(11000023T000002157177)Outstanding Young Talents Program of Capital Medical University(B2305).
文摘Venous sinus stent implantation is an emerging endovascular treatment technique effectively applied in diseases such as cerebral venous sinus thrombosis.However,arterial stents are commonly used in clinical practice for venous sinus stent implantation,which is off-label and carries high risks and poor prognosis,highlighting the necessity of developing venous sinus-specific stents.This narrative review discusses the current situation and problems of venous sinus stent implantation and looks forward to the design focus and future development prospects of venous sinus-specific stents.
基金supported by the Anhui Provincial Natural Science Foundation (grant number 1508085QH194)
文摘The sustained-release properties of the biodegradable nano-drug delivery systems were used to improve the residence time of the chemotherapeutic agent in the body. These drug delivery systems were widely used to deliver chemotherapeutic drugs. The 5-fluorouracil loaded chitosan nanoparticles prepared in this paper have the above advantage. Here, we found that when the mass ratio of 5-fluorouracil and chitosan was 1:1, the maximum drug loading of nanoparticles was 20.13 ± 0.007%, the encapsulation efficiency was 44.28 ± 1.69%, the particle size was 283.9 ± 5.25 nm and the zeta potential was 45.3 ± 3.23 mV. The prepared nanoparticles had both burst-release and sustained-release phases in vitro release studies.In addition, the inhibitory effect of the prepared nanoparticles on gastric cancer SGC-7901 cells was similar to that of 5-fluorouracil injection, and the blank vector had no obvious inhibitory effect on SGC-7901 cells. In the pharmacokinetic study of rats in vivo, we found that AUC(0-t), MRT(0-t) and t1/2 z of nanoparticles were significantly increased in vivo compared with 5-fluorouracil solution, indicating that the prepared nanoparticles can play a role in sustained-release.
基金sponsored by the Scientific Research Fund of Heilongjiang Provincial Education Department(11551117)China Postdoctoral Foundation(20090460875)+1 种基金Pre-research Fund(2009KYG-01)Youth Skeleton Teacher Fund(10KXQ-07)of Harbin Normal University
文摘ZnS nanobelts with large aspect ratio are successfully synthesized on a large scale through thermally evaporating of ZnS powder with a trace of SnO_2 powder using gold coated Si wafer as the substrate at 1100°C.The results indicate that the as-obtained ZnS nanobelts are about 10 nm in thickness and hundreds of micrometers in length,and the aspect ratio reaches more than 104.Substrate dependent experiments are conducted to better study the growth mechanism of the ZnS nanobelts.Subsequently,optical properties of the as-synthesized ZnS nanobelts are also investigated by using a cathodoluminescence(CL) system,which shows the existence of a strong ultraviolet emission at 342 nm and two poor emission peaks at 522 nm and 683 nm at room temperature,respectively.
基金supported by National Key Research and Development Program of China(No.2018YFC1106600)National Natural Science Foundation of China(Grant No.51871004)+1 种基金NSFC/RGC Joint Research Scheme(Grant No.51661165014)the partial financial support in the framework of the RFBR project 20-58-S52001МНТ_а.
文摘In the present work,the biomedical as-cast pure Mg,Mg–1 Ca and Mg–2 Sr alloys were processed with equal channel angular pressing(ECAP)technique to develop ultrafine microstructure within the materials,and their microstructures,mechanical properties,degradation behavior,cytocompatibility in vitro and biocompatibility in vivo were studied comprehensively.Finer-gained microstructures and improved mechanical properties of these three materials after ECAP were confirmed compared to their as-cast counterparts.Moreover,after ECAP the degradation rate of pure Mg was increased while that of Mg–1 Ca or Mg–2 Sr alloys decreased compared to the ascast counterparts.Additionally,good in vitro cytocompatibility and in vivo biocompatibility of these three materials were revealed by cell cultural tests using osteoblastic MC3 T3-E1 and human mesenchymal stem cells(h MSC)and in vivo animal tests at the lateral epicondyle of SD-rats’femur.This study offers an alternative powerful avenue to achieve good comprehensive properties of magnesium-based biodegradable metals.It might also help to extend the applied range of magnesium-based biodegradable metals in orthopedic field.
基金supported by the National Natural Science Foundation of China(31772508)。
文摘A new species,Synanthedon elaeagnus sp.nov.feeding on Elaeagnus mollis,is described from Shanxi,China.This new species is similar to Synanthedon ulmicola Yang&Wang,1989 in general morphology,but it differs from this latter species by features of the forewing,female and male genitalia.Neighbor-joining and maximum likelihood analysis both recover Synanthedon elaeagnus sp.nov.as a well-supported monophyletic lineage with a high support value based on COI gene sequences.The key features of this new species are illustrated.
文摘The effect of annealing temperature on the formation of the PtSi phase. distribution of silicides and the surface morphologies of silicides films is investigated by XPS. AFM. It is shown that the phase sequences of the films change from Pt-Pt2Si-PtSi-Si to Pt+Pt2Si+PtSi-PtSi-Si or Pt+Pt2Si+PtSi-PtSi-st with an increase of annealing temperature and the reason for the formation of mixed layers is discussed.
文摘The nanohydroxyapatites (HAP) and its biological effects have been studied using ultraviolet absorption spectrum, X-ray diffraction (XRD) structure analysis, fluorescent and infrared spectrum of absorption and MTT method. The nanohyd- roxyapatites are prepared and made by using Sol-gel method, in which the parameters of process and reaction are controlled as: PH 】9, Ca/P = 1.67, sintering temperature of 1100?C and sintering time 2 hours. The results of the study show that nanohydroxyapatites can absorb the amino acid molecules, the absorption is better for stronger acidity of amino acids. We also find that the nanohydroxyapatites and complex of nanoHAP+ nanoCrO2 can all restrain the proliferation of cells, but their toxiciteis are all first degree or minor, but the restrained effect of the latter is smaller than that of the former, although they can decrease the relative proliferation rate of cells. The nanohydroxyapatites can also change the molecular structure of human serum albumin.
文摘The solidified microstructure of a Ni-Cu-Si cast alloy has been investigated, and a kind of banding structure was observed. The results showed that, the banding structure was composed of coarser particles which were Ni3Si type of precipitates and similar to the fine particles precipitate uniformly distributed within matrix of Ni solid solution, in both crystal structure and composition. The formation of bandings was resulted from cast thermal stress and dislocation walls. It was found that the cracks propagated along these bandings in tensile test. The banding structure can be depressed by reducing the cast thermal stress, which can improve the tensile ductility.
文摘Detailed crystallographic analysis has been undertaken on the various combinations Of 24 martensite variants in the 18R martensite of a Cu-Zn-Al shape memory alloy. Based upon the calculated crystallographic data, the interface energy of different twin interfaces was calculated using a lowangle-grain-interface model. For the variant/variant pairs in a self-accommodating group. the A/C type and A/B type interfaces have low interface energy, and A/D type interface is an intermediate one. In contrast, the intervariant interfaces that belong to different plate groups have high intrface energy. The calculated results are consiStent with the previous observations of the mobility of intervariant interfaces.
文摘Magnesium alloys with unique biodegradable trait raise great interests among researchers.However,overquick degradation rate has become the biggest problem limiting the further application of biodegradable magnesium alloys1.Plasma ion implantation has been considered good and convinient sur-
基金National Key Research and Development Program of China(No.2018YFE0104200)National Natural Science Foundation of China(Nos.52175274,82172065,51875310)Tsinghua Precision Medicine Foundation and Tsinghua-Toyota Joint Research Fund.
文摘Laser powder bed fusion(L-PBF)has been used to fabricate biodegradable Mg implants of WE43 alloy,but the degradation is too fast compared with the term bone reconstruction.Previous studies show that high temperature oxidation(HTO)can successfully inhibit the degradation of WE43 alloy.In this work,the influence of HTO on L-PBF samples of WE43 alloy was investigated regarding tensile,compressive,and abrasive resistance,as well as in vitro cytotoxicity,cell proliferation,hemolysis,and osteogenesis.Compared with the as-built L-PBF samples,HTO increased grain size and grain texture,stabilized and coarsened precipitates,and caused discontinuous static recrystallization in the matrix.The oxide layer at the surface of the HTO samples improved surface roughness,hydrophilia,hardness,and abrasive resis-tance.The tensile strength decreased slightly from 292 to 265 MPa,while the elongation substantially increased from 10.97%to 16.58%after HTO.The in vitro cell viability,cell proliferation,hemolysis,and osteogenic effect were considerably enhanced due to the improvement of surface quality and the initial inhibition of excessive Mg^(2+)releasement.Overall,HTO is of great benefit to the surface performance,ductility,and biocompatibility of WE43 alloy fabricated by L-PBF for biodegradable applications.
文摘Postoperative anatomical reconstruction and prevention of local recurrence after tumor resection are two vital clinical challenges in osteosarcoma treatment.A three-dimensional(3D)-printed porous Ti6Al4V scaffold(3DTi)is an ideal material for reconstructing critical bone defects with numerous advantages over traditional implants,including a lower elasticity modulus,stronger bone-implant interlock,and larger drug-loading space.Simvastatin is a multitarget drug with anti-tumor and osteogenic potential;however,its efficiency is unsatisfactory when delivered systematically.Here,simvastatin was loaded into a 3DTi using a thermosensitive poly(lactic-co-gly-colic)acid(PLGA)-polyethylene glycol(PEG)-PLGA hydrogel as a carrier to exert anti-osteosarcoma and oste-ogenic effects.Newly constructed simvastatin/hydrogel-loaded 3DTi(Sim-3DTi)was comprehensively appraised,and its newfound anti-osteosarcoma mechanism was explained.Specifically,in a bone defect model of rabbit condyles,Sim-3DTi exhibited enhanced osteogenesis,bone in-growth,and osseointegration compared with 3DTi alone,with greater bone morphogenetic protein 2 expression.In our nude mice model,simvastatin loading reduced tumor volume by 59%-77%without organic damage,implying good anti-osteosarcoma activity and biosafety.Furthermore,Sim-3DTi induced ferroptosis by upregulating transferrin and nicotinamide adenine dinucleotide phosphate oxidase 2 levels in osteosarcoma both in vivo and in vitro.Sim-3DTi is a promising osteogenic bone substitute for osteosarcoma-related bone defects,with a ferroptosis-mediated anti-osteosarcoma effect.