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
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
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
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
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
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 th...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
Endowing implant surfaces with combined antibacterial and osteogenic properties by drug-loaded coatings has made great strides,but how to achieve the combined excellence of infection-triggered bactericidal and in vivo...Endowing implant surfaces with combined antibacterial and osteogenic properties by drug-loaded coatings has made great strides,but how to achieve the combined excellence of infection-triggered bactericidal and in vivo-proven osteogenic activities without causing bacterial resistance still remains a formidable challenge.Herein,antimicrobial peptides(AMPs)with osteogenic fragments were designed and complexed on the surface of silver nanoparticle(AgNP)through hydrogen bonding,and the collagen structure-bionic silk fibroin(SF)was applied to carry AgNPs@AMPs to achieve infection-triggered antibacterial and osteointegration.As verified by TEM,AMPs contributed to the dispersion and size-regulation of AgNPs,with a particle size of about 20 nm,and a clear protein corona structure was observed on the particle surface.The release curve of silver ion displayed that the SF-based coating owned sensitive pH-responsive properties.In the antibacterial test against S.aureus for up to 21 days,the antibacterial rate had always remained above 99%.Meanwhile,the underlying mechanism was revealed,originating from the destruction of the bacterial cell membranes and ROS generation.The SF-based coating was conducive to the adhesion,diffusion,and proliferation of bone marrow stem cells(BMSCs)on the surface,and promoted the expression of osteogenic genes and collagen secretion.The in vivo implantation results showed that compared with the untreated Ti implants,SF-based coating enhanced osseointegration at week 4 and 8.Overall,the AgNPs@AMPs-loaded SF-based coating presented the ability to synergistically inhibit bacteria and promote osseointegration,possessing tremendous potential application prospects in bone defects and related-infection treatments.展开更多
Polyetheretherketone(PEEK)has been an alternative material for titanium in bone defect repair,but its clinical application is limited by its poor osseointegration.In this study,a porous structural design and activated...Polyetheretherketone(PEEK)has been an alternative material for titanium in bone defect repair,but its clinical application is limited by its poor osseointegration.In this study,a porous structural design and activated surface modification were used to enhance the osseointegration capacity of PEEK materials.Porous PEEK scaffolds were manufactured via fused deposition modeling and a polydopamine(PDA)coating chelated with magnesium ions(Mg^(2+))was utilized on the surface.After surface modification,the hydrophilicity of PEEK scaffolds was significantly enhanced,and bioactive Mg^(2+)could be released.In vitro results showed that the activated surface could promote cell proliferation and adhesion and contribute to osteoblast differentiation and mineralization;the released Mg^(2+)promoted angiogenesis and might contribute to the formation of osteogenic H-type vessels.Furthermore,porous PEEK scaffolds were implanted in rabbit femoral condyles for in vivo evaluation of osseointegration.The results showed that the customized three-dimensional porous structure facilitated vascular ingrowth and bone ingrowth within the PEEK scaffolds.The PDA coating enhanced the interfacial osseointegration of porous PEEK scaffolds and the released Mg^(2+)accelerated early bone ingrowth by promoting early angiogenesis during the coating degradation process.This study provides an efficient solution for enhancing the osseointegration of PEEK materials,which has high potential for translational clinical applications.展开更多
Additive manufacturing has received attention for the fabrication of medical implants that have customized and complicated structures.Biodegradable Zn metals are revolutionary materials for orthopedic implants.In this...Additive manufacturing has received attention for the fabrication of medical implants that have customized and complicated structures.Biodegradable Zn metals are revolutionary materials for orthopedic implants.In this study,pure Zn porous scaffolds with diamond structures were fabricated using customized laser powder bed fusion(L-PBF)technology.First,the mechanical properties,corrosion behavior,and biocompatibility of the pure Zn porous scaffolds were characterized in vitro.The scaffolds were then implanted into the rabbit femur critical-size bone defect model for 24 weeks.The results showed that the pure Zn porous scaffolds had compressive strength and rigidity comparable to those of cancellous bone,as well as relatively suitable degradation rates for bone regeneration.A benign host response was observed using hematoxylin and eosin(HE)staining of the heart,liver,spleen,lungs,and kidneys.Moreover,the pure Zn porous scaffold showed good biocompatibility and osteogenic promotion ability in vivo.This study showed that pure Zn porous scaffolds with customized structures fabricated using L-PBF represent a promising biodegradable solution for treating large bone defects.展开更多
In contrast to polymer bioresorbable stents(BRS)that exhibited suboptimal performance in clinical trials due to their deficient mechanical properties,metallic BRS with improved mechanical strength have made their way ...In contrast to polymer bioresorbable stents(BRS)that exhibited suboptimal performance in clinical trials due to their deficient mechanical properties,metallic BRS with improved mechanical strength have made their way into the clinic and have demonstrated more promising results.In the roadmap of research and development of metallic BRS,magnesium and iron based biodegradable metal stents had been clinically used,and the zinc based biodegradable metal stents had been trailed in Mini-Pigs.In this mini-review paper,we demonstrate the current technology levels and point out the future R&D direction of metallic BRS.Magnesium based BRS should target for decreasing struct thickness meanwhile balancing with enough supporting strength.Iron based BRS should move towards high efficient absorption,conversion,metabolism,elimination of its degradation products.Zn based BRS should strive to improve mechanical stability,creep resistance and biocompatibility.Future R&D directions of metallic BRS should move towards new materials such as Molybdenum,intelligent stent integrated with degradable biosensors,and new stent with multiple biofunctions,such as NO release.展开更多
Rare earth elements(REEs)have been long applied in magnesium alloys,among which the mischmetal-containing WE43 alloy has already got the CE mark approval for clinical application.A considerable amount of REEs(7 wt%)is...Rare earth elements(REEs)have been long applied in magnesium alloys,among which the mischmetal-containing WE43 alloy has already got the CE mark approval for clinical application.A considerable amount of REEs(7 wt%)is needed in that multi-phased alloy to achieve a good combination of mechanical strength and corrosion resistance.However,the high complex RE addition accompanied with multiple second phases may bring the concern of biological hazards.Single-phased Mg-RE alloys with simpler compositions were proposed to improve the overall performance,i.e.,“Simpler alloy,better performance”.The single-phased microstructure can be successfully obtained with typical high-solubility REEs(Ho,Er or Lu)through traditional smelting,casting and extrusion in a wide compositional range.A good corrosion resistance with a macroscopically uniform corrosion mode was guaranteed by the homogeneously single-phased microstructure.The bimodal-grained structure with plenty of sub-grain microstructures allow us to minimize the RE addition to<1 wt%,without losing mechanical properties.The single-phased Mg-RE alloys show comparable mechanical properties to the clinically-proven Mg-based implants.They exhibited similar in-vitro and in-vivo performances(without local or systematic toxicity in SD-rats)compared to a high purity magnesium.In addition,metal elements in our single-phased alloys can be gradually excreted through the urinary system and digestive system,showing no consistent accumulation of RE in main organs,i.e.,less burden on organs.The novel concept in this study focuses on the simplification of Mg-RE based alloys for biomedical purpose,and other biodegradable metals with single-phased microstructures are expected to be explored.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.
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supported by the National Natural Science Foundation of China(Grant numbers 32071327,32101087)Shaanxi Science and Technology Association(2022JQ-312).
文摘Endowing implant surfaces with combined antibacterial and osteogenic properties by drug-loaded coatings has made great strides,but how to achieve the combined excellence of infection-triggered bactericidal and in vivo-proven osteogenic activities without causing bacterial resistance still remains a formidable challenge.Herein,antimicrobial peptides(AMPs)with osteogenic fragments were designed and complexed on the surface of silver nanoparticle(AgNP)through hydrogen bonding,and the collagen structure-bionic silk fibroin(SF)was applied to carry AgNPs@AMPs to achieve infection-triggered antibacterial and osteointegration.As verified by TEM,AMPs contributed to the dispersion and size-regulation of AgNPs,with a particle size of about 20 nm,and a clear protein corona structure was observed on the particle surface.The release curve of silver ion displayed that the SF-based coating owned sensitive pH-responsive properties.In the antibacterial test against S.aureus for up to 21 days,the antibacterial rate had always remained above 99%.Meanwhile,the underlying mechanism was revealed,originating from the destruction of the bacterial cell membranes and ROS generation.The SF-based coating was conducive to the adhesion,diffusion,and proliferation of bone marrow stem cells(BMSCs)on the surface,and promoted the expression of osteogenic genes and collagen secretion.The in vivo implantation results showed that compared with the untreated Ti implants,SF-based coating enhanced osseointegration at week 4 and 8.Overall,the AgNPs@AMPs-loaded SF-based coating presented the ability to synergistically inhibit bacteria and promote osseointegration,possessing tremendous potential application prospects in bone defects and related-infection treatments.
基金supported by grants from the National Natural Science Foundation of China(No.51871239,No.32101087,No.52171244).
文摘Polyetheretherketone(PEEK)has been an alternative material for titanium in bone defect repair,but its clinical application is limited by its poor osseointegration.In this study,a porous structural design and activated surface modification were used to enhance the osseointegration capacity of PEEK materials.Porous PEEK scaffolds were manufactured via fused deposition modeling and a polydopamine(PDA)coating chelated with magnesium ions(Mg^(2+))was utilized on the surface.After surface modification,the hydrophilicity of PEEK scaffolds was significantly enhanced,and bioactive Mg^(2+)could be released.In vitro results showed that the activated surface could promote cell proliferation and adhesion and contribute to osteoblast differentiation and mineralization;the released Mg^(2+)promoted angiogenesis and might contribute to the formation of osteogenic H-type vessels.Furthermore,porous PEEK scaffolds were implanted in rabbit femoral condyles for in vivo evaluation of osseointegration.The results showed that the customized three-dimensional porous structure facilitated vascular ingrowth and bone ingrowth within the PEEK scaffolds.The PDA coating enhanced the interfacial osseointegration of porous PEEK scaffolds and the released Mg^(2+)accelerated early bone ingrowth by promoting early angiogenesis during the coating degradation process.This study provides an efficient solution for enhancing the osseointegration of PEEK materials,which has high potential for translational clinical applications.
基金supported by the National Key R&D Program of China[grant number 2018YFE0104200]the National Natural Science Foundation of China[grant numbers 51901003,51931001,52171233,51875310]+1 种基金the Beijing Natural Science Foundation[grant number L212014]the Open Project of NMPA Key Laboratory for Dental Materials[grant number PKUSS20200401].
文摘Additive manufacturing has received attention for the fabrication of medical implants that have customized and complicated structures.Biodegradable Zn metals are revolutionary materials for orthopedic implants.In this study,pure Zn porous scaffolds with diamond structures were fabricated using customized laser powder bed fusion(L-PBF)technology.First,the mechanical properties,corrosion behavior,and biocompatibility of the pure Zn porous scaffolds were characterized in vitro.The scaffolds were then implanted into the rabbit femur critical-size bone defect model for 24 weeks.The results showed that the pure Zn porous scaffolds had compressive strength and rigidity comparable to those of cancellous bone,as well as relatively suitable degradation rates for bone regeneration.A benign host response was observed using hematoxylin and eosin(HE)staining of the heart,liver,spleen,lungs,and kidneys.Moreover,the pure Zn porous scaffold showed good biocompatibility and osteogenic promotion ability in vivo.This study showed that pure Zn porous scaffolds with customized structures fabricated using L-PBF represent a promising biodegradable solution for treating large bone defects.
基金supported by Longhua District Project(2022035)National Natural Science Foundation of China(Grant No.51931001 and U22A20121)+1 种基金Fund for International Cooperation and Exchange between NSFC(China)and CNR(Italy)(NSFC-CNR Grant No.52011530392)Fund for International Cooperation and Exchange between NSFC(China)and RFBR(Russia)(NSFC-RFBR Grant No.52111530042).
文摘In contrast to polymer bioresorbable stents(BRS)that exhibited suboptimal performance in clinical trials due to their deficient mechanical properties,metallic BRS with improved mechanical strength have made their way into the clinic and have demonstrated more promising results.In the roadmap of research and development of metallic BRS,magnesium and iron based biodegradable metal stents had been clinically used,and the zinc based biodegradable metal stents had been trailed in Mini-Pigs.In this mini-review paper,we demonstrate the current technology levels and point out the future R&D direction of metallic BRS.Magnesium based BRS should target for decreasing struct thickness meanwhile balancing with enough supporting strength.Iron based BRS should move towards high efficient absorption,conversion,metabolism,elimination of its degradation products.Zn based BRS should strive to improve mechanical stability,creep resistance and biocompatibility.Future R&D directions of metallic BRS should move towards new materials such as Molybdenum,intelligent stent integrated with degradable biosensors,and new stent with multiple biofunctions,such as NO release.
基金This work was supported by the National Key R&D Program of China(Grant No.2021YFC2400700),the National Natural Science Foundation of China(Grant No.52101283)the Science and Technology Planning Project of Guangzhou(Grant No.202201011454)+1 种基金the NSFC Incubation Program of GDPH(Grant No.KY012021165)the High-level Hospital Construction Project(Grant No.KJ012019520).
文摘Rare earth elements(REEs)have been long applied in magnesium alloys,among which the mischmetal-containing WE43 alloy has already got the CE mark approval for clinical application.A considerable amount of REEs(7 wt%)is needed in that multi-phased alloy to achieve a good combination of mechanical strength and corrosion resistance.However,the high complex RE addition accompanied with multiple second phases may bring the concern of biological hazards.Single-phased Mg-RE alloys with simpler compositions were proposed to improve the overall performance,i.e.,“Simpler alloy,better performance”.The single-phased microstructure can be successfully obtained with typical high-solubility REEs(Ho,Er or Lu)through traditional smelting,casting and extrusion in a wide compositional range.A good corrosion resistance with a macroscopically uniform corrosion mode was guaranteed by the homogeneously single-phased microstructure.The bimodal-grained structure with plenty of sub-grain microstructures allow us to minimize the RE addition to<1 wt%,without losing mechanical properties.The single-phased Mg-RE alloys show comparable mechanical properties to the clinically-proven Mg-based implants.They exhibited similar in-vitro and in-vivo performances(without local or systematic toxicity in SD-rats)compared to a high purity magnesium.In addition,metal elements in our single-phased alloys can be gradually excreted through the urinary system and digestive system,showing no consistent accumulation of RE in main organs,i.e.,less burden on organs.The novel concept in this study focuses on the simplification of Mg-RE based alloys for biomedical purpose,and other biodegradable metals with single-phased microstructures are expected to be explored.