Considering the compatibility between degradation and bioactivity of magnesium-based implants for bone repair, micro-arc oxidation is used to modify the magnesium alloy surface in aqueous electrolytes, allowing stront...Considering the compatibility between degradation and bioactivity of magnesium-based implants for bone repair, micro-arc oxidation is used to modify the magnesium alloy surface in aqueous electrolytes, allowing strontium, calcium, and phosphorus to be incorporated into the coating. The thickness, composition, morphology and phase of this Sr-Ca-P containing coating are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer and X-ray diffraction. The in vitro and in vivo degradation of the coating is evaluated by immersion test, electrochemical test and implantation test. Moreover, the cytocompatibility is tested with osteoblast cell according to ISO 10993. The results show that St, Ca and P elements are incorporated into the oxide coating, and a refined structure with tiny discharging micro-pores is observed on the surface of the coating. The Sr-Ca-P coating possesses a better corrosion resistance in vitro and retards the degradation in vivo. Such coating is expected to have significant medical applications on orthopedic implants and bone repair materials.展开更多
Magnesium-based alloys are frequently reported as potential biodegradable orthopedic implant materials. Controlling the degradation rate and mechanical integrity of magnesium alloys in the physiological environment is...Magnesium-based alloys are frequently reported as potential biodegradable orthopedic implant materials. Controlling the degradation rate and mechanical integrity of magnesium alloys in the physiological environment is the key to their applications. In this study, calcium phosphate （Ca-P） coating was prepared on AZ60 magnesium alloy using phosphating technology. AZ60 samples were immersed in a phosphating solution at 37 ± 2 ℃ for 30 min, and the solution pH was adjusted to 2.6 to 2.8 by adding NaOH solution. Then, the samples were dried in an attemperator at 60 ℃. The degradation behavior was studied in vivo using Ca-P coated and uncoated magnesium alloys. Samples of these two different materials were implanted into rabbit femora, and the corrosion resistances were evaluated after 1, 2, and 3 months. The Ca-P coated samples corroded slower than the uncoated samples with prolonged time. Significant differences （p 〈 0.05） in mass losses and corrosion rates between uncoated samples and Ca-P coated samples were observed by micro-computed tomography. The results indicate that the Ca-P coating could slow down the degradation of magnesium alloy in vivo.展开更多
Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid...Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.展开更多
Calcium-phosphate compounds（Ca-P） coating was prepared on an Mg-A1 alloy（AZ60）. Biodegradation of Ca-P coated magnesium alloy was evaluated in simulated body fluid（SBF） by examining the changes in magnesium ion ...Calcium-phosphate compounds（Ca-P） coating was prepared on an Mg-A1 alloy（AZ60）. Biodegradation of Ca-P coated magnesium alloy was evaluated in simulated body fluid（SBF） by examining the changes in magnesium ion concentration and pH value, which indicated that the Ca-P coating on magnesium alloy strongly affected the cor- rosion of magnesium alloy. Osteoblast MC3T3-E1 cells were utilized to investigate the cellular eytocompatibility. The cytocompatibility was measured by carrying out a series of tests, such as cholecystokinin-octapeptide（CCK-8） test, alkaline phosphatase activity（ALP） test, cellular morphology of hematoxylin-eosin（HE） staining and the induc- tion of apoptosis. It was found that the cell function showed better in the Ca-P coated Mg-alloy extract than in the uncoated magnesium alloy extract. In summary, the results indicate that the Ca-P coating can improve the corrosion resistance of magnesium alloy and elevate cellular proliferation and differentiation of osteoblast MC3T3-E1 cells.展开更多
A chemical method was used to deposit dicalcium phosphate dehydrate coatings on AZ91 magnesium alloy. The aim was to improve the biodegradation behavior of magnesium alloy in a simulated body fluid. The microstructure...A chemical method was used to deposit dicalcium phosphate dehydrate coatings on AZ91 magnesium alloy. The aim was to improve the biodegradation behavior of magnesium alloy in a simulated body fluid. The microstructures of the coating before and after immersion in the simulated body fluid were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD） The results indicated that the dicalcium phosphate dehydrate coatings exhibited two morphologies during the pre-calcification process. The titration speed of the pre-calcification process had great influence on the morphologies of the pre-calcification coatings. As the soaking time increased, the diffraction peaks of dicalcium phosphate dehydrate disappeared and hydroxyapatite precipitated on the coated substrate surfaces. This indicates the dissolution of dicalcium phosphate dehydrate during the immersion process. The structures of the dicalcium phosphate dehydrate coatings and the formation mechanisms of the hydroxyapatite coatings were investigated in detail.展开更多
The burst release of Zn 2+from the naked pure Zn and Zn-based alloys could induce local and sys-temic toxicity,which limits their clinical applications as biodegradable implants.In order to inhibit the explosive relea...The burst release of Zn 2+from the naked pure Zn and Zn-based alloys could induce local and sys-temic toxicity,which limits their clinical applications as biodegradable implants.In order to inhibit the explosive release of zinc ions,a protective Ca-P coating was synthesized on biodegradable Zn al-loy.The microstructure,corrosion resistance,antibacterial activity,and biosafety of the Ca-P coating are systematically investigated.Electrochemical tests revealed that Ca-P protective layer has enhanced the anti-corrosion behavior of Zn alloy.Furthermore,Ca-P protective layer showed good biocompatibility,as demonstrated by significantly increased cell viability,good attachment,and spreading at a higher cell density.Besides,the Ca-P coating could also retain the antibacterial ability and inhibit the bacterial ad-hesion.The Ca-P protective layer synthesized on biodegradable Zn alloy can be considered and applied in future biomedical applications.展开更多
Synchrotron radiation X-ray fluorescence （SR-XRF） approach was applied to analyzing of Chinstrap penguin （ Pygoscelis Antarctica） cortical bone. The method enabled the in situ determination of Ca and P concentrati...Synchrotron radiation X-ray fluorescence （SR-XRF） approach was applied to analyzing of Chinstrap penguin （ Pygoscelis Antarctica） cortical bone. The method enabled the in situ determination of Ca and P concentrations and the Ca/P ratio in cortical bone. The preliminary results show that ： （ 1 ） there is the bone site-related difference for Ca and P concentrations. The mean values for the investigated parameters （ on a dry-weight basis） are： 30.7% （Ca） and 14.9% （P） for the femoral cortical bone, 21.4% （Ca） and 11.5% （P） for wing cortical bone. （2） The variation for the Ca/P ratio in cortical bone is lower than those for Ca and P separately. This is in agreement with the previous report that the specificity of the Ca/P ratio is better than that of Ca and P concentrations and is more reliable for the diagnosis of bone disorders. The authors suggest that further studies be conducted to establish norreal values of Ca, P and Ca/P ratio for polar animals and provide a basis for the diagnosis of bone disorders.展开更多
To improve the anti-corrosion behaviors of magnesium alloy in the inner environment of human body,a bioactive Ca-P coating was deposited on the AZ60 magnesium alloy by a novel simple method.The morphologies of the Ca-...To improve the anti-corrosion behaviors of magnesium alloy in the inner environment of human body,a bioactive Ca-P coating was deposited on the AZ60 magnesium alloy by a novel simple method.The morphologies of the Ca-P coatings formed under different treatment time were studied by scanning electron microscopy（SEM）.The corrosion behaviors of Ca-P coating were investigated by electrochemical polarization test and electrochemical impedance spectroscopy in both 3％（mass fraction） NaCl solution and simulated body fluid（SBF）.Immersion test in SBF was performed to evaluate the corrosion rate of Ca-P coated magnesium alloy.X-Ray diffraction（XRD） analysis result shows that the coating mentioned above mainly consists of dicalcium phosphate dehydrate（CaHPO4·2H2O,DCPD） and β-tricalcium phosphate dehydrate[β-TCP,Ca3（PO4）2],which exhibits good corrosion resistance.After magnesium alloy was immersed in 1 mol/L NaOH solution at 80 ℃ for 2 h,hydroxyapatite [Ca10（PO4）6（OH）2,HA]appeared on the magnesium alloy substrate,which can further decrease the corrosion rate of AZ60 magnesium alloy in SBF.展开更多
Non-mycorrhizal Brassica does not produce specialized root structures such as cluster or dauciform roots but is an effective user of P compared with other crops. In addition to P-uptake, utilization and remobilization...Non-mycorrhizal Brassica does not produce specialized root structures such as cluster or dauciform roots but is an effective user of P compared with other crops. In addition to P-uptake, utilization and remobilization activity, acquisition of orthophosphate （Pi） from extracellular sparingly P-sources or unavailable bound P-forms can be enhanced by biochemical rescue mechanisms such copious H＋-efflux and/or carboxylates exudation into rhizosphere by roots via plasmalemma H＋ ATPase and anion channels triggered by P-starvation. To visualize the dissolution of sparingly soluble Ca-phosphate （Ca-P）, newly formed Ca-P was suspended in agar containing other essential nutrients. With NH4＋ applied as the N source, the precipitate dissolved in the root vicinity can be ascribed to rhizosphere acidification, whereas no dissolution occurred with nitrate nutrition. To observe in situ rhizospheric pH changes, images were recorded after embedding the roots in agar containing bromocresol purple as a pH indicator. P-tolerant cultivar showed a greater decrease in pH than the sensitive cultivar in the culture media （the appearance of typical patterns of various colors of pH indicator in the root vicinity）, and at stress P-level this acidification was more prominent. In experiment 2, low P-tolerant class-I cultivars （Oscar and Con-II） showed a greater decrease in solution media pH than low P-sensitive class-II （Gold Rush and RL-18） cultivars, and P-contents of the cultivars was inversely related to decrease in culture media pH. To elucidate P-stress- induced remodeling and redesigning in a root architectural system, cultivars were grown in rhizoboxes in experiment 3. The elongation rates of primary roots increased as P-supply increased, but the elongation rates of the branched zones of primary roots decreased. The length of the lateral roots and topological index values increased when cultivars were exposed to a P-stress environment. To elucidate Pi-uptake kinetics, parameters related to P influx： maximal 展开更多
基金financially supported by the National High Technology Research and Development Program of China (No. 2015AA033701)the Chinese Academy of Sciences-Croucher Founding Scheme for Joint Laboratories (Ref. CAS 14303)Foundation of Jiangsu Collaborative Innovation Center of Biomedical Functional Materials
文摘Considering the compatibility between degradation and bioactivity of magnesium-based implants for bone repair, micro-arc oxidation is used to modify the magnesium alloy surface in aqueous electrolytes, allowing strontium, calcium, and phosphorus to be incorporated into the coating. The thickness, composition, morphology and phase of this Sr-Ca-P containing coating are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer and X-ray diffraction. The in vitro and in vivo degradation of the coating is evaluated by immersion test, electrochemical test and implantation test. Moreover, the cytocompatibility is tested with osteoblast cell according to ISO 10993. The results show that St, Ca and P elements are incorporated into the oxide coating, and a refined structure with tiny discharging micro-pores is observed on the surface of the coating. The Sr-Ca-P coating possesses a better corrosion resistance in vitro and retards the degradation in vivo. Such coating is expected to have significant medical applications on orthopedic implants and bone repair materials.
基金Acknowledgment This work is supported by the National Natural Science Foundation of China （No.31070841）.
文摘Magnesium-based alloys are frequently reported as potential biodegradable orthopedic implant materials. Controlling the degradation rate and mechanical integrity of magnesium alloys in the physiological environment is the key to their applications. In this study, calcium phosphate （Ca-P） coating was prepared on AZ60 magnesium alloy using phosphating technology. AZ60 samples were immersed in a phosphating solution at 37 ± 2 ℃ for 30 min, and the solution pH was adjusted to 2.6 to 2.8 by adding NaOH solution. Then, the samples were dried in an attemperator at 60 ℃. The degradation behavior was studied in vivo using Ca-P coated and uncoated magnesium alloys. Samples of these two different materials were implanted into rabbit femora, and the corrosion resistances were evaluated after 1, 2, and 3 months. The Ca-P coated samples corroded slower than the uncoated samples with prolonged time. Significant differences （p 〈 0.05） in mass losses and corrosion rates between uncoated samples and Ca-P coated samples were observed by micro-computed tomography. The results indicate that the Ca-P coating could slow down the degradation of magnesium alloy in vivo.
基金supported by the National Natural Science Foundation of China(Grant No.21978066)Basic Research Program of Hebei Province for Natural Science Foundation and Key Basic Research Project(Grant No.18964308D)the Key Program of Natural Science Foundation of Hebei Province(Grant No.B2020202048).
文摘Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.
基金Supported by the National Natural Science Foundation of China（No.31070841）.
文摘Calcium-phosphate compounds（Ca-P） coating was prepared on an Mg-A1 alloy（AZ60）. Biodegradation of Ca-P coated magnesium alloy was evaluated in simulated body fluid（SBF） by examining the changes in magnesium ion concentration and pH value, which indicated that the Ca-P coating on magnesium alloy strongly affected the cor- rosion of magnesium alloy. Osteoblast MC3T3-E1 cells were utilized to investigate the cellular eytocompatibility. The cytocompatibility was measured by carrying out a series of tests, such as cholecystokinin-octapeptide（CCK-8） test, alkaline phosphatase activity（ALP） test, cellular morphology of hematoxylin-eosin（HE） staining and the induc- tion of apoptosis. It was found that the cell function showed better in the Ca-P coated Mg-alloy extract than in the uncoated magnesium alloy extract. In summary, the results indicate that the Ca-P coating can improve the corrosion resistance of magnesium alloy and elevate cellular proliferation and differentiation of osteoblast MC3T3-E1 cells.
基金Project(51272055) supported by the National Natural Science Foundation of China
文摘A chemical method was used to deposit dicalcium phosphate dehydrate coatings on AZ91 magnesium alloy. The aim was to improve the biodegradation behavior of magnesium alloy in a simulated body fluid. The microstructures of the coating before and after immersion in the simulated body fluid were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD） The results indicated that the dicalcium phosphate dehydrate coatings exhibited two morphologies during the pre-calcification process. The titration speed of the pre-calcification process had great influence on the morphologies of the pre-calcification coatings. As the soaking time increased, the diffraction peaks of dicalcium phosphate dehydrate disappeared and hydroxyapatite precipitated on the coated substrate surfaces. This indicates the dissolution of dicalcium phosphate dehydrate during the immersion process. The structures of the dicalcium phosphate dehydrate coatings and the formation mechanisms of the hydroxyapatite coatings were investigated in detail.
基金supported by the National Natural Science Foundation of China(No.31700819)the Young Elite Scientists Sponsorship Program by CAST(YESS,No.2018QNRC001).
文摘The burst release of Zn 2+from the naked pure Zn and Zn-based alloys could induce local and sys-temic toxicity,which limits their clinical applications as biodegradable implants.In order to inhibit the explosive release of zinc ions,a protective Ca-P coating was synthesized on biodegradable Zn al-loy.The microstructure,corrosion resistance,antibacterial activity,and biosafety of the Ca-P coating are systematically investigated.Electrochemical tests revealed that Ca-P protective layer has enhanced the anti-corrosion behavior of Zn alloy.Furthermore,Ca-P protective layer showed good biocompatibility,as demonstrated by significantly increased cell viability,good attachment,and spreading at a higher cell density.Besides,the Ca-P coating could also retain the antibacterial ability and inhibit the bacterial ad-hesion.The Ca-P protective layer synthesized on biodegradable Zn alloy can be considered and applied in future biomedical applications.
基金grants from the National Natural Science Foundation of China(Project No.40306001) the Foundation for the Author of National Excellent Doctoral Dissertation of P.R.China(Grant No.200354)from Ministry of Education of China and Chinese Academy of Sciences.It was partially support by BSRF(Project No.SR-03097).
文摘Synchrotron radiation X-ray fluorescence （SR-XRF） approach was applied to analyzing of Chinstrap penguin （ Pygoscelis Antarctica） cortical bone. The method enabled the in situ determination of Ca and P concentrations and the Ca/P ratio in cortical bone. The preliminary results show that ： （ 1 ） there is the bone site-related difference for Ca and P concentrations. The mean values for the investigated parameters （ on a dry-weight basis） are： 30.7% （Ca） and 14.9% （P） for the femoral cortical bone, 21.4% （Ca） and 11.5% （P） for wing cortical bone. （2） The variation for the Ca/P ratio in cortical bone is lower than those for Ca and P separately. This is in agreement with the previous report that the specificity of the Ca/P ratio is better than that of Ca and P concentrations and is more reliable for the diagnosis of bone disorders. The authors suggest that further studies be conducted to establish norreal values of Ca, P and Ca/P ratio for polar animals and provide a basis for the diagnosis of bone disorders.
基金Supported by the National Natural Science Foundation of China（No.31070841）, the National Key Basic Research and Development Program of China（No.2010CB631001） and the Science ＆ Technology Pillar Program of Changchun City, China （No. 11KZ30）.
文摘To improve the anti-corrosion behaviors of magnesium alloy in the inner environment of human body,a bioactive Ca-P coating was deposited on the AZ60 magnesium alloy by a novel simple method.The morphologies of the Ca-P coatings formed under different treatment time were studied by scanning electron microscopy（SEM）.The corrosion behaviors of Ca-P coating were investigated by electrochemical polarization test and electrochemical impedance spectroscopy in both 3％（mass fraction） NaCl solution and simulated body fluid（SBF）.Immersion test in SBF was performed to evaluate the corrosion rate of Ca-P coated magnesium alloy.X-Ray diffraction（XRD） analysis result shows that the coating mentioned above mainly consists of dicalcium phosphate dehydrate（CaHPO4·2H2O,DCPD） and β-tricalcium phosphate dehydrate[β-TCP,Ca3（PO4）2],which exhibits good corrosion resistance.After magnesium alloy was immersed in 1 mol/L NaOH solution at 80 ℃ for 2 h,hydroxyapatite [Ca10（PO4）6（OH）2,HA]appeared on the magnesium alloy substrate,which can further decrease the corrosion rate of AZ60 magnesium alloy in SBF.
基金Japan Society for the Promotion of Science (JSPS)for financial support, which enabled him to pursue this researchwork
文摘Non-mycorrhizal Brassica does not produce specialized root structures such as cluster or dauciform roots but is an effective user of P compared with other crops. In addition to P-uptake, utilization and remobilization activity, acquisition of orthophosphate （Pi） from extracellular sparingly P-sources or unavailable bound P-forms can be enhanced by biochemical rescue mechanisms such copious H＋-efflux and/or carboxylates exudation into rhizosphere by roots via plasmalemma H＋ ATPase and anion channels triggered by P-starvation. To visualize the dissolution of sparingly soluble Ca-phosphate （Ca-P）, newly formed Ca-P was suspended in agar containing other essential nutrients. With NH4＋ applied as the N source, the precipitate dissolved in the root vicinity can be ascribed to rhizosphere acidification, whereas no dissolution occurred with nitrate nutrition. To observe in situ rhizospheric pH changes, images were recorded after embedding the roots in agar containing bromocresol purple as a pH indicator. P-tolerant cultivar showed a greater decrease in pH than the sensitive cultivar in the culture media （the appearance of typical patterns of various colors of pH indicator in the root vicinity）, and at stress P-level this acidification was more prominent. In experiment 2, low P-tolerant class-I cultivars （Oscar and Con-II） showed a greater decrease in solution media pH than low P-sensitive class-II （Gold Rush and RL-18） cultivars, and P-contents of the cultivars was inversely related to decrease in culture media pH. To elucidate P-stress- induced remodeling and redesigning in a root architectural system, cultivars were grown in rhizoboxes in experiment 3. The elongation rates of primary roots increased as P-supply increased, but the elongation rates of the branched zones of primary roots decreased. The length of the lateral roots and topological index values increased when cultivars were exposed to a P-stress environment. To elucidate Pi-uptake kinetics, parameters related to P influx： maximal
