The mechanical properties and the crystal morphological structures of the dynamically photocrosslinked polypropylene(PP)/ethylene-propylene-diene terpolymer(EPDM) blends have been studied by means of mechanical tests,...The mechanical properties and the crystal morphological structures of the dynamically photocrosslinked polypropylene(PP)/ethylene-propylene-diene terpolymer(EPDM) blends have been studied by means of mechanical tests, wide-angle X-ray diffraction(WAXD), and differential scanning calorimetry(DSC). The dynamically photocrosslinking of the PP/EPDM blends can improve the mechanical properties considerably, especially the notched Izod impact strength at low temperatures. The data obtained from the mechanical tests show that the notched Izod impact strength of the dynamically photocrosslinked sample with 30% EPDM at -20 ℃ is about six times that of the uncrosslinked sample with the same EPDM component. The results from the gel content, the results of WAXD, and the DSC measurements reveal the enhanced mechanism of the impact strength for the dynamically photocrosslinked PP/EPDM blends as follows: (1) There exists the crosslinking of the EPDM phase in the photocrosslinked PP/EPDM blends; (2) The β-type crystal structure of PP is formed and the content of α-type crystal decreases with increasing the EPDM component; (3) The graft copolymer of PP-g-EPDM is formed at the interface between the PP and EPDM components. All the above changes of the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of the PP/EPDM blends at low temperatures.展开更多
The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length a...The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length and the concentration of alkyl benzene sulfonic acids on the rate of degradation reaction were discussed. It was found that in the initial stage of degradation, the cyclicity ratio and the average fused ring number did not change considerably, but the percentage of uncyclized parts content varied significantly. The suitable mechanism was supposed.展开更多
Bone tissue engineering(BTE)has been proven to be an effective method for the treatment of bone defects caused by different musculoskeletal disorders.Photocrosslinkable hydrogels(PCHs)with good biocompatibility and bi...Bone tissue engineering(BTE)has been proven to be an effective method for the treatment of bone defects caused by different musculoskeletal disorders.Photocrosslinkable hydrogels(PCHs)with good biocompatibility and biodegradability can significantly promote the migration,proliferation and differentiation of cells and have been widely used in BTE.Moreover,photolithography 3D bioprinting technology can notably help PCHs-based scaffolds possess a biomimetic structure of natural bone,meeting the structural requirements of bone regeneration.Nanomaterials,cells,drugs and cytokines added into bioinks can enable different functionalization strategies for scaffolds to achieve the desired properties required for BTE.In this review,we demonstrate a brief introduction of the advantages of PCHs and photolithography-based 3D bioprinting technology and summarize their applications in BTE.Finally,the challenges and potential future approaches for bone defects are outlined.展开更多
Tissue engineering provides a promising strategy for auricular reconstruction.Although the first international clinical breakthrough of tissue-engineered auricular reconstruction has been realized based on polymer sca...Tissue engineering provides a promising strategy for auricular reconstruction.Although the first international clinical breakthrough of tissue-engineered auricular reconstruction has been realized based on polymer scaffolds,this approach has not been recognized as a clinically available treatment because of its unsatisfactory clinical efficacy.This is mainly since reconstruction constructs easily cause inflammation and deformation.In this study,we present a novel strategy for the development of biological auricle equivalents with precise shapes,low immunogenicity,and excellent mechanics using auricular chondrocytes and a bioactive bioink based on biomimetic microporous methacrylate-modified acellular cartilage matrix(ACMMA)with the assistance of gelatin methacrylate(GelMA),poly(ethylene oxide)(PEO),and polycaprolactone(PCL)by integrating multi-nozzle bioprinting technology.Photocrosslinkable ACMMA is used to emulate the intricacy of the cartilage-specific microenvironment for active cellular behavior,while GelMA,PEO,and PCL are used to balance printability and physical properties for precise structural stability,form the microporous structure for unhindered nutrient exchange,and provide mechanical support for higher shape fidelity,respectively.Finally,mature auricular cartilage-like tissues with high morphological fidelity,excellent elasticity,abundant cartilage lacunae,and cartilage-specific ECM deposition are successfully regenerated in vivo,which provides new opportunities and novel strategies for the fabrication and regeneration of patient-specific auricular cartilage.展开更多
The multiple antibiotic resistance regulatory protein(MarR) binds to two promoter sites on the marO operator in Escherichia coli.Our study showed that more than one MarR dimer proteins bound to either of its two promo...The multiple antibiotic resistance regulatory protein(MarR) binds to two promoter sites on the marO operator in Escherichia coli.Our study showed that more than one MarR dimer proteins bound to either of its two promoter sites(Site I and Site II),suggesting that MarR might form higher complexes than homodimers when bound to DNA inside E.coli cells.To further verify this hypothesis,we site-specifically incorporated a photocrosslinking probe at the interface between two MarR dimer proteins.Photolysis in living E.coli cells revealed a covalent linkage between the two interdimer subunits of MarR,suggesting that MarR forms dimer of dimers in vivo.展开更多
Guided bone regeneration membranes have been effectively applied in oral implantology to repair bone defects.However,typical resorbable membranes composed of collagen(Col)have insufficient mechanical properties and hi...Guided bone regeneration membranes have been effectively applied in oral implantology to repair bone defects.However,typical resorbable membranes composed of collagen(Col)have insufficient mechanical properties and high degradation rate,while non-resorbable membranes need secondary surgery.Herein,we designed a photocrosslinkable collagen/polycaprolactone methacryloyl/magnesium(Col/PCLMA/Mg)composite membrane that provided spatiotemporal support effect after photocrosslinking.Magnesium particles were added to the PCLMA solution and Col/PCLMA and Col/PCLMA/Mg membranes were developed;Col membranes and PCL membranes were used as controls.After photocrosslinking,an interpenetrating polymer network was observed by scanning electron microscopy(SEM)in Col/PCL and Col/PCL/Mg membranes.The elastic modulus,swelling behavior,cytotoxicity,cell attachment,and cell proliferation of the membranes were evaluated.Degradation behavior in vivo and in vitro was monitored according to mass change and by SEM.The membranes were implanted into calvarial bone defects of rats for 8 weeks.The Col/PCL and Col/PCL/Mg membranes displayed much higher elastic modulus(p<0.05),and a lower swelling rate(p<0.05),than Col membranes,and there were no differences in cell biocompatibility among groups(p>0.05).The Col/PCL and Col/PCL/Mg membranes had lower degradation rates than the Col membranes,both in vivo and in vitro(p<0.05).The Col/PCL/Mg groups showed enhanced osteogenic capability compared with the Col groups at week 8(p<0.05).The Col/PCL/Mg composite membrane represents a new strategy to display space maintenance and enhance osteogenic potential,which meets clinical needs.展开更多
Block copolymers poly（endo-N-3,5-bis（trifluoromethyl）biphenyl-norbornene-pyrrolidine）-block-poly（exo-N-（cinnamoyloxyethyl）-7-oxanorborn-5-ene-2,3-dicarboximide）（endo-PTNP-b-exo-PCONBI） and poly（exo-N-3,5-bi...Block copolymers poly（endo-N-3,5-bis（trifluoromethyl）biphenyl-norbornene-pyrrolidine）-block-poly（exo-N-（cinnamoyloxyethyl）-7-oxanorborn-5-ene-2,3-dicarboximide）（endo-PTNP-b-exo-PCONBI） and poly（exo-N-3,5-bis（trifluoromethyl）biphenyl-norbornene-pyrrolidine）-block-poly（exo-N-（cinnamoyloxyethyl）-7-oxanorborn-5-ene-2,3-dicarboximide）（exo-PTNP-b-exo-PCONBI） were synthesized by ring-opening metathesis polymerization. The endo- or exoPTNP served as the high dielectric functional chain, and exo-PCONBI acted as the crosslinking segment. The endo-PTNPb-exo-PCONBI, in which endo-PTNP has a high content of trans double bond and adopts isotactic configuration, shows a dielectric constant（？） of 15.5, whereas exo-PTNP-b-exo-PCONBI, in which exo-PTNP has 67% trans double bonds and atactic microstructure, displays relatively low ？ of 7.1. The cinnamate groups in exo-PCONBI were crosslinked to form three-dimensional network by cycloaddition reaction under UV irradiation. Exposed to UV-light for 10 min, the cinnamate group in polymer films has a crosslinking conversion of 36%, as determined by UV-Vis absorption measurements. By photocrosslinking, the polymer film has an increased ？ of 16.6, a dielectric loss of 0.03, an elevated glass-transition temperature of 137 ？C, and an enhanced decomposition temperature of 405 ？C, compared to those of polymer films without irradiation.展开更多
Hollow polymer particles are widely used in various industries as coatings and thermal insulation materials.The encapsulation capabilities of various functional molecules and/or nanomaterials also provide access to ap...Hollow polymer particles are widely used in various industries as coatings and thermal insulation materials.The encapsulation capabilities of various functional molecules and/or nanomaterials also provide access to applications such as drug delivery,heat storage,and catalysis,as well as self-healing materials.In this study,we successfully fabricated hollow polymer particles from poly(vinyl cinnamate)(PVC)particles using LED light(λ=265 nm)through interfacial photocrosslinking.Furthermore,we systematically studied the effect of various parameters(solid contents of parent particles,photoirradiation time,photoirradiation power,and polymer chain length)on the polymer shell thickness of the hollow PVC particles fabricated by interfacial photocrosslinking.These findings are expected to further promote the use of hollow polymer particles in pharmaceutical and material applications.展开更多
he multiple antibiotic resistance regulatory protein(MarR) binds to two promoter sites on the marO operator in Escherichia coli.Our study showed that more than one MarR dimer proteins bound to either of its two promot...he multiple antibiotic resistance regulatory protein(MarR) binds to two promoter sites on the marO operator in Escherichia coli.Our study showed that more than one MarR dimer proteins bound to either of its two promoter sites(Site I and Site II),suggesting that MarR might form higher complexes than homodimers when bound to DNA inside E.coli cells.To further verify this hypothesis,we site-specifically incorporated a photocrosslinking probe at the interface between two MarR dimer proteins.Photolysis in living E.coli cells revealed a covalent linkage between the two interdimer subunits of MarR,suggesting that MarR forms dimer of dimers in vivo.展开更多
The recent developments in the photoinitiated cross-linking of polyethylene and the significant breakthrough of its industrial application are reviewed. The enhanced photo-initiation system, the dynamics of photoiniti...The recent developments in the photoinitiated cross-linking of polyethylene and the significant breakthrough of its industrial application are reviewed. The enhanced photo-initiation system, the dynamics of photoinitiated crosslinking, the optimum conditions, the crystal morphological structures and related properties, and the photo- and thermo-oxidation stability of photocrosslinked polyethylene (XLPE) materials have been elucidated systematically. A new technique for producing photocrosslinked XLPE-insulated wire and cable is described in detail. It can be expected that the future applications of photocrosslinking technique of polyolefins will be very promising.展开更多
文摘The mechanical properties and the crystal morphological structures of the dynamically photocrosslinked polypropylene(PP)/ethylene-propylene-diene terpolymer(EPDM) blends have been studied by means of mechanical tests, wide-angle X-ray diffraction(WAXD), and differential scanning calorimetry(DSC). The dynamically photocrosslinking of the PP/EPDM blends can improve the mechanical properties considerably, especially the notched Izod impact strength at low temperatures. The data obtained from the mechanical tests show that the notched Izod impact strength of the dynamically photocrosslinked sample with 30% EPDM at -20 ℃ is about six times that of the uncrosslinked sample with the same EPDM component. The results from the gel content, the results of WAXD, and the DSC measurements reveal the enhanced mechanism of the impact strength for the dynamically photocrosslinked PP/EPDM blends as follows: (1) There exists the crosslinking of the EPDM phase in the photocrosslinked PP/EPDM blends; (2) The β-type crystal structure of PP is formed and the content of α-type crystal decreases with increasing the EPDM component; (3) The graft copolymer of PP-g-EPDM is formed at the interface between the PP and EPDM components. All the above changes of the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of the PP/EPDM blends at low temperatures.
文摘The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length and the concentration of alkyl benzene sulfonic acids on the rate of degradation reaction were discussed. It was found that in the initial stage of degradation, the cyclicity ratio and the average fused ring number did not change considerably, but the percentage of uncyclized parts content varied significantly. The suitable mechanism was supposed.
基金supported by Beijing Natural Science Foundation(Grant No.L202033)the Key Program of National Natural Science Foundation of China(Grant No.21935011)+2 种基金the Military Medical Science and Technology Youth Training Program(Grant No.19QNP052)the Basic Strengthening Research Program(2020-JCJQ-ZD-264-3-2)the Military training injury prevention and treatment research(21XLS29).
文摘Bone tissue engineering(BTE)has been proven to be an effective method for the treatment of bone defects caused by different musculoskeletal disorders.Photocrosslinkable hydrogels(PCHs)with good biocompatibility and biodegradability can significantly promote the migration,proliferation and differentiation of cells and have been widely used in BTE.Moreover,photolithography 3D bioprinting technology can notably help PCHs-based scaffolds possess a biomimetic structure of natural bone,meeting the structural requirements of bone regeneration.Nanomaterials,cells,drugs and cytokines added into bioinks can enable different functionalization strategies for scaffolds to achieve the desired properties required for BTE.In this review,we demonstrate a brief introduction of the advantages of PCHs and photolithography-based 3D bioprinting technology and summarize their applications in BTE.Finally,the challenges and potential future approaches for bone defects are outlined.
基金supported by the National Key Research and Development Program of China(2017YFC1103900)the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences(2017-I2M-1-007,2021-I2M-1-052)the National Natural Science Foundation of China(81871502,81871575).
文摘Tissue engineering provides a promising strategy for auricular reconstruction.Although the first international clinical breakthrough of tissue-engineered auricular reconstruction has been realized based on polymer scaffolds,this approach has not been recognized as a clinically available treatment because of its unsatisfactory clinical efficacy.This is mainly since reconstruction constructs easily cause inflammation and deformation.In this study,we present a novel strategy for the development of biological auricle equivalents with precise shapes,low immunogenicity,and excellent mechanics using auricular chondrocytes and a bioactive bioink based on biomimetic microporous methacrylate-modified acellular cartilage matrix(ACMMA)with the assistance of gelatin methacrylate(GelMA),poly(ethylene oxide)(PEO),and polycaprolactone(PCL)by integrating multi-nozzle bioprinting technology.Photocrosslinkable ACMMA is used to emulate the intricacy of the cartilage-specific microenvironment for active cellular behavior,while GelMA,PEO,and PCL are used to balance printability and physical properties for precise structural stability,form the microporous structure for unhindered nutrient exchange,and provide mechanical support for higher shape fidelity,respectively.Finally,mature auricular cartilage-like tissues with high morphological fidelity,excellent elasticity,abundant cartilage lacunae,and cartilage-specific ECM deposition are successfully regenerated in vivo,which provides new opportunities and novel strategies for the fabrication and regeneration of patient-specific auricular cartilage.
基金supported by research grants from the National Natural Science Foundation of China(91013005, 21001010 and 20932006 to P.R.C.)National Key Basic Research Foundation of China(2010CB912300 to P.R.C.)
文摘The multiple antibiotic resistance regulatory protein(MarR) binds to two promoter sites on the marO operator in Escherichia coli.Our study showed that more than one MarR dimer proteins bound to either of its two promoter sites(Site I and Site II),suggesting that MarR might form higher complexes than homodimers when bound to DNA inside E.coli cells.To further verify this hypothesis,we site-specifically incorporated a photocrosslinking probe at the interface between two MarR dimer proteins.Photolysis in living E.coli cells revealed a covalent linkage between the two interdimer subunits of MarR,suggesting that MarR forms dimer of dimers in vivo.
基金This study was supported by the Innovation research program[HHKT-00-03]the National Natural Science Foundation of China[grant numbers 82170929,81970908,51901003,81200814,and 81771039].
文摘Guided bone regeneration membranes have been effectively applied in oral implantology to repair bone defects.However,typical resorbable membranes composed of collagen(Col)have insufficient mechanical properties and high degradation rate,while non-resorbable membranes need secondary surgery.Herein,we designed a photocrosslinkable collagen/polycaprolactone methacryloyl/magnesium(Col/PCLMA/Mg)composite membrane that provided spatiotemporal support effect after photocrosslinking.Magnesium particles were added to the PCLMA solution and Col/PCLMA and Col/PCLMA/Mg membranes were developed;Col membranes and PCL membranes were used as controls.After photocrosslinking,an interpenetrating polymer network was observed by scanning electron microscopy(SEM)in Col/PCL and Col/PCL/Mg membranes.The elastic modulus,swelling behavior,cytotoxicity,cell attachment,and cell proliferation of the membranes were evaluated.Degradation behavior in vivo and in vitro was monitored according to mass change and by SEM.The membranes were implanted into calvarial bone defects of rats for 8 weeks.The Col/PCL and Col/PCL/Mg membranes displayed much higher elastic modulus(p<0.05),and a lower swelling rate(p<0.05),than Col membranes,and there were no differences in cell biocompatibility among groups(p>0.05).The Col/PCL and Col/PCL/Mg membranes had lower degradation rates than the Col membranes,both in vivo and in vitro(p<0.05).The Col/PCL/Mg groups showed enhanced osteogenic capability compared with the Col groups at week 8(p<0.05).The Col/PCL/Mg composite membrane represents a new strategy to display space maintenance and enhance osteogenic potential,which meets clinical needs.
基金financially supported by the National Natural Science Foundation of China(Nos.21574041 and 21374030)Large Instruments Open Foundation of East China Normal University(No.20151006)
文摘Block copolymers poly（endo-N-3,5-bis（trifluoromethyl）biphenyl-norbornene-pyrrolidine）-block-poly（exo-N-（cinnamoyloxyethyl）-7-oxanorborn-5-ene-2,3-dicarboximide）（endo-PTNP-b-exo-PCONBI） and poly（exo-N-3,5-bis（trifluoromethyl）biphenyl-norbornene-pyrrolidine）-block-poly（exo-N-（cinnamoyloxyethyl）-7-oxanorborn-5-ene-2,3-dicarboximide）（exo-PTNP-b-exo-PCONBI） were synthesized by ring-opening metathesis polymerization. The endo- or exoPTNP served as the high dielectric functional chain, and exo-PCONBI acted as the crosslinking segment. The endo-PTNPb-exo-PCONBI, in which endo-PTNP has a high content of trans double bond and adopts isotactic configuration, shows a dielectric constant（？） of 15.5, whereas exo-PTNP-b-exo-PCONBI, in which exo-PTNP has 67% trans double bonds and atactic microstructure, displays relatively low ？ of 7.1. The cinnamate groups in exo-PCONBI were crosslinked to form three-dimensional network by cycloaddition reaction under UV irradiation. Exposed to UV-light for 10 min, the cinnamate group in polymer films has a crosslinking conversion of 36%, as determined by UV-Vis absorption measurements. By photocrosslinking, the polymer film has an increased ？ of 16.6, a dielectric loss of 0.03, an elevated glass-transition temperature of 137 ？C, and an enhanced decomposition temperature of 405 ？C, compared to those of polymer films without irradiation.
基金Environmental Restoration and Conservation Agency,Grant/Award Number:JPMEERF20221R03Japan Society for the Promotion of Science,Grant/Award Number:21H02004Leading Initiative for Excellent Young Researchers,and MEXT,Japan。
文摘Hollow polymer particles are widely used in various industries as coatings and thermal insulation materials.The encapsulation capabilities of various functional molecules and/or nanomaterials also provide access to applications such as drug delivery,heat storage,and catalysis,as well as self-healing materials.In this study,we successfully fabricated hollow polymer particles from poly(vinyl cinnamate)(PVC)particles using LED light(λ=265 nm)through interfacial photocrosslinking.Furthermore,we systematically studied the effect of various parameters(solid contents of parent particles,photoirradiation time,photoirradiation power,and polymer chain length)on the polymer shell thickness of the hollow PVC particles fabricated by interfacial photocrosslinking.These findings are expected to further promote the use of hollow polymer particles in pharmaceutical and material applications.
文摘he multiple antibiotic resistance regulatory protein(MarR) binds to two promoter sites on the marO operator in Escherichia coli.Our study showed that more than one MarR dimer proteins bound to either of its two promoter sites(Site I and Site II),suggesting that MarR might form higher complexes than homodimers when bound to DNA inside E.coli cells.To further verify this hypothesis,we site-specifically incorporated a photocrosslinking probe at the interface between two MarR dimer proteins.Photolysis in living E.coli cells revealed a covalent linkage between the two interdimer subunits of MarR,suggesting that MarR forms dimer of dimers in vivo.
基金The project was successively supported by the National Natural Science Foundation of China(No. 5880104, No. 59543002 and No. 59773030).
文摘The recent developments in the photoinitiated cross-linking of polyethylene and the significant breakthrough of its industrial application are reviewed. The enhanced photo-initiation system, the dynamics of photoinitiated crosslinking, the optimum conditions, the crystal morphological structures and related properties, and the photo- and thermo-oxidation stability of photocrosslinked polyethylene (XLPE) materials have been elucidated systematically. A new technique for producing photocrosslinked XLPE-insulated wire and cable is described in detail. It can be expected that the future applications of photocrosslinking technique of polyolefins will be very promising.
