Some precision electronics such as signal transmitters need to not only emit effective signal but also be protected from the external electromagnetic(EM)waves.Thus,directional electromagnetic interference(EMI)shieldin...Some precision electronics such as signal transmitters need to not only emit effective signal but also be protected from the external electromagnetic(EM)waves.Thus,directional electromagnetic interference(EMI)shielding materials(i.e.,when the EM wave is incident from different sides of the sample,the EMI shielding effectiveness(SE)is rather different)are strongly required;unfortunately,no comprehensive literature report is available on this research field.Herein,Nicoated melamine foams(Ni@MF)were obtained by a facile electroless plating process,and multiwalled carbon nanotube(CNT)papers were prepared via a simple vacuum-assisted self-assembly approach.Then,step-wise asymmetric poly(butylene adipate-co-terephthalate)(PBAT)composites consisting of loose Ni@MF layer and compact CNT layer were successfully fabricated via a facile solution encapsulation approach.The step-wise asymmetric structures and electrical conductivity endow the Ni@MF/CNT/PBAT composites with unprecedented directional EMI shielding performances.When the EM wave is incident from Ni@MF layer or CNT layer,Ni@MF-5/CNT-75/PBAT exhibits the total EMI SE(SET)of 38.3 and 29.5 dB,respectively,which illustrates theΔSET of 8.8 dB.This work opens a new research window for directional EMI shielding composites with step-wise asymmetric structures,which has promising applications in portable electronics and next-generation communication technologies.展开更多
A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temp...A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temperature and dissolved oxygen（DO） on cold active lipase production by batch culture of metagenomic library recombinant clone（CAPL3） from deep-sea sediment were investigated. First, a two-stage temperature control strategy was developed, in which the temperature was kept at 34 ℃ for the first 15 h, and then switched to30 ℃. The cold active lipase activity and productivity reached 315.2 U·ml^-1and 8.08 U·ml^-1·h^-1, respectively,increased by both 14.5% compared to the results obtained with temperature controlled at 30℃. In addition, different DO control modes were conducted, based on the data obtained from the different DO control strategies and analysis of kinetics parameters at different DO levels. A step-wise temperature and DO control strategy were developed to improve lipase production, i.e., temperature and DO level were controlled at 34℃, 30% during 0–15 h;30 ℃, 30% during 15–18 h, and 30 ℃, 20% during 18–39 h. With this strategy, the maximum lipase activity reached 354.6 U·ml^-1at 39 h, which was 28.8% higher than that achieved without temperature and DO control（275.3 U·ml^-1）.展开更多
Native-like endothelium regeneration is a prerequisite for material-guided small-diameter vascular regeneration.In this study,a novel strategy is proposed to achieve phase-adjusted endothelial healing by step-wise mod...Native-like endothelium regeneration is a prerequisite for material-guided small-diameter vascular regeneration.In this study,a novel strategy is proposed to achieve phase-adjusted endothelial healing by step-wise modification of parallel-microgroove-patterned(i.e.,micropatterned)nanofibers with polydopamine-copper ion(PDA-Cu^(2+))complexes,polylysine(PLys)molecules,and Cys-Ala-Gly(CAG)peptides(CAG@PLys@PDA-Cu^(2+)).Using electrospun poly(L-lactide-co-caprolactone)random nanofibers as the demonstrating biomaterial,step-wise modification of CAG@PLys@PDA-Cu^(2+)significantly enhanced substrate wettability and protein adsorption,exhibited an excellent antithrombotic surface and outstanding phase-adjusted capacity of endothelium regeneration involving cell adhesion,endothelial monolayer formation,and the regenerated endothelium maturation.Upon in vivo implantation for segmental replacement of rabbit carotid arteries,CAG@PLys@PDA-Cu^(2+)modified grafts(2 mm inner diameter)with micropatterns on inner surface effectively accelerated native-like endothelium regeneration within 1 week,with less platelet aggregates and inflammatory response compared to those on non-modified grafts.Prolonged observations at 6-and 12-weeks post-implantation demonstrated a positive vascular remodeling with almost fully covered endothelium and mature smooth muscle layer in the modified vascular grafts,accompanied with well-organized extracellular matrix.By contrast,non-modified vascular grafts induced a disorganized tissue formation with a high risk of thrombogenesis.In summary,step-wise modification of CAG@PLys@PDA-Cu^(2+)on micropatterned nanofibers can significantly promote endothelial healing without inflicting thrombosis,thus confirming a novel strategy for developing functional vascular grafts or other blood-contacting materials/devices.展开更多
It is of significance to prepare biodegradable electromagnetic interference(EMI)shielding materials with high EMI shielding effectiveness(SE)in order to solve electromagnetic and environmental pollution problems.In th...It is of significance to prepare biodegradable electromagnetic interference(EMI)shielding materials with high EMI shielding effectiveness(SE)in order to solve electromagnetic and environmental pollution problems.In this paper,environmentally friendly EMI shielding silver nanowires(AgNWs)/poly(L-lactic acid)(PLLA)/poly(D-lactic acid)(PDLA)/ferroferric oxide(Fe_(3)O_(4))composites with step-wise asymmetric structures were prepared by a facile one-step non-solvent-induced phase separation method.The conductive AgNW network was constructed at a low mass fraction of 5 wt.%on the surface of stereo-complexed crystalline poly(lactic acid)(SC-PLA)film(1.08×10^(4) S/m).Moreover,magnetic Fe_(3)O_(4)is mainly distributed in the skeleton of porous SC-PLA film.Due to the synergistic effect of AgNWs and Fe_(3)O_(4),the EMI SE of SC-PLA films reaches up to 50.3 dB.Interestingly,SC-PLA film modified with triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane(TTO)demonstrates an outstanding water contact angle of about 150.2°compared with the pure PLLA film(134.7°),stemming from the synergistic effect of denser SC-PLA nano-protrusions and low-surface-energy TTO.Thus,we successfully fabricated the high EMI shielding SC-PLA film with wonderful superhydrophobicity,which extends the application performance and service life of portable electronics in moist environments.展开更多
基金Science and Technology Plan Project of Guizhou Province(No.[2019]1084 and[2018]5781)National Natural Science Foundation of China(No.51963003)+3 种基金The Youth Science and Technology Talent Growth Project of Guizhou Province Education Department(No.[2018]106)Outstanding Youth Program of Guizhou Province(No.20170439178)The Key project of Fundamental research in Guizhou province[2020]1Z044Scientific Research Project of Introduced Talents of Guizhou University(No.(2017)07)are acknowledged for the financial support.
文摘Some precision electronics such as signal transmitters need to not only emit effective signal but also be protected from the external electromagnetic(EM)waves.Thus,directional electromagnetic interference(EMI)shielding materials(i.e.,when the EM wave is incident from different sides of the sample,the EMI shielding effectiveness(SE)is rather different)are strongly required;unfortunately,no comprehensive literature report is available on this research field.Herein,Nicoated melamine foams(Ni@MF)were obtained by a facile electroless plating process,and multiwalled carbon nanotube(CNT)papers were prepared via a simple vacuum-assisted self-assembly approach.Then,step-wise asymmetric poly(butylene adipate-co-terephthalate)(PBAT)composites consisting of loose Ni@MF layer and compact CNT layer were successfully fabricated via a facile solution encapsulation approach.The step-wise asymmetric structures and electrical conductivity endow the Ni@MF/CNT/PBAT composites with unprecedented directional EMI shielding performances.When the EM wave is incident from Ni@MF layer or CNT layer,Ni@MF-5/CNT-75/PBAT exhibits the total EMI SE(SET)of 38.3 and 29.5 dB,respectively,which illustrates theΔSET of 8.8 dB.This work opens a new research window for directional EMI shielding composites with step-wise asymmetric structures,which has promising applications in portable electronics and next-generation communication technologies.
基金Supported by the Hi-Tech Research and Development Program of China(863 program of China2012AA092103)China Ocean Mineral Resources R&D Association(DY125-15-T-06)
文摘A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temperature and dissolved oxygen（DO） on cold active lipase production by batch culture of metagenomic library recombinant clone（CAPL3） from deep-sea sediment were investigated. First, a two-stage temperature control strategy was developed, in which the temperature was kept at 34 ℃ for the first 15 h, and then switched to30 ℃. The cold active lipase activity and productivity reached 315.2 U·ml^-1and 8.08 U·ml^-1·h^-1, respectively,increased by both 14.5% compared to the results obtained with temperature controlled at 30℃. In addition, different DO control modes were conducted, based on the data obtained from the different DO control strategies and analysis of kinetics parameters at different DO levels. A step-wise temperature and DO control strategy were developed to improve lipase production, i.e., temperature and DO level were controlled at 34℃, 30% during 0–15 h;30 ℃, 30% during 15–18 h, and 30 ℃, 20% during 18–39 h. With this strategy, the maximum lipase activity reached 354.6 U·ml^-1at 39 h, which was 28.8% higher than that achieved without temperature and DO control（275.3 U·ml^-1）.
基金This work was supported by National Key Research and Development Program of China(2018YFC1105800 to WL)China Postdoctoral Science Foundation(2020M681322 to BY)National Natural Science Foundation of China(31870967 to WL and 81701841 to WW).
文摘Native-like endothelium regeneration is a prerequisite for material-guided small-diameter vascular regeneration.In this study,a novel strategy is proposed to achieve phase-adjusted endothelial healing by step-wise modification of parallel-microgroove-patterned(i.e.,micropatterned)nanofibers with polydopamine-copper ion(PDA-Cu^(2+))complexes,polylysine(PLys)molecules,and Cys-Ala-Gly(CAG)peptides(CAG@PLys@PDA-Cu^(2+)).Using electrospun poly(L-lactide-co-caprolactone)random nanofibers as the demonstrating biomaterial,step-wise modification of CAG@PLys@PDA-Cu^(2+)significantly enhanced substrate wettability and protein adsorption,exhibited an excellent antithrombotic surface and outstanding phase-adjusted capacity of endothelium regeneration involving cell adhesion,endothelial monolayer formation,and the regenerated endothelium maturation.Upon in vivo implantation for segmental replacement of rabbit carotid arteries,CAG@PLys@PDA-Cu^(2+)modified grafts(2 mm inner diameter)with micropatterns on inner surface effectively accelerated native-like endothelium regeneration within 1 week,with less platelet aggregates and inflammatory response compared to those on non-modified grafts.Prolonged observations at 6-and 12-weeks post-implantation demonstrated a positive vascular remodeling with almost fully covered endothelium and mature smooth muscle layer in the modified vascular grafts,accompanied with well-organized extracellular matrix.By contrast,non-modified vascular grafts induced a disorganized tissue formation with a high risk of thrombogenesis.In summary,step-wise modification of CAG@PLys@PDA-Cu^(2+)on micropatterned nanofibers can significantly promote endothelial healing without inflicting thrombosis,thus confirming a novel strategy for developing functional vascular grafts or other blood-contacting materials/devices.
基金This work was supported by the National Natural Science Foundation of China(Nos.52263003 and 51963003)the Guizhou Provincial Science and Technology Projects(Nos.[2020]1Z044 and ZK[2022]Maj019).
文摘It is of significance to prepare biodegradable electromagnetic interference(EMI)shielding materials with high EMI shielding effectiveness(SE)in order to solve electromagnetic and environmental pollution problems.In this paper,environmentally friendly EMI shielding silver nanowires(AgNWs)/poly(L-lactic acid)(PLLA)/poly(D-lactic acid)(PDLA)/ferroferric oxide(Fe_(3)O_(4))composites with step-wise asymmetric structures were prepared by a facile one-step non-solvent-induced phase separation method.The conductive AgNW network was constructed at a low mass fraction of 5 wt.%on the surface of stereo-complexed crystalline poly(lactic acid)(SC-PLA)film(1.08×10^(4) S/m).Moreover,magnetic Fe_(3)O_(4)is mainly distributed in the skeleton of porous SC-PLA film.Due to the synergistic effect of AgNWs and Fe_(3)O_(4),the EMI SE of SC-PLA films reaches up to 50.3 dB.Interestingly,SC-PLA film modified with triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane(TTO)demonstrates an outstanding water contact angle of about 150.2°compared with the pure PLLA film(134.7°),stemming from the synergistic effect of denser SC-PLA nano-protrusions and low-surface-energy TTO.Thus,we successfully fabricated the high EMI shielding SC-PLA film with wonderful superhydrophobicity,which extends the application performance and service life of portable electronics in moist environments.
