Circular dichroism(CD)spectroscopy has been widely demonstrated for detecting chiral molecules.However,the determination of chiral mixtures with various concentrations and enantiomeric ratios can be a challenging task...Circular dichroism(CD)spectroscopy has been widely demonstrated for detecting chiral molecules.However,the determination of chiral mixtures with various concentrations and enantiomeric ratios can be a challenging task.To solve this problem,we report an enhanced vibrational circular dichroism(VCD)sensing platform based on plasmonic chiral metamaterials,which presents a 6-magnitude signal enhancement with a selectivity of chiral molecules.Guided by coupled-mode theory,we leverage both in-plane and out-of-plane symmetry-breaking structures for chiral metamaterial design enabled by a two-step lithography process,which increases the near-field coupling strengths and varies the ratio between absorption and radiation loss,resulting in improved chiral light-matter interaction and enhanced molecular VCD signals.Besides,we demonstrate the thin-film sensing process of BSA andβ-lactoglobulin proteins,which contain secondary structures a-helix andβ-sheet and achieve a limit of detection down to zeptomole level.Furthermore,we also,for the first time,explore the potential of enhanced VCD spectroscopy by demonstrating a selective sensing process of chiral mixtures,where the mixing ratio can be successfully differentiated with our proposed chiral metamaterials.Our findings improve the sensing signal of molecules and expand the extractable information,paving the way toward label-free,compact,small-volume chiral molecule detection for stereochemical and clinical diagnosisapplications.展开更多
Wearable sensors have drawn vast interest for their convenience to be worn on body to monitor and track body movements or exercise activities in real time.However,wearable electronics rely on powering systems to funct...Wearable sensors have drawn vast interest for their convenience to be worn on body to monitor and track body movements or exercise activities in real time.However,wearable electronics rely on powering systems to function.Herein,a self-powered,porous,flexible,hydrophobic and breathable nanofibrous membrane based on electrospun polyvinylidene fluoride(PVDF)nanofiber has been developed as a tactile sensor with low-cost and simple fabrication for human body motion detection and recognition.Specifically,effects of multi-walled carbon nanotubes(CNT)and barium titanate(BTO)as additives to the fiber morphology as well as mechanical and dielectric properties of the piezoelectric nanofiber membrane were investigated.The fabricated BTO@PVDF piezoelectric nanogenerator(PENG)exhibits the highβ-phase content and best overall electrical performances,thus selected for the flexible sensing device assembly.Meanwhile,the nanofibrous membrane demonstrated robust tactile sensing performance that the device exhibits durability over 12,000 loading test cycles,holds a fast response time of 82.7 ms,responds to a wide pressure range of 0-5 bar and shows a high relative sensitivity,especially in the small force range of 11.6 V/bar upon pressure applied perpendicular to the surface.Furthermore,when attached on human body,its unique fibrous and flexible structure offers the tactile sensor to present as a health care monitor in a self-powered manner by translating motions of different movements to electrical signals with various patterns or sequences.展开更多
Mesenchymal stem/stromal cells(MSCs)have demonstrated therapeutic efficacy for bone regeneration in animal and clinical studies.Although MSCs were initially thought to differentiate to various cell types to replace th...Mesenchymal stem/stromal cells(MSCs)have demonstrated therapeutic efficacy for bone regeneration in animal and clinical studies.Although MSCs were initially thought to differentiate to various cell types to replace the injured/diseased tissue,it is now accepted that these cells secrete factors to promote tissue repair.1 Among these factors,small extracellular vesicles(sEVs)of size 50–200 nm,which include the exosomes,have been identified as the principal agent mediating the wide-ranging therapeutic efficacy of MSCs.2 Several studies have also reported the therapeutic effects of MSC-sEVs to enhance bone repair in animal models,as recently reviewed.3 However,the cellular processes and mechanisms mediated by MSC-sEVs in bone regeneration remain to be fully elucidated.展开更多
基金supported by RIE Advanced Manufacturing and Engineering(AME)Programmatic Grant Project(Grant A18A5b0056,A18A4b0055)Advanced Research and Technology Innovation Center(ARTIC)Project(WBS:A-0005947-20-00)+1 种基金Ministry of Education(MOE)Tier two Project(MOE-T2EP50220-0014)NRF Competitive Research Programme(NRF-CRP15-2015-02)。
文摘Circular dichroism(CD)spectroscopy has been widely demonstrated for detecting chiral molecules.However,the determination of chiral mixtures with various concentrations and enantiomeric ratios can be a challenging task.To solve this problem,we report an enhanced vibrational circular dichroism(VCD)sensing platform based on plasmonic chiral metamaterials,which presents a 6-magnitude signal enhancement with a selectivity of chiral molecules.Guided by coupled-mode theory,we leverage both in-plane and out-of-plane symmetry-breaking structures for chiral metamaterial design enabled by a two-step lithography process,which increases the near-field coupling strengths and varies the ratio between absorption and radiation loss,resulting in improved chiral light-matter interaction and enhanced molecular VCD signals.Besides,we demonstrate the thin-film sensing process of BSA andβ-lactoglobulin proteins,which contain secondary structures a-helix andβ-sheet and achieve a limit of detection down to zeptomole level.Furthermore,we also,for the first time,explore the potential of enhanced VCD spectroscopy by demonstrating a selective sensing process of chiral mixtures,where the mixing ratio can be successfully differentiated with our proposed chiral metamaterials.Our findings improve the sensing signal of molecules and expand the extractable information,paving the way toward label-free,compact,small-volume chiral molecule detection for stereochemical and clinical diagnosisapplications.
基金National Research Foundation(Sustainable Tropical Data Centre Test bed:A-0009465-05-00)L.J.C would like to acknowledge the support from NUS Research Scholarship(GOSU00000042 PVO ARS-FOE 101 IS).
文摘Wearable sensors have drawn vast interest for their convenience to be worn on body to monitor and track body movements or exercise activities in real time.However,wearable electronics rely on powering systems to function.Herein,a self-powered,porous,flexible,hydrophobic and breathable nanofibrous membrane based on electrospun polyvinylidene fluoride(PVDF)nanofiber has been developed as a tactile sensor with low-cost and simple fabrication for human body motion detection and recognition.Specifically,effects of multi-walled carbon nanotubes(CNT)and barium titanate(BTO)as additives to the fiber morphology as well as mechanical and dielectric properties of the piezoelectric nanofiber membrane were investigated.The fabricated BTO@PVDF piezoelectric nanogenerator(PENG)exhibits the highβ-phase content and best overall electrical performances,thus selected for the flexible sensing device assembly.Meanwhile,the nanofibrous membrane demonstrated robust tactile sensing performance that the device exhibits durability over 12,000 loading test cycles,holds a fast response time of 82.7 ms,responds to a wide pressure range of 0-5 bar and shows a high relative sensitivity,especially in the small force range of 11.6 V/bar upon pressure applied perpendicular to the surface.Furthermore,when attached on human body,its unique fibrous and flexible structure offers the tactile sensor to present as a health care monitor in a self-powered manner by translating motions of different movements to electrical signals with various patterns or sequences.
基金This work was funded by National University of Singapore(No.R221000114114,R221000134114)National Medical Research Council Singapore(No.R221000123213)SKL and WST are supported by the Agency for Science,Technology and Research under its Health and Biomedical Sciences Industry Alignment Fund Pre-Positioning(No.H19H6a0026).
文摘Mesenchymal stem/stromal cells(MSCs)have demonstrated therapeutic efficacy for bone regeneration in animal and clinical studies.Although MSCs were initially thought to differentiate to various cell types to replace the injured/diseased tissue,it is now accepted that these cells secrete factors to promote tissue repair.1 Among these factors,small extracellular vesicles(sEVs)of size 50–200 nm,which include the exosomes,have been identified as the principal agent mediating the wide-ranging therapeutic efficacy of MSCs.2 Several studies have also reported the therapeutic effects of MSC-sEVs to enhance bone repair in animal models,as recently reviewed.3 However,the cellular processes and mechanisms mediated by MSC-sEVs in bone regeneration remain to be fully elucidated.
