Chymosin is one of the critical enzymes in cheese making.Herein,we proposed a novel fluorometric assay for chymosin determination.Firstly,covalent organic frameworks(COF)were synthesized and exfoliated to 2-dimensiona...Chymosin is one of the critical enzymes in cheese making.Herein,we proposed a novel fluorometric assay for chymosin determination.Firstly,covalent organic frameworks(COF)were synthesized and exfoliated to 2-dimensional COF nanosheets(COF NS)by ultrasound treatment.Gold nanoparticles(Au NPs)were loaded with COF NS to prepare AuNPs/COF NS(Au@COF NS).Secondly,rhodamine B(RhB)modified substrate peptide(Pep)for chymosin was linked with Au@COF NS to construct a Pep-Au@COF NS nanocomposite.For the sensing principle,fluorescence of RhB was quenched by Au@COF NS and the fluorescence intensity was weak due to the fluorescence resonance energy transfer between COF NS and RhB of Pep.However,in the presence of chymosin,the RhB was released by specific cleavage of the substrate peptide by chymosin and resulted in the recovery of fluorescence.The increased fluorescence intensity was proportional to the increase of chymosin concentration and thus a“turn on”fluorescent sensor for chymosin was constructed.The sensor showed a linear range in the concentration of 0.05-60.00μg/mL for the detection of chymosin with a detection limit of 20 ng/mL.The sensor was used to quantify chymosin in rennet product with good selectivity,which has the potential applications in cheese manufacturing.展开更多
Circulating tumor cells(CTCs)are important markers for cancer.The part of tumor cells that are detached from the primary tumor or metastatic tumor and enter the blood circulation is called CTCs.It is crucial to develo...Circulating tumor cells(CTCs)are important markers for cancer.The part of tumor cells that are detached from the primary tumor or metastatic tumor and enter the blood circulation is called CTCs.It is crucial to develop a rapid,accurate,and easy-to-implement diagnostic system for CTCs for early tumor diagnosis and for monitoring progression of the disease.In this work,we reported a colorimetric and fluorescent dual-mode assay for the detection of CTCs.Our assay used magnetic nanoparticles and aptamer for CTCs capture and gold nanoparticles-loaded covalent organic frameworks(Au@COFs)for signal amplification,respectively.The magnetic nanoparticles were modified with folic acid to capture CTCs by interaction between folic acid and the folate receptor overexpressed on the surface of tumor cells.The covalent organic frameworks were engineered to have both nitro-reductase-like and glucose–oxidase-like activities.The nitro-reductase-like activity converted the substrate p-nitrophenol to p-nitroaniline for colorimetric detection,and the glucose-oxidase-like activity enabled fluorescence detection.Specifically,Au@COFs catalyzed glucose oxidation and generated hydrogen peroxide to oxidize Fe 2+to Fe 3+,which converted MIL(Al)-MOF to MIL(Fe)-MOF through ion exchange,resulting in the fluorescence quenching of MIL(Al)-MOF.Our assay showed high sensitivity with a detection limit of 17 cells/mL using MCF-7 cells as model cancer cells.This work provided an e fficient and ultrasensitive strategy for CTCs detection and has potential applications in cancer identification and diagnosis.Dual-mode detection system,combining colorimetric and fluorescent signals,integration of magnetic nanoparticles and aptamers for CTC capture,and utilization of covalent organic frameworks loaded with gold nanoparticles for signal amplification can improve sensitivity and accuracy.展开更多
In this study,the flexural and longitudinal shear performances of two types of precast lightweight steel–ultra-high performance concrete(UHPC)composite beams are investigated,where a cluster UHPC slab(CUS)and a norma...In this study,the flexural and longitudinal shear performances of two types of precast lightweight steel–ultra-high performance concrete(UHPC)composite beams are investigated,where a cluster UHPC slab(CUS)and a normal UHPC slab(NUS)are connected to a steel beam using headed studs through discontinuous shear pockets and full-length shear pockets,respectively.Results show that the longitudinal shear force of the CUS is greater than that of the NUS,whereas the interfacial slip of the former is smaller.Owing to its better integrity,the CUS exhibits greater flexural stiffness and a higher ultimate bearing capacity than the NUS.To further optimize the design parameters of the CUS,a parametric study is conducted to investigate their effects on the flexural and longitudinal shear performances.The square shear pocket is shown to be more applicable for the CUS,as the optimal spacing between two shear pockets is 650 mm.Moreover,a design method for transverse reinforcement is proposed;the transverse reinforcement is used to withstand the splitting force caused by studs in the shear pocket and prevent the UHPC slab from cracking.According to calculation results,the transverse reinforcement can be canceled when the compressive strength of UHPC is 150 MPa and the volume fraction of steel fiber exceeds 2.0%.展开更多
基金supported by Major Science and Technology Project of Yunnan Province(202302AE090022)Key Research and Development Program of Yunnan(202203AC100010)+4 种基金the National Natural Science Foundation of China(32160597,32160236,32371463)National Key Research and Development Program of China(2022YFC2601604)Cardiovascular Ultrasound Innovation Team of Yunnan Province(202305AS350021)Spring City Plan:the High-Level Talent Promotion and Training Project of Kunming(2022SCP001)Graduate Tutor Team of Yunnan Province,and the Second Phase of"Double-First Class"Program Construction of Yunnan University.
文摘Chymosin is one of the critical enzymes in cheese making.Herein,we proposed a novel fluorometric assay for chymosin determination.Firstly,covalent organic frameworks(COF)were synthesized and exfoliated to 2-dimensional COF nanosheets(COF NS)by ultrasound treatment.Gold nanoparticles(Au NPs)were loaded with COF NS to prepare AuNPs/COF NS(Au@COF NS).Secondly,rhodamine B(RhB)modified substrate peptide(Pep)for chymosin was linked with Au@COF NS to construct a Pep-Au@COF NS nanocomposite.For the sensing principle,fluorescence of RhB was quenched by Au@COF NS and the fluorescence intensity was weak due to the fluorescence resonance energy transfer between COF NS and RhB of Pep.However,in the presence of chymosin,the RhB was released by specific cleavage of the substrate peptide by chymosin and resulted in the recovery of fluorescence.The increased fluorescence intensity was proportional to the increase of chymosin concentration and thus a“turn on”fluorescent sensor for chymosin was constructed.The sensor showed a linear range in the concentration of 0.05-60.00μg/mL for the detection of chymosin with a detection limit of 20 ng/mL.The sensor was used to quantify chymosin in rennet product with good selectivity,which has the potential applications in cheese manufacturing.
基金financially supported by Major science and technology project of Yunnan Province(202302AE090022)Key Research and Development Program of Yunnan(202203AC100010)+6 种基金the National Natural Science Foundation of China(32160597,32160236,32371463)National Key Research and Development Program of China(2022YFC2601604)Cardiovascular Ultrasound Innovation Team of Yunnan Province(202305AS350021)Spring City Plan:the High-level Talent Promotion and Training Project of Kunming(2022SCP001)the Association Foundation Program of Yunnan Provincial Science and TechnologyDepar tmentKunming Medical University(202101AY070001-278)the second phase of“Double-First Class”program construction of Yunnan University。
文摘Circulating tumor cells(CTCs)are important markers for cancer.The part of tumor cells that are detached from the primary tumor or metastatic tumor and enter the blood circulation is called CTCs.It is crucial to develop a rapid,accurate,and easy-to-implement diagnostic system for CTCs for early tumor diagnosis and for monitoring progression of the disease.In this work,we reported a colorimetric and fluorescent dual-mode assay for the detection of CTCs.Our assay used magnetic nanoparticles and aptamer for CTCs capture and gold nanoparticles-loaded covalent organic frameworks(Au@COFs)for signal amplification,respectively.The magnetic nanoparticles were modified with folic acid to capture CTCs by interaction between folic acid and the folate receptor overexpressed on the surface of tumor cells.The covalent organic frameworks were engineered to have both nitro-reductase-like and glucose–oxidase-like activities.The nitro-reductase-like activity converted the substrate p-nitrophenol to p-nitroaniline for colorimetric detection,and the glucose-oxidase-like activity enabled fluorescence detection.Specifically,Au@COFs catalyzed glucose oxidation and generated hydrogen peroxide to oxidize Fe 2+to Fe 3+,which converted MIL(Al)-MOF to MIL(Fe)-MOF through ion exchange,resulting in the fluorescence quenching of MIL(Al)-MOF.Our assay showed high sensitivity with a detection limit of 17 cells/mL using MCF-7 cells as model cancer cells.This work provided an e fficient and ultrasensitive strategy for CTCs detection and has potential applications in cancer identification and diagnosis.Dual-mode detection system,combining colorimetric and fluorescent signals,integration of magnetic nanoparticles and aptamers for CTC capture,and utilization of covalent organic frameworks loaded with gold nanoparticles for signal amplification can improve sensitivity and accuracy.
基金This study was supported by the National Natural Science Foundation of China(Grant No.U1934205)the Natural Science Foundation of Jiangsu Province(Nos.18KJA580005,19KJA570001,and YSZX-02-2022-01-B).
文摘In this study,the flexural and longitudinal shear performances of two types of precast lightweight steel–ultra-high performance concrete(UHPC)composite beams are investigated,where a cluster UHPC slab(CUS)and a normal UHPC slab(NUS)are connected to a steel beam using headed studs through discontinuous shear pockets and full-length shear pockets,respectively.Results show that the longitudinal shear force of the CUS is greater than that of the NUS,whereas the interfacial slip of the former is smaller.Owing to its better integrity,the CUS exhibits greater flexural stiffness and a higher ultimate bearing capacity than the NUS.To further optimize the design parameters of the CUS,a parametric study is conducted to investigate their effects on the flexural and longitudinal shear performances.The square shear pocket is shown to be more applicable for the CUS,as the optimal spacing between two shear pockets is 650 mm.Moreover,a design method for transverse reinforcement is proposed;the transverse reinforcement is used to withstand the splitting force caused by studs in the shear pocket and prevent the UHPC slab from cracking.According to calculation results,the transverse reinforcement can be canceled when the compressive strength of UHPC is 150 MPa and the volume fraction of steel fiber exceeds 2.0%.
