The performance of gold and polystyrene nanoparticles was investigated using quartz crystal microbalance (QCM) as sensor platform;β-Galactosidase antibody with corresponding antigen was utilized for the immunoreactio...The performance of gold and polystyrene nanoparticles was investigated using quartz crystal microbalance (QCM) as sensor platform;β-Galactosidase antibody with corresponding antigen was utilized for the immunoreaction. The development of the immunosensor included: 1) formation of self assembled monolayers on quartz crystals;2a) immobilization of p-aminothiophenol functionalized gold nanoparticles on carboxyl-terminated self assembled monolayer, or 2b) immobilization of polystyrene nanoparticles on crystals modified with p-aminothiophenol self assembled monolayer;3) attachment of monoclonal anti β-Gal on nanoparticles;and 4) detection of target analyte. The nanoparticles used were synthesized in house and characterized by transmission electron microscopy and infrared spectroscopy. The results revealed that antibodies were strongly attached to functionalized gold nanoparticles;the weaker immobilization of antibodies to polystyrene nanoparticles provoked their detachment during antigen detection. When cross reactivity of polystyrene nanoparticles was checked using a different antigen (Brucella), displacement of antibody was not recorded, demonstrating specificity of the reaction. To the best of our knowledge this is the first direct comparison between behaviors of biosensors developed with two commonly used nanoparticles. The results showed that both nanoparticles produced biosensors capable to detect β-Gal. Nevertheless biosensors developed using polystyrene nanoparticles are simpler, cheaper and more eco-friendly than those developed using gold nanoparticles.展开更多
The aims of this study was to examine the effect of the osmotic (NaCl) water stress on, growth and accumulation of endogenous compatible solutes of Bacillus amyloliquefaciens and Microbacterium oleovorans, biocontrol ...The aims of this study was to examine the effect of the osmotic (NaCl) water stress on, growth and accumulation of endogenous compatible solutes of Bacillus amyloliquefaciens and Microbacterium oleovorans, biocontrol agents against Fusarium verticillioides. Triptic soya broth media were modified ionically to 0.99;0.98;0.97 and 0.96 aw with NaCl. The endogenous contents of the intracellular compatible solutes glycine-betaine and ectoine were quantified. Cells grown under ionic solute stress showed accumulation of significant amounts of both amino acids in all treatments. The growth rate of F. verticillioides was decreased significantly by interaction with B. amyloliquefaciens and M. oleovorans physiologically adapted at 0.96 aw. This study have demonstrated the ability to synthesize betaine and ectoine under high-osmolality conditions of B. amyloliquefaciens and M. oleovorans cells. Such ecophysiological manipulation, especially to water stress, may increase the potential for biological control of F. verticillioides at field under wider aw conditions.展开更多
Recent advances in large area graphene growth have led to many applications in different areas. In the present study, chemical vapor deposited （CVD） monolayer graphene supported on glass substrate electrochemical bi...Recent advances in large area graphene growth have led to many applications in different areas. In the present study, chemical vapor deposited （CVD） monolayer graphene supported on glass substrate electrochemical biosensing applications was examined as electrode material for We report a facile strategy for covalent functionalization of CVD monolayer graphene by electrochemical reduction of carboxyphenyl diazonium salt prepared in situ in acidic aqueous solution. The carboxyphenyl-modified graphene is characterized using Raman spectroscopy, X-ray photoelectron spectroscopy （XPS）, and atomic force microscopy （AFM）, as well as electrochemical impedance spectroscopy （hIS）. We also show that the number of grafted carboxyphenyl groups on the graphene surface can be controlled by the number of cyclic voltammetry （CV） scans used for electrografting. We further present the fabrication and characterization of an immunosensor based on immobilization of ovalbumin antibody on the graphene surface after the activation of the grafted carboxylic groups via EDC/NHS chemistry. The binding between the surface-immobilized antibodies and ovalbumin was then monitored using Faradaic EIS in [Fe（CN）6]^3-/4- solution. The percentage change of charge transfer resistance （Rct） after binding exhibited a linear dependence for ovalbumin concentrations ranging from 1.0 pg·mL^-1 to 100 ng·mL^-1, with a detection limit of 0.9 pg·mL^-1. Our results indicate good sensitivity of the developed functionalized CVD graphene platform, paving the way for using CVD monolayer graphene in a variety of electrochemical biosensing devices.展开更多
文摘The performance of gold and polystyrene nanoparticles was investigated using quartz crystal microbalance (QCM) as sensor platform;β-Galactosidase antibody with corresponding antigen was utilized for the immunoreaction. The development of the immunosensor included: 1) formation of self assembled monolayers on quartz crystals;2a) immobilization of p-aminothiophenol functionalized gold nanoparticles on carboxyl-terminated self assembled monolayer, or 2b) immobilization of polystyrene nanoparticles on crystals modified with p-aminothiophenol self assembled monolayer;3) attachment of monoclonal anti β-Gal on nanoparticles;and 4) detection of target analyte. The nanoparticles used were synthesized in house and characterized by transmission electron microscopy and infrared spectroscopy. The results revealed that antibodies were strongly attached to functionalized gold nanoparticles;the weaker immobilization of antibodies to polystyrene nanoparticles provoked their detachment during antigen detection. When cross reactivity of polystyrene nanoparticles was checked using a different antigen (Brucella), displacement of antibody was not recorded, demonstrating specificity of the reaction. To the best of our knowledge this is the first direct comparison between behaviors of biosensors developed with two commonly used nanoparticles. The results showed that both nanoparticles produced biosensors capable to detect β-Gal. Nevertheless biosensors developed using polystyrene nanoparticles are simpler, cheaper and more eco-friendly than those developed using gold nanoparticles.
文摘The aims of this study was to examine the effect of the osmotic (NaCl) water stress on, growth and accumulation of endogenous compatible solutes of Bacillus amyloliquefaciens and Microbacterium oleovorans, biocontrol agents against Fusarium verticillioides. Triptic soya broth media were modified ionically to 0.99;0.98;0.97 and 0.96 aw with NaCl. The endogenous contents of the intracellular compatible solutes glycine-betaine and ectoine were quantified. Cells grown under ionic solute stress showed accumulation of significant amounts of both amino acids in all treatments. The growth rate of F. verticillioides was decreased significantly by interaction with B. amyloliquefaciens and M. oleovorans physiologically adapted at 0.96 aw. This study have demonstrated the ability to synthesize betaine and ectoine under high-osmolality conditions of B. amyloliquefaciens and M. oleovorans cells. Such ecophysiological manipulation, especially to water stress, may increase the potential for biological control of F. verticillioides at field under wider aw conditions.
文摘Recent advances in large area graphene growth have led to many applications in different areas. In the present study, chemical vapor deposited （CVD） monolayer graphene supported on glass substrate electrochemical biosensing applications was examined as electrode material for We report a facile strategy for covalent functionalization of CVD monolayer graphene by electrochemical reduction of carboxyphenyl diazonium salt prepared in situ in acidic aqueous solution. The carboxyphenyl-modified graphene is characterized using Raman spectroscopy, X-ray photoelectron spectroscopy （XPS）, and atomic force microscopy （AFM）, as well as electrochemical impedance spectroscopy （hIS）. We also show that the number of grafted carboxyphenyl groups on the graphene surface can be controlled by the number of cyclic voltammetry （CV） scans used for electrografting. We further present the fabrication and characterization of an immunosensor based on immobilization of ovalbumin antibody on the graphene surface after the activation of the grafted carboxylic groups via EDC/NHS chemistry. The binding between the surface-immobilized antibodies and ovalbumin was then monitored using Faradaic EIS in [Fe（CN）6]^3-/4- solution. The percentage change of charge transfer resistance （Rct） after binding exhibited a linear dependence for ovalbumin concentrations ranging from 1.0 pg·mL^-1 to 100 ng·mL^-1, with a detection limit of 0.9 pg·mL^-1. Our results indicate good sensitivity of the developed functionalized CVD graphene platform, paving the way for using CVD monolayer graphene in a variety of electrochemical biosensing devices.
