Ultrasensitive Biosensing Of Critical Hazard Factors Of Food Safety Based On The Functional Nanomaterial

High yield of nanoparticle dimers, trimers, core-shell nanostructures, and multilayermembranes have been controllably assembled in this dissertation, based on the functionalgold, silver, carbon nanomaterials as well as the molecular recongnition system ofantigen-antibody immune response and nucleic acid probe. Following the thoroughlyinvestigation of the plasmonic resonance, chiral absorption and electron transfer propertiesand generation mechanisms of the assembled superstructures, ultrasensitive biosensingmethods have been developed in this dissertation, which has successfully realized thesensitive, rapid detections of critical hazard factors of food safety such as antibotics, biotoxins,and environmental hormones.Firstly, gold and silver nanoparticles were modified with pairs of monoclonal antibodyand antigen, respectively. By regulating the corresponding molar ratio and couplingconditions, controllable assemblies of gold-silver nanoparticle dimers were achieved withhigh yield. Due to the specific conformation and matching interaction of bridgingbiomolecules, the nanoparticle dimers tended to display as scissor-like geometry. Theconsistency of preference of specific-enantiomeric sign, broke the enantiomeric equivalenceof the nanoparticle pairs, resulted in the enantiomeric excess, and eventually acquired strong,bisignate chiroplasmonic absorption in the visible part of the circularly dichroism spectra.Secondly, chiral silver nanoparticles have been achieved by controllably growing alongthe scaffold of the nucleic acid, based on the cytosine-rich DNA template and the well-known―metal-base‖mispairing. The chiroplasmonic absorption can be enhanced by the strongelectromagnetic coupling from―hot-spot‖of metal nanoparticle dimers, resulting in theconstruction of strong chiral nanoparticle trimers based on the gold and silver nanomaterials.Meanwhile, the subsequent growing silver nanoparticle has also improved the chiral signal ofthe former assembled dimers, owing to the plasmonic resonance and electromagnetic couplingeffects. Besides, monodispersed gold-silver core shell nanostructures have also been obtained,with the silver grown under the guidance of the DNA template. The intrinsically largeelectromagentic enhancement factor of core-shell nanostructures, has further improved theplasmonic chiral absorption, and ultimately achieved intense chiral nanoparticle colloids.Thirdly, an ultrasensitive chiroplasmonic biosensing method has been developed, takingadvantage of gold-silver chiral heterodimers structures and the chiral signal sensitive responseto the concentration of heterodimers. The developed novel biosensor has not only successfullyrealized the supersensitive detections of analytes with small molecular weight such asBisphenol A of0.002ng/mL (8.77×1012M) and small peptide of0.0008ng/mL (8.04×1013M), but also achieved the detection of biological protein of5×1010ng/mL (1.52×1020M). The surprising ultrasensitivity of this developed method should attribute to thebisignate shape of chiral spectrum, strongly plasmonic coupling of the incident polarized lightwith the nanostructures, and inherent chirality of biomacromolecules.Lastly, paper supported membrane nanostructure with multilayers of carbon nanotubeshave been constructed through layer-by-layer assembly technology. Then a rapid, sensitive detection method for neomycin biosensing has been developed, based on the configuration ofcarbon nanotubes on the paper support and electron transfer principle. The limit of detectionof neomycin was0.04ng/mL, with the recovery ranging from93.55to110.44%in the milk.