Research On Assembling Strategies Of Silver Nanoparticle Composites On Gold Film And Their Applications To Biosensors Based On Surface Plasmon Resonance

Silver nanocomposites exhibit unique physical and chemical properties,such as high specific surface area,high conductivity,high catalytic and reactive activities,which made them suitable for the fabrication of biosensors.Surface plasmon resonance(SPR)biosensor is a type of optical biosensor based on the phenomenon of plasmon resonance at the interface of metal and dielectric materials.Since the refractive index of the materials near the interface,which could affect the plasmon resonance significantly,was determined by the types,morphologies and masses of the substances connected on the surface of metal materials,SPR biosensors could be employed in the real-time and labelfree determination of biomolecules and ligand binding-kinetics by monitoring the optical angle or wavelength shifts of SPR induced by the biochemical events on the sensing surface.Compared to other common analytical techniques,such as fluorescence and isotope labeling,SPR technique could simplify the operations in the analytical procedures and retain the bioactivities of biomolecules in the analytical system.By using SPR biosensors,many information about the biological system,such as concentrations and binding constants of biomolecules,could be obtain rapidly and easily.In this thesis,assembling strategies of silver nanoparticle composites on gold film and their applications to the development of biosensors were investigated.1.A novel surface plasmon resonance(SPR)biosensor based on Ag nanocubes/chitosan composite was fabricated for mouse IgG detection.Silver nanocubes(Ag NCs),synthesized via sulfide-mediated protocol,were modified by 3-Mercaptopropinic acid(MPA)and mixed with chitosan and glutaraldehyde.Then,the Ag NCs/chitosan composite was deposited on a gold film by spin-coating.Antibodies were immobilized on the sensing film with aldehyde groups via Schiff alkali reaction.Transmission electron microscopy(TEM)and UV-Vis spectroscopy were employed to characterize the morphologies of the sensing films during the fabrication procedure.Electronic coupling of the surface plasmon waves originating from the Ag NCs and the gold film lead to the remarkable amplification of the SPR response,which results in the sensitivity enhancement of the SPR biosensor.Compared to the traditional SPR biosensor based on MPA,the concentration of mouse IgG with minimum detectable SPR response obtained by the fabricated biosensor is about 4 times lower.2.A novel polydopamine-silver nanoparticle-polydopamine-gold(PDA-Ag NPsPDA-Au)film-based SPR biosensor for horse IgG detection was developed via layer-bylayer self-assembling.A PDA layer was assembled on the Au film firstly,and then Ag ions were reduced in situ to Ag NPs by PDA,subsequently the top layer of PDA was assembled,which could prevent Ag NPs from being oxidized.Finally,antibodies were immobilized on the top layer of PDA by Schiff alkali reaction.The morphology and thickness of the sensing film were characterized by using scanning electron microscope(SEM)and Talystep.Experimental results show that the PDA-Ag NPs-PDA-Au sensing film is stable,regenerative,selective and sensitive for the detection of horse IgG.The minimum concentration of horse IgG with detectable SPR response obtained by the developed biosensors is 2-fold and 4-fold lower than that obtained with biosensor based on PDA modified gold film and MPA,respectively.