Application Of GNPs-Based Core-Shell Nanostructure In Dark-Field Microscopic Imaging Detection

Up to now,many nano-probes,such as gold nanoparticles(GNPs),silver nanoparticles and gold nanorods,have been extensively applied in optical microscopy imaging analysis and detection due to their superior optical properties.Among many plasma nanoprobes,GNPs have attracted the attention of researchers due to its unique advantages.As one of plasmonic nanomaterials,GNPs have become a popular probe because of simple synthesis process,stable optical signal and outstanding biocompatibility.Further,the absorption belt of GNPs is located at visible region and the change of its localized surface plasmon resonance(LSPR)can be observed by the naked eye.GNPs have been extensively applied in optical microscopy imaging analysis and detection due to their superior optical properties.Therefore,many sensing detection methods based GNPs have applied in chemistry,biology and other fields.In this paper,based on the single-particle detection(SPD)method of dark-field microscopic imaging,core-shell nanomaterials were used as probe to construct a highly sensitive detection platform for biomolecules and enzyme activities.The main work is as follows:(1)First,spherical and monodispersed GNPs were prepared.Then,the GNP@Mn O₂core-shell nanoparticles were synthesized through modifying the manganese dioxide sheet.In this chapter,GNP@Mn O₂NPs were used as probe to quickly and sensitively detect the amount of xanthine oxidase(XOD)in human serum.In this system,this enzyme catalyzed the oxidation of xanthine to form H₂O₂and uric acid.H₂O₂could etch the Mn O₂layer on the surface of GNP@Mn O₂NPs into Mn²⁺.Due to the LSPR properties of GNPs,the scattering color of the GNP@Mn O₂NPs changes significantly at the single-particle level.This method displayed a linear range(0.02-4 m U/m L)and a lower detection limit(LOD)(7.82?U/m L).The content of uric acid in the system will increase during the detection process.Therefore,quercetin was selected as a natural active substance to explore the inhibitory effect on XOD.The results showed that quercetin can inhibit the activity of XOD and effectively reduce the formation of uric acid.This way has great potential in the prevention and treatment of hyperuricemia and gout.Moreover,this assay proposed in this chapter does not require complicated and expensive equipment and displays tremendous potential in clinical diagnosis.(2)Hydroquinone(HQ)is widely applied in chemical production and other fields as one of the odorous phenolic compounds.The excessive HQ has serious threats to human body and the environment.In this chapter,a dark-field microscopic imaging method for single particle detection is developed to monitor HQ in aqueous solution.Due to the reduction of HQ,the Mn O₂layer of GNP@Mn O₂core-shell nanoparticles can be easily etched and lead to decomposition of the nanomaterials.Since the LSPR peak of GNPs is very sensitive to the change of the surrounding environment,the etching process will cause the obvious LSPR peak shift.At the same time,the color of nanoparticles will have a distinct change under the microscope.The method achieves a LOD of0.19 n M and a linear detection range of 0.001-2.5?M.The sensing assay also obtained satisfactory recovery.(3)In this chapter,we synthesized GNP@CeO₂core-shell nanoparticles by coating ceric oxide(CeO₂)to the gold nanospheres.The morphology and size of the core-shell nanostructures were characterized by optical microscopy imaging,dynamic light scattering,ultraviolet-visible spectrophotometry and transmission electron microscopy.These results show that the GNP@CeO₂core-shell nanostructure have good monodispersion,uniform size and stability.We hope the core-shell nanoparticles can exhibit more application prospects in dark-field microscopy imaging analysis.