title: Facile Synthesis of Au-Coated Magnetic Nanoparticles and Their Application in Bacteria Detection via a SERS Method.
abstract: This study proposes a facile method for synthesis of Au-coated magnetic nanoparticles (AuMNPs) core/shell nanocomposites with nanoscale rough surfaces. MnFe2O4 nanoparticles (NPs) were first modified with a uniform polyethylenimine layer (2 nm) through self-assembly under sonication. The negatively charged Au seeds were then adsorbed on the surface of the MnFe2O4 NPs through electrostatic interaction for Au shell formation. Our newly developed sonochemically assisted hydroxylamine seeding growth method was used to grow the adsorbed gold seeds into large Au nanoparticles (AuNPs) to form a nanoscale rough Au shell. Au-coated magnetic nanoparticles (AuMNPs) were obtained from the intermediate product (Au seeds decorated magnetic core) under sonication within 5 min. The AuMNPs were highly uniform in size and shape and exhibited satisfactory surface-enhanced Raman scattering (SERS) activity and strong magnetic responsivity. PATP was used as a probe molecule to evaluate the SERS performance of the synthesized AuMNPs with a detection limit of 10(-9) M. The synthesized AuMNPs were conjugated with Staphylococcus aureus (S. aureus) antibody for bacteria capture and separation. The synthesized plasmonic AuNR-DTNB NPs, whose LSPR wavelength was adjusted to the given laser excitation wavelength (785 nm), were conjugated with S. aureus antibody to form a SERS tag for specific recognition and report of the target bacteria. S. aureus was indirectly detected through SERS based on sandwich-structured immunoassay, with a detection limit of 10 cells/mL. Moreover, the SERS intensity at Raman peak of 1331 cm(-1) exhibited a linear relationship to the logarithm of bacteria concentrations ranging from 10(1) cells/mL to 10(5) cells/mL.
authors.affiliation: Beijing Institute of Radiation Medicine , Beijing 100850, P. R. China.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Wang
authors.forename: Xuezhong
authors.initials: X
authors.lastname: Wu
authors.affiliation: Beijing Institute of Radiation Medicine , Beijing 100850, P. R. China.|College of Life Sciences and Bio-Engineering, Beijing University of Technology , Beijing 100124, P. R. China.
authors.forename: Chongwen
authors.initials: C
authors.lastname: Wang
authors.affiliation: Beijing Institute of Radiation Medicine , Beijing 100850, P. R. China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Rong
authors.affiliation: Beijing Institute of Basic Medical Sciences , Beijing 100850, P. R. China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Ding
authors.affiliation: Beijing Institute of Basic Medical Sciences , Beijing 100850, P. R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Beijing Institute of Basic Medical Sciences , Beijing 100850, P. R. China.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Li
authors.affiliation: Beijing Institute of Basic Medical Sciences , Beijing 100850, P. R. China.
authors.forename: Ningsheng
authors.initials: N
authors.lastname: Shao
authors.forename: Peitao
authors.initials: P
authors.lastname: Dong
authors.affiliation: Beijing Institute of Radiation Medicine , Beijing 100850, P. R. China.
authors.forename: Rui
authors.initials: R
authors.lastname: Xiao
authors.affiliation: Beijing Institute of Radiation Medicine , Beijing 100850, P. R. China.
authors.forename: Shengqi
authors.initials: S
authors.lastname: Wang
mesh_terms: D006046:Gold; D058185:Magnetite Nanoparticles; D053768:Metal Nanoparticles; D012834:Silver; D013059:Spectrum Analysis, Raman; D013211:Staphylococcus aureus
chemical_list: D058185:Magnetite Nanoparticles; D012834:Silver; D006046:Gold
keywords: Au-coated magnetic nanoparticles; AuNRs; Staphylococcus aureus; antibody; surface-enhanced Raman spectroscopy