| Surface-enhanced raman scattering-based lateral flow immunoassay（SERS-LFA）was a new immunoassay approach which combines SERS detection technology with traditional immunochromatographic.Due to its simplicity,high efficiency and high-sensitivity,SERS-based immunoassay has been widely used in the detection of nucleic acid,virus,toxin,clinical diagnostic markers,food safety and other detection fields.The high sensitivity of SERS-based immunoassay must be based on SERS tags with high SERS performance.In recent years,The study of core-shell nanomaterials have become a hotspot in the field of SERS-based immunoassay.Compared with single metal nanoparticles,the core-shell composite nanomaterials have unique physical and chemical properties,which can improve the disadvantage of the fabrication of gold,silver and other precious metals with non-uniform particle size,easy aggregation and other shortcomings.Gold-coated Silicon core-shell composite nanomaterials（SiO2@Au core-shell NPs）combine the advantages of the silica spheres with light weight,easy preparation and the gold shell with high SERS performance.Which can be used as high performance SERS tags applicated in SERS-based immunoassay.However,the fabrication of high performance SiO2@Au core-shell NPs was very complicated and difficult.So the practical application of SiO2@Au core-shell NPs as SERS Tags has been limited in the field of SERS-LFA.In order to overcome this difficulties,we proposed a facile and effective method with ultrasonic-assistedPEI-mediatedseedgrowthmethodforfabricationof high-performance SiO2@Au core-shell NPs in first time.The SiO2@Au core-shell NPs play as SERS tags has been successfully used in lateral flow immunoassay and accomplished the detection of Human IgM in high sensitivity and rapidly.A new method of SERS-LFA based on SiO2@Au core-shell NPs was established and successfully applied for the rapid and highly sensitive detection of Ricin,Enterotoxin B and Botulinum toxin A.In this work,we report a sonochemically assisted seed growth method for facile synthesis of monodisperse SiO2@Au core-shell NPs for the first time.Cationic polyethyleneimine（PEI）was used to form a cationic thin interlayer with numerous primary amine groups for easy adsorption of dense Au seeds on the silica surface and keeping the nanostructure stability during shell growth.Sonication was used instead of traditionally used mechanical stirring to shorten the reaction time.The entire reaction process for Au shell formation was completed within 5 min.Moreover,the thickness of the Au shell was easily controlled outside the silica cores of different sizes.Compared with the traditional synthesis method,the reported method is the most convenient synthesis route for preparation of high-performance SiO2@Au core–shell NPs to date.The pre-fabricated SiO2@Au core-shell NPs were suspended in 100μM DTNB ethanol solution incubated for 1h under sonication to fabricate SiO2@Au core-shell NPs SERS Tags with characteristic spectra of DTNB.Then gold-coated sillicon shell SERS tags was used to replace the colloidal gold for the specific antibody labeling and test strip assembling,to establish a new method of SERS immunochromatographic based on SiO2@Au core-shell NPs.With this method,a rapid and highly sensitive detection of human IgM has been completed,and the SERS detection sensitivity of Human IgM was as low as 0.1ng/ml.A new SERS-based immunoassay based on SiO2@Au core-shell NPs was developed in this paper for the ultrosensitivity detection of ricin,enterotoxin B and botulinum toxin A.The specific labeled antibodies of the toxins were conjugated to the surface of the SERS tags by covalent bonds,and the immune complex was captured in the test line of the NC membrane by specific immune reaction.We can complete the detection of three toxins by testing and analyzing the SERS signals of test line,and the LOD of three toxins was as low as 0.1ng/ml,0.05ng/ml and 0.1ng/ml respectively.The sensitivity was 100times higher than Colloidal gold-based immunochromatographic assay methods using the same indirect competitive immunoassay methods. |
