Synthesis And Application Of Core-Shell-Heterostructured Magnetic-Plasmonic Nanoassemblies With Highly Retained Magnetic-Plasmonic Activities In Bioanalysis

Multifunctional nanoparticles(NPs)comprising of more than one NP components have been widely used in biomedical,disease diagnosis,food safety,and environmental monitoring.Among of them,gold magnetic nanoparticles(GMNPs)containing magnetic and plasmonic components exhibit remarkable advantages in biolabeling,bioimaging,bioanalysis,and bioseparation because of its intrinsic optical and magnetic properties However,most of previously reported GMNPs show a typical"gold coated magnetic" core-shell nanostructure.However,the shell of gold nanoparticles could greatly weak the saturation magnetization of GMNPs because of its strong magnetic shielding properties.Ideal GMNPs should simultaneously possess strong magnetic reponse and excellent plasmonic signal transducers.Theoretically,when magnetic components as the shell of the plasmonic materials to form a novel "magnetic coated gold"core-shell-heterostructured nanocomposite,the magnetic response can be retained because the inherent magnetic properties of magnetic components cannot be shielded by the plasmonic components.Recently,various strategies including size segregation,entropy-driven,surface charge,and chemical polarity have been used to order and direct NPs distribution by modulating the phase separation of different NPs components in multifunctional nanomaterials.In this study,we report the polymer-mediated self-assembly strategy of magnetic-plasmonic nanoassemblies(MPNAs)by coassembling oleylamine-coated gold nanoparticles(OA-AuNPs)with oleic acid-coated iron oxide nanoparticles(OC-IONPs)into polymer nanobeads.The synthesized MPNAs exhibit a typical core-shell structure,wherein OA-AuNPs preferentially aggregate and form a plasmonic core and OC-IONPs assemble a magnetic shell.Due to the OC-IONPs distributed in the shell layer,the as-prepared MPNAs achieved the maximum retention of magnetic responsiveness property due to the absence of magnetic shielding from the plasmonic component.The obtained MPNAs were characterized with excellent magnetic properties and plasmonic activities.Using the new MPNAs as the probe of lateral flow immunoassay(LFIA)platform,it can simultaneously realize the magnetic separation of the target analyte from complex sample matrix,and output the plasmonic signal,thereby significantly improve the detection performance of the LFIA.First,a rapid detection method for the detection of anti-hepatitis C antibodies(anti-HCV)in human serum was developed using a MPNA7:3(using 7 mg OA-AuNPs and 3 mg OC-IONPs as building blocks)with an average particle size of 225 nm combined with sandwich LFIA platform(MPNA7:3-LFIA).The visual detection limit(vLOD)of this method is as high as 0.24 pg mL-1,which is 62.5,15.8,and 4.0 times higher than that of AuNP30(with a particle size of 30 nm),PNA10(using 10 mg OA-AuNPs as building blocks),and MNA10(using 10 mg OC-IONPs as building blocks),respectively.The detection results of MPNA7 3-LFIA is in good agreement with the results of enzyme-linked immunosorbent assay(ELISA),indicating that the MPNA7:3-LFIA has high accuracy and reliability.Secondly,a 160 nm magnetic-plamsonic nanomaterial(marked MPNA160)was prepared by adjusting the synthesis parameters.A rapid and highly sensitive competitive LFIA quantitative detection strategy for ochratoxin A(OTA)in grape juice was established using MPNA160 as a novel bifunctional probe(MPNA160-LFIA).This strategy exhibits a good linear relationship when the OTA concentration in grape juice is in the range of 0.098-12.5 ng mL-1,and it meets the linear regression equation y=-0.1791n(.x)+0.4771(R2=0.985).When the OTA concentration of grape juice is in the range of 0.098 ng mL-1 to 12.5 ng mL-1,a good linear relationship was exhibited and the regression equation is y=-0.1791n(x)+0.4771(R2=0.985),The MPNA160-LFIA only showed a significant signal response when detecting OTA,but for 7 common mycotoxins,including aflatoxin B1(AFBi),aflatoxin B2(AFB2),aflatoxin Gi(AFG1),deoxynivalenol(DON),zearalenone(ZEN),fumonisin(FBi)and citrinin(CIT)have no significant signal responses.The intra-and inter-assay recoveries for OTA spiked grape juice were of 92.31%-108.97%,and the variation coefficients were of 1.55%-11.97%,indicating that the proposed strategy has an accepted accuracy and precision.The analytical reliability of the MPNA160-LIFA was further confirmed with liquid chromatography-tandem mass spectrometry(LC-MS)and the results revealed that the MPNA160-LIFA strategy is comparable with LC-MS for the quantitative detection of OTA in grape juice.