Preparation Of Multi-functionalized Bimetallic Nanomaterials And Their Applications In Electrochemiluminescence Immunoassay

With the rapid development of nanoscience,the metallic namomaterials based signal amplification strategy show tremendous potential in improving the sensitivity and selectivity of immunosensor.It's well known that bimetallic nanocrystals exhibit enhanced performance especially in electrocatalytic activity than their monometallic counterparts due to possible synergetic effects.However,it remains great challenge to make metallic nanomaterials possess more functionality for simplifying the experimental operation as well as enhancing the reacted efficiency.For this reason,various functional bimetallic nanocomposites including co-reactant fuctionalized core-shell Pd-Au hexoctahedrons,luminescent fuctionalized Pd@Au nanoparticles and self-catalyzed luminescence nanocomposite were synthesized.Besides,the possible reacted mechanisms of co-reactant and catalyzer for luminophor were proposed.Combining the ECL sensing technology and biotechnology,these multi-functionalized nanomaterials were applied for developing a series of highly-sensitive immunosensors,which successfully achieved the quantitative detection of different antigens.The main results are as following:1.An electrochemiluminescence immunosensor based on co-reactant functionalized core-shell hexoctahedronsAdding the co-reactants into detection solution suffered from the increase of reagent demand and measurement error.Using core-shell hexoctahedrons as nano-carriers successfully achieved the abundant immobilization of co-reactant as well as signal amplification of ECL,which could simplify the experiment operations and efficiently improve sensitivity of immunosensor.It has been reported that the luminophore S2O82-could produce a very strong ECL signal when the detection solution contained norfloxacin(NFLX),which was about 350 times higher than that ofS2O82-alone.With the goal of immobilizing abundant NFLX molecules on the surface of electrode,amino-terminated PAMAM which possesses a high density of surface active groups is used for loading NFLX through amide linkage to form PAMAM-NFLX complex.Thus,the resultant PAMAM-NFLX can serve as a novel co-reactant to efficiently amplify the ECL signal of peroxydisulfate-oxygen(S2O82--O2)system.Meanwhile,convex Pd-Au hexoctahedrons(Pd@Au HOHs)with core-shell structure were synthesized using a facile chemical reduction method.The Pd@Au HOHs nor only possess good biocompatibility and outstanding electronic properties,but also further enhance the ECL signal by promoting the generation of intermediate free radical HO· during the ECL reaction of S2O82--O2 system.Besides,Pd@Au HOHs could massively assemble detection antibody and the PAMAM-NFLX complex in view of their high specific surface area.Based on above perspectives,a sandwich-type ECL immunosensor is fabricated for the detection of thyroid stimulating hormone(TSH).The proposed immunosensor shows high sensitivity and specificity,and successfully achieves the detection of TSH in practical human blood serum with desirable results.2.The research on electrochemiluminescence immunosensor based on luminophore capped core-shell nanoparticles as signal tracers and ferrocenyl compounds as signal enhancersThe previous way of synthesizing luminol or its analogue capped namomaterials mainly need boiling condition and yield luminescent fuctionalized monometallic nanoparticles.However,it's well known that bimetallic nanocrystals exhibit enhanced performance especially in electrocatalytic activity than their monometallic counterparts.In order to synthesize luminescent fuctionalized bimetallic nanomaterials,N-(aminobutyl)-N-(ethylisoluminol)(ABEI),an analogue of luminol,is chosen as the reductant and luminescence reagent to prepare electrochemiluminescent Pd@Au core-shell nanoparticles(ABEI-Pd@Au NPs)at room temperature.By this way,the ABEI molecules are successfully immobilized without tedious post-modifications.Besides,the nanoparticles exhibit good performances in ECL signal amplification for ABEI-H2O2 system because of their excellent catalytic activity.For further enhancing the luminescence efficiency,ferrocene monocarboxylic acid(Fc)as catalyzer is grafted on the surface of ABEI-Pd@Au NPs with the aid of L-cysteine(L-Cys).Simultaneously immobilizing ABEI and Fc on the surface of Pd@Au nanoparticles means that the actual concentrations of them in the microenvironment on nanoparticles surface is much higher than that in bulk solution,leading to better catalytic efficiency.Based on sandwiched immunoreactions,the bifunctionalized nanomaterials are employed as immobilizing platforms to fabricate a “signa on” ECL immunosensor for human collagen type IV(Col IV)detection.Consequently,the proposed immunosensor provides a wide linear detection ranging from 1 pg·m L-1 to 10 ng·m L-1.This workprovides a novel method for signal amplification and will extend the application of ABEI-H2O2 system in bioanalysis.3.An electrochemiluminescence immunosensor based on self-catalyzed luminescence emitter coupled with Pd Cu@carbon nanohorn hybridThe conventional luminol-based ECL reactions are mainly based on intermolecular interactions between luminescent agents and catalyzer,which are usually accompanied with high energy loss.To achieve the immobilization of luminophore luminol as well as improve the interaction efficiency between luminol and its catalyzer,an electrochemiluminescence(ECL)signal amplified strategy based on self-catalyzed luminol derivative and carbon nanohorn-based hybrid for luminol/H2O2 system was firstly proposed.And thereby successfully fabricates an ultrasensitive ECL immunosensor for the detection of biomarker of heart failure.For signal tag fabrication,3,4,9,10-perylenetetracarboxylic acid(PTCA)conjugated luminol(PTC-Lu)as a novel self-catalyzed luminescence emitter was prepared.The luminescence emitter possesses high luminous efficiency due to the enhancing effect of PTCA.Meanwhile,the aromaticity of PTC-Lu molecule makes them easily be functionalized for achieving effective immobilization in sensing.Then the PTC-Lu is effectively assembled on the Pd Cu@SWCNHs nanohybrid to form PTC-Lu/Pd Cu@SWCNHs nanocomposite via ?-? stacking,based on which the hydrophilicity and stability of SWCNHs can be obviously improved.Meanwhile,Pd Cu@SWCNHs nanohybrid as novel enzymatic mimic exhibites superior electrocatalytic performance toward H2O2 that could further amplify the ECL signal of luminol/H2O2 system.More notably,good biocompatibility and high specific surface area of Pd Cu nanocubes make the composite possess excellent property for loading detection antibody.Based upon above,the proposed “signal on” immunosensor achieved the detection of N-terminal pro-brain natriuretic peptides(NT-pro BNP)in clinical human serum samples with desirable results.This work successfully achieves the immobilization of luminophore as well as promotes the catalytic efficiency.Moreover,the novel Pd Cu@SWCNHs nanohybrid would have potential applications in biotechnology and clinical diagnosis as enzymatic mimic.