Enhancement Effect Of P-iodophenol On Gold Nanoparticle-catalyzed Chemiluminescence And Its Applications

Chemiluminescence?CL?analysis is an analytical method for the determination of target compounds based on the light intensity generated during a chemical reaction.CL,as a trace analysis method,has the advantages of simple equipment,high sensitivity and wide linear range.Luminol which can be oxidized by various oxidants is a commonly used chemiluminescence reagent.Nanomaterial is one kind of new catalysts for luminol CL reaction.However,the reported nanoparticle-catalyzed CL reactions still suffered from some drawbacks.Firstly,almost all of the proposed luminol CL systems catalyzed by nanomaterials were flash type CL which needed to be coupled with a flow injecting system.Secondly,the catalytic activity of nanomaterials was still lower than that of HRP,which restricted their applications in clinical analysis,especially in early diagnosis of diseases.Hence,the development of novel CL systems is still in demand.Enhancers are the compounds that can enhance the CL signal.At present,many kinds of enhancers have been found in luminol-H₂O₂-HRPCLsystem,suchasfluorescein,naphthols,hexahydroxybenzothiazole,substituted phenol derivatives,lophine derivatives and analogues,substituted boronic acid derivatives,water-soluble macromolecules,surfactants,and so on.Therefore,my research selected gold nanoparticle-catalyzed luminol-H₂O₂ CL reaction as research object,which was reported in 2005 by Cui?group,and investigated the feasibility of using traditional enhancers to improve the CL performance of gold nanoparticle-catalyzed luminol-H₂O₂ CL reaction.Firstly,we investigated the enhancement effect of nine compounds on the Au NPs-catalyzed luminol CL system.PIP was the best enhancer for the luminol CL system.And the Au NPs of 25 nm in diameter was found to be the best catalyst in the PIP-enhanced luminol CL system.The mechanism showed that superoxide anion(O₂^·-)and singlet oxygen?¹O₂?generated from dissolved oxygen played important role during the CL reaction.We speculated that the enhanced CL signal of luminol-O₂-Au NPs CL system may be derived from the attachment of iodobenzene derivatives on the surface of Au NPs.The formed PIP-capped Au NPs may facilitate the generation of O₂^·-radical from dissolved oxygen and enhanced CL signal.Then,the proposed novel CL system was applied to the detection of compounds containing-SH and guanidine groups because of the strong binding ability of-SH and guanidine groups on the surface of Au NPs.Finally,we tried to apply the PIP-enhanced luminol CL system to CL immunoassay?CLIA?for the detection of rabbit IgG?as model analyte?.The gold surface is very important for the PIP-enhanced CL system.But in the immunoassay,the gold surface was modified with antibody and blocker resulting in unfavorable detection.Therefore,hydroxylamine reduction method was employed in my research to generate a new gold surface on the gold nanoparticles,enabling the non-stripping detection of rabbit IgG.We optimized the experimental conditions,including the concentration of luminol,PIP,and NaOH which is the dilution solution of luminol,the concentration of HAuCl₄ and NH₂OH,the time of reduction reaction?T_R?,blocking reagents,and the concentration of Au NPs-labeled goat-anti-rabbit IgG secondary antibody.The linear range of rabbit IgG determined under the optimized experimental conditions was from 0.5 to 50 ng mL^-1.The limit of detection was 0.4 ng mL^-1.The established method also showed good selectivity and reproducibility?RSD 2.4%?.The proposed method can easily be extended to the detection of other proteins,specific sequences of DNA,small molecules,or even cells.