title: Highly sensitive homogenous immunoassay of cancer biomarker using silver nanoparticles enhanced fluorescence correlation spectroscopy.
abstract: In this paper, we developed a highly sensitive homogeneous immunoassay by combining fluorescence correlation spectroscopy (FCS) with silver nanoparticles (SNPs)-antibody conjugates as probes. We first synthesized 14nm SNPs in aqueous solution and then modified SNPs with 11-mercaptoundecanoicacid (MUA) via SNP-S bond. Resonance light scattering correlation spectroscopy (RLSCS) was utilized to characterize SNPs and MUA-functionalized SNPs (MUA-SNPs). The immune reaction of alpha fetal protein (AFP) antigen and its antibody was used as a reaction model and AFP labeled with Alexa Fluor 647 was used as the tracer antigen in homogeneous competitive immunoassay. We observed that the antigen-antibody complexes showed the significant increase in the diffusion times and fluorescence intensity compared to free dye-labeled antigen. On the advantages of the effects of SNPs on fluorescence enhancement and diffusion time, the homogeneous competitive immunoassay was performed by the two-component model analysis of FCS. Under the optimal condition, the detection limit was 1.5pM and the linear range was from 6pM to 60pM (R>0.99). This assay was successfully applied for the determination of the AFP level in human serum samples, the relative standard deviation was about 5%, and the recoveries were over 90%.
authors.affiliation: College of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiaotong University, Shanghai, PR China.
authors.forename: Lichuan
authors.initials: L
authors.lastname: Tang
authors.forename: Chaoqing
authors.initials: C
authors.lastname: Dong
authors.forename: Jicun
authors.initials: J
authors.lastname: Ren
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D007107:Immune System; D007118:Immunoassay / Q000379:methods*; D057230:Limit of Detection; D053768:Metal Nanoparticles / Q000737:chemistry*; D051379:Mice; D046529:Microscopy, Electron, Transmission / Q000379:methods; D036103:Nanotechnology / Q000379:methods; D015203:Reproducibility of Results; D012834:Silver / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D000509:alpha-Fetoproteins / Q000737:chemistry
chemical_list: D014408:Biomarkers, Tumor; D000509:alpha-Fetoproteins; C067297:8-aminohexylamino cAMP; D012834:Silver; D000242:Cyclic AMP