title: Fluorescence enhancement of silver nanoparticle hybrid probes and ultrasensitive detection of IgE.
abstract: An ultrasensitive protein assay method was developed based on silver nanoparticle (AgNP) hybrid probes and metal-enhanced fluorescence. Two aptamer based silver nanoparticles, Aptamer/Oligomer-A/Cy3-modified AgNPs (Tag-A) and Aptamer/Oligomer-B/Cy3-modified AgNPs (Tag-B) were hybridized to form a silver nanoparticle aggregate that produced a red shift and broadening of the Localized Surface Plasmon Resonance (LSPR) peak. The enhanced fluorescence resulted from the increased content of Cy3 molecules and their emission resonance coupled to the broadened localized surface plasmon (LSP) of AgNP aggregate. The separation distance between Cy3 and AgNPs was 8 nm which was the most optimal for metal enhanced fluorescence and the separation distance between adjacent AgNPs was about 16 nm and this was controlled by the lengths of oligomer-A and oligomer-B. The protein array was prepared by covalently immobilizing capture antibodies on aldehyde-coated slide. After addition of protein IgE sample, two kinds of aptamer-modified AgNPs (Tag-A and Tag-B) were employed to specifically recognize IgE and form the AgNP aggregate on the arrays based on their hybridization. The detection property of the aptamer-modified AgNP aggregate was compared to two other modified aptamer-based probes, aptamer-modified Cy3 and Tag-A. The modified AgNP hybrid probe (Tag-A and Tag-B) showed remarkable superiority in both sensitivity and detection limit due to the formed AgNP aggregate. The new hybrid probe also produced a wider linear range from 0.49 to 1000 ng/mL with the detection limit reduced to 40 pg/mL (211 fM). The presented method showed that the newly designed strategy of combining aptamer-based nanomaterials to form aggregates results in a highly sensitive optical detection method based on localized surface plasmon.
authors: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, People's Republic of China.
authors: Hui
authors: H
authors: Li
authors: Weibing
authors: W
authors: Qiang
authors: Maika
authors: M
authors: Vuki
authors: Danke
authors: D
authors: Xu
authors: Hong-Yuan
authors: HY
authors: Chen
mesh_terms: D000818:Animals; D052157:Aptamers, Nucleotide / Q000737:chemistry; D002232:Carbocyanines / Q000737:chemistry; D006041:Goats; D007073:Immunoglobulin E / Q000032:analysis*; D053768:Metal Nanoparticles / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D020349:Surface Plasmon Resonance
chemical_list: D052157:Aptamers, Nucleotide; D002232:Carbocyanines; C089187:cyanine dye 3; D007073:Immunoglobulin E; D012834:Silver