title: Luminol-labeled gold nanoparticles for ultrasensitive chemiluminescence-based chemical analyses.
abstract: We report a study on chemiluminescence-based chemical analyses using luminol molecules covalently attached to 10 nm diameter gold nanoparticles (GNPs). Chemiluminescence (CL) has been systematically studied under two schemes by varying the concentrations of luminol-labeled GNPs and [Fe(CN)6](3-) catalyst, respectively. The CL signal of luminol-labeled GNPs is enhanced by 5 to 10 times compared to the bulk luminol solutions of the same concentration. The log-log plot of the CL signal versus the number of luminol-labeled GNPs suspended in a standard 96-well plate shows two characteristic linear curves with distinct slopes across eight orders of magnitude variation in the GNP quantity (from 1.82 × 10(2) to 1.82 × 10(10) GNPs per well). The detection limit represented by the cross-point of these two curves can reach down to ~6.1 × 10(5) GNPs per well (corresponding to 1.0 × 10(-14) M GNP and 2.4 × 10(-11) M equivalent luminol concentration). The attachment of luminol molecules to GNP nano-carriers allows a large amount of luminol to be placed in a greatly reduced volume (or area) toward developing miniaturized CL sensors. We have demonstrated this by preloading dried luminol-labeled GNPs in homemade microwell arrays (with a volume of ~12 μL per well). A linear log-log curve can be obtained across the full range from 1 × 10(3) to 1 × 10(10) GNPs per microwell. The CL signal was detectable with as few as ~1000 GNPs. We have further applied this microwell method to the detection of highly diluted blood samples, in both intact and lysed forms, which releases Fe(3+)-containing hemoglobin to catalyze luminol CL. The lysed blood sample can be detected even after a 10(8) fold dilution (corresponding to ~0.18 cells per well). This ultrasensitive CL detection method may be readily adapted for developing various miniaturized multiplex biosensors for rapid chemical/biochemical analyses.
authors.affiliation: Department of Chemistry, Kansas State University, Manhattan, KS 66506, USA. junli@ksu.edu.
authors.forename: Lateef U
authors.initials: LU
authors.lastname: Syed
authors.forename: Luxi Zhang
authors.initials: LZ
authors.lastname: Swisher
authors.forename: Hannah
authors.initials: H
authors.lastname: Huff
authors.forename: Caitlin
authors.initials: C
authors.lastname: Rochford
authors.forename: Fengli
authors.initials: F
authors.lastname: Wang
authors.forename: Jianwei
authors.initials: J
authors.lastname: Liu
authors.forename: Judy
authors.initials: J
authors.lastname: Wu
authors.forename: Mark
authors.initials: M
authors.lastname: Richter
authors.forename: Sivasai
authors.initials: S
authors.lastname: Balivada
authors.forename: Deryl
authors.initials: D
authors.lastname: Troyer
authors.forename: Jun
authors.initials: J
authors.lastname: Li
mesh_terms: D000818:Animals; D006046:Gold / Q000737:chemistry*; D008163:Luminescent Measurements / Q000379:methods*; D008165:Luminol / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D012756:Sheep
chemical_list: D008165:Luminol; D006046:Gold