title: Sensitive detection of a tumor marker, α-fetoprotein, with a sandwich assay on a plasmonic chip.
abstract: Two types of plasmonic silver- and gold-coated grating biosensor chips (plasmonic chip) were applied in the detection of α-fetoprotein (AFP) with a sandwich imunoassay and surface plasmon field-enhanced fluorescence. On the plasmonic chip, unlabeled marker in the sandwich immunoassay was first quantitatively detected over a wide range between 10(-12) and 10(-8) g/mL. The affinity constants between AFP and anti-AFP antibody, which were obtained by fitting the experimental data to the Langmuir isotherm adsorption curve, were 1 × 10(8) g(-1) mL regardless of the kind of metal in the plasmonic chips. Although the fluorescence intensity on the silver plasmonic chip was 5 times larger than that on the gold plasmonic chip, the limit of detection (LOD) was on the order of 10(-11) g/mL and not improved with a silver plasmonic chip. Herein, we used a new setup that generated less dispersions of both the fluorescence intensity for nonspecific adsorption and the background (optical blank) signal and improved the LOD of AFP to 4 pg/mL (55 fM) with the silver plasmonic chip. With the highly sensitive detection in the sandwich immunoassay, the development of a plasmonic chip for clinical diagnosis by a blood test is promising.
authors.affiliation: †Health Research Institute, AIST, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan.|§Department of Chemistry, Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Tawa
authors.affiliation: †Health Research Institute, AIST, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan.|§Department of Chemistry, Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
authors.forename: Fusanori
authors.initials: F
authors.lastname: Kondo
authors.affiliation: †Health Research Institute, AIST, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan.
authors.forename: Chisato
authors.initials: C
authors.lastname: Sasakawa
authors.affiliation: ‡Konica Minolta Inc., No.1 Sakuramachi, Hino-shi, Tokyo 191-8511, Japan.
authors.forename: Kousuke
authors.initials: K
authors.lastname: Nagae
authors.affiliation: ‡Konica Minolta Inc., No.1 Sakuramachi, Hino-shi, Tokyo 191-8511, Japan.
authors.forename: Yukito
authors.initials: Y
authors.lastname: Nakamura
authors.affiliation: ‡Konica Minolta Inc., No.1 Sakuramachi, Hino-shi, Tokyo 191-8511, Japan.
authors.forename: Akitoshi
authors.initials: A
authors.lastname: Nozaki
authors.affiliation: ‡Konica Minolta Inc., No.1 Sakuramachi, Hino-shi, Tokyo 191-8511, Japan.
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Kaya
mesh_terms: D000327:Adsorption; D014408:Biomarkers, Tumor / Q000032:analysis*; D015374:Biosensing Techniques / Q000295:instrumentation*; D005453:Fluorescence; D006801:Humans; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D014408:Biomarkers, Tumor; D000509:alpha-Fetoproteins