title: Quantitative analysis of human serum leptin using a nanoarray protein chip based on single-molecule sandwich immunoassay.
abstract: We report a method for the quantitative analysis of human serum leptin, which is a protein hormone associated with obesity, using a nanoarray protein chip based on a single-molecule sandwich immunoassay. The nanoarray patterning of a biotin-probe with a spot diameter of 150 nm on a self-assembled monolayer functionalized by MPTMS on a glass substrate was successfully accomplished using atomic force microscopy (AFM)-based dip-pen nanolithography (DPN). Unlabeled leptin protein molecules in human serum were detected based on the sandwich fluorescence immunoassay by total internal reflection fluorescence microscopy (TIRFM). The linear regression equation for leptin in the range of 100 zM-400 aM was determined to be y=456.35 x+80,382 (R=0.9901). The accuracy and sensitivity of the chip assay were clinically validated by comparing the leptin level in adult serum obtained by this method with those measured using the enzyme-linked immunosorbent assay (ELISA) performed with the same leptin standards and serum samples. In contrast to conventional ELISA techniques, the proposed chip methodology exhibited the advantages of ultra-sensitivity, a smaller sample volume and faster analysis time.
authors.affiliation: Department of Chemistry and Research Institute of Physics and Chemistry (RINPAC), Chonbuk National University, 664-14, 1-Ga, Duckjin-Dong, Duckjin-Gu, Jeonju 561-756, South Korea.
authors.forename: Seungah
authors.initials: S
authors.lastname: Lee
authors.forename: Shinae
authors.initials: S
authors.lastname: Lee
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Ko
authors.forename: Hyungil
authors.initials: H
authors.lastname: Jung
authors.forename: Jung Dong
authors.initials: JD
authors.lastname: Kim
authors.forename: Joon Myong
authors.initials: JM
authors.lastname: Song
authors.forename: Jaebum
authors.initials: J
authors.lastname: Choo
authors.forename: Seong Kug
authors.initials: SK
authors.lastname: Eo
authors.forename: Seong Ho
authors.initials: SH
authors.lastname: Kang
mesh_terms: D001710:Biotin; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D020738:Leptin / Q000097:blood*; D008856:Microscopy, Fluorescence; D040081:Protein Array Analysis / Q000379:methods*
chemical_list: D020738:Leptin; D001710:Biotin