title: Ultra-sensitive plasmonic nanometal scattering immunosensor based on optical control in the evanescent field layer.
abstract: Novel, fluorescence-free detection of biomolecules on nanobiochips was investigated based on plasmonic nanometal scattering in the evanescent field layer (EFL) using total internal reflection scattering (TIRS) microscopy. The plasmonic scattering of nanometals bonded to biomolecules was observed at different wavelengths by an electromagnetic field in the EFL. The changes in the scattering of nanometals on the gold-nanopatterned chip in response to the immunoreaction between silver nanoparticles and antibodies allowed fluorescence-free detection of biomolecules on the nanobiochips. Under optimized conditions, the TIRS immunoassay chip detected different amounts of immobilized antigen, i.e., human cardiac troponin I. The sandwich immuno-reaction was quantitatively analyzed in the dynamic range of 720 zM-167 fM. The limit of detection (S/N=4) was 600 zM, which was ~140 times lower than limits obtained by previous total internal reflection fluorescence and dark field methods. These results demonstrate the possibility for a fluorescence-free biochip nanoimmunoassay based on the scattering of nanometals in the EFL.
authors.affiliation: Department of Applied Chemistry, College of Applied Science, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Republic of Korea.
authors.forename: Seungah
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Graduate School, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Republic of Korea.
authors.forename: Guenyoung
authors.initials: G
authors.lastname: Park
authors.affiliation: Department of Chemistry, Graduate School, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Republic of Korea.
authors.forename: Suresh Kumar
authors.initials: SK
authors.lastname: Chakkarapani
authors.affiliation: Department of Applied Chemistry, College of Applied Science, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Republic of Korea; Department of Chemistry, Graduate School, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Republic of Korea. Electronic address: shkang@khu.ac.kr.
authors.forename: Seong Ho
authors.initials: SH
authors.lastname: Kang
mesh_terms: D000906:Antibodies / Q000737:chemistry / Q000276:immunology*; D015374:Biosensing Techniques / Q000379:methods*; D006046:Gold / Q000737:chemistry; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008853:Microscopy; D053758:Nanoparticles / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D019210:Troponin I / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification*
chemical_list: D000906:Antibodies; D019210:Troponin I; D012834:Silver; D006046:Gold
keywords: Fluorescence-free; Nanobiochip; Nanoparticle detection; Plasmonic nanometal scattering; Total internal reflection scattering microscopy