title: Poly(amidoamine)-dendrimer-modified gold surfaces for anomalous reflection of gold to detect biomolecular interactions.
abstract: Label-free protein detecting chip technology has encouraged a number of discoveries, as it is a powerful analytical tool in the postgenomic era. In particular, we have focused on a unique characteristic of anomalous reflection of gold (AR) as a new class of label-free detection method for a protein chip system. In this paper, in order to improve the sensitivity of detection of biomolecular interactions by the AR method, we have constructed three-dimensional (3D) nanostructures on gold surfaces with a series of well-defined structures of poly(amidoamine) dendrimers (PAMAMs) from generation 2 to 4 (G2, G3, and G4) tethering biotin moieties as capturing agents for avidin and antibiotin IgG. Comparison of features of such 3D nanostructured surfaces with a diamine-modified flat-like surface revealed a 2-fold increase in the amount of avidin for 3D surfaces relative to the flat surface, and surface-assisted nonspecific interactions were significantly suppressed. We thus obtained 91% coverage for avidin detection on the PAMAM G4-modified surface, indicating a theoretically maximum attainable absorption considering a hexagonal-packed arrangement as a saturated monomolecular layer. In the antibiotin IgG assay, the PAMAM G4-modified surface clearly improved the amount of proteins captured compared to that for the flat surface, indicating that an appropriate density of capturing agents played a more important role in the interaction of larger molecular-sized proteins such as antibiotin IgG, which requires more space for interaction than the medium-sized avidin. These findings should assist in the development of a simple and practical tool for high-throughput protein detection, particularly with the AR method.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan.
authors.forename: Amir
authors.initials: A
authors.lastname: Syahir
authors.forename: Kin-Ya
authors.initials: KY
authors.lastname: Tomizaki
authors.forename: Kotaro
authors.initials: K
authors.lastname: Kajikawa
authors.forename: Hisakazu
authors.initials: H
authors.lastname: Mihara
mesh_terms: D000042:Absorption; D000577:Amides / Q000737:chemistry; D000588:Amines / Q000737:chemistry*; D000818:Animals; D001360:Avidin / Q000737:chemistry; D001710:Biotin / Q000737:chemistry; D002417:Cattle; D050091:Dendrimers / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D007074:Immunoglobulin G / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D018625:Microscopy, Atomic Force / Q000379:methods; D040081:Protein Array Analysis / Q000379:methods; D011506:Proteins / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000577:Amides; D000588:Amines; D050091:Dendrimers; D007074:Immunoglobulin G; D011506:Proteins; D001360:Avidin; D001710:Biotin; D006046:Gold