title: Lectin-carbohydrate interactions on nanoporous gold monoliths.
abstract: Monoliths of nanoporous gold (np-Au) were modified with self-assembled monolayers of octadecanethiol (C18-SH), 8-mercaptooctyl α-D-mannopyranoside (αMan-C8-SH), and 8-mercapto-3,6-dioxaoctanol (HO-PEG2-SH), and the loading was assessed using thermogravimetric analysis (TGA). Modification with mixed SAMs containing αMan-C8-SH (at a 0.20 mole fraction in the SAM forming solution) with either octanethiol or HO-PEG2-SH was also investigated. The np-Au monoliths modified with αMan-C8-SH bind the lectin Concanavalin A (Con A), and the additional mass due to bound protein was assessed using TGA analysis. A comparison of TGA traces measured before and after exposure of HO-PEG2-SH modified np-Au to Con A showed that the non-specific binding of Con A was minimal. In contrast, np-Au modified with octanethiol showed a significant mass loss due to non-specifically adsorbed Con A. A significant mass loss was also attributed to binding of Con A to bare np-Au monoliths. TGA revealed a mass loss due to the binding of Con A to np-Au monoliths modified with pure αMan-C8-SH. The use of mass losses determined by TGA to compare the binding of Con A to np-Au monoliths modified by mixed SAMs of αMan-C8-SH and either octanethiol or HO-PEG2-SH revealed that binding to mixed SAM modified surfaces is specific for the mixed SAMs with HO-PEG2-SH but shows a significant contribution from non-specific adsorption for the mixed SAMs with octanethiol. Minimal adsorption of immunoglobulin G (IgG) and peanut agglutinin (PNA) towards the mannoside modified np-Au monoliths was demonstrated. A greater mass loss was found for Con A bound onto the monolith than for either IgG or PNA, signifying that the mannose presenting SAMs in np-Au retain selectivity for Con A. TGA data also provide evidence that Con A bound to the αMan-C8-SH modified np-Au can be eluted by flowing a solution of methyl α-D-mannopyranoside through the structure. The presence of Con A proteins on the modified np-Au surface was also confirmed using atomic force microscopy (AFM). The results highlight the potential for application of carbohydrate modified np-Au monoliths to glycoscience and glycotechnology and demonstrate that they can be used for capture and release of carbohydrate binding proteins in significant quantities.
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA ; UM-St. Louis Center for Nanoscience, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.
authors.forename: Yih Horng
authors.initials: YH
authors.lastname: Tan
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.
authors.forename: Kohki
authors.initials: K
authors.lastname: Fujikawa
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.
authors.forename: Papapida
authors.initials: P
authors.lastname: Pornsuriyasak
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA ; UM-St. Louis Center for Nanoscience, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.
authors.forename: Allan J
authors.initials: AJ
authors.lastname: Alla
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.
authors.forename: N Vijaya
authors.initials: NV
authors.lastname: Ganesh
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Demchenko
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA ; UM-St. Louis Center for Nanoscience, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Stine