Lectin-carbohydrate interactions on nanoporous gold monoliths

Yih Horng Tan; Kohki Fujikawa; Papapida Pornsuriyasak; Allan J Alla; N Vijaya Ganesh; Alexei V Demchenko; Keith J Stine

doi:10.1039/C3NJ00253E

Lectin-carbohydrate interactions on nanoporous gold monoliths

New J Chem. 2013 Jul 1;37(7):2150-2165. doi: 10.1039/C3NJ00253E.

Authors

Yih Horng Tan¹, Kohki Fujikawa², Papapida Pornsuriyasak², Allan J Alla¹, N Vijaya Ganesh², Alexei V Demchenko², Keith J Stine¹

Affiliations

¹ 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.
² Department of Chemistry and Biochemistry, University of Missouri - Saint Louis, Saint Louis, MO 63121, USA.

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.

Grants and funding

R01 GM090254/GM/NIGMS NIH HHS/United States