ABSTRACT
Monodisperse gold nanoparticles (GNPs) were synthesized in a water-in-oil emulsion system (reverse micelles) composed of 80% N-methylmorpholine N-oxide (NMMO)/20% H2O and dodecane, stabilized with an anionic surfactant: bis(2-ethylhexyl)sulfosuccinate sodium salt. Cellooligomers with a degree of polymerization of 6 or 15 (ßGlc6 or ßGlc15, respectively), which were labeled at each reducing end group with thiosemicarbazide (TSC) and dissolved in the aqueous NMMO phase, were successfully conjugated to the surfaces of GNPs in situ during spontaneous NMMO-mediated gold reduction. As-synthesized ßGlc6-GNPs and ßGlc15-GNPs had average diameters of 11.3 ± 2.1 and 10.5 ± 0.7 nm, respectively, while their surface sugar densities were 0.21 and 0.51 chains nm-2, respectively. Concanavalin A (ConA), a lectin that recognizes non-reducing end groups of glucose residues, aggregated with ßGlc15-GNPs with higher sensitivity than it did with ßGlc6-GNPs, possibly as a result of the sugar density on the GNP surfaces. The aggregates were rapidly re-suspended by adding methyl-ß-d-glucopyranoside as a binding inhibitor. Other lectins and proteins showed no interaction with ßGlc-GNPs. Therefore, clustering of glucose non-reducing ends on the GNP surfaces via strong intermolecular association of cellooligomers, possibly led to high affinity for ConA. This facile synthesis route to structural carbohydrate-decorated GNPs has potential applications in carbohydrate-nanometal conjugate nano-biosensor development.
