Polymer-modified gold nanoparticles via RAFT polymerization: a detailed study for a biosensing application

Glycopolymers of polyacrylamide derivatives with mannose were prepared via the living radical polymerization of a reversible addition–fragmentation chain transfer reagent. The polymers obtained showed narrow polydispersities. The polymer terminal group was reduced to a thiol, and the resulting polymers were mixed with gold nanoparticles to prepare glycopolymer-substituted gold nanoparticles. The mannose density was adjusted by varying the copolymer preparation and the glycopolymer–polyacrylamide mixture. The colloidal stability of the polymer-coated gold nanoparticles is dependent on the mannose density. Polymer-coated nanoparticles with low mannose densities showed better colloidal stabilities. The molecular recognition abilities of the polymer were investigated using UV-vis spectroscopy. The polymer-coated nanoparticles showed strong protein recognition abilities because of multivalent binding effects. Polymers with high mannose densities showed stronger recognition abilities. The molecular recognition abilities of the glycopolymer–polyacrylamide mixed nanoparticles are dependent on the mannose density. An immunochromatographic assay was performed using the polymer-coated nanoparticles. The color was detected from the gold nanoparticles in the nanoparticle systems with strong molecular recognition and good colloid stability.