Spontaneous immobilization of both a fluorescent dye and a functional sugar during the fabrication of submicron-sized PMMA particles in an aqueous solution

Abstract Fluorescent particles with sugar chains immobilized on the particle surface are expected to be widely used as a fluorescent probe for biomaterial imaging and a fluorescent label for cell imaging as well as a highly accurate detection tool for toxic proteins and pathogenic viruses. Based on the expectation, a facile and environmentally friendly method for the one-pot incorporation of a fluorescent dye and alkylated functional sugar molecules during the fabrication of submicron-sized polymethyl methacrylate (PMMA) particles was established in the present work. This method used coumarin 7 as a hydrophobic fluorescent dye and octyl-β- d -glucopyranoside (octyl-glc), in which an octyl group is glycoside bound to a glucose skeleton, as a functional sugar. During PMMA particle formation by soap-free emulsion polymerization, coumarin 7 was spontaneously incorporated into the PMMA particles. At the same time, due to its hydrophobicity, the octyl group entered the PMMA particles, and due to its hydrophilicity, the glucose was in contact with the water medium. The immobilization of octyl-glc on the particle surfaces was evaluated using concanavalin A (ConA) as a lectin, which has a selective affinity for glucose. It was found that the characteristics of fluorescence and ConA adsorption were maintained, even after immersing the sugar-immobilized fluorescent PMMA particles in water for one and a half years, indicating that coumarin 7 was retained inside the PMMA particles, and octyl-glc was stably immobilized for a long time on the surface layer of the PMMA particle by using an octyl group as an anchor. Furthermore, as shown by the confocal laser scanning microscopy images of the water-dispersed particles, coumarin 7 was incorporated into almost all the particles, which were dispersed without aggregation in water, indicating that the sugar-immobilized fluorescent PMMA particles enable high-accuracy fluorescence analysis and imaging.