Facile one-pot preparation and functionalization of luminescent chitosan-poly(methacrylicacid) microspheres based on polymer–monomer pairs

Abstract

In this paper, we present a facile and robust approach to synthesize multifunctionalorganic/inorganic composite microspheres with chitosan-poly(methacrylic acid)(CS-PMAA) shells and cadmium tellurium/iron oxide nanoparticle cores. Due to the strongelectrostatic interaction between the negatively charged nanoparticles and the protonatedCS polymers, the CS/nanoparticle complexes were utilized as templates for the subsequentpolymerization of methacrylic acid. The resulting composite microspheres withluminescence and magnetic properties have regular morphologies and narrow sizedistributions. In contrast to previous reports, this route was based on a one-pot strategywithout the aid of surfactants, organic solvent, or polymerizable ligands in aqueoussolution. The encapsulated CdTe semiconductor nanocrystals inside the microspheresexhibited strong and stable photoluminescence properties in the pH range 5.0–11.0.When the pH was adjusted below 4, the photoluminescence decreased sharply andeven quenched completely. However, the weakened fluorescence emission could berecovered to some degree upon an increase of pH above 5. Additionally, when bothFe3O4 and CdTe nanoparticles were encapsulated within CS-PMAA microspheres, the magneticcontent of the microspheres could be efficiently controlled by tuning the feeding molar ratioof MAA monomers and glucosamine units of CS. From the preliminary attempts, it wasfound that the multifunctional microspheres as imaging agents could improvethe rate and extent of cellular uptake under short-term exposure to an appliedmagnetic field, and so exhibit a great potential as bioactive molecule carriers.