Synthesis and Characterization of NIR Fluorescent Polystyrene/Polystyrylbisphosphonate Core Shell Microspheres

This study describes the design, construction, and characterization of NIR fluorescent Polystyrene/Polystyrylbisphosphonate (PS/PStBP) core shell microspheres. For this purpose, we synthesized polystyrene (PS) microspheres of narrow-size distribution, styrylbis-phosphonate (StBP) - a new bisphosphonic vinylic monomer and benzyl heptamethine cyanine (BHC) - a new hydrophobic NIR fluorescent dye. The PS particles were activated by mild ozonolysis and the new hydrophobic NIR dye was encapsulated by a single step swelling process within the oxidized PS microspheres. Graft polymerization of the StBP monomer onto the entrapped BHC oxidized PS microspheres, afforded formation of the desired NIR fluorescent PS/PStBP core-shell microspheres. Analysis of the new particles demonstrated the encapsulation of the dye, the location of the bisphosphonic groups on the surface of the particles and its typical hydroxyapatite binding activity.