Preparation of fluorescent carboxyl and amino functionalized polystyrene particles by miniemulsion polymerization as markers for cells

A series of fluorescent polystyrene latex particles with carboxyl and amino functionalities on their surface were synthesized by the miniemulsion technique. The fluorescent dye N-(2,6-diisopropylphenyl)perylene-3,4-dicarboximide (PMI) was incorporated into the copolymer nanoparticles formulated from styrene and acrylic acid or styrene and aminoethyl methacrylate hydrochloride. The resulting latexes were stable and showed a monodisperse size distribution. The particle size depended on the amount and nature of the functional comonomer and was in the range 100-175 nm. All latexes were characterized by transmission electron microscopy (TEM), dynamic light scattering, UV-Vis spectroscopy and zeta potential measurements. The amount of surface functional groups was determined by electrolyte titration. Furthermore, the functionalized fluorescent particles were utilized as markers for HeLa cells and cell uptake was visualized using fluorescence microscopy. The correlation of the uptake of nanoparticles with the surface charge was determined by FACS measurements.