Thermoresponsive Nanospheres with Entrapped Fluorescent Conjugated Polymers for Cellular Labeling

Thermoresponsive fluorescent nanospheres were prepared by entrapping fluorescent conjugated polymers (FCP) into biocompatible copolymerized nanospheres comprised of methacryloyloxyethyltrimethylammonium chloride and n-isopropylacrylamide. A systematic study allowed monodisperse nanospheres ranging from 50 to 150 nm to be produced by precisely controlling the amount of monomer, initiator, and solvent during the dispersion polymerization process. The as-synthesized fluorescent nanospheres exhibited reversible temperature-dependent fluorescence with strong emission at lower temperature (20 °C) and weak emission at higher temperature (50 °C). Cell viability assays showed that the nanoshperes were nontoxic. The cellular imaging showed a rapid response in fluorescence intensity change upon variation of temperature in HeLa cells, indicating that our fluorescent probes are promising as in situ thermometers for labeling cells.