Preparation of Spiropyran-Terminated PNIPAM for Fluorescence Imaging of Live Cells

Spiropyran-terminated poly(N-isopropylacrylamide) (SP-PNIPAM) with different molecular weights were prepared by atom transfer radical polymerization. Their photochromic property, fluorescence property and critical transition temperature were investigated. SP-PNIPAM was tested as polymer dyes for cell fluorescence imaging. SP and SP-PNIPAM emitted red fluorescence if excited. Spiropyran could diffuse through the cell membrane into the cell, and thus fixed and living cells could be stained. When being used as fluorescence dyes for cell imaging, the dye performances of SP-PNIPAM depended on their molecular weights. SP-PNIPAM could just be internalized into living cells by the cell endocytosis process, thus could be selectively used for fluorescence imaging of living cells.