To mimic the fluorescence enhancement behavior of green fluorescent protein (GFP)

an amphiphilic polymer

poly (ethylene glycol)-chromophore-poly (-caprolactone) (PEG-c-PCL)

was successfully prepared by ring-opening polymerization using chromophore-endcapped PEG as the macroinitiator.1H- and 13C nuclear magnetic resonance (1H and 13C-NMR)

Fourier transform infrared spectroscopy (FTIR)

gel permeation chromatography (GPC) and ultraviolet-visible absorption (UV-Vis) were applied to study the structure and properties of PEG-c-PCL.Both the chromophore and PEG-c-PCL gave similar UV-Vis spectra with a maximum absorption peak at about 371 nm.From the emission spectra

the chromophore had an emission peak at about 427 nm

while PEG-c-PCL showed a 6 nm red-shift

attributable to the influence of polymerization.The amphiphilic PEG-c-PCL could self-assemble into nanoparticles with a diameter of about 160 nm

which was confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements.Importantly

the emission intensity of PEG-c-PCL increased by about 55 times after self-assembly into nanoparticles

and the emission peak showed a 14 nm red-shift in the emission spectrum.These phenomena could be attributed to the chromophores rotation restriction and the increased interactions after self-assembly.Finally

the self-assembled PEG-c-PCL nanoparticles were successfully used in cell imaging

illustrating the potential application of this new kind of fluorescent polymer.