The effect of polymer nanostructure on diffusion of small molecules using tryptophan as a FRET probe

Abstract

The amino acid L-tryptophan has been converted into a polymerizable monomer which has been incorporated into a range of cross-linked polymeric nanogels prepared by emulsion polymerization. By using time-lapse fluorescence spectroscopy the diffusion time of a small molecule Forster resonance energy transfer (FRET) pair, dansyl amide, into the central nanogel domain has been monitored through the decreased emission of the L-tryptophan FRET donor. In this initial study it has been found that diffusion of the small molecule into the nanogels is affected by altering the synthetic parameters (cross-linking density and co-monomer hydrophobicity). When increasing the cross-linking density of the nanogels the uptake diffusion time increased, while increasing the hydrophobicity of the co-monomer (and consequently lowering the glass-transition temperature (Tg)) caused a decrease in the diffusion time.