Preparation of fluorescein-modified polymer dots and their application in chiral discrimination of lysine enantiomers.

ABSTRACT

Fluorescein-functionalized fluorescent polymer dots (F-PDs) were prepared by a facile one-pot method by magnetic stirring under mild conditions based on carboxymethylcellulose (CMC) and fluorescein as the precursors. The obtained F-PDs exhibited a nanoscale size of 3.2 ± 1.1 nm, excellent water solubility, and bright yellow fluorescence emission with a fluorescence quantum yield of 12.0%. The fluorescent probe displays rapid and sensitive chiral discrimination for lysine focused on different complexation abilities between lysine enantiomers and Cu2+. The concentration of L-lysine in the range 4 to 14 mM (R2 = 0.997) was measured by the fluorescence intensity ratio (I513/I429); the exitation wavelength was set to λex = 365 nm. The detection limit was 0.28 mM (3σ/slope). Importantly, this sensor accurately predicted the enantiomeric excess (ee) of lysine enantiomers at the designed concentration (lysine 20 mM; Cu2+ 10 mM) ranges. The proposed sensor was successfully applied to determine L-lys (recovery 95.8-101%; RSD 0.465-3.34%) and ee values (recovery 98.5-102%; RSD 2.61-3.21%) in human urine samples using the standard addition method.