Design and fabrication of fluorescein-labeled starch-based nanospheres

Fluorescein isothiocyanate (FITC) is covalently attached onto the starch acetate, and the fluorescein-labeled starch acetate can self-assemble to form uniform nanospheres in water. The size of the fluorescent nanospheres can be easily controlled by adjusting the polymer concentration in acetone and the proportions of the water and organic phases. The fluorescent intensity of the nanospheres increases with increasing pH, and its fluorescent intensity has no major effect in the physiologically relevant range from pH 5.7 to pH 8 compared with free FITC. Fluorescence quenching studies prove that the fluorescent nanospheres showed a super fluorescent stability without self-association. The fluorescent nanospheres are degradable and can be potential applied for pH-sensing in biological samples.