Preparation and application of a novel core-shell organic nanoparticle as a fluorescence probe in the determination of nucleic acids

A novel type of core-shell organic nanoparticles (pyrene/poly-acrylic acid; PAA) has been prepared by precipitation polymerization under ultrasonic irradiation. It was characterized by transmission electron microscopy (TEM) and fluorescence lifetime. The lifetime is about 5 mu s, which is much longer than conventional organic dyes' fluorescence lifetime. As the surface of the core-shell organic nanoparticles is covered with abundant carboxylic groups, the nanoparticles are water-soluble, stable and biocompatible. At pH 6.4, maximum fluorescence is produced, with the maximum excitation and emission wavelengths of 338 nm and 397 nm, respectively. Under optimum conditions, the calibration graphs are linear over the range of 4.0 x 10(-5) similar to 1.0 x 10(-2) mg mL(-1) for calf thymus DNA (ct-DNA) and 2.0 x 10(-4) similar to 1.0 X 10(-2) mg mL(-1) for fish sperm DNA (fs-DNA). The detection limits were 3.6 x 10(-5) mg mL(-1) and 1.4 x 10(-4) mg mL(-1) for ct-DNA and fs-DNA, respectively. The method was applied to the determination of ct-DNA and fs-DNA in synthetic samples and the results were satisfactory. The method is sensitive, stable, rapid and tolerant towards most interfering substances.