Fluorescence Determination of L-Cysteine in Wound Dressings by Fluoroscein Coated Gold Nanoparticles

Abstract

ABSTRACTA new method for the fluorimetric determination of L-cysteine in wound care dressings is reported using coated fluorescein gold nanoparticles. The procedure was performed with a continuous flow manifold to automate the process to improve the precision. Aqueous gold nanoparticles (size: 10.5 ± 1.2 nm) that were noncovalently adsorbed to fluorescein were employed for the determination of L-cysteine. The fluorescence of the fluorescein-gold nanoparticle compound was lower than the fluorescein fluorescence and increased in the presence of L-cysteine due to fluorescence resonance energy transfer. The fluorescence of the solution containing the fluorescein-gold nanoparticles was enhanced by a factor of 7.5 following the addition of L-cysteine. This effect was not observed when other amino acids were introduced. This fluorescence enhancement was used for the determination of L-cysteine. Good linearity was observed from 0.8 to 4.1 µM of L-cysteine, and the detection limit was 0.1 µM. The method was successfully employed to determine L-cysteine in wound care dressings.