Silver nanoparticle-supported hydroxyapatite as a material for visual detection of urinary cysteine

Abstract

A new approach for colorimetric detection of cysteine in a urine sample has been established based on the aggregations of silver nanoparticles (AgNPs) on hydroxyapatite (HAp). The silver ion-modified hydroxyapatite (Ag–HAp) via ion-exchange was used to extract cysteine from samples and the formation of AgNPs, confirmed by Transmission Electron Microscopy (TEM), occurred after NaBH₄ treatment. Different cluster sizes of AgNPs on HAp resulting from various amounts of cysteine induced a color change from yellow to pink or violet as the concentration of cysteine increased. The linear range for cysteine determination was in the range of 0–105 μM with a detection limit of 2.03 μM. Sample pretreatment and standard addition allowed detection of cysteine in urine samples, and a percentage of recovery in the range of 94.4 to 102.8% was obtained.