Label-free silver nanoparticles for the naked eye detection of entecavir

A simple, rapid, field-portable colorimetric method for the detection of entecavir was proposed based on the color change caused by the aggregation of silver nanoparticles. Neutralization of the electrostatic repulsion from each silver nanoparticle resulted in the aggregation of AgNPs and a consequent color change of AgNPs from yellow to wine-red, which provided a platform for rapid and field-portable colorimetric detection of entecavir. The concentration of entecavir could be determined with naked eye or UV–vis spectrometer. The proposed method can be used to detect entecavir in human urine with a detection limit of 1.51 μg mL−1, within 25 min by naked eye observation without the aid of any advanced instrument or complex pretreatment. Results from UV–vis spectra showed that the absorption ratio was linear with the concentration of entecavir in the range of 5.04–25.2 μg mL−1 and 1.01–5.04 μg mL−1 with linear coefficients of 0.9907 and 0.9955, respectively. The selectivity of AgNPs detection system for entecavir is excellent comparing with other ions and analytes. Due to its rapid, visible color changes, and excellent selectivity, the AgNPs synthesized in this study are suitable to be applied to on-site screening of entecavir in human urine.