Sensitive determination of 6-mercaptopurine based on the aggregation of phenylalanine-capped gold nanoparticles

Abstract

The purpose of the present work was to design a colorimetric method for the determination of 6-mercaptopurine (6-MP). 6-MP is a useful drug for the treatment of leukemia. Gold nanoparticles (NPs) are known to undergo a change in colour upon aggregation. Hence, in the present work phenylalanine-capped gold NPs were used as a colorimetric probe for the determination of 6-MP. Transmission electron microscopy (TEM) measurements revealed that the phenylalanine-capped gold NPs ranged from 6 to 9nm in size. The UV–vis spectrophotometric measurements showed that the surface plasmon resonance (SPR) band of the metallic NPs was positioned at 516nm. The effect of 6-MP addition on the SPR band of the gold NPs was investigated at pH 8 and 5. At pH 8, only a slight change in the position and intensity of the SPR band was observed. However, at pH 5, the SPR band of the gold NPs was broadened as well as red shifted in the presence of 6-MP. The colour of the gold NPs changed from red to dark purple. The ratio of the absorbance of the gold NPs at 600 and 516nm versus the concentration of 6-MP was found to be linear in the range 0.2–1.8μM. The limit of detection (LOD) of the colorimetric method for the determination of 6-MP was calculated to be 0.647μM.