A fast, selective and sensitive colorimetric method was developed for the determination of creatinine. It is based on the finding that creatinine causes the aggregation of silver nanoparticles capped with 2,2-thiodiacetic acid, while other biomolecules do not exert an effect. As a result, the color of the solution changes from yellow to green which can be detected visually or by spectrophotometry. The aggregation of the AgNPs was confirmed by UV–vis absorptiometry and transmission electron microscopy. This colorimetric probe allows creatinine to be rapidly quantified with a 3.0 nMlimit of detection. The ratio of absorptions at 560 and 390 nm is linearly correlated to the concentration of creatinine in the 0.01 to 1.0 μM range. The method was successfully applied to the determination of creatinine in (spiked) human serum plasma and urine samples and gave recoveries that ranged from 89.4 to 102.1 %. The method was also validated by using the Jaffe standard method.
