Use of Water Soluble and Phosphorescent MPA-capped CdTe Quantum Dots for the Detection of Urea

To describe a method for the determination of urea in blood serum using urease enzyme and 3-MPA-capped CdTe quantum dots. The method is based on the increase in pH of the solution as a result of the reaction between urea and urease, which causes an increase in the phosphorescence signal of MPA-CdTe quantum dots in the pH range of 2.5-5.0. Under the optimum conditions, the linear range of urea was 0.016-0.16 mM (1-10 mg/L) and the limit of detection based on 3 s/b was calculated as 0.003 mM (0.17 mg/L). The relative standard deviation was calculated as 3.4% at 4 mg/L urea concentration (n=7). The method was applied to human serum samples. The same samples were analyzed by an independent laboratory and the results were not statistically different, at 95% confidence level (F test). The proposed method does not need sample pretreatment, is simple, selective, and cost-effective for the determination of urea in serum samples.