Finally, urine samples were studied to evaluate the applicability of the proposed GNRred-based electrochemical sensor for UA sensing. Fig. 4 illustrates the analysis of urine samples. A welldefined UA voltammetric peak at +0.39V with very good S/N characteristicswas clearly noticed allowing its identification in the samples in less than 100 s. Quantitatively, the levels of UA found in healthy individuals were 1.30_ 0.03mM with excellent precision, RSDs