Enzyme-free colorimetric determination of uric acid based on inhibition of gold nanorods etching

Abstract

• An enzyme-free colorimetric method for sensitive detection of UA was established. • LSPR absorption peak shift (Δλ) of AuNRs before and after inhibition was used to quantitative determination of UA. • The proposed method could overcome the limitation of deviation from beer's law caused by too low or too high absorbance. An enzyme-free colorimetric method for sensitive detection of uric acid (UA) was established, which was achieved by inhibiting the etching of gold nanorods (AuNRs). The longitudinal direction of AuNRs would be gradually etched by I 2 , as an oxidant, generated by the reaction between MnO 2 nanosheets (MnO 2 NS) and I − . Benefitted from the length change, the localized surface plasmon resonance (LSPR) peak of AuNRs showed an obvious blue shift, led to the color change of AuNRs solution. Once UA was introduced, MnO 2 NS was reduced to Mn 2+ rapidly. As a result, the formation of I 2 was reduced and the etching of AuNRs was inhibited. Therefore, a simple method for the assay of UA was achieved with UV–vis absorption spectra and bare eyes, respectively. In optimization conditions, LSPR absorption peak shift (Δλ) of AuNRs before and after inhibition enabled the sensitive detection of UA in the range of 0.8−30 μM and 30−300 μM, the detection limit of low concentration range was 0.76 μM. The developed method has been utilized for determining UA in clinical samples with satisfactory results.