Au@Cu2O@SDS composite nanorods for dual-mode sensing of histidine

The content of histidine (His) in urine is one of the important reference indicators for the diagnosis of certain diseases. The research on using nanomaterials as substitutes for organic fluorescent probes and natural enzymes is receiving increasing attention. In this study, Au@Cu₂O composite nanorods (CNRs) coated with sodium dodecyl sulfate (SDS) (Au@Cu₂O@SDS CNRs) were prepared. It was found that the obtained Au@Cu₂O@SDS CNRs emits weak fluorescence at 372 nm when excited at 280 nm, and the presence of His leads to an enhanced fluorescence. On the other hand, the Au@Cu₂O@SDS CNRs exhibits oxidase-like activity, which can catalyze the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) without the need of H₂O₂ to form blue-colored oxidized TMB (TMBox). However, the addition of His results in a decrease in absorbance at 652 nm. Thus, a fluorescence and colorimetric dual-mode sensing system responsive to His was successfully constructed. Under the optimum conditions, the increase in fluorescence (ΔF) and decrease in absorbance (ΔA) of the system are closely related to His concentration ranging from 0.5-60 μM and 0.3–25 μM with the detection limit of 0.22 and 0.26 μM, respectively. More importantly, the dual-mode sensing system was utilized for the detection of His in human urine samples with satisfactory recovery (90.1 % ∼109.4 %), confirming its good potential for application.