Rapid and sensitive colorimetric detection of dopamine based on the enhanced-oxidase mimicking activity of cerium(iv)

Abstract

Dopamine (DA) exists as a meaningful neurotransmitter which is extremely useful for the diagnosis of neurological disorders. For this reason, monitoring the levels of DA is greatly important. A facile colorimetric method is described here for measuring DA using tetravalent cerium ions (Ce⁴⁺). Inspired by the intrinsic oxidase-like activity of Ce⁴⁺, it can directly oxidize the substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of oxygen (O₂) without requiring hydrogen peroxide (H₂O₂). Interestingly, when DA is introduced, the catalytic oxidation ability of Ce⁴⁺ is significantly enhanced, and a dark blue color of oxidized TMB (oxTMB) can be observed instantly. This boost is benefited from the fact that more superoxide radicals (˙O₂⁻) are generated with the addition of DA. In view of this, a facile approach for colorimetric determination of DA has been realized. Within the range of 6.5–520 nM, the absorption intensity of oxTMB is proportional to the concentration of DA and the detection limit is 2.88 nM. What is more, the detection can be accomplished in 3 min at room temperature, which is extremely important for real-time and rapid bioanalysis. This sensor has been successfully applied to measure DA in biological samples. Such an economical, simple, rapid, and sensitive method shows great potential application prospects in clinical early diagnosis.