Colorimetric and Photothermal Creatinine Determination Using MoS₂ Nanosheet Cocatalyst with Cu²⁺/Creatinine Complexes

Creatinine (CRE) has been considered to be a critical biomarker for assessing renal dysfunction and muscular metabolism. In this study, we developed a dual-mode colorimetric and photothermal CRE sensor for selective detection of CRE using gum arabic-treated molybdenum disulfide with copper ions (GA-MoS2@Cu2+). In the system, GA-MoS2 nanosheets can be used as a cocatalyst in the copper Fenton-like reaction. Moreover, in the presence of CRE, the copper Fenton-like reaction can be accelerated through cocatalysis of GA-MoS2 nanosheets, which increases the electron transfer capacity of the system. This facilitates the production of larger amounts of reactive oxygen species (ROS) and promotes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). The catalytic activity of GA-MoS2@Cu2+/CRE increases with higher concentrations of CRE. The oxidized TMB (TMBox) served as a signal for the colorimetric and photothermal sensors due to its visible and near-infrared (NIR) light absorbance. Heat was generated in proportion to the concentration of CRE when light from an NIR laser was absorbed by TMBox in the reaction solution. The proposed sensor demonstrated linear detection ranges of 0.5–500 and 5–500 μM, with limits of detection (LODs) of 0.19 and 3.30 μM, respectively, with a very fast assay time. In addition, the applicability and viability of the sensor were successfully demonstrated in human serum tests with recoveries of 95–108%. These results demonstrate the capability and feasibility of the sensors, with the advantages of high sensitivity, selectivity, cost-effectiveness, and portability for use in clinical detection and point-of-care testing.