A smartphone-enabled colorimetric sensor based on Au-CuO nanozyme for visual and quantitative detection of antihypertensive drug hydralazine

In the present study, we have unfolded a smartphone-assisted colorimetric approach for the visual detection of the antihypertensive drug, Hydralazine (Hyz) in the buffer and pharmaceutical samples. The method stands on the oxidase mimetic property of gold-decorated copper oxide (Au-CuO), which is synthesized using a facile one-step chemical reduction process. The synthesis of Au-CuO was successfully concluded using several characterization techniques. Au-CuO showed amplified oxidase mimicking behavior towards 3,3',5,5'-tetramethylbenzidine (TMB) which was used as a colorimetric substrate in the subsistence of oxygen dissolved in the reaction medium. Employing the competitive inhibition property of Hyz to TMB, a colorimetric method has been designed for the quantification of Hyz. The method manifested good accuracy and reproducibility in 1 mu M-75 mu M concentration range with a significant detection limit of 600 nM. Further, the technique was extended for smartphone-based digital image colorimetry (DIC) sensing of Hyz by capturing images of developed color corresponding to different Hyz concentrations with as developed RGB software and their analysis. The work opens a simple approach to medical diagnosis for the visual detection of high blood pressure patients in remote areas.