A colorimetric strategy and smartphone-based test strip for the detection of glucose based on the peroxidase activity of a hemin-derived nanozyme

Nanozymes are nanomaterials with catalytic properties similar to enzymes and offer advantages over natural enzymes such as lower cost, ease of storage, and convenience for large-scale preparation. Thus, they have received increasing attention and are extensively applied in fields such as chemistry, sensing, food, environment, and medicine. Herein, a hemin-derived nanozyme (Hemin-CDs) was prepared using hemin as the precursor and used to substitute the natural horseradish peroxidase (HRP) for colorimetric detection. The prepared Hemin-CDs exhibit excellent water dispersibility, stability and superior peroxidase-like activity. They catalyze the oxidative coupling of colorless 4-aminoantipyrine (4-AAP) with <i>N</i>-ethyl-<i>N</i>-(2-hydroxy-3-sulfopropyl)-3-methylaniline sodium salt (TOOS) in the presence of H₂O₂, forming a purple quinone diimine dye with an absorption peak at 554 nm, which enables the quantification of H₂O₂ by measuring the absorbance. Quantitative detection of glucose was further demonstrated under physiological conditions. The detection of H₂O₂ and glucose takes only 10 minutes, with linear ranges of 1-150 μM and 2.5-300 μM, and LODs of 0.867 μM and 1.026 μM, respectively. Glucose in human serum was successfully detected with satisfactory recoveries (87.5-104.0%). Furthermore, a test strip was developed, and a smartphone was utilized to recognize the color of the test position, enabling rapid and accurate quantification of glucose concentrations within 5 minutes, which promises to enhance the accessibility and convenience of glucose testing.