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 N-ethyl-N-(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.