Engineering a Single Amino Acid Bionanozyme for Ultrasensitive Detection of Biomarkers: A WHO‐REASSURE‐ Aligned Approach

Abstract The development of advanced biosensing materials that adhere to the WHO‐REASSURE standards is crucial in resource‐constrained environments. Conventional peroxidase (POD) enzymes, essential for sensitive and selective colorimetric assays, encounter challenges such as high production costs, operational instability, complex fabrication processes, and non‐reusability. In response to these challenges, an affordable, easily synthesized, and environmentally friendly single amino acid bionanozyme (F‐Cu) have been engineered. This bionanozyme harnesses phenylalanine (F) and redox‐active Cu 2 ⁺ ions to create 2D hierarchical van der Waals crystals. The F‐Cu nanosheets exhibit rapid and real‐time POD‐mimicking catalytic activity, efficiently reducing hydrogen peroxide (H₂O₂), and demonstrating robustness under extreme pH, long‐term storage, and elevated temperatures. Additionally, the F‐Cu bionanozyme facilitates user‐friendly, sensitive, and specific equipment‐free visual detection of biomarkers, including Hydrogen peroxide (H₂O₂), dopamine (DA), and nitrite ions (NO 2 − ), with detection limits as low as 5, 1.5, and 4 µ m , respectively. These results underscore the alignment of the F‐Cu bionanozyme with the WHO‐REASSURE standards and its potential to address the future requirements of point‐of‐care diagnostics, biotechnology, food safety, and analytical chemistry applications.