Colorimetric detection of cancer biomarker by using porous Mn-N-C single-atom nanozyme with peroxidase-like activity

Glutathione (GSH) is a critical antioxidant in biological systems involved in various cellular processes such as cell proliferation and apoptosis, and is considered as one of the cancer biomarkers. However, the conventional methods for detecting GSH levels often involve complex and time-consuming preparation and sophisticated equipment, posing challenges for rapid and straightforward analysis. Herein, we develop a colorimetric nanosensor using porous single-atom nanozymes (SAzymes), particularly those consisting of atomically dispersed metals on nitrogen-doped carbon supports (M-N-C), to monitor GSH quantitatively. The Mn-N-C SAzymes catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide (H₂O₂), resulting in a measurable color change. The high porosity of the Mn-N-C SAzymes offers a large surface area accommodating a high density of accessible active sites for efficient catalysis. The addition of GSH in this system leads to a notable reduction in color intensity, offering an effective method for the quantitative measurement of GSH. The Mn-N-C SAzymes demonstrate high efficacy in the rapid colorimetric detection of GSH, with a low detection limit of 0.70 μM and a broad dynamic range of 0-40 μM. This method is further applied for a simple and rapid colorimetric analysis of the cancer biomarker in various biological samples, including tissues and serum. Demonstrating the potential for diagnostic applications, this approach offers a promising tool for clinical diagnostics, enabling reliable and convenient monitoring of GSH levels, which is crucial for assessing disease progression.