Detection of <scp>d</scp>-Amino Acids in Saliva for Gastric Cancer Diagnosis Using Pt/MXene Plasmonic Nanozymes

Developing noninvasive strategies for gastric cancer diagnosis is urgent since the current clinical methods usually cause discomfort and risk of infection to patients. Herein, we develop a noninvasive and highly sensitive method for detecting d-amino acids (DAAs) in saliva as a potential biomarker for early gastric cancer diagnosis. By using a novel Pt/Ti₃C₂T_<i>x</i> nanozyme probe, we demonstrate enhanced peroxidase-like activity and photothermal performance under near-infrared (NIR) light irradiation. This probe effectively catalyzes the conversion of H₂O₂, produced by the reaction of DAA and DAA oxidase, into reactive oxygen species, significantly accelerating the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine to its oxidized state. The depth of the resulting blue color is directly proportional to the DAA concentration in the saliva. Our method not only ensures high sensitivity and specificity for DAA detection but also establishes a dual-mode detection platform that enhances both colorimetric and thermal signals under NIR light irradiation. This platform has been successfully applied in the analysis of 45 clinical saliva samples, confirming its feasibility and diagnostic accuracy for early gastric cancer screening. This study offers a rapid and noninvasive diagnostic approach for clinical patients with gastric cancer, providing a promising alternative to current invasive methods.