1：Experimental Design and Method Selection:

The study employs a hydrothermal synthesis method to prepare PEI-based carbon dots (C-dots) and utilizes their fluorescence properties for UA detection. The mechanism involves fluorescence quenching by periodate oxidation and recovery by UA reduction.

2：Sample Selection and Data Sources:

Human saliva samples were collected from five individuals, filtered, and diluted 100-fold with phosphate buffer for analysis.

3：List of Experimental Equipment and Materials:

Chemicals include polyethylenimine, uric acid, periodate, and various salts from Sigma-Aldrich; phosphate buffers from J.T. Baker; ultrapure water from a Milli-Q system; equipment includes autoclave, filter membranes, dialysis tubes, TEM (JEOL JEM-2010), UV-Vis spectrophotometer (Jasco V-670), FTIR spectrophotometer (Varian 640), fluorescence spectrophotometer (Cary Eclipse), XRD (PANalytical X'Pert PRO), XPS (PHI 5000 VersaProbe), and microplate reader (Synergy 4).

4：4). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: C-dots were synthesized hydrothermally at 300°C for 2 hours, purified by filtration and dialysis. For UA detection, C-dots and periodate were mixed with UA samples in phosphate buffer (pH 11), incubated for 30 minutes, and fluorescence was measured at 365/473 nm using a microplate reader.

5：Data Analysis Methods:

Fluorescence intensities were analyzed to determine UA concentrations, with statistical methods including standard deviation, recovery, relative error, and Student's t-test for validation against a commercial assay.