1：Experimental Design and Method Selection:

A one-pot bottom-up hydrothermal strategy was employed for synthesizing PEGylated WS2 nanoparticles using sodium tungstate, thiourea, hydroxylamine hydrochloride, and PEG-

2：This method was chosen to simplify synthesis and avoid post-modification steps. Sample Selection and Data Sources:

4 Murine breast cancer cells (4T1 cell line) and Balb/c mice were used for in vitro and in vivo experiments, respectively. Chemicals were analytical grade from suppliers like Sigma-Aldrich and Shanghai Aladdin Reagent Co. Ltd.

3：List of Experimental Equipment and Materials:

Equipment included a Philips Tecnai G2 F20 HRTEM for morphology, Axis Ultra DLD XPS spectrometer, Nicolet IR AVATAR-360 FTIR spectrometer, Hitachi U-3600 UV-vis spectrophotometer, Malvern Zetasizer for DLS and zeta potential, thermocouple thermometer for temperature measurement, 808-nm laser for photothermal tests, microplate reader (Bio-tek) for MTT assay, inverted fluorescence microscope for cell imaging, CT scanner for imaging, and thermal infrared imager. Materials included sodium tungstate, thiourea, hydroxylamine hydrochloride, PEG-400, ethanol, DMSO, RPMI-1640 medium, fetal bovine serum, streptomycin-penicillin, MTT, Calcein AM, PI, and ICG.

4：Experimental Procedures and Operational Workflow:

Synthesis involved dissolving precursors in PEG-400 and heating in an autoclave at 180°C for 12 h, followed by washing with ethanol. Characterization included TEM, XPS, FTIR, UV-vis, DLS, and zeta potential measurements. Photothermal performance was tested with varying concentrations and laser powers. Cytotoxicity was assessed via MTT assay on 4T1 cells. In vivo studies involved intratumoral injection of NPs in mice, laser irradiation, CT imaging, weight monitoring, and histology examinations.

5：Data Analysis Methods:

Data were analyzed using standard techniques; for example, cell viability was calculated from absorbance at 490 nm, and temperature changes were recorded and correlated with experimental conditions.