1：Experimental Design and Method Selection:

The study involved designing a multifunctional peptide coating for gold nanorods (AuNRs) to achieve enzyme-responsive behavior. The peptide consists of a cell-penetrating Tat sequence, an MMP-9 cleavable sequence, and a zwitterionic antifouling sequence. AuNRs were synthesized using a seed-mediated growth method and modified via ligand exchange with peptides. In vitro and in vivo experiments were conducted to evaluate cellular uptake, photothermal effects, tumor accumulation, and therapeutic efficacy.

2：Sample Selection and Data Sources:

Human liver cancer HepG2 cells were used for in vitro studies. Male nude mice with xenograft tumors (HepG2 cells) were used for in vivo experiments. Data were collected through various assays including ICP-MS, MTT assay, and histological analysis.

3：List of Experimental Equipment and Materials:

Gold nanorods (AuNRs), peptides (responsive and non-responsive), MMP-9 enzyme, cell culture materials (DMEM, FBS), lasers (808 nm), TEM, DLS, UV-vis spectroscopy, ICP-MS, fluorescence microscope, and other reagents as listed in the materials section.

4：Experimental Procedures and Operational Workflow:

AuNRs were prepared and coated with peptides. Characterization included TEM, DLS, zeta potential, and UV-vis spectroscopy. In vitro studies involved cell uptake assays with and without MMP-9, cytotoxicity tests, and photothermal effects. In vivo studies included blood circulation analysis, tumor accumulation, photothermal therapy, and histological examination.

5：Data Analysis Methods:

Data were analyzed using one-way and two-way ANOVA in Origin software, with statistical significance set at p < 0.05.