Bovine serum albumin (bsa)

The contact angle of water and diiodomethane were assessed by a contact angle tester (OCA25, Dataphysics, Germany), then the surface energy was calculated by the method of Owens two-liquid [8 (link)].
The adherent protein was evaluated by bicinchoninic acid protein assay kit (BCA, TIANGEN, China). The cages (G-PEEK, G-PEEK/Ta-5, G-PEEK/Ta-10 and G-PEEK/Ta-15) were covered by the protein solutions (including 30 μg/mL fibronectin (Fn, Macklin, China) and 5 mg/mL bovine serum albumin (BSA, Macklin, China)) in 12-well plates. After being incubated 4 h at 37 °C, the unabsorbed proteins were cleaned with PBS 3 times. Finally, under shaking at 37 °C, the cages were covered by 5% sodium dodecyl sulfate (SDS) to thoroughly set free the absorbed proteins, then were evaluated by the BCA assay kit.

IHC was routinely performed, as previously described [13 (link)], on 4‐mm sections of formalin‐fixed paraffin‐embedded (FFPE) tissues. Paraffin sections were heated at 65°C for 4 h. Tumor tissue sections were deparaffinized and hydrated through an alcohol gradient to water. The sections were subjected to microwave antigen retrieval in 0.01 μmol/L citrate buffer (pH = 6.0; Zeye Biotech, Shanghai, China) for 10 min. Then, endogenous peroxidase activity was blocked with 3% hydrogen peroxide (Zeye Biotech, Shanghai, China) for 10 min. After incubating with 5% bovine serum albumin (20 μL, Macklin, Shanghai, China) for 1 h at room temperature, sections were incubated with anti‐mouse CD8 (1:50, 66868‐1, Proteintech, Rosemont, IL, USA) overnight at 4°C. Subsequently, sections were incubated with rabbit anti‐mouse CD8 antibody (1:200, ab217344, Abcam, Cambridge, MA, USA) for 1 h at 37°C. Sections were afterward incubated following the instructions of a DAB substrate kit (G1212, Servicebio, Wuhan, Hubei, China). Then, the sections were counterstained with hematoxylin (20 μL, aladdin, Shanghai, China), dehydrated (70%, 80%, 90%, 95%, 100%, 100% ethanol, Macklin, Shanghai, China), and mounted. Integrated optical density values for CD8 protein were calculated using Image‐Pro Plus 6.0 (MEDIA CYBERNETICS, Rockville, Maryland, USA).

All glassware and stirring magnets were washed with aqua regia (HCl : HNO₃ volume ratio = 3 : 1) and rinsed with ultrapure water thoroughly. Gold(iii) chloride trihydrate (HAuCl₄·3H₂O, Macklin, China), bovine serum albumin (BSA, Macklin, China), sodium hydroxide (NaOH, Macklin, China), ethanol (Macklin, China), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC, Macklin, China), ethylenediamine (EDA, Macklin, China), doxorubicin hydrochloride (DOX·HCl, Macklin, China), triethylamine (TEA, Macklin, China), dimethyl sulfoxide (DMSO, Macklin, China) and tetrahydrofuran (THF, Macklin, China) were used as received.

The raw sludge was produced from wastewater bio-treatment and leather-making process in Kanghuida Co., Ltd. (Hebei, China). The tannery sludge was stored at 4 °C before use to ensure that the properties were stable. The properties of separated sludge supernatant (4000 rpm, 10 min) and dried solid (105 °C, 24 h) are shown in Table S1.† Folin-phenol reagent (2 mol L⁻¹), sodium hydroxide (NaOH, ≥99.7%), potassium carbonate (Na₂CO₃, ≥99.7%), sodium tartrate (C₄H₄Na₂O₆, ≥99.7%), and bovine serum albumin (BSA, ≥99.7%) were all purchased from Macklin Biochemical Co., Ltd. (Shanghai, China). Copper sulfate (CuSO₄, ≥99.7%), anthracenone (C₁₄H₁₀O, ≥99.7%) and sulfuric acid (H₂SO₄, ≥98%) were all purchased from National Drug Group Chemical Reagent Co., Ltd. (Shanghai, China), and used without further purification.