Fetal bovine serum (fbs)

Gelatin (type A; from porcine skin, 300 g bloom) was purchased from Sigma-Aldrich. Carbobenzoxy-l-glutaminylglycine (Z–Gln–Gly) and fetal bovine serum (FBS) were both purchased from Shanghai Macklin Biochemical Co., Ltd., Shanghai, China. Transglutaminase (mTG, 200 U/g) was obtained from Shanghai Yuanye Bio-Technology Co., Ltd., Shanghai, China. Human cervical cancer cell line HeLa cells and DMEM were obtained from Wuhan Prosser Life Technology Co., Ltd., Wuhan, China. All other reagents were local products of analytical grade and were used as received without further purification.

Two-week-old SD rats (Vital River Laboratory Animal Technology, China) were used to extract rat bone mesenchymal stem cells (BMSCs). The medullary cavity of rat's femur and tibia were rinsed with MEM-α medium (Gibco, USA) containing 10% fetal bovine serum (Gibco, USA). BMSCs were cultured in standard conditions (37 ​°C, 95%/5% air/CO₂) and seeded in complete media, which consisted of MEM-α containing 10% fetal bovine serum and 1% penicillin and streptomycin (Macklin, China). The culture medium was changed every 2 days. Cells were digested with 0.05% trypsin-ethylenediaminetetraacetic acid (EDTA) (Gibco, USA) for following experiments.

All reagents were not purified further before use. Methylbenzene, hydrochloric acid (HCl), lysine (Lys), arginine (Arg), titanium tetrachloride (TiCl₄), tetrabutyltitanate, gold (III) chloride (HAuCl₄·3H₂O), leucine (Leu), cysteine (Cys), proline (Pro), glycine (Gly), barium hydroxide octahydrate (Ba(OH)₂·8H₂O), formic acid, ethylene diamine tetraacetic disodium (EDTA−2Na), chloroplatinic acid (H₂PtCl₆), 3,3′,5,5′−tetramethylbenzidine (TMB, ≥99%), L−histidine (L−His), glutathione (GSH), glutamic acid (Glu), and fetal bovine serum were purchased from Macklin Biochemical Co., Ltd. (Shanghai, China). Sodium borohydride (NaBH₄), disodium hydrogen phosphate (Na₂HPO₄), p−Benzoquinone (p−BQ), isopropanol (IPA), potassium nitrate (KNO₃), citric acid, ascorbic acid (AA), and sodium nitrate (NaNO₃) were purchased from Sinopharm Chemical Reagents Co., Ltd. (Shanghai, China).