2.1. Reagents
Escherichia coli BL21 (DE3) and plasmids containing pET-3c, an ampicillin-resistance gene, and isopropyl β-D-1-thiogalactopyranoside (IPTG) were provided by Invitrogen (Carlsbad, CA). Plasmid extraction and gel recovery kits as well as restriction enzymes and ligase were purchased from Guangzhou Tianjin Biotechnology Co., Ltd. (China). EGF were supplied by Jinan University Biopharmaceutical R&D Center (Guangzhou, China). All other reagents were provided by GBCBIO Technologies Inc. (Guangdong, China).
NIH/3T3 (ATCC CRL-7724) cells were purchased from Chinese Academy of Sciences (Shanghai, China) and cultured in RPMI 1640 supplemented with 10% fetal bovine serum (FBS) (Gibco, New York, USA). HaCaT cells (ATCC CRL-2310) were purchased from Chinese Academy of Sciences and cultured in DMEM supplemented with 10% FBS. All cell culture plates and bottles were obtained from Corning Company (Corning, NY).