2.1 Materials
The raw materials required to conduct the experiments are mentioned as follows. The chicken eggs were purchased from a local farm less than 7 days after laying. The surface of the egg was washed in deionized water and sterilized in ethanol (75%). Then, egg white (EW) was separated from the yolk, also called as albumin, and used in the preparation of hydrogels without any further treatment. Sodium alginate (SA), calcium chloride (CaCl2) and gelatin (Gel) (type A from porcine skin, 300 blooms) were purchased from Sigma-Aldrich (USA) and used in same condition as received. The HUVECs were obtained from Zhongqiaoxinzhou Biotech (China).