*2.1. Macroscopic Observation of the Wounds*

Representative images of wound healing process at different time intervals across all the experimental groups are shown in Figure 1. Collagen-treated groups showed faster wound healing process (complete healing after 14 days from wound incision) compared to control group, in detail, the wound regions were covered with epidermis and the wound areas were closed. With the time extending, wound area of each group decreased gradually. On day 3, each group showed different degree of collagen absorption and wound areas of BCS, PCS, ACS, BCE I and BCE II treated groups were obviously smaller than control and woundplast groups; on day 7, the wounds of the groups treated with BCS, PCS, ACS, BCE I, and BCE II contracted further and scabbed, the wounds of control and woundplast groups had only a small amount of granulation tissue; on day 14, dried blood fall-off from the wound and the wounds healed completely. The wounds which were treated with PCS, ACS, BCE I, and BCE II were smooth and no pigmentation. Interestingly, ACS and PCS treated groups exhibited faster healing than control, woundplast, BCS and BCE I groups, however, BCE II treated group had better healing ability than other groups.

**Figure 1.** The different stages of wound healing in rats treated with collagens. BCS—bovine collagen sponge, PCS—pepsin soluble collagen sponge, ACS—acid soluble collagen sponge, BCE I—bovine collagen electrospun I, BCE II—bovine collagen electrospun II.
