Abstract: BACKGROUND: Metformin and Eomecon chionantha Hance both exhibit anti-inflammatory and vascular protective properties. Metformin has been proven to promote tissue repair through various mechanisms, such as reducing oxidative stress. 
OBJECTIVE: To investigate the antibacterial, anti-inflammatory, and wound-healing effects of metformin combined with Eomecon chionantha Hance on deep second-degree burn wounds.
METHODS: (1) In vitro experiments: The effects of Eomecon chionantha Hance, Eomecon chionantha Hance + low-dose metformin (10 mmol/L), and Eomecon chionantha Hance + high-dose metformin (100 mmol/L) on the level of reactive oxygen species in RAW264.7 cells (or L929 cells) induced by hydrogen peroxide were detected. The effects of Eomecon chionantha Hance, Eomecon chionantha Hance + low-dose metformin (10 mmol/L), and Eomecon chionantha Hance + high-dose metformin (100 mmol/L) on the scratch healing ability of L929 cells were detected. The effects of Eomecon chionantha Hance, Eomecon chionantha Hance + low-dose metformin (10 mmol/L), and Eomecon chionantha Hance + high-dose metformin (100 mmol/L) on the expression of phosphorylated nuclear factor κB p65 and nuclear factor κB p65 protein in RAW264.7 cells induced by lipopolysaccharide were detected. The inhibitory effects of Eomecon chionantha Hance, Eomecon chionantha Hance + low dose metformin (10 mmol/L), and Eomecon chionantha Hance + high dose metformin (100 mmol/L) on Staphylococcus aureus were detected by test tube double dilution method combined with agar dilution plate method and bacterial live and dead staining. (2) In vivo animal experiment: The hemostatic properties of Eomecon chionantha Hance were observed by liver laceration model and tail amputation model of SD rats. 16 SD rats were selected, and 4 deep second-degree burn wounds with a diameter of 2 cm were established on the back of each rat. Staphylococcus aureus suspension was applied to the wound 4 hours after modeling. 24 hours after the bacterial liquid was applied, the rats were divided into four groups for intervention, with four rats in each group: the modeling group was injected with normal saline subcutaneously, and the wound was wetted with gauze soaked in normal saline. The Eomecon chionantha Hance group was wetted with gauze soaked in Eomecon chionantha Hance. The low-dose metformin Eomecon chionantha Hance group was injected with 10 mmol/L metformin 1 mL subcutaneously, and the wound was wetted with gauze soaked in Eomecon chionantha Hance. The high-dose metformin Eomecon chionantha Hance group was injected with 100 mmol/L metformin 1 mL subcutaneously, and the wound was wetted with gauze soaked in Eomecon chionantha Hance. The subcutaneous administration time was 1, 2, 4, and 6 days, and the gauze was changed every day. Within 7 days after administration, the wound healing, wound tissue morphology, wound oxidative stress indicators, inflammatory factors, and angiogenesis-related protein expressions were observed. 
RESULTS AND CONCLUSION: (1) Compared with the Eomecon chionantha Hance alone, metformin combined with Eomecon chionantha Hance had stronger reactive oxygen scavenging ability, antibacterial ability, cell migration promotion ability and inhibition of nuclear factor κB inflammatory signaling pathway, and the effect of Eomecon chionantha Hance combined with high-dose metformin was more obvious. (2) Eomecon chionantha Hance had a good hemostatic effect, which could shorten the hemostatic time and reduce the amount of bleeding. Compared with Eomecon chionantha Hance alone, metformin combined with Eomecon chionantha Hance could better promote wound healing, improve wound tissue morphology, inhibit inflammatory response and oxidative stress response, and increase vascular endothelial growth factor protein expression, and the effect of Eomecon chionantha Hance combined with high-dose metformin was more obvious. (3) The results show that metformin combined with Eomecon chionantha Hance can promote the repair of deep second-degree burn wounds through antibacterial, anti-inflammatory, antioxidant, and cell migration promotion. 

Key words: metformin">, Eomecon chionantha Hance">, burn">, wound healing, oxidative stress">, deep second-degree burn">, engineered skin material