Abstract: BACKGROUND: Combined radiation and wound injury appeared mainly in patients with tumor radiotherapy and nuclear radiation accidents. The radiation destroys the repair mechanism, resulting in delayed or prolonged wound healing. It still lacks an effective therapeutic strategy currently. 
OBJECTIVE: To prepare multifunctional wound dressings based on the multiple clinical symptoms of combined radiation and wound injury, which are designed to be antibacteria, promoted healing and analgesics. 
METHODS: Using levofloxacin, fibroin and lidocaine hydrochloride as raw materials, 3D bioprinting technology was applied to prepare the multifunctional wound dressing. (1) The multifunctional dressing was placed on a fixed culture plate coated with Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, and incubated at 37 °C overnight to detect the diameter of the antibacterial zone. (2) 40 Kunming mice were randomly divided into trauma group, radiation and trauma model group, treatment group and positive drug group, with 10 mice in each group. Mice in the radiation and trauma model group, treatment group and positive drug group were irradiated by 60Co gamma rays. After 1 hour of radiation, a full-layer skin defect wound with a diameter of 1 cm was made on the back of each mouse in the four groups. Normal saline was applied to the wounds of the trauma group and the radiation and trauma model group. Trethanolamine cream was applied to the wounds of the positive drug group. Multifunctional dressing was applied to the wounds of the treatment group. The dressing was changed every 2 days, and the treatment was continued for 14 days. Wound healing rate and serum interleukin-6 level were measured at 3, 7 and 14 days after wound modeling. 14 days after the wound modeling, the skin tissue of the wound was obtained and received hematoxylin-eosin staining, Masson staining and cytokeratin-14 immunohistochemical staining. 
RESULTS AND CONCLUSION: (1) 3D-printed multifunctional wound dressing had good antibacterial activity. The antibacterial zone diameters against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were (4.15±0.09), (4.18±0.23) and (4.35±0.13) cm, respectively. (2) With the extension of modeling time, the wound healed gradually. The wound healing rate of the treatment group and the positive drug group was higher than that of the radiation and trauma model group at 3, 7 and 14 days after modeling (P < 0.01, P < 0.001). The wound healing rate of the treatment group was higher than that of the positive drug group. With the extension of modeling time, the serum interleukin level of mice increased first and then decreased. The serum interleukin level in the treatment group at 3, 7 and 14 days after modeling was lower than that in the radiation and trauma model group. Hematoxylin-eosin staining and Masson staining exhibited that inflammatory cells infiltrated the granuloma tissue in the trauma group, and the dermal collagen fibers were densely arranged. The normal structure of epidermis and dermis was destroyed and inflammatory cells were infiltrated in the radiation and trauma model group. In the treatment group, normal skin mucosal tissue was observed, the epidermis was arranged closely, and the sweat glands, hair follicles and dermal collagen fibers were arranged regularly. In the positive drug group, the arrangement of epidermal layer was tight, and the arrangement of sweat glands, hair follicles and dermal collagen fibers was regular. Cytokeratin-14 immunohistochemical staining displayed that the epidermal tissue thickness in the treatment group was lower than that in the other three groups (P < 0.01, P < 0.001). (3) The results confirm that the 3D-printed multifunctional dressing has multiple functions of local anesthesia, anti-infection and promoting healing.

Key words: 3D printing, combined radiation and wound injury, wound healing, multifunctional dressing, dressing, fibroin