Study On Bio-inspired Self-assembled Peptide Hydrogel For Radiation-induced Skin Injury Repair

As the largest organ of the body,the skin has multiple functions such as barrier,regulation,immunity and metabolism,and is the body’s first line of defense against external stimuli.Because of this,it is often the most vulnerable to damage.As one of the main methods of cancer treatment,radiation therapy can induce severe skin damage,which has become a health problem that cannot be ignored.When radiation-induced skin injury(RISI)occurs,symptoms such as erythema,hair loss,dryness,and even skin ulcers and fibrosis can occur at the injury site,seriously affecting the patient’s health and quality of life.Therefore,it is necessary to find effective measures to repair RISI.Peptide nanomaterials are an important biomaterial with the advantages of easy synthesis,easy modification and good biocompatibility,which have many applications in biomedicine.And peptides self-assembled into hydrogels usually have the advantages of 3D porous structure,good moisturizing ability and air permeability,which show a broad application prospect in the field of skin repair.Therefore,this paper proposes to design a self-assembled peptide hydrogel for improving the repair effect of RISI.Firstly,an antioxidant heparin-mimetic peptide KYKYEYEYAGEGDSS-4Sa(K16)was designed and synthesized by solid-phase synthesis(SPPS)in this work.It has antioxidant properties due to the presence of phenolic hydroxyl group in the structure of tyrosine(Y,Tyr),while a small molecule of p-sulfobenzoic acid is attached to the end of the peptide chain,and the sulfonic acid group in its structure,together with the carboxyl group on aspartic acid(D,Asp)and the hydroxyl group on serine(S,Ser),mimics the functional group of heparin,thus making the K16 peptide able to induce angiogenesis without the addition of exogenous growth factors.At the same time,the presence of the sulfonic acid group gives the peptide the ability to adsorb inflammatory cytokines.In vitro gel formation and structural characterization showed that the K16 peptide could self-assemble to form nanofibrous hydrogels with 3D porous structure,which mimicked the structure of ECM,and the formed hydrogels had good rheological properties and β-folded conformation that facilitated assembly stability.Then,this paper explored the antioxidant properties of the hydrogel by in vitro DPPH and ABTS and intracellular reactive oxygen species(ROS)scavenging experiments,and the results showed that it could effectively eliminate free radicals and ROS in vitro,thus improving oxidative stress;this paper further applied γ-H2 AX immunofluorescence staining and cell clone formation experiments to test the radiation protection properties of the material,and the results showed that K16 hydrogel could inhibit the damage of cellular DNA by radiation and showed good radiation protection ability;meanwhile,after co-incubation of K16 hydrogel with inflammatory cytokines in vitro,ELISA results showed a significant decrease in the content of pro-inflammatory cytokines,indicating that K16 hydrogel can adsorb inflammatory factors and thus has certain anti-inflammatory ability.Next,the effect of K16 hydrogel on cell proliferation and migration was examined after co-culture with 3T3 cells,and the results showed that K16 peptide hydrogel has good biological activity to promote cell proliferation and migration;meanwhile,this paper investigated the ability of K16 hydrogel to promote angiogenesis by in vitro angiogenesis assay and the results showed that co-culture of K16 hydrogel with HUVECs in Matrigel matrix gel induced more angiogenesis compared with the Matrigel group.Finally,this paper established a radiation-induced skin injury model by topical irradiation of the legs of BALB/c mice with X-rays and treated it with K16 hydrogel dressing.The injured skin areas of the mice were photographed and recorded,and the results showed that the K16 hydrogel inhibited the deterioration of the skin injury at the early stage and accelerated the wound healing and epidermal regeneration at the later stage.Meanwhile,damaged skin tissues at different time points were collected and analyzed in pathological sections.The results of HE,Masson and CD68,CD31,α-SMA immunohistochemical staining showed that K16 hydrogel significantly reduced inflammatory infiltration at the wound site,promoted neovascularization and collagen deposition,thus facilitating the repair of RISI.And the results of ELISA assay of cytokine content in skin tissues also showed that K16 can effectively reduce the level of pro-inflammatory cytokines,which facilitates the regression of inflammation and tissue remodeling.In summary,this paper designed an antioxidant heparin-mimetic peptide for radiation-induced skin injury,it can self-assembled into a hydrogel and then mimic ECM,eliminate ROS,reduce inflammation,promote angiogenesis,thus promote RISI repair.