Introduction

Radiation resembles the standard treatment protocol for cancer types such as head and neck, breast, and lung cancers [1]. However, many complications are associated with radiotherapy reactions, limiting the radiotherapy dose and treatment effect. Radiation-induced skin injury (RISI) is a common but debilitating side effect; various degrees of radiodermatitis occur in 95% of cancer patients following radiotherapy [2B, F). C, N, and O were identified in IFI6, C and O presented in SA, and Na, CI, and Ca appeared in PDA@GO. These findings suggest that IFI6, SA, and PDA@GO were found in the composite sponge. GO sheets were obtained using a modified Hummer’s method with an average size of 2 μm measured using Image J software and a thickness of about 1.5 nm measured by Atomic Force Microscope [18]. To characterize the chemical composition of the Fe3O4NPs-GO-PDA composite thin film, Jang et al. suggested that the C peak (284.08 eV), the peak of C−C (284.08 eV), and the peak of O 1s (531.95 eV) were remarkably dominant, suggesting that the composite system consisted of GO sheets; C−O and C−N binding energies were observed at 286.56 and 285.79 eV, respectively, suggesting that the PDA contains C−N bonds [19].

Liu et al. found characteristic absorption bands of GO sheets at 1054 cm−1 (alkoxy), 1224 cm−1 (epoxy), 1401 cm−1 (carboxyl; C–O), and 1724 cm−1 (carboxyl; C=O) [18]. The new adsorption peak at 1579 cm−1 of the MPDA@GO composites may be attributed to the deformation vibration of N–H bonding and the stretching vibration of C–N bonding. The FTIR results in this paper are consistent with these findings (Fig. 2D), suggesting that the reaction may have occurred between epoxide groups of GO and amine groups of PDA during the preparation of PDA@GO composites. There are no reports of the characteristic absorption peak of IFI6. However, we believe that the 3400 cm−1 position may be associated with the composition of IFI6.

To further test the loading of IFI6, sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis was conducted (Fig. 2C). We found that the IFI6- PDA@GO/SA material expressed IFI6, consistent with the IFI6 protein bands as reported [13], suggesting that IFI6 was successfully tested. IFI6-PDA@GO/SA displays a typical nanostructure, and the diameter is about 162 nm, PDI = 0.19, and zeta potential = − 14.64 mV (Fig. 2G). The ultraviolet spectrum of IFI6-PDA@GO/SA showed no evident change in 400–800 nm (Fig. 2E). Zhao et al. synthesized polyelectrolyte complex nanoparticles for plasmid delivery [20]. Nanosized SA solids ranged from 0.04% to 0.08%, and higher concentrations resulted in larger agglomerate-like solution systems. Active targeting of small particles has advantages over passive targeting of large nanospheres due to the enhanced permeability and retention effect. ** novel hydrogel wound dressings; to this end, various antibacterial agents have been introduced into the hydrogels. Huang et al. reported that the hydrogels containing PDA@Ag5GO1 (Ag5GO1 denotes that the mass ratio between Ag and GO is 5:1) exhibited effective antibacterial properties and high inhibition of E. coli and S. aureus [23]. Liu et al. showed that CNF hydrogels and MPDA@GO (1:2)/CNF composite hydrogels showed no antibacterial effect against E. coli and S. aureus [18]. The (MPDA-TH)@GO (1:2)/CNF composite hydrogel inhibited E. coli growth with a zone width of 15 mm, whereas the drug-loaded composite hydrogel exhibited a zone width of 18 mm against S. aureus. This finding suggests that the inhibition zone of the (MPDA-TH)@GO (1:2)/CNF composite hydrogel depends on the released TH from the composite hydrogel. MRSA (G+) and E. coli (G−) in the control group grew well; however, PDA@GO inhibited growth (Fig. 3B, D). PDA@GO /SA inhibited bacterial growth to a greater extent, and IFI6- PDA@GO /SA did not show sufficient bacteriostasis. These findings may be related to the fact that IFI6 has no reported antibacterial activity, while GO and SA have been reported to have good antibacterial activity.

In vitro cytological study of IFI6-PDA@GO/SA

We performed flow cytometry assays to determine the potential role of IFI6 in apoptosis. IFI6 is only expressed in higher eukaryotes [12]. Radiation significantly increased the apoptosis rate (Fig. 4A, C). Compared with Group B, Group E had a lower apoptosis rate (P < 0.05), and the effect in Group E was higher than that of Group D. This finding suggests that IFI6-PDA@GO/SA significantly reduces apoptosis and that the increased IFI6 protein in Group E participates in regulating apoptosis. These phenomena may be related to anti-ROS mechanisms.

Fig. 4
figure 4

The in vitro cytological study of IFI6-PDA@GO/SA. A + C Flow cytometry and its total apoptosis rate results. B In vitro tube formation assay. D, E The number of nodes and total length of tubes in Group B. *P < 0.05

Full size image

IFI6 overexpression resulted in decreased apoptosis in irradiated HaCaT and WS1 cells compared with control skin cells, suggesting a survival-promoting function of IFI6. The effect of IFI6 on mitochondrial membrane potential was investigated (an essential indicator of mitochondrial function) using JC-1 staining [13]. After irradiation, the authors showed that IFI6-silenced WS1 cells had decreased mitochondrial membrane potential. IFI6 regulated melanoma development and growth through E2F2-mediated DNA replication [24] and promoted breast cancer cell metastasis by inducing deregulation of the mitochondrial redox state [25]. In the present study, we showed that overexpression of IFI6 in HaCaT cells promoted cell survival through anti-apoptosis and guided local aggregation of surviving cells by promoting cell migration, suggesting a new function of IFI6 promoting tumor cell survival. Yin et al. found that overexpression of CTD-3252C9.4 facilitated apoptosis of pancreatic cancer cells in vitro and in vivo [7), suggesting a potential interaction between IFI6 and SSBP1 under radiation induction. In the heat shock response (HSR), SSBP 1 relocates to the nucleus by interacting with heat shock transcription factor 1 (HSF1) [36]. Jia et al. proposed that IFI6 is involved in HSF1 mediated HSR [13]. As expected, radiation enhanced HSF1 transcriptional activity was blocked in IFI6 knockout cells but enhanced in IFI6-overexpressing cells. HSF1-mediated HSR is a typical anti-toxic stress response, including heat shock and oxidative stress.

As shown in the immunohistochemistry studies, Group A showed less expression of IFI6 and its downstream pathway SSBP1/HSF1 protein, and the positive expression of related proteins (Group B) increased significantly after 30 Gy radiation (Fig. 7A, B). IFI6-PDA@GO/SA (Group E) had the most potent effect of promoting protein expression (P < 0.05). As shown in Fig. 7C, D, the IFI6 protein in wound tissue significantly increased, suggesting that IFI6-PDA@GO/SA material released IFI6 into the wound. IFI6 co-localizes with SSBP1 to initiate the expression of HSF1, thereby mediating the downstream HSR. Elevated expression of heat shock proteins regulated by HSF1 is radioprotective for tumor cells [36]. HSF1 targets genes such as ppl to interact with AKT1, a kinase that mediates a variety of cell growth and survival signal transduction processes [13]. These states illustrate the complex mechanisms by which IFI6 regulates the radiation sensitivity of human skin cells.

The effect of IFI6-PDA@GO/SA on the immune microenvironment

Immune cells, particularly regulatory T (Treg) cells, play a critical role in wound healing. When wound formation and inflammatory responses occur, immune cells help clear foreign antigens [37]. Treg cells suppress the activation of the immune system and prevent pathological self-reactivity such as autoimmune diseases. Cytokines participate in cell–cell interactions and communication and are involved in cell migration, proliferation, and inflammatory responses. Kim et al. found that CD4+ and CD8+ Treg cells in cm had a variety of cytokines and growth factors [38]. CD4+ and CD8+ Treg cells stimulated HaCaT keratinocyte migration through EMT and upregulation of MMP-1.

To determine whether the IFI6-PDA@GO/SA regulates the immune microenvironment within the wound and explore the mechanism, wound-draining lymph nodes were collected 14 days after irradiation. Flow cytometry showed that Group E had significant activation of CD4+ and CD8 +T cells (Fig. 8A, B). These findings suggest that Treg cells which contains various cytokines and growth factors, stimulates cell migration and proliferation to promote wound healing. IFI6-PDA@GO/SA also promoted the infiltration of NK and M1 cells (Fig. 8C, D). Sobecki et al. demonstrated that the lack of hypoxia-inducible factor (HIF)-1α in NK cell α hypomorphic mice exhibit the cytokine interferon-γ and impaired release of granulocyte–macrophage colony-stimulating factor as part of a blunted immune response [39]. HIF-1 in NK cells α is the link that balances antimicrobial skin defenses and overall repair.

Fig. 8
figure 8

The effect of IFI6-PDA@GO/SA on the immune microenvironment. A Percentages of CD4+ T cells. B Percentages of CD8+ T cells. C Cells were gated on the CD45+ population and then on CD49b+ to identify NK cells. D Cells were further gated on F4/80+ CD86hi to identify M1 macrophages. *P < 0.05

Full size image

It is worth highlighting that we found that IFI6-PDA@GO/SA elevated NK cells more significantly than CD4+ and CD8+ cells. On the other hand, IFI6-PDA@GO/SA promoted CD4+ and CD8+ expression in wound cells, thereby increasing T cell activation and NK cell infiltration, realizing the synergistic effect of reducing sensitization in RISI.

Conclusions

We designed and fabricated a nanomaterial combining IFI6 for RISI wound healing. Based on our overall evaluation of IFI6-PDA@GO/SA nanomaterials, we conclude that GO possesses excellent antibacterial activity, infrastructure, and biocompatibility. PDA possesses excellent anti-ROS and bioadhesion properties. SA possesses excellent antibacterial activity and moisture retention. The most important finding is that IFI6 promotes cell proliferation, migration, and vascularization and stimulates the immune microenvironment. The five components work together to promote RISI healing. IFI6 acts synergistically to reduce oxidative stress and inflammation by activating the SSBP1/HSF1 signaling pathway.

IFI6-PDA@GO/SA improves inflammation in RISI wounds and induces granulation tissue formation, angiogenesis, and collagen deposition, resulting in faster wound closure. We believe this nanomaterial provides a valuable alternative and promising strategy for RISI wound repair.