Background During the process of periodontal soft tissue regeneration, oxidative stress caused by various factors often leads to delayed tissue repair. Traditional restorative materials have shown limited efficacy in addressing this issue. Therefore, the development of hydrogel materials with antioxidant properties holds promising potential to offer more choices for the repair of periodontal soft tissue biomaterials.

Objective To prepare a composite hydrogel of melanin nanoparticles-silk fibroin-tannic acid (MNPs-SF-TA) and assess the impact of melanin nanoparticles (MNPs) content on the hydrogel's microstructure, antioxidant performance, and cellular compatibility.

Methods MNPs were prepared and different concentrations of MNPs were added to silk fibroin (SF), followed by the addition of tannic acid (TA) for chemical crosslinking, resulting in the formation of MNPs-SF-TA composite hydrogel. The hydrogel was divided into experimental groups: MNPs1-SF-TA (1 mg/mL), MNPs2-SF-TA (2 mg/mL), MNPs4-SF-TA (4 mg/mL), and a control group: SF-TA (0 mg/mL). The surface morphology of the hydrogel was observed using scanning electron microscopy (SEM). The radical scavenging ability and antioxidant capacity of the hydrogel were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) assay, and Cu²⁺ assay. The cellular compatibility of the hydrogel material was assessed using the CCK-8 assay and Calcein-AM/PI live/dead cell fluorescent staining method.

Results MNPs and MNPs-SF-TA composite hydrogel were successfully prepared. The DPPH, ABTS, and Cu²⁺ assays all demonstrated that the scavenging ability of free radicals and antioxidant capacity of MNPs-SF-TA hydrogel increased with the increasing concentration of MNPs (P < 0.05), reaching a peak at 4 mg/mL. The CCK-8 results showed that cell proliferation activity, as indicated by the increased absorbance, enhanced with prolonged observation time. With the same observation time, the cell proliferation activity of each group decreased with the increasing concentration of MNPs, and the MNPs2-SF-TA group was significantly higher than the MNPs4-SF-TA group (P < 0.05). The results of Calcein-AM/PI fluorescence staining were consistent with these findings.

Conclusion MNPs-SF-TA composite hydrogel is successfully prepared, and the hydrogel exhibits strong ROS scavenging ability and good cellular compatibility when the concentration of MNPs is 2 mg/mL. Therefore, MNPs-SF-TA hydrogel holds great promise as a novel biomaterial for periodontal soft tissue repair and may serve as a potential alternative to traditional materials in this field.