Multifunctional injectable iCPC@MgO bioadhesive with inherent anti-inflammatory potential for periodontitis treatments

Abstract

Effectively addressing inflammation in periodontitis poses challenges, as conventional injectable hydrogels typically necessitate the addition of drugs to achieve significant anti-inflammatory effects, which are often hampered by poor drug solubility, rapid degradation, and systemic side effects. To overcome these obstacles, we developed a multifunctional injectable hydrogel, iCPC@MgO, engineered with inherent anti-inflammatory, antibacterial, and osteogenic properties through the strategic incorporation of natural compounds. The hydrogel design aimed to harness the intrinsic potential of natural materials: xylitol provides anti-inflammatory and biofilm-disrupting properties, while caffeic acid introduces catechol groups for wet tissue adhesion. The synthesis of hydrogels involved three steps: the esterification reaction of xylitol and succinic acid to form poly(xylitol succinate) (PXS) polymer, which then reacted with caffeic acid and citric acid to create the iCPC copolymer. This polymer was subsequently cross-linked with magnesium oxide particles to yield the final iCPC@MgO injectable adhesive. The 1H NMR spectrum and Fourier Transform Infrared Spectroscopy (FTIR) analyses confirmed successful polymerization of both PXS and iCPC polymers. The rheological characterization and adhesion measurements demonstrated the successful synthesis of iCPC@MgO hydrogel, exhibiting injectability with a lap shear adhesive strength about 30 kPa, surpassing fibrin glue performance. Meanwhile, this hydrogel further demonstrated sustained Mg2⁺ release, correlating with its degradation profile. Molecular dynamics simulations revealed that the PXS polymer, synthesized via esterification of xylitol and succinic acid, competitively binds to the MD2 protein with an affinity comparable to that of the established antagonist Eritoran. It effectively suppressed NF-κB activation and inhibited IL-6 protein release at 6, 12, and 24 hours in human gingival fibroblasts (HGFs). Meanwhile, iCPC@MgO hydrogel could activate the Wnt/β-catenin pathway to promote osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs), as evidenced by a significant increase in alkaline phosphatase activity (P＜0.05) and 2.0-fold higher expression of RUNX2 compared with controls (P＜0.05) in vitro. Antibacterial assays demonstrated the efficacy of the iCPC@MgO hydrogel against Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, achieving a half-biofilm inhibition rate at 4 mg mL-1. In vitro metabolomics assays revealed that the hydrogel disrupts bacterial glycolysis and peptidoglycan synthesis, while upregulating riboflavin-derived metabolites (e.g., FMN, FAD), thereby stimulating intrinsic antibiotic synthesis pathways. In a rat periodontitis model, the iCPC@MgO hydrogel reduced alveolar bone loss by 0.78 ± 0.071 mm compared to 0.96 ± 0.084 mm in the control group (p < 0.01). The normalized subgingival microbiota diversity was evaluated using 16S rRNA sequencing, revealing no adverse effects on microbial flora biodiversity. The immunohistochemical results showed a decrease in the pro-inflammatory cytokines IL-1β and TNF-α in the periodontal surrounding tissues. Histological analysis confirmed enhanced collagen organization, reduced osteoclast activity, and increased periostin, promoting bone regeneration. Combining eco-friendly synthesis, injectability, and multifunctionality with inherent anti-inflammatory potential, the iCPC@MgO hydrogel represents a paradigm shift in the treatment of periodontitis. Its TLR4-MD2 antagonism specifically addresses the inflammation in periodontitis without delivery any drugs. This platform holds promise for broader applications in inflammatory tissue repair, emphasizing the untapped potential of natural polymers in translational medicine.