Inhibition of Periodontitis Induction Using a Stimuli-Responsive Hydrogel Carrying Naringin

Background: Developing a drug carrier with favorable handling characteristics that can respond to environmental changes after inflammation, such as pH changes, may be beneficial for treating periodontitis. This study aims to investigate the preclinical feasibility of using naringin, a naturally derived polymethoxylated flavonoid compound with anti-inflammatory properties, to inhibit periodontitis induction via a thermogelling and pH-responsive injectable hydrogel. Methods: The hydrogel was made of amphipathic carboxy-methyl-hexanoyl chitosan (CHC), beta-glycerol phosphate (beta-GP), and glycerol. Thermogelling and pH-responsive characteristics of the hydrogel, as well as cell viability after treatment with the hydrogel containing naringin, were evaluated in vitro. Hydrogel was subgingivally delivered when experimental periodontitis was induced in vivo, and therapeutic effect was evaluated with microcomputed tomography imaging, histology, and expression of inflammation-associated genes, including toll-like receptor (TLR) 2, the receptor for advanced glycation end products (RAGE), myeloid differentiation primary response gene-88, and tumor necrosis factor (TNF)-alpha. Results: The hydrogel was consistently fluidic at 4 degrees C but rapidly gelled at 37 degrees C. Release of naringin was faster at pH 5.5 to 6.5, and viability was significantly promoted by treatment with 0.85% naringin. Naringin-carrying CHC-beta-GP-glycerol hydrogel sites showed significantly reduced periodontal bone loss (P < 0.05) and inflammatory infiltration (P < 0.01) as well as significantly downregulated TLR2 (P < 0.05), RAGE (P < 0.01), and TNF-alpha (P < 0.05) relative to the sites with experimental periodontitis alone. Conclusion: Naringin-carrying CHC-beta-GP-glycerol colloidal hydrogel can be used to inhibit induction of experimental periodontitis with favorable handling and inflammation-responsive characteristics.