Preparation of an injectable zinc-containing hydrogel with double dynamic bond and its potential application in the treatment of periodontitis

Abstract

Periodontal tissue regeneration continues to face significant clinical challenges. Periodontitis leads to alveolar bone resorption and even tooth loss due to persistent microbial infection and persistent inflammatory response. As a promising topical drug delivery system, the application of hydrogels in the controlled release of periodontal bioactive drugs has aroused great interest. Therefore, the design and preparation of an injectable hydrogel with self-repairing properties for periodontitis treatment is still in great demand. In this study, polysaccharide-based self-healing hydrogels with antimicrobial osteogenic properties were developed. Zinc ions are introduced into a dynamic cross-linking network formed by dynamic Schiff bases between carboxymethyl chitosan and oxidized hyaluronic acid via coordination bonds. The OC-Zn hydrogels exhibited good tissue adhesion, good fatigue resistance, excellent self-healing ability, low cytotoxicity, good broad-spectrum antimicrobial activity, and osteogenic activity. Therefore, the designed hydrogels allow the development of drug delivery systems as a potential treatment for periodontitis.

Scheme 1. Schematic of the fabrication route of multifunctional OC–Zn hydrogels with the potential for periodontitis.

Fig. 1. (A) ¹H NMR spectra of HA and OHA. (B) Photograph displaying the mixing of OHA/Zn²⁺ and CMCS to form OC–Zn hydrogel, as well as the compression process of OC–Zn hydrogel (scale bar: 1 cm). (C) and (D) FT-IR spectra of HA, OHA, OC and OC–Zn hydrogels. Gelation time (E), representative SEM images (F) of OC and OC–Zn hydrogels. OC–Zn3, OC–Zn6, and OC–Zn12 represent hydrogels with final ZnCl₂ concentrations of 0.03, 0.06, and 0.12% (w/v), respectively.

Fig. 2. (A) Image of the injectable of OC–Zn hydrogel into various shapes. (B) Swelling ratio and degradation trend of the OC–Zn hydrogels at the pH of 7.4. (C) Rheology characterizations (G′, G′′) of OC, OC–Zn3, OC–Zn6, and OC–Zn12 hydrogels. (D) The OC–Zn hydrogel adapting to the movement of the finger joint. (E) Self-healing property of OC–Zn3 hydrogel. (F) Hydrogel adhesion mechanism.

Fig. 3. (A) Hemolysis ratio of hydrogels. (B) Cell viability of MC3T3 cells after 1, 3, and 5 days of incubation with hydrogels (*: p < 0.05; ***: p < 0.001). (C) Fluorescence images of hPDLSCs treated with the hydrogels (scale bar: 100 μm).

Fig. 4. Antibacterial activity evaluation of prepared hydrogels. (A) Representative photographs (10⁶-fold dilution) and (B) quantitative results of survival bacteria colonies on agar plates after incubating the bacterial suspension with the prepared hydrogels (***: p < 0.001). (C) Quantitative results of survival bacteria colonies on agar plates after incubating the bacterial suspension with the prepared hydrogels within 24 h. (D) TEM images of bacterial morphology of control group and treated with OC–Zn12 hydrogel.

Fig. 5. Anti-biofilm activity evaluation of prepared hydrogels. (A) Representative crystal violet staining images of biofilm treated with different hydrogels and (B) the biofilm biomass (n = 3). (C) CLSM images of F. nucleatum and S. aureus biofilms grown for 48 h and treated with hydrogels for 12 h. Green is live cells. Red is dead cells.

Fig. 6. (A) ALP staining of hPDLSCs on day 7 (scale bar: 100 μm). (B) ARS staining on day 21 (scale bar: 100 μm).