Dexamethasone-loaded zeolitic imidazolate frameworks nanocomposite hydrogel with antibacterial and anti-inflammatory effects for periodontitis treatment

Abstract

Periodontitis is a bacterial-induced, chronic inflammatory disease characterized by progressive destruction of tooth-supporting structures. Pathogenic bacteria residing in deep periodontal pockets after traditional manual debridement can still lead to local inflammatory microenvironment, which remains a challenging problem and an urgent need for better therapeutic strategies. Here, we integrated the advantages of metal-organic frameworks (MOFs) and hydrogels to prepare an injectable nanocomposite hydrogel by incorporating dexamethasone-loaded zeolitic imidazolate frameworks-8 (DZIF) nanoparticles into the photocrosslinking matrix of methacrylic polyphosphoester (PPEMA) and methacrylic gelatin (GelMA). The injectable hydrogel could be easily injected into deep periodontal pockets, achieving high local concentrations without leading to antibiotic resistance. The nanocomposite hydrogel had high antibacterial activity and constructs with stable microenvironments maintain cell viability, proliferation, spreading, as well as osteogenesis, and down-regulated inflammatory genes expression in vitro. When evaluated on an experimental periodontitis rat model, micro-computed tomography and histological analyses showed that the nanocomposite hydrogel effectively reduced periodontal inflammation and attenuated inflammation-induced bone loss in a rat model of periodontitis. These findings suggest that the nanocomposite hydrogel might be a promising therapeutic candidate for treating periodontal disease.

Keywords: Methacrylic gelatin; Methacrylic polyphosphoester; Nanocomposite hydrogel; Periodontitis; Zeolitic imidazolate frameworks.

Graphical abstract

Scheme 1

(a) Schematic illustration showing the synthesis processes for DZIF nanoparticles. (b) Schematic showing nanocomposite hydrogel preparation by photocrosslinking methacrylic polyphosphoester (PPEMA) (c) and methacrylic gelatin (GelMA) (d). (e) Schematic showing antibacterial and anti-inflammation application via injection into deep periodontal pockets.

Fig. 1

Characterization of nanoparticles. (a) Photographs and schematic diagram of ZIF and DZIF solution; (b) Representative SEM and TEM images of ZIF and DZIF nanoparticles; (c) UV–vis spectra of acid treated ZIF and DZIF solution; (d) Standard curve of DEX at 242 ​nm; (e) DLS image of ZIF and DZIF in water; (f) FTIR spectra of the DEX, ZIF nanoparticles, and DZIF nanoparticles; (g) TGA curves of the DEX, ZIF nanoparticles, and DZIF nanoparticles; (h) XRD analysis of ZIF and DZIF nanoparticles.

Fig. 2

Characterization of nanocomposite hydrogels. (a) Schematic diagram of hydrogel formation; (b) Photographs and representative SEM images of PGel and DZIF@PGel hydrogel; (c) Representative compressive stress–strain curves of with different GEL and PPE ratios; (d) Swelling curves of Gel and PGel hydrogel; (e) FTIR spectra of DZIF, Gel and DZIF@PGel hydrogel; (f) TGA curves of PGel, ZIF@ PGel and DZIF@PGel hydrogel. DEX release profile of DZIF nanoparticles (c) and DZIF@PGel hydrogel (d) in PBS with different pH values.

Fig. 3

In vitro antibacterial activity assessment of nanoparticles and nanocomposite hydrogels. (a) Schematic illustration of hydrogels and their antibacterial properties; (b) Antibacterial activity of ZIF and DZIF nanoparticles against S. mutans; (c) Antibacterial activity of different hydrogels against S. mutans; (d) Statistical analysis of crystal violet staining assay of S. mutans biofilms treated with hydrogels; (e) Representative SEM images of S. mutans biofilms after exposure to different nanocomposite hydrogels for 24 ​h; (f) Statistical analysis of antibacterial activity of different nanocomposite hydrogels against planktonic P. gingivalis bacteria; (g) Representative SEM images of P. gingivalis biofilms after exposure to different nanocomposite hydrogels for 48 ​h; (g) Representative live/dead images of biofilm (S.mutans and P. gingivalis), live bacteria were stained green, and dead bacteria were stained red. (Error bar represents mean ​± ​SD, ∗p ​< ​0.05, ∗∗p ​< ​0.01, ∗∗∗p ​< ​0.001.). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4

Biological assessment in vitro and anti-inflammatory properties of the nanocomposite hydrogels. (a) Viability of Human gingival fibroblasts (HGFs) and rat osteoblasts (OBs) separately cultured with hydrogels doped with different concentrations of ZIF or DZIF nanoparticles by CCK-8 assay; (b, c) Live (green)/dead (Red) staining of HGFs and OBs cultured with hydrogels for 1 ​d and 3 ​d; (d, e) Expression distribution of vimentin and collagen I in HGFs and osterix in OBs was investigated by CLSM on day 2; (f) Schematic illustration of periodontitis pathogenesis including pathogen accumulation, inflammatory factor release, and immune cell recruitment, eventually leading to periodontal tissue destruction; (g) Representative TEM images of periodontal ligament tissues with or without inflammatory status (N, nucleus; c.f, collagen fiber); (h) Schematic illustration of inflammation effect in an osteogenic microenvironment; (i) Statistical analysis of the relative Runx2 expression of BMSCs treated with DZIF hydrogel compared with ZIF hydrogel after LPS stimulation for 24 ​h; (j) Statistical analysis of the relative expression of inflammatory factors, IL-6, (k) TNF-a, and (l) IL-17α, in HGFs after LPS stimulation for 24 ​h (Error bar represents mean ​± ​SD, ∗p ​< ​0.05, ∗∗p ​< ​0.01, ∗∗∗p ​< ​0.001.). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 5

The nanocomposite hydrogels effectively attenuated inflammation-induced bone loss in vivo. (a) Schematic diagram and photographs showing treatment and harvest timepoints in an experimental periodontitis rat model; (b, c) Representative three-dimensional (3D) reconstructions and (d) 2D slices of maxillae in all groups using micro-CT. (e) Sequential fluorescence labeling of bone formation in non-decalcified bone sections (red, Alizarin Red S label; green, calcein label); (f) Statistical analysis of gingival index (GI) evaluated according to the scoring criteria; (g, h) The vertical distance between alveolar bone crest (ABC) and cemento-enamel junction (CEJ) at three predetermined sites each on buccal and palatal surfaces (n ​= ​5 per group, Error bar represents mean ​± ​SD, ∗p ​< ​0.05, ∗∗p ​< ​0.01, ∗∗∗p ​< ​0.001.). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 6

Histological staining of periodontal tissue. (a) Histological H&E-stained sections of maxillae from each group are shown. The vertical line extends from the CEJ to the ABC. (b) Masson's trichrome-stained sections of maxillae from each group are shown. (c) TRAP staining and immunofluorescence staining of MMP9 and TNF-α from each group; (d) Statistical analysis of ABC-CEJ distance as determined by H&E staining in each group. (e) The number of osteoclasts as determined by TRAP staining in each group. (Error bar represents mean ​± ​SD, ∗p ​< ​0.05, ∗∗p ​< ​0.01, ∗∗∗p ​< ​0.001).