The Construction Of In Situ Injectable Chitosan-based Thermosensitive Hydrogel As A Sustained Delivery System And Its Application In The Fields Of Periodontal Therapy

Periodontal disease is a world-wide prevalent chronic infection which is caused by acummulation of bacterial in dental plaque. Biodegradable and injectable thermosensitive hydrogel was called one of the most convenient, reliable methods to prevent periodontal disease.Chitosan (CS), a nature well-known parvus polysaccharide, got much application in pharmaceutical and medical fields as a promising biomaterial due to many unique advantages. Quaternized chitosan - N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (HTCC) introduced quaternary amino groups into CS chain to render it soluble in water.An in situ injectable thermosensitive hydrogel constitutes of CS, HTCC withα,β-glycerophosphate (α,β-GP) was synthesized. The gelling point can be set at a temperature above 25°C. The transition process can be controlled by adjusting the weight ratio of CS to HTCC, or different final concentration ofα,β-GP and it effectively retarded the release of ornidazole (Onz) and chlorhexidine (Chx). The antibacterial activity to Porphyromonas gingivalis,Prevotella intermedia and Actinobacillus actinomycetemcomitans was determined through minimum inhibitory concentrations (MIC) and inhibitory zone measurement which are recommended by CLSI/NCCLS. Three periodontal pathogens strains were susceptible to CS and HTCC and a combination of CS and HTCC at weight ratio of 5 to 1 was the most potent inhibitor mixture. In addition, CS-HTCC/α,β-GP thermosensitive hydrogel exhibited stronger antibacterial activity with the larger inhibitory zone than CS/GP thermosensitive hydrogel.The MTT assay revealed that CS at 0.2 g/mL to 2000 g/mL exhibit excellent cytocompatibility to human periodontal liganment cells(HPDLCs), While HTCC showed strong cytotoxicity to HPDLCs at the concentration of 2000, 1000, 100 and 50 g/mL. Transmission electron microscope (TEM) scan indicated that the architecture of HPDLCs at a concentration of 1000 g/mL was seriously destroyed. CS/HTCC-GP thermosensitive hydrogel was found to increase the proliferation of HPDLCs and promote the ALP activity in vitro.Flow cytometry (FCM) revealed that CS/HTCC-GP thermosensitive hydrogel can increase the proliferation activity of HPDLCs. Whereas, HTCC at 3 mg/mL we observed apoptosis, and there was not observed in CS at the same concentration. HTCC can increase the secret of the volume of IL-1βand TNF-αcompared with CS. And basic fibroblast growth factor (bFGF) can inhibit the secret of IL-1βand TNF-α. The extract of CS/HTCC-GP thermosensitive hydrogel can decrease the secret of IL-1βand TNF-α. The CS/HTCC-GP solution was injected intramuscularly into the rumps of rats and resulted in non-specific inflammation reaction. CS/HTCC-GP thermosensitive hydrogel loading with or without bFGF is promising to enhance new bone regeneration, periodontal ligament formation and new cement of dogs. All results indicated that CS/HTCC-GP thermosensitive hydrogel exhibit excellent biocompatibility and biological function and has potential to utilize as an injectable local drug delivery vehicle and as a tissue-engineering scaffold for periodontal disease therapy.