A Thermosensitive Gel Containing Biodegradable Nanoparticles Carrying Calcium Hydroxide as Antibacterial Intracanal Therapy

Aim: To characterise and evaluate mucoadhesive strength and antibacterial properties of a nanotechnological formulation forendodontic disinfection based on biodegradable nanoparticles dispersed in a thermosensitive gel containing calcium hydroxide(Ca(OH) 2 -NPs-gel).Methodology: Morphology of Ca(OH) 2 -NPs-gel was studied using transmission electron microscopy. Moreover, Ca(OH) 2 -NPs-gel was sterilised using gamma irradiation (25 kGy), and the stability after the sterilisation process was studied by measuringCa(OH) 2 -NPs-gel average size, polydispersity index, zeta potential and encapsulation efficiency. To assess the ex vivo mucoad-hesive strength, extracted single-rooted human teeth were used to measure the force necessary to separate the formulationfrom the teeth. In addition, the short-time stability of Ca(OH) 2 -NPs-gel was evaluated monthly, analysing entrapment efficacy,backscattering and transmittance of Ca(OH) 2 -NPs-gel stored at different temperatures (4°C, 25°C and 37°C). Furthermore, theantibacterial analysis of Ca(OH) 2 -NPs-gel was performed against Enterococcus faecalis inoculated in extracted human single-root teeth and evaluated by confocal and scanning electron microscopy. Finally, the metabolic activity of bacteria was studiedthrough a resazurin assay to evaluate bacterial survival after treatment.Results: Ca(OH) 2 -NPs-gel owned a round shape and a smooth surface without particle aggregation. Sterilisation did not inducean alteration in Ca(OH) 2 -NPs-gel physicochemical properties and Ca(OH) 2 -NPs-gel presented a high adhesion strength. In addi-tion, 4°C was the best temperature to store Ca(OH) 2 -NPs-gel. Regarding the antibacterial therapeutic efficacy, Ca(OH) 2 -NPs-gelpossesses suitable antibacterial properties, indicating that it efficiently reduces bacterial biofilms.Conclusion: Calcium hydroxide-loaded PLGA nanoparticles dispersed in a thermosensitive gel have been developed, optimisedand characterised, obtaining excellent antibacterial properties and achieving bacterial disinfection levels similar to those ofcommercial formulations.