Quality-by-design approach for development and optimization of bupivacaine-loaded nanostructured lipid carrier in situ gel: In vitro, Ex vivo, and In vivo studies for enhanced periodontal anesthesia

Periodontal anesthesia is essential for effective pain management during dental treatments, but achieving prolonged and efficient anesthesia remains a challenge. This study aimed to develop, and optimize bupivacaine (BUP)-loaded nanostructured lipid carriers (NLCs) for periodontal anesthesia using a design of experiment approach, representing a novel strategy for sustained drug delivery in dental applications. BUP-loaded NLCs were prepared using the emulsion evaporation-solidification at low-temperature method, with formulation optimization conducted via a central composite design involving two factors (glyceryl monostearate and clove oil concentrations) and three levels. The impact of these factors on particle size, drug release, and % entrapment efficiency was systematically evaluated. The optimized formulation exhibited a particle size of 195 nm, drug release of 89.2%, and entrapment efficiency of 90.12%. Characterization studies using TEM, FTIR, DSC, and XRD confirmed the structural and chemical stability of the formulation. In vitro release studies demonstrated a sustained release profile, while ex vivo permeation studies indicated high drug permeation across buccal mucosa. The anesthetic efficacy was validated through tail flick tests, revealing an effect lasting up to 9 hours. Furthermore, BUP-NLC-loaded in situ gel showed significant potential for providing prolonged and effective surface anesthesia in periodontal pockets, offering a promising alternative for enhancing dental pain management.