Modulation of Phase Inversion Dynamics and Buccal Permeation in Borneol-Based In Situ Forming Matrices by Triacetin

The modulation of phase inversion dynamics and molecular transport is critical for optimizing in situ forming matrix (ISM) systems. This study elucidates the distinct roles of borneol and triacetin in tailoring the physicochemical properties of a borneol-based ISM for buccal delivery. Using real-time interfacial microscopy and confocal laser scanning microscopy (CLSM), the solvent exchange mechanisms and matrix evolution were characterized. Results demonstrated that triacetin concentration is a critical determinant of matrix density structure. Conversely, borneol functioned as a dual-action agent, accelerating phase inversion while simultaneously enhancing mucosal permeability. Comparative diffusion studies using hydrophilic sodium fluorescein (SF) and lipophilic Nile red (NR) revealed that molecular release was governed by viscosity- and polarity-dependent diffusion controls. Kinetics analysis indicated non-Fickian release for SF, whereas NR diffusion was partition-limited due to hydrophobic affinity. Ultimately, the interplay between the permeation-enhancing effects of borneol and the release-retarding capacity of triacetin offers a tunable platform for designing precise, controlled-release intraoral delivery systems.