Nanocomposite sublingual films: a scoping review of formulation trends and translational gaps

Sublingual films are promising drug delivery platforms due to their rapid hydration and drug release, and the incorporation of nanoparticles can further improve drug solubility, bioavailability, and therapeutic efficacy. Therefore, this study aims to identify, map, and synthesize the available evidence on nanocomposite films for sublingual drug delivery. This scoping review was conducted in accordance with the Joanna Briggs Institute (JBI) framework and reported following the PRISMA extension for Scoping Reviews (PRISMA-ScR). A total of 226 articles were initially identified, of which 31 met the inclusion criteria (2014-2025). Among them, microemulsions, and cyclodextrin complexes were the most frequently investigated systems (6/31), followed by nanofibers (5/31), polymeric nanoparticles (4/31), niosomes (3/31), and nanocrystals (3/31). Overall, these technologies were primarily selected to enhance drug solubility, dissolution, and mucosal transport. Other nanostructures, including nanocapsules, liposomes, micelles, and transferosomes, were each reported (1/31). Regarding film-forming matrices, synthetic and semisynthetic polymers were predominantly used (26/31), particularly HPMC, PVA, and PVP, whereas natural polymers were underexplored (5/31), highlighting a reliance on conventional pharmaceutical excipients. However, few studies provided robust pharmacological evidence (2/31) or comprehensive toxicity assessments (5/31), revealing important gaps. Moreover, 13 studies performed permeation evaluations, indicating that a substantial proportion of the evidence remains limited to physicochemical characterization without functional assessment of drug transport across the mucosa. Similarly, bioavailability was investigated in fewer than one-third of the studies (9/31), although the available evidence generally demonstrated improved bioavailability compared with conventional formulations. Furthermore, significant methodological heterogeneity in disintegration protocols and mucosal models hinders the comparability of clinical outcomes. Overall, this scoping review highlights nano-based sublingual films as promising strategies to improve drug bioavailability, while emphasizing the need for more standardized methodologies and rigorous pharmacological and safety evaluations to facilitate their translational advancement toward clinical application.