Nanocomplex-integrated polymeric film boosts GLP-1 peptide analogue buccal permeation by 3.4% across porcine mucosa.

Injectable peptide therapeutics, while effective, face significant patient adherence challenges, particularly for chronic conditions like type 2 diabetes mellitus and obesity managed with GLP-1 receptor agonists (GLP-1 RAs). Noninvasive routes, such as buccal administration, are highly desirable but are severely limited by peptides' poor epithelial permeability and physicochemical instability. Current buccal delivery methods often rely on permeation enhancers, which can have safety concerns or limited efficacy. This study addresses the critical gap in developing a stable, effective, and non-invasive buccal delivery platform for GLP-1 RAs.

Researchers developed a buccal peptide delivery platform by electrostatically complexing chitosan oligosaccharide (COS) with a model GLP-1 RA peptide molecule. This process generated monodisperse nanocomplexes, which were then optimized using design of experiments (DoE) and stabilized via lyophilization. Cytotoxicity was assessed in TR-146 cells at 1 mg/mL over 180 min. Mechanistic analyses investigated membrane lipid remodeling, endocytic pathways, and tight junction/desmosomal protein redistribution. The nanocomplexes were subsequently incorporated into a bilayer film consisting of a pullulan/sodium carboxymethyl cellulose mucoadhesive layer and an Eudragit RLPO backing layer. GLP-1 RA permeation was measured across porcine buccal mucosae from nanocomplexes in solution and from the integrated bilayer film, compared to GLP-1 RA in solution alone.

The optimized process yielded monodisperse nanocomplexes approximately 100 nm in size with low polydispersity and a positive surface charge of ~+20 mV. Lyophilization successfully preserved nanocomplex integrity and colloidal characteristics for at least one month when stored at 4 °C, also retaining the GLP-1 RA's secondary structure. Minimal cytotoxicity was observed in TR-146 cells at concentrations up to 1 mg/mL over 180 min. Mechanistic studies revealed that nanocomplexes induce membrane lipid remodeling, involve dynamin-dependent endocytosis, and cause redistribution of tight junction and desmosomal proteins, suggesting active modulation of epithelial barrier properties. The most significant finding regarding permeation was:

Nanocomplexes in solution achieved ~13% GLP-1 RA permeation across porcine buccal mucosae at 3 hours (apparent permeability coefficient (Papp) ~3.8 × 10-6 cm/s). When these nanocomplexes were incorporated into the bilayer film, permeation reached ~3.4% (Papp ~1.2 × 10-6 cm/s). Crucially, the GLP-1 RA in solution alone demonstrated an absence of flux across the buccal mucosa.