Development of a hydroxypropyl methyl cellulose/polyacrylic acid interpolymer complex formulated buccal mucosa adhesive film to facilitate the delivery of insulin for diabetes treatment.

Buccal mucosa administration is a promising method for insulin (INS) delivery with good compliance. However, buccal mucosa delivery systems still face challenges of long-term mucosal adhesion, sustained drug release, and mucosal drug penetration. To address these issues, a double-layer film consisting of a hydroxypropyl methylcellulose/polyacrylic acid interpolymer complex (IPC)-formulated mucoadhesive layer and an ethylcellulose (EC)-formulated waterproof backing layer (IPC/EC film) was designed. Protamine (PTM) and INS were co-loaded in the mucoadhesive layer of the IPC/EC film (PTM-INS-IPC/EC film). In ex vivo studies with porcine buccal mucosa, this film exhibited robust adhesion, with an adhesion force of 120.2 ± 20.3 N/m and an adhesion duration of 491 ± 45 min. PTM has been shown to facilitate INS mucosal transfer. Pharmacokinetic studies indicated that the PTM-INS-IPC/EC film significantly improved the absorption of INS, exhibiting a 1.45 and 2.24-fold increase in the area under the concentration-time curve (AUC) compared to the INS-IPC/EC film and free INS, respectively. Moreover, the PTM-INS-IPC/EC film effectively stabilized the blood glucose levels of type 1 diabetes mellitus (TDM) rats with post oral glucose administration, maintaining lower glucose levels for approximately 8 h. Hence, the PTM-INS-IPC/EC film provides a promising noninvasive INS delivery system for diabetes treatment.