At present, the main form of insulin administration is the invasive subcutaneous (s.c.) route and, for many patients, this means managing their glucose levels with multiple daily injections, which is both painful and difficult to administer chronically. To increase patient compliance, products are slowly reaching the market that are more patient friendly, such as the insulin patch-pump systems, including Omnipod and V-Go, but also the inhaled-insulin Afrezza® and the buccal insulin Oral-lyn™. In this review, we outline the history of insulin, the various options that are currently available in practice for insulin delivery, and the non-invasive delivery systems that have entered the different stages of clinical trials over the past decade.

The aim of this work was to formulate chitosan (CS)-based nanoparticles (NPs) loaded with ketorolac tromethamine (KT) intended for topical ocular delivery. NPs were prepared using ionic gelation method incorporating tri-polyphosphate (TPP) as cross-linker. Following the preparation, the composition of the system was optimized in terms of their particle size, zeta potential, entrapment efficiency (EE) and morphology, as well as performing structural characterization studies using Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The data suggested that the size of the NPs was affected by CS/TPP ratio where the diameter of the NPs ranged from 108.0 ± 2.4 nm to 257.2 ± 18.6 nm. A correlation between drug EE and the corresponding drug concentration added to the formulation was observed, where the EE of the NPs increased with increasing drug concentration, for up to 10 mg/mL. FT-IR and DSC revealed that KT was dispersed within the NPs where the phosphate groups of TPP were associated with the ammonium groups of CS. The in vitro release profile of KT from CS NPs showed significant differences (p < 0.05) compared to KT solution. Furthermore, mucoadhesion studies revealed adhesive properties of the formulated NPs. The KT-loaded NPs were found to be stable when stored at different storage conditions for a period of 3 months. The ex vivo corneal permeation studies performed on excised porcine eye balls confirmed the ability of NPs in retaining the drug on the eye surface for a relatively longer time. These results demonstrate the potential of CS-based NPs for the ocular delivery of KT.

Chitosan exhibits unique properties making it a suitable material for drug delivery. Considering the rising popularity of hydrogels in this field, this work offers a comprehensive study of hydrogels constituted by chitosan and cross-linked with 1,3,5-benzene tricarboxylic acid (BTC; also known as trimesic acid). Hydrogels were prepared by cross-linking chitosan with BTC in different concentrations. The nature of the gels was studied through oscillatory amplitude strain and frequency sweep tests within the linear viscoelastic region (LVE) limit. The flow curves of the gels revealed shear thinning behavior. High G′ values imply strong cross-linking with improved stability. The rheological tests revealed that the strength of the hydrogel network increased with the cross-linking degree. Hardness, cohesiveness, adhesiveness, compressibility, and elasticity of the gels were determined using a texture analyzer. The scanning electron microscopy (SEM) data of the cross-linked hydrogels showed distinctive pores with a pore size increasing according to increasing concentrations (pore size range between 3–18 µm). Computational analysis was performed by docking simulations between chitosan and BTC. Drug release studies employing 5-fluorouracil (5-FU) yielded a more sustained release profile with 35 to 50% release among the formulations studied in a 3 h period. Overall, this work demonstrated that the presence of BTC as cross-linker leads to satisfactory mechanical properties of the chitosan hydrogel, suggesting potential applications in the sustained release of cancer therapeutics.

Insulin delivery via the buccal route has shown long-standing promise for diabetes therapy, but clinical translation remains limited. Most systems address only part of the delivery problem, whereas a viable product must simultaneously provide adequate insulin residence time, effective mucus and epithelial permeation, stability, dose consistency, safety, and manufacturability. This review examines the biological and formulation barriers that limit buccal insulin delivery and compares the major platform types, including mucoadhesive films and patches, nanocarrier-based systems, deformable vesicles, chemistry-led permeation approaches, and device-enabled strategies. Stability, alongside limited permeability, is considered a key barrier, while aggregation and excipient-related instability remain insufficiently addressed. The review also discusses why promising preclinical findings often fail to translate, exhibiting low bioavailability, variability, safety concerns, and scale-up challenges recurring across platforms. Overall, further progress in buccal insulin delivery will depend on formulation strategies that better integrate permeation enhancement, stability preservation, and translational feasibility.

Insulin delivery via the buccal route has shown long-standing promise for diabetes therapy, but clinical translation remains limited. Most systems address only part of the delivery problem, whereas a viable product must simultaneously provide adequate insulin residence time, effective mucus and epithelial permeation, stability, dose consistency, safety, and manufacturability. This review examines the biological and formulation barriers limiting buccal insulin delivery and compares major platform types, including mucoadhesive films and patches, nanocarrier-based systems, deformable vesicles, chemistry-led permeation approaches, and device-enabled strategies. Stability, alongside limited permeability, is considered a key barrier, while aggregation and excipient-related instability remain insufficiently addressed. This review also discusses why promising preclinical findings often fail to translate, exhibiting low bioavailability, variability, safety concerns, and scale-up challenges recurring across platforms. Overall, further progress in buccal insulin delivery will depend on formulation strategies that better integrate permeation enhancement, stability preservation, and translational feasibility.