Transmucosal delivery of insulin for diabetes therapy : development and evaluation of a mucoadhesive buccal patch comprising insulin loaded transfersomes

Background and Aim: The International Diabetes Federation suggests in 2017, around 451 million adults around the globe were affected by diabetes mellitus. Worldwide, invasive subcutaneous injection devices remain the standard for diabetes treatment. To increase patient adherence, and to help reduce the anxiety of painful daily administration of insulin this study investigated the prospect of using ultradeformable vesicles, known as transfersomes, to act as carriers and permeation enhancers for the delivery of insulin. The overall aim was the development of a double-layered patch, in which the transfersomes were embedded in the mucoadhesive layer, and the presence of an outer impermeable layer enabled the formation of a novel unidirectional immobilized delivery system for buccal delivery of insulin. Methods: A reverse phase HPLC method was developed and validated, according to ICH guidelines, for the detection and quantification of insulin. Vesicles were formed using a thin-film hydration technique with bath sonication, and manual extrusion was used for further downsizing. Throughout the project, vesicles were evaluated for particle size, polydispersity index, zeta potential and insulin encapsulation efficiency (EE, %). Permeability of insulin was studied across TR146 buccal cell line, and sulforhodamine B (SRB) assay was used for in-vitro cytotoxicity screening. Minitab factorial design was employed to optimise mucoadhesiveness of lyophilised patches. Results and Discussion: Analysis and quantification of insulin with HPLC demonstrated insulin to degrade much faster in acidic conditions. Preliminary studies led to the selection of Span 60, which was combined with the phospholipid DPPE (1,2-dipalmitoyl-3-sn-phosphatidylethanolamine) to produce transfersomes. Membrane ii | P a g e fluidity was enhanced by the addition of Tween 80 and reduction of cholesterol content. Based on toxicity studies, the two promising formulations consisted of Span 60 (40%), DPPE (20%), Tween 80 (20%), cholesterol (15%), with either 5% dicetyl phosphate (D5E) or 5% sodium glycodeoxycholate (S5E). Insulin release from patch S [sodium alginate (2% w/v), HPMC (0.5% w/v), Sorbitol (5% w/v) and PEG 400 (0.25% w/v)] was found to occur as burst release with 75% of the total insulin being released in the first 30 minutes. The most promising percentage drug release (66.5%), in 6 hours, was with patch S containing the transfersomal formulation D5E. Conclusion: This thesis demonstrated an excellent approach in delivering insulin via a non-invasive route by combining novel transfersomes as permeation enhancers within an optimised mucoadhesive buccal patch. Furthermore, the project led to the generation of new data and observations concerning the influence of extrusion and vortexing on vesicle size, use of CytoSMART for cell imaging, use of actinomycin D as positive control in SRB cytotoxicity assays with TR146 cells and influence of the cryoprotectant sorbitol on mucoadhesion combined with HPMC, sodium alginate and chitosan in freeze-dried patches