Development and physico-mechanical characterisation of lyophilised chitosan wafers as potential protein drug delivery systems via the buccal mucosa

Lyophilised wafers from chitosan have been developed as potential protein drug delivery systems via the buccal mucosa. Wafers were prepared by lyophilising aqueous gels of the polymer incorporating varying concentrations of glycerol as plasticizer and d-mannitol as cryoprotectant. The different formulations were characterised by their physico-mechanical properties in order to select the optimum system for further development. The optimised formulation with 6.5 mg each of both plasticizer and cryoprotectant was loaded with bovine serum albumin and lyophilised with or without annealing. Differential scanning calorimetry was used to determine the appropriate lyophilisation cycle by evaluating thermal events before lyophilisation and possible phase separation of bovine serum albumin after lyophilisation. Texture analysis was employed to investigate the in vitro mucoadhesive properties in tensile mode, residual moisture content by thermo-gravimetric analysis while hydration capacity and drug release studies were performed in 0.1 M phosphate buffered saline. Microscopic architecture and crystallinity were examined using scanning electron microscopy and X-ray diffractometry respectively. The ease of hydration, in vitro mucoadhesive characteristics, microscopic architecture and BSA release were influenced by the annealing process. A 7 h cumulative percentage drug release of 91.5% and 80.1% was observed for the annealed and non-annealed wafers respectively. The results showed the potential of employing lyophilised chitosan wafers for buccal mucosa delivery of protein based drugs.

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► Stable chitosan based lyophilised wafers containing protein drug, glycerol and mannitol.
► Process of annealing an essential step during freeze-drying to achieve desirable characteristics.
► Annealing affects functional properties including hydration capacity, microscopic architecture, in vitro mucoadhesion and drug dissolution.
► Sustained release of bovine serum albumin from annealed chitosan wafers achieved with cumulative percent release above 90%.