Comparison of the micro- and macrostructural characteristics of biopolymer cast films

In addition to the chemical composition the molecular architecture has a decisive impact on the formulation of polymeric drug delivery systems. An ideal buccal polymeric film or patch dosage form should be flexible, elastic, soft, yet adequately strong. The microstructural characteristics through the molecular ordering determine the mechanical properties of free films. In the present study sodium alginate–Carbopol cast films containing vitamin B12 were formulated. The sodium alginate (SA) concentration was changed from 3 to 6 wt% and the proportion of Carbopol (CP) was varied in the formulations. Texture analysis was carried out for the macrostructural characterization of films based on their mechanical properties and positron annihilation lifetime spectroscopy (PALS) was applied to track the microstructural changes based on the ortho-positronium (o-Ps) lifetime values as a function of their composition. The results indicated that the combination of the evaluation of o-Ps lifetime discrete values with the characteristics of lifetime distribution curves enabled the selection of homogeneous films of required mechanical properties.