EVALUATION OF MICROCAPSULE PERMEABILITY VIA INVERSE SIZE-EXCLUSION CHROMATOGRAPHY

In verse aqueous size exclusion chromatography (SEC) was adopted to me asure the permeability of microcapsules (hollow hydrogel spheres with diameter < 1 mm) using dextran molecular weight standards. Alginate/po ly(L-lysine)/alginate microcapsules were chosen as a column substrate. Data from column SEC experiments were verified by kinetic studies of solute size exclusion. The permeability of tested microcapsules was mo dified by the reaction time with 0.05wt.-% poly(L-lysine) (PLL), The e xclusion limit of the microcapsules prepared at 5-min reaction time wa s found to be 100,000, while the microcapsules that were allowed to re act with PLL for 20 min became less permeable and their exclusion limi t was approximately 50,000. Based on relationships between solute size and molecular weight, the exclusion limits determined with dextrans w ere converted to the size and approximate molecular weight of protein presumably excluded by the capsular membrane at ''ideal'' conditions, The results from both column SEC and batch experiments suggest that th e standard algnate/PLL/alginate capsules are permeable to immunoglobul ins of IgG class, Unlike other techniques which utilize only a limited number of solutes, inverse SEC enables one to examine the capsule per meability to a homologous series of molecular weight standards. Invers e SEC also provides an opportunity to evaluate the properties of a lar ge series of capsules directly by comparing their calibration curves. In addition, undesirable enthalpic effects in permeability studies wit h globular proteins as test solutes can be minimized or eliminated by using the inert molecular weight standards such as polysaccharides. (C ) 1996 Academic Press, Inc.