Influence of Heat Treatment on Loading of Polymeric Multilayer Microcapsules with Rhodamine B.

Layer-by-layer assembled polymeric multilayer capsules (PMC) of micrometer sizes are permeable for molecules below 1 KDa; therefore, the efficacy of such capsules in the delivery of low molecular weight water soluble bioactive compounds and drugs is frequently challenged. Thermally induced contraction of hollow PMC is explored here to enhance their loading efficacy with model compound, fluorescent rhodamine B (RhB). Four bilayered capsules obtained of poly(diallyldimethylammonium chloride)/polystyrene sulfonate ([PDADMAC/PSS]4 ) or poly-l-arginine/dextran sulfate ([PARG/DS]4 ) on sacrificial CaCO3 spherical microparticles are postloaded with RhB at ambient or elevated temperatures. The influence of heat on capsule loading is determined quantitatively by varying the amounts of capsules in the batch and keeping the concentration of RhB constant. The applied heat improves the loading efficacy of [PDADMAC/PSS]4 capsules at concentrations up to 2.25 × 109 capsules mL-1 , but has a reversed effect on [PARG/DS]4 capsules at all studied concentrations ((0-3.5) × 109 capsules mL-1 ).