Sporopollenin Microcapsules for Dye Encapsulation

In order to obtain sporopollenin microcapsules devoid from the sporoplasm core we used the extraction protocol as described in previous work²⁷ and showed in ESI.† A 0.05 g tablet was first prepared from the sporopollenin powder (by using a tablet press with pressure of 10 tons). 10 mL of the Carbopol Aqua SF-1 nanogel was prepared by loading it with 1 mM rhodamine 6G dye followed by addition of 20 vol% ethanol. The sporopollenin tablet was then added to the nanogel suspension while stirring. Submitting the sporopollenin to high pressure allows squashing of its elastic capsules so that their trilite scars open to encapsulate the concentrated rhodamine 6G-loaded nanogel suspension. Ethanol improves the wetting of the sporopollenin interior to facilitate this loading process. The sample was then stirred for about 2 hours, dessicated and filtered by vacuum filtration set, and the solid was washed with 1 L of DI water. Washing the solid is an important step as it allows removal of the dye residue that has remained at the outer surface of the sporopollenin. A small amount of the washed sporopollenin was put into a Petri dish and suspended in DI water. The sample was observed under a fluorescence microscope BX-51 (Olympus, Japan) and CLSM to trace the location of the fluorescent dye and its release from the sporopollenin.