Development of natural sporopollenin microcapsules: from bee pollen to versatile biomaterials

Abstract The outer layer of the pollen grain, which plays a crucial role in the continuity of terrestrial plant life, has received significant attention due to its robustness, chemical inertness, and biocompatible structure made of sporopollenin. Herein, we present a straightforward method for producing high-purity (up to 97%) polymeric sporopollenin biocapsules (S-BioCaps) from bee pollen, exploring new plant sources for S-BioCaps, and diversifying the available morphologies to broaden the applications of pollen-based microcapsules. Following a purification process involving defatting, acidolysis, and several washing steps, we removed the inner components of the pollen grains and reduced the protein content to 2%. Confocal laser scanning and scanning electron microscopy images showed that the hollow and 3D S-BioCaps microstructure were preserved, while laser diffraction particle size analysis validated their monodisperse distribution across each pollen type within the size range of 15 to 24 μm. S-BioCaps tended to exhibit hydrophobic behavior when assessed through water dispersion and water marble analysis. Moreover, we sought to figure out the chemical changes occurring in specimens through Fourier-transform infrared analysis, and findings were consistent with simultaneous thermal analysis, where the thermal decomposition of sporopollenin biopolymer reached up to 457 °C. Overall, this work demonstrates a straightforward approach for utilizing pollen grains from Echium sp., Jasione sp., Papaver sp., Amaranthaceae, and Helianthemum sp., collected with the assistance of honeybees, to produce stable S-BioCaps with diverse morphologies, thereby broadening their potential applications as drug delivery microcarriers. Graphical abstract