Sporopollenin-Based Drug Delivery Systems

Sporopollenin is a highly cross-linked biopolymer forming the exine layer of pollen and spores. Its extraordinary chemical stability, uniform micro-sized architecture and inherent biocompatibility have inspired the development of sporopollenin exine capsules (SECs) as versatile drug delivery vehicles. Extraction protocols typically employ sequential acidolysis and organic solvent washes to remove cytoplasmic contents while preserving the intricate pore network of the exine shell. The resulting hollow microcapsules can be loaded with a wide range of therapeutic agents—small molecules, proteins and nucleic acids—via passive diffusion, vacuum-assisted infusion or solvent exchange. Surface phenolic and carboxyl functionalities enable further chemical modification for targeted or stimuli-responsive drug release. Within the gastrointestinal tract, SECs demonstrate mucoadhesive interactions that prolong residence time and permit site-specific release under pH or enzymatic triggers. Beyond oral delivery, tailored preparation of thin-walled or cage-like SECs extends aerosolisation and parenteral application. Emerging approaches exploit the mechanical resilience of sporopollenin to generate soft microgels with environmentally responsive swelling, broadening applications in controlled release, vaccinology and nutraceutical delivery.

Research from Nature Portfolio

A facile remodelling of pollen shells has been shown to yield soft, stimuli-responsive microgels. By selectively altering substructures within the sporopollenin shell, researchers achieved reversible swelling in response to temperature and ionic strength, shedding light on structure–property relationships and opening avenues for environmentally triggered drug release. In parallel, novel extraction techniques have enabled the production of inflated SECs from thin-walled pollen species, overcoming previous limitations to mechanical stability and preserving nanoscale architecture for enhanced payload capacity and dispersibility. Finally, investigations into architecturally intricate dandelion-derived SECs demonstrated that mild phosphoric acid reflux can remove proteins without compromising cage-like morphology, achieving high loading efficiencies of model proteins. These advances collectively underscore the adaptability of sporopollenin microcapsules and provide foundational platforms for next-generation delivery systems.

Sporopollenin-Based Drug Delivery Systems publication trend

The graph below shows the total number of articles in sporopollenin-based drug delivery systems across all publications each year (not limited to Nature Index journals).

Technical terms

Sporopollenin exine capsule (SEC): A hollow microcapsule obtained by extracting and purifying the sporopollenin outer shell of pollen or spores.

Acidolysis: A chemical process using acid treatment to remove internal biomolecules from pollen or spore shells while preserving shell integrity.

Mucoadhesion: The property of a material to adhere to mucosal tissues, prolonging residence time and facilitating targeted drug release.

Pickering emulsion: A colloidal emulsion stabilised by solid particles adsorbed at the interface between immiscible phases.

References

1. Sporopollenin, The Least Known Yet Toughest Natural Biopolymer. Frontiers in Materials (2015).
2. Eco-friendly streamlined process for sporopollenin exine capsule extraction. Scientific Reports (2016).
3. Hollow Pollen Shells to Enhance Drug Delivery. Pharmaceutics (2014).
4. Protein free microcapsules obtained from plant spores as a model for drug delivery: ibuprofen encapsulation, release and taste masking. Journal of Materials Chemistry B (2013).
5. Transformation of hard pollen into soft matter. Nature Communications (2020).
6. Inflated Sporopollenin Exine Capsules Obtained from Thin-Walled Pollen. Scientific Reports (2016).
7. Extraction of cage-like sporopollenin exine capsules from dandelion pollen grains. Scientific Reports (2018).
8. All-aqueous emulsions stabilized by sporopollenin exine capsules. Food Hydrocolloids (2024).