Innovations - SEC

Sporopollenin exine capsules (SECs)

Next Generation Possibilities

What are Sporopollenin exine capsules (SECs)?

SECs (sometimes termed sporoderm microcapsules, SDMCs) are hollowed microparticles derived from the outer shell of pollen grains, and are composed primarily of sporopollenin, a highly durable biopolymer. These capsules retain the intricate, species-specific morphology of pollen and exhibit exceptional chemical, thermal, and mechanical stability. Being hollow, many SEC applications involves them to be loaded with drugs, proteins, or other active agents for applications in drug delivery, bioengineering, and environmental remediation. Their biocompatibility and resistance to harsh conditions make them ideal candidates for microencapsulation and targeted delivery systems. Due to their unique surface structures, SECs can also be functionalized or coated with various materials to enhance their properties for specific applications.

How are SECs made?

SECs can be obtained by subjecting pollen to an extraction process to remove the lipid and protein rich pollenkitt material, polysaccharide-rich intine layer and the cytoplasmic sporoplast content, which contains genetic materials.

The extraction processes are generally classified into two distinct processes; Chemical extraction, whereby the pollen particles are agitated in hot solutions of concentrated acids such as sulfuric and phosphoric acids, or concentrated alkalis such as potassium hydroxide for extended periods of time, and enzymatic extraction, whereby defatted pollen is sequentially treated with enzymes. By leveraging sporopollenin’s robustness and resilience, these extraction process results in a hollow sporopollenin shell that still retains the pollen unique and intricate architectures, while being devoid of other susceptible polymers and allergens such as proteins.

R.C. Mundargi, M.G. Potroz, J.H. Park, J. Seo, J.H. Lee, N.-J. Cho, Extraction of sporopollenin exine capsules from sunflower pollen grains, RSC advances, 6 (2016) 16533-16539.
J.M. Ageitos, S. Robla, L. Valverde-Fraga, M. Garcia-Fuentes, N. Csaba, Purification of hollow sporopollenin microcapsules from sunflower and chamomile pollen grains, Polymers, 13 (2021) 2094.
S.M. Alshehri, H.A. Al-Lohedan, A.A. Chaudhary, E. Al-Farraj, N. Alhokbany, Z. Issa, S. Alhousine, T. Ahamad, Delivery of ibuprofen by natural macroporous sporopollenin exine capsules extracted from Phoenix dactylifera L, European Journal of Pharmaceutical Sciences, 88 (2016) 158-165.
C. Jungfermann, F. Ahlers, M. Grote, S. Gubatz, S. Steuernagel, I. Thom, G. Wetzels, R. Wiermann, Solution of sporopollenin and reaggregation of a sporopollenin-like material: a new approach in the sporopollenin research, Journal of plant physiology, 151 (1997) 513-519.
M.G. Potroz, R.C. Mundargi, J.J. Gillissen, E.L. Tan, S. Meker, J.H. Park, H. Jung, S. Park, D. Cho, S.I. Bang, Plant‐based hollow microcapsules for oral delivery applications: toward optimized loading and controlled release, Advanced Functional Materials, 27 (2017) 1700270.

Can SECs be made from any pollen?

A diverse range of pollen and spore species have shown its propensity to be successfully extracted to result in hollow SECs.

These source materials include sunflower, ragweed, chamomile, pine, maize, dandelion, lycopodium, date palm and hazelnut, and this list is growing. By leveraging the unique physical architecture of the respective pollen sources, various loading quantities, sequences and release profiles can be achieved to tailor to the varied applications downstream.

"Chemical Processing Strategies to Obtain Sporopollenin Exine Capsules from Multi-Compartmental Pine Pollen.“Journal of Industrial and Engineering Chemistry 2017; 53, 375-85.
Inflated Sporopollenin Exine Capsules Obtained from Thin-Walled Pollen."Scientific Reports 2016; 6, 28017. "
Extraction of Cage-Like Sporopollenin Exine Capsules from Dandelion Pollen Grains.“ Scientific Reports 2018; 8, 6565.
Extraction of Sporopollenin Exine Capsules from Sunflower Pollen Grains." RSC Advances 2016; 6(20), 16533-16539.

What are applications of SECs?

Due to their unique properties, including high chemical stability, biodegradability, and tunable surface functionality, SECs have demonstrated a wide range of applications, most notably those that leverage on its hollow microcapsule properties.

Some key applications include microencapsulation where SECs serve as protective shells for sensitive compounds, such as enzymes, vitamins, probiotics, and fragrances, shielding them from environmental degradation and enabling their sustained release. SECs have also been shown to be loaded with drugs, allowing for controlled and targeted drug release in pharmaceutical applications. Their biocompatibility makes them suitable carriers for oral, transdermal, and injectable drug formulations. SECs can also been applied in biosensing and diagnostics where their highly structured porous architecture enables the immobilization of biomolecules, allowing detection of toxins, pollutants, and biomarkers, or with magnetic, fluorescent, or conductive materials, creating smart materials for applications in catalysis, soft robotics, energy storage, and electronic devices. SECs can act as natural adsorbents for heavy metals, dyes, and pollutants and has seen applications in purification due to their ability to sequester contaminants.

Ref: Eco-friendly streamlined process for sporopollenin exine capsule extraction

"Natural Sunflower Pollen as a Drug Delivery Vehicle." Small 2016; 12(9), 1167-1173.
Encapsulation and Controlled Release Formulations of 5-Fluorouracil from Natural Lycopodium Clavatum Spores." Journal of Industrial and Engineering Chemistry 2016; 36, 102-108.
"Preparation of Highly Monodisperse Electroactive Pollen Biocomposites." Chemistry of Nanomaterials for Energy, Biology and More 2016; 2(5), 414-418.
Plant-Based Hollow Microcapsules for Oral Delivery Applications: Towards Optimized Loading and Controlled Release." Advanced Functional Materials 2017; 27(31), 1700270.
"Microrobots Derived from Variety Plant Pollen Grains for Efficient Environmental Clean Up and as an Anti-Cancer Drug Carrier." Advanced Functional Materials 2020; 2000112.