No abstract

In nature, pollen grains play a vital role for encapsulation. Many pollen species exist which are often used as human food supplements. Dynamic image particle analysis, scanning electron microscopy, and confocal microscopy analysis confirmed the size, structural uniformity, and macromolecular encapsulation in sunflower pollen, paving the way to explore natural pollen grains for the encapsulation of therapeutic molecules.

The development of a micromotor with unique spiky morphology based on sporopollenin exine capsules (SECs) is reported here. A widely abundant natural material extracted from sunflower pollen grains, the SECs are physically robust, highly monodisperse microcapsules that are ornamented with spiky appendages, opening the door to exploring bubble generation on this unique biomaterial surface. Partial platinum coating on the SEC surface enables catalytic decomposition of hydrogen peroxide that leads to bubblepropelled motion of individual SECs. Moreover, the hollow capsule architecture provides a large internal cavity for macromolecular encapsulation, as demonstrated here by the loading and transport of bovine serum albumin. Taking advantage of the sporopollenin biopolymer's capacity for heavy metal binding, it is further demonstrated that fluid mixing induced by the motion and bubble generation of the SEC micromotors dramatically improves heavy metal binding and removal. The bioinspired micromotors combine the advantageous properties of SECs with autonomous motion ability, resulting in a multifunctional platform for drug delivery and water purification applications.

A simple extraction process was developed to isolate sunflower sporopollenin exine capsules (SECs). The sunflower SECs holds significant potential as biomaterial for applications in drug delivery, cosmetics, and food technology.

Efficient oral administration of protein-based therapeutics faces significant challenges due to degradation from the highly acidic conditions present in the stomach and proteases present in the digestive tract. Herein, investigations into spike-covered sunflower sporopollenin exine capsules (SECs) for oral protein delivery using bovine serum albumin (BSA) as a model drug are reported and provide significant insights into the optimization of SEC extraction, SEC loading, and controlled release. The phosphoric-acid-based SEC extraction process is optimized. Compound loading is shown to be driven by the evacuation of air bubbles from SEC cavities through the porous SEC shell wall, and vacuum loading is shown to be the optimal loading method. Three initial BSA-loading proportions are evaluated, leading to a practical loading efficiency of 22.3 ± 1.5 wt% and the determination that the theoretical maximum loading is 46.4 ± 2.5 wt%. Finally, an oral delivery formulation for targeted intestinal delivery is developed by tableting BSA-loaded SECs and enteric coating. BSA release is inhibited for 2 h in simulated gastric conditions followed by 100% release within 8 h in simulated intestinal conditions. Collectively, these results indicate that sunflower SECs provide a versatile platform for the oral delivery of therapeutics.

Sporopollenin exine capsules (SECs) extracted from Lycopodium clavatum spores are an attractive biomaterial possessing a highly robust structure suitable for microencapsulation strategies. Despite several decades of research into SEC extraction methods, the protocols commonly used for L. clavatum still entail processing with both alkaline and acidolysis steps at temperatures up to 180 °C and lasting up to 7 days. Herein, we demonstrate a significantly streamlined processing regimen, which indicates that much lower temperatures and processing durations can be used without alkaline lysis. By employing CHN elemental analysis, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and dynamic image particle analysis (DIPA), the optimum conditions for L. clavatum SEC processing were determined to include 30 hours acidolysis at 70 °C without alkaline lysis. Extending these findings to proof-of-concept encapsulation studies, we further demonstrate that our SECs are able to achieve a loading of 0.170 ± 0.01 g BSA per 1 g SECs by vacuum-assisted loading. Taken together, our streamlined processing method and corresponding characterization of SECs provides important insights for the development of applications including drug delivery, cosmetics, personal care products, and foods.

Herein, the exploration of natural plant‐based “spores” for the encapsulation of macromolecules as a drug delivery platform is reported. Benefits of encapsulation with natural “spores” include highly uniform size distribution and materials encapsulation by relatively economical and simple versatile methods. The natural spores possess unique micromeritic properties and an inner cavity for significant macromolecule loading with retention of therapeutic spore constituents. In addition, these natural spores can be used as advanced materials to encapsulate a wide variety of pharmaceutical drugs, chemicals, cosmetics, and food supplements. Here, for the first time a strategy to utilize natural spores as advanced materials is developed to encapsulate macromolecules by three different microencapsulation techniques including passive, compression, and vacuum loading. The natural spore formulations developed by these techniques are extensively characterized with respect to size uniformity, shape, encapsulation efficiency, and localization of macromolecules in the spores. In vitro release profiles of developed spore formulations in simulated gastric and intestinal fluids have also been studied, and alginate coatings to tune the release profile using vacuum‐loaded spores have been explored. These results provide the basis for further exploration into the encapsulation of a wide range of therapeutic molecules in natural plant spores.

With mounting evidence that nanomaterials can trigger adverse innate immune responses such as complement activation, there is increasing attention to the development of strategies that mask the complement-activating properties of nanomaterials. The current gold standard to reduce complement activation of nanomaterials is the covalent attachment of polymer coatings on nanomaterial surfaces, even though this strategy provides only moderate protection against complement activation. Akin to protein coronas that form on nanomaterial surfaces in physiological fluids, noncovalent strategies based on protein adsorption would offer a simplified, biomimetic approach to mitigate complement activation. Herein, we demonstrate that precoating graphene-based nanomaterials with purified, natural proteins enables regulatory control of nanomaterial-triggered complement activation. When the graphene-based nanomaterials were coated with complement factor H, nearly complete protection (>90% reduction) against complement activation (a "stealth effect") was achieved. By contrast, coating the nanomaterials with a passivating layer of bovine or human serum albumins achieved moderate protection (∼40% reduction), whereas immunoglobulin G amplified complement activation by several-fold. Taken together, our results demonstrate that surface-bound factor H, as well as serum albumins, can prevent graphene oxide-triggered complement activation, thereby offering a facile approach to inhibit complement activation completely down to naturally occurring levels.