Sporopollenin Exine Capsules Research Articles

Fe-N catalyst derived from and supported on Lycopodium clavatum sporopollenin exine capsules for the oxygen reduction reaction

A carbon-supported electrocatalyst, featuring carbon nanotubes anchored on 3D porous graphitic carbon, was developed with the aim to perform in the operating conditions of alkaline fuel cells and metal air batteries. The catalyst was developed via two steps: first powders of Sporopollenin exine capsules used as a bio-based carbon support were activated via CO2 gasification to obtain a high specific area and porosity, second the derived porous carbons were impregnated by an iron salt and a nitrogen source, to be carbonised in Nitrogen at high temperature. The prepared catalyst demonstrated an efficient oxygen reduction reaction activity showing a half-wave potential of ~ 0.775 V vs. Reversible hydrogen electrode, comparable with that of commercial 20 wt% Pt/C in alkaline conditions, a good stability after accelerated degradation testing, retaining ~ 86% of the initial limiting current density, and a higher diffusion limited current density (6.3 vs. 5.1 mA cm− 2) than the commercial counterpart. Overall, we show the suitability of Sporopollenin exine capsule as support for electrocatalysis and a promising methodology to develop sustainable catalysts for the oxygen reduction reaction.

Characterization of sustainable biocompatible materials based on chitosan: cellulose composites containing sporopollenin exine capsules

In this work, photothermal beam deflection spectrometric technique (BDS) is applied for non-contact and non-destructive characterization of chitosan (CS): cellulose (CEL) biocomposites with incorporated sporopollenin exine capsules (SEC). The objective was to determine the structural and thermal properties of synthesized CS:CEL:SEC composites with varying amounts of SEC, and to validate the BDS by photopyroelectric calorimetry (PPE) as an independent technique. It was found that CS:CEL biocomposites without SEC exhibit low porosities, which are on the order of 0.005 %, but can be increased by augmenting the content of CEL in the composite and/or by incorporation of SEC. By increasing the SEC content of CS:CEL composites to 50 % (w/w), the porosity increased up to 0.17 %. SEC also increases the surface roughness of biocomposite by over 2000-times to reach the roughness amplitude of 6 μm in composites with 50 % SEC. The thermal conductivities of investigated biocomposites were in the range of 40–80 mWm−1 K−1, while the thermal diffusivities were on the order of fractions of mm2s−1. With first validation of BDS results for thermal properties of CS:CEL-based composites, which show agreement with PPE results to within 5 %, this study confirms BDS technique as a perspectives tool for non-destructive characterization of CS:CEL:SEC biocomposites.

Ultrafast and one-step coating sporopollenin exine capsules with metal-phenolic networks for bio-composite applications

Sporopollenin exine capsules (SECs), extracted from plant pollen grains, are becoming increasingly popular as natural microcapsules for a broad spectrum of bio-composite applications due to their plentiful supply, resilience to chemicals and physical stress, unique species-specific designs, exceptional consistency in structure, and significant internal volume. However, SECs have a relatively bioinert interface hindering their application in biomaterials. Thus, surface modification is an efficient strategy to convert SECs into biocompatible materials better for biological applications. Previous approaches predominantly depend on labor-intensive, multi-stage procedures that are time-consuming. Herein, we report an ultrafast, one-step, and effective modification strategy to render SECs biocompatibility by coating them with ferric ions and tannic acids, which endow them with a better cell adhesion property. In summary, our results show that this ultrafast and one-step biocompatibility strategy enhances the functional characteristics of SECs and holds wide-ranging implications for bio-composite applications..

An Ecofriendly Nature-Inspired Microcarrier for Enhancing Delivery, Stability, and Biocidal Efficacy of Phage-Based Biopesticides.

In pursuit of sustainable agricultural production, the development of environmentally friendly and effective biopesticides is essential to improve food security and environmental sustainability. Bacteriophages, as emerging biocontrol agents, offer an alternative to conventional antibiotics and synthetic chemical pesticides. The primary challenges in applying phage-based biopesticides in agricultural settings are their inherent fragility and low biocidal efficacy, particularly the susceptibility to sunlight exposure. This study addresses the aforementioned challenges by innovatively encapsulating phages in sporopollenin exine capsules (SECs), which are derived from plant pollen grains. The size of the apertures on SECs could be controlled through a non-thermal and rapid process, combining reinflation and vacuum infusion techniques. This unique feature facilitates the high-efficiency encapsulation and controlled release of phages under various conditions. The proposed SECs could encapsulate over 9 log PFU g-1 of phages and significantly enhance the ultraviolet (UV) resistance of phages, thereby ensuring their enhanced survivability and antimicrobial efficacy. The effectiveness of SECs encapsulated phages (T7@SECs) in preventing and treating bacterial contamination on lettuce leaves is further demonstrated, highlighting the practical applicability of this novel biopesticide in field applications. Overall, this study exploits the potential of SECs in the development of phage-based biopesticides, presenting a promising strategy to enhancing agricultural sustainability.

Seed coating with biocontrol bacteria encapsulated in sporopollenin exine capsules for the control of soil-borne plant diseases

Coating seeds with biocontrol agents represents an effective approach for managing soil-borne plant diseases. However, improving the viability of biocontrol microorganisms on the seed surface or in the rhizosphere remains a big challenge due to biotic and abiotic stresses. In this work, we developed a microbial seed coating strategy that uses sporopollenin exine capsules (SECs) as carriers for the encapsulation of the biofilm-like biocontrol bacteria. SECs was extracted from camellia bee pollen, and then characterized by Fourier Transform infrared spectroscopy (FTIR), elemental analysis and thermal gravity analysis (TG). The Paenibacillus polymyxa ZF129, a biocontrol bacterium, was introduced into SECs using the vacuum-incubation method and characterized by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Notably, the ZF129 cell formed a biofilm-like structure inside the SECs, which enhanced their tolerance to acidic stress. As a proof of concept, we applied ZF129-loaded SECs to coat pak choi seeds using a straightforward plate-shaking technique. The coated seeds demonstrated a high control efficacy of up to 60.46 % against clubroot disease. Overall, this study sheds light on the application of SECs as promising carrier for the encapsulation of biofilm-like biocontrol bacteria, further augmenting the biocontrol functionality of microbial seed coating.

Inhalation of Bioorthogonal Gene‐Editable Spiky‐Pollen Reprograms Tumor‐Associated Macrophages for Lung Cancer Immunotherapy

AbstractAs a major component of tumor infiltration, tumor‐associated macrophages (TAMs) primarily promote the M2 phenotype of tumors in the tumor microenvironment. Additionally, the overexpression of anti‐phagocytic molecules in TAMs facilitates tumor cell evasion of TAMs’ phagocytic arrest. Therefore, there is an urgent need to develop a reliable strategy to reprogram TAMs for more effective anti‐tumor outcomes. In this study, innovative inhalable bioorthogonal gene‐editable microparticles (SPR) have been engineered that reprogram TAMs for lung cancer therapy based on spike‐covered sunflower sporopollenin exine capsules (SECs). These microparticles utilize SECs as delivery vehicles, with reduced palladium (Pd) nanoparticles on their surface carrying CRISPR/Cas9 lipid nanoparticles (LNP‐RNPs) that specifically knock down the anti‐phagocytic SIRPα gene on TAMs. The SPR microparticles employ a tripartite strategy to reprogram the TAMs: the physical stimulation through pollen spikes, the production of a Toll‐like receptor 7 agonist (imiquimod, IMD) via Pd‐mediated bioorthogonal catalysis, and the employment of CRISPR/Cas9 gene editing. In an orthotopic mouse model, the inhalation of SPR microparticles not only reprograms macrophages efficiently but also bolsters their tumor‐fighting abilities. Notably, the cured mice show no signs of recurrence even upon re‐exposure to the tumor, indicating a long‐lasting anti‐tumor effect.

Harnessing the Power of Nature: Monodisperse Pickering Emulsion Droplets and Yolk‐Shell Microcapsules Utilizing Bee Pollen Particles

AbstractThe preparation of monodisperse Pickering emulsions currently can only be achieved using microfluidics or membrane emulsification, limiting its widespread applications in many fields. Here, by simply introducing naturally occurring pollen grains during mechanical emulsification, it becomes extremely feasible to fabricate uniform Pickering emulsions. The process of shearing and turbulence leads to a constant reduction in the size of the droplets of the dispersed phase. The robust exine of the pollen grains in the continuous phase enables them to retain their structural integrity during emulsification, resulting in the formation of a single pollen‐in‐water‐in‐oil structure. Meanwhile, the intrinsic monodispersity of the pollen grains allows for the resulting emulsions to be similarly uniform, and they can be easily collected through centrifugation. As a result, this novel methodology achieves the effective formulation of monodisperse Pickering emulsions in an unprecedented way. Furthermore, the utilization of sporopollenin exine capsules (SECs) as a replacement for pollen, in conjunction with sol–gel interfacial engineering, enables the attainment of “yolk‐shell” dual‐shell microcapsules. This approach not only effectively addresses the issue of cargo leakage in SECs but also imparts exceptional uniformity and stability to the microcapsules.

Sporopollenin exine capsules modulate the function of microglial cells.

Immune cells are the housekeepers of the human body. They protect the body from pathogens, cellular damage, and foreign matter. Proper activation of immune cells is of great significance to diseases such as infection, inflammation, and neurodegeneration. However, excessive activation of cells can be detrimental. An ideal biomaterial could enhance the cellular immune function without proinflammation. In this work, we used sporopollenin exine capsules (SEC) from pollen to promote functions of primary microglia, a typical resident immune cell of the brain. We found that microglia aggregated around SEC and did not undergo any proinflammation. SEC improved the viability, migration, phagocytosis, and anti-inflammatory ability of microglia. By exploring the underlying mechanism of microglial activation without the production of cytotoxic pro-inflammatory cytokines, we found that SEC protects microglia against inflammation induced by lipopolysaccharide (LPS), an immunostimulatory factor, through the toll-like receptor 4 (TLR4) signaling pathway in a myeloid differentiation factor 88-dependent manner. These findings might shed light on the potential application of SEC in microglia transplantation for treatment of microglia-associated degenerative central nervous system diseases.

All-aqueous emulsions stabilized by sporopollenin exine capsules

The efficacy of sporopollenin exine capsules (SpECs) for stabilization of all-aqueous emulsions was assessed. Cytoplasmic substances were removed from Lycopodium clavatum spores to obtain the SpECs. SpECs had a comparable morphology with the parent spores, and a size of ∼31 μm. The all-aqueous emulsions were prepared with polyethylene glycol (PEG) and dextran (Dex) at different PEG: Dex concentration ratios between 2:9 and 18:1. Confocal microscopy imaging showed that the emulsions were Dex-continuous at PEG: Dex concentration ratios of 2:9 and 4:8 and PEG-continuous at the ratios ≥6:7. When the SpECs were initially suspended within the PEG phase, the Dex-continuous emulsions could not be stabilized. The SpECs also failed to stabilize the emulsion with a ratio of 6:7, where the emulsions transitioned to PEG-continuous. However, the SpECs could stabilize a bottom emulsion phase, consisting of Dex-rich droplets within the PEG exterior phase, at concentration ratios ≥8:6. We hypothesized that a Pickering-type stabilization mechanism at the aqueous-aqueous interface of Dex droplets account for the emulsion stability, together with a possible formation of SpEC particle rafts. The emulsion stability at a concentration ratio of 8:6 was dependent on its pH; stable emulsions were formed at pH 7, but at pHs 2 and 4, the emulsions became unstable. These results were attributed to the high ζ-potential (−31 mV) of the SpECs at pH 7. These results show that repulsion between dispersed droplets was more important than the packing of the particles at the interface itself.

Synthesis of a Graphene-Encapsulated Fe3C/Fe Catalyst Supported on Sporopollenin Exine Capsules and Its Use for the Reverse Water–Gas Shift Reaction

Synthesis of a Graphene-Encapsulated Fe₃C/Fe Catalyst Supported on Sporopollenin Exine Capsules and Its Use for the Reverse Water–Gas Shift Reaction

Sporopollenin exine capsules with polypeptide multilayer films promoting cell adhesion

Sporopollenin exine capsules (SECs), extracted from plant pollen, are emerging as attractive and natural microcapsules for a wide range of bio-composite applications due to their abundant availability, chemical and mechanical robustness, species-specific architectural features, striking structural uniformity, and large inner cavity. However, SECs have a predominantly hydrophobic interface hindering their application in biomaterials. Thus, developing robust surface functionalization strategies to increase their hydrophilicity would open the door to interfacing microcapsules with cells. Herein, we create SECs with increased surface hydrophilicity coated by polypeptide multilayer films using layer-by-layer (LbL) self-assembly technology. Furthermore, human bone marrow-derived stem cells adhere more to these LbL-treated SECs acting as seed cells for tissue engineering. In summary, our findings demonstrate that LbL modification of SECs improves their functional properties and has broad implications across bio-composite applications.

Spore exines increase vitamin D clinical bioavailability by mucoadhesion and bile triggered release.

Sporopollenin exine capsules (SpECs) are microcapsules derived from the outer shells (exines) of plant spore and pollen grains. This work reports the first clinical study on healthy volunteers to show enhanced bioavailability of vitamin D encapsulated in SpECs from Lycopodium clavatum L. spore grains vs vitamin D alone, and the first evidence (in vitro, ex vivo and in vivo) of mechanisms to account for the enhancement and release of the active in the small intestine. Evidence for mucoadhesion of the SpECs contributing to the mechanism of the enhancement is based on: (i) release profile over time of vitamin D in a double blind cross-over human study showing significant release in the small intestine; (ii) in vivo particle counting data in rat showing preferred retention of SpECs vs synthetic beads; (iii) ex vivo99mTc labelling and counting data using rat small intestine sections showing preferred retention of SpECs vs synthetic beads; (iv) in vitro mucoadhesion data. Triggered release by bile in the small intestine was shown in vitro using solid state NMR and HPLC.

Natural pollen exine-templated synthesis of photocatalytic metal oxides with high surface area and oxygen vacancies

Pollen grains in nature possess highly hierarchical structure been created through evolution process for over millions of years. Here, we report eco-friendly synthesis of highly photocatalytic metal oxides (ZnO, CeO2, and Fe2O3) using sporopollenin exine capsules (SECs), the hard structure of pollen, as a template. We generate carboxylate groups on the SECs to induce electrostatic interactions between the metal ions in the precursor solution and the surface of the SECs. The pollen-templated metal oxide structure is synthesized by aggregating metal oxide nanoparticles with the size of 10–20 nm on the micro-sized SECs framework, which have maintained unique morphology of the pollen. These metal oxides display excellent performance of organic pollutants degradation under visible light, owing to high surface area and oxygen vacancies which allow higher reaction rates and promote separation of photogenerated electron-hole pairs.

Different Plant Sporopollenin Exine Capsules and Their Multifunctional Usage.

Sporopollenin exine capsules (SECs) are highly resistant to heat and various acids and bases. They are also cheap, highly porous, eco-friendly polymer biomaterials with stable microencapsulation capacity. Due to their strong and uniquely shaped exine layers, they can allow growth on metal oxide materials, as a biotemplate for use in different applications. In this study, first, a single SEC extraction method was applied to three different pollens from Pinus, Fraxinus excelsior, and Tilia. Scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, and thermogravimetric/differential thermal analysis (TGA/DTA) measurements both before and after the extraction process were performed to observe changes in surface area, morphology, porous structure, and degradation properties. The protein content and removal were analyzed by elemental and spectrophotometric analyses. Then, SECs were loaded by passive and centrifuge loading for drug delivery, and the loading capacities were analyzed by Fourier transform infrared spectroscopy and spectrophotometry. The method was successful in opening the pores and maintaining the structural integrity of SECs. It was determined that the morphology and porosity affected the encapsulation efficiency. According to the loading capacities, Tilia SECs were the most efficient SECs for both loading methods. In addition, three different SECs were hydrothermally coated with cobalt and then heat-treated to obtain a metal oxide structure. A CO3O4 supercapacitor electrode constructed using CO3O4-F. excelsior SEC powder had the best surface area parameters. The electrode showed a maximum specific capacity of 473 F/g for over 3000 continuous cycles of galvanostatic charge–discharge (GCD).

The Uptake of Sporopollenin Exine Capsules and Associated Bioavailability of Adsorbed Oestradiol in Selected Aquatic Invertebrates

Lycopodium clavatum sporopollenin exine capsules (SpECs) are known to both adsorb and absorb chemicals. The aim of the present work was to determine whether oestradiol (E2) is ‘bioavailable’ to bioindicator species, either pre-adsorbed to, or in the presence of, SpECs. SpEC uptake was confirmed for Daphnia magna and Dreissena bugensis. E2 levels varied among treatments for Caenorhabditis elegans though there was no relationship to SpEC load. E2 was not detected in D. bugensis tissues. Expression changes of general stress and E2-specific genes were measured. For C. elegans, NHR-14 expression suggested that SpECs modulate E2 impacts, but not general health responses. For D. magna, SpECs alone and with E2 changed Vtg1 and general stress responses. For D. bugensis, SpECS were taken up but no E2 or change in gene expression was detected after exposure to E2 and/or SpECs. The present study is the first to investigate SpECs and bound chemical dynamics.

Facile isolation and analysis of sporopollenin exine from bee pollen

We present facile methods to obtain purified sporopollenin exine capsules, and provide mass balances for classical and novel purification procedures. An ionic liquid, tetrabutyl phosphonium hydroxide turned out to be the most effective in removing the intine wall. The sporopollenin capsules were investigated by fluorescent microscopy, AFM, solid-state NMR and infrared Raman spectroscopy. The latter two methods showed that sunflower and rape exines have different proportions of O-aliphatic and aromatic constituents. Purified exine capsules were coated with functionalized fluorophores. The procedures presented in this paper could contribute to further spread of the applications of this hollow, and chemically highly resistant material.

Carboxymethylpachymaran/alginate gel entrapping of natural pollen capsules for the encapsulation, protection and delivery of probiotics with enhanced viability

There are multiple obstacles for the storage and digestion of probiotic products because of their poor viability. This study developed a new core-shell structure (sporopollenin exine capsules (SECs) as the core and Ca-alginate (Alg)/carboxymethylpachymaran (CMP) gel as the shell) for the protection of probiotics, which could not only enhance the storage and lyophilization stability of probiotics, but also achieve sustained release in the gastrointestinal tract. By using (L. plantarum) as the model probiotic, the loading process (SECs-encapsulated L. plantarum, SL) was optimized with the maximum probiotic loading capacity reaching 1.17 × 1010 CFU/g. In the Ca-Alg/CMP shell, the introduction of CMP could improve the thermal stability of the shell. Also, the CMP content could affect the swelling behavior and microstructure of the shell by influencing the hydrogen bonds between CMP and Alg, and thus could regulate the release behavior of probiotics. Compared with Ca-Alg coated SL gel (ASG), the Ca-Alg/CMP coated SL gel (ACSG) showed superior properties in terms of sustainable release and lyophilization stability: the number of viable cells exceeded 107 CFU/mL and was about 1.68 × 107 CFU/mL and 1.44 × 107 CFU/mL before and after lyophilization, respectively. Besides, ACSG (1.44 × 107 CFU/mL for day 0 and 2.09 × 106 CFU/mL for day 90 at 4 °C) showed an obvious advantage over ASG (2.01 × 105 CFU/mL for day 0 and 5.66 × 102 CFU/mL for day 90 at 4 °C) in achieving high storage stability. Overall, this core-shell structure may be utilized in the food industry for better protection and delivery of probiotics.

Tuning of Molecular Interactions between Zein and Tannic Acid to Modify Sunflower Sporopollenin Exine Capsules: Enhanced Stability and Targeted Delivery of Bioactive Macromolecules.

There are multiple obstacles for the storage and digestion of orally administered bioactive macromolecules. This study developed a low-cost and sustained-release delivery system (sporopollenin exine capsules with zein/tannic acid modification) of proteins with excellent storage stability, and at the same time provided insights into the sustained-release mechanism through exploring the interaction between zein and tannic acid (TA). β-Galactosidase (β-Gal) was utilized as a model protein and loaded into sporopollenin exine capsules (SECs), which were then coated with the zein/TA system. Under the optimized zein/TA conditions, the zein/TA system showed better performance than the zein alone system in the sustained release of β-Gal, with the residual activity of about 70.26% after 24 h of simulated digestion. Evaluation of the storage stability demonstrated a β-Gal residual activity of nearly 90% for 28 days at 25 °C. Additionally, FTIR analysis demonstrated that the stability of the zein/TA system depends on both hydrogen bonding and certain covalent bonding through the Schiff-base reaction, and the sustained release is regulated by the bonding strength.

Sporopollenin Exine Microcapsules as Potential Intestinal Delivery System of Probiotics.

Despite several decades of research into encapsulation of bacteria, most of the proposed technologies are in the form of immobilized cultures. In this work, sporopollenin exine capsules (SECs) opened, using silica particles which act as pressing micro-probes, and loaded with Lactobacillus casei (L. casei) cells, are described for the first time. The proposed encapsulation provided ≈30× higher encapsulation yield (30.87%), compared to direct compression of SECs (0.99%). Encapsulated L. casei cells show 1.21- and 2.25-folds higher viability compared to free cells, in in vitro simulated fasted and fed media representing the human gastrointestinal (GI) tract, respectively. Encapsulated L. casei can proliferate inside the SECs, generating enough pressure to cause the SECs to burst and release the viable and metabolically active cells. The noticeable difference with the application of the SECs as a means of encapsulation is that the SECs may act as a bioreactor and provide time for the encapsulated cells to multiply thousands of times before being released, following the SEC's burst. The unique advantages of SECs alongside the proposed encapsulation method, demonstrates the potential application of SECs as delivery system of probiotics to the distal part of the human GI tract.

Designable Carboxymethylpachymaran/Metal Ion Architecture on Sunflower Sporopollenin Exine Capsules as Delivery Vehicles for Bioactive Macromolecules.

There are multiple obstacles in the gastrointestinal tract (GIT) for oral administration of bioactive macromolecules. Here, we engineered an oral delivery vehicle (sporopollenin exine capsules with carboxymethylpachymaran (CMP)/metal ion modification) with targeted release based on food-grade ingredients and processing operations. Then, the interaction and binding mechanisms between CMP and metal ions in the vehicle were investigated. By using β-galactosidase (β-Gal) as a model protein, the systems were characterized for the surface morphology and monitored by the in vitro release profile of β-Gal. Notably, the CMP/metal ion systems not only markedly decreased the CMP dosage but also achieved a valid long-term release compared with the previously reported CMP system. Among all the systems, the CMP/3% AlCl3 system showed the best ability to control the release with the maximum residual activity of β-Gal at nearly 72% after 24 h of treatment. Subsequently, the interaction mechanism between CMP and metal ions within the system was characterized by the perspectives of microstructure, rheological properties, and spectroscopy characteristics. The results indicated that the low pH conditions are conducive to the further cross-linking of CMP and metal ions, resulting in a high gel strength and thus a dense structure, which can impact the controlled release of β-Gal in the GIT. Overall, the system may be utilized in the administration of medical and functional foods, specifically for the delivery of bioactive proteins via the oral route.