Hollow pollen shells to enhance drug delivery

The development of multifunctional materials for water pollution remediation using pollen and sporopollenin

Pollen is a promising material for water treatment owing to its renewable nature, abundant sources, and vast reserves. The natural polymer sporopollenin, found within pollen exine, possesses a distinctive layered porous structure, mechanical strength, and stable chemical properties, which can be utilized to prepare sporopollenin exine capsules (SECs). Leveraging these attributes, pollen or SECs can be used to develop water pollution remediation materials. In this review, the structure of pollen is first introduced, followed by the categorization of various methods for extracting SECs. Then, the functional expansion of pollen adsorbents, with an emphasis on their recyclability, reusability, and visual sensing capabilities, as opposed to mere functional group modification, is discussed. Furthermore, the progress made in utilizing pollen as a biological template for synthesizing catalysts is summarized. Intriguingly, pollen can also be engineered into self-propelled micromotors, enhancing its potential application in adsorption and catalysis. Finally, the challenges associated with the application of pollen in water pollution treatment are discussed. These challenges include the selection of environmentally friendly, non-toxic reagents in synthesizing pollen water remediation products and the large-scale application after synthesis. Moreover, the multifunctional synthesis and application of different water remediation products are prospected.

Bio-inspired drug delivery systems: A new attempt from bioinspiration to biomedical applications

Natural organisms have evolved sophisticated and multiscale hierarchical structures over time to enable survival. Currently, bionic design is revolutionizing drug delivery systems (DDS), drawing inspiration from the structure and properties of natural organisms that offer new possibilities to overcome the challenges of traditional drug delivery systems. Bionic drug delivery has contributed to a significant improvement in therapeutic outcomes, providing personalized regimens for patients with various diseases and enhancing both their quality of life and drug efficacy. Therefore, it is important to summarize the progress made so far and to discuss the challenges and opportunities for future development. Herein, we review the recent advances in bio-inspired materials, bio-inspired drug vehicles, and drug-loading platforms of biomimetic structures and properties, emphasizing the importance of adapting the structure and function of organisms to meet the needs of drug delivery systems. Finally, we highlight the delivery strategies of bionics in DDS to provide new perspectives and insights into the research and exploration of bionics in DDS. Hopefully, this review will provide future insights into utilizing biologically active vehicles, bio-structures, and bio-functions, leading to better clinical outcomes.

Conservation and diversity of the pollen microbiome of Pan-American maize using PacBio and MiSeq

Pollen is a vector for diversification, fitness-selection, and transmission of plant genetic material. The extent to which the pollen microbiome may contribute to host diversification is largely unknown, because pollen microbiome diversity within a plant species has not been reported, and studies have been limited to conventional short-read 16S rRNA gene sequencing (e.g., V4-MiSeq) which suffers from poor taxonomic resolution. Here we report the pollen microbiomes of 16 primitive and traditional accessions of maize (corn) selected by indigenous peoples across the Americas, along with the modern U.S. inbred B73. The maize pollen microbiome has not previously been reported. The pollen microbiomes were identified using full-length (FL) 16S rRNA gene PacBio SMRT sequencing compared to V4-MiSeq. The Pan-American maize pollen microbiome encompasses 765 taxa spanning 39 genera and 46 species, including known plant growth promoters, insect-obligates, plant pathogens, nitrogen-fixers and biocontrol agents. Eleven genera and 13 species composed the core microbiome. Of 765 taxa, 63% belonged to only four genera: 28% were Pantoea, 15% were Lactococcus, 11% were Pseudomonas, and 10% were Erwinia. Interestingly, of the 215 Pantoea taxa, 180 belonged to a single species, P. ananatis. Surprisingly, the diversity within P. ananatis ranged nearly 10-fold amongst the maize accessions analyzed (those with ≥3 replicates), despite being grown in a common field. The highest diversity within P. ananatis occurred in accessions that originated near the center of diversity of domesticated maize, with reduced diversity associated with the north-south migration of maize. This sub-species diversity was revealed by FL-PacBio but missed by V4-MiSeq. V4-MiSeq also mis-identified some dominant genera captured by FL-PacBio. The study, though limited to a single season and common field, provides initial evidence that pollen microbiomes reflect evolutionary and migratory relationships of their host plants.

Natural sporopollenin microcapsules: biological evaluation and application in regulating hepatic toxicity of diclofenac sodium in vivo

Diclofenac sodium (DIC) is a pain reliever and anti-nociceptive medication. Significant limitations of DIC treatment stem from its adverse effects. This study investigates the feasibility of using natural Lycopodium clavatum sporopollenin (LCS) microcapsules loaded with DIC to mitigate the hepatotoxicity associated with DIC treatment. In addition, LCS microcapsules were tracked in the blood, stomach, small intestine, and feces of rats to demonstrate their morphological integrity and uptake behavior. Four groups (6 per group) of adult male albino rats were administered normal saline (control), empty LCS (30 mg kg-1), plain DIC (10 mg kg-1), and DIC-loaded LCS (40 mg kg-1) orally for seven consecutive days. The first comprehensive histological examination of the rat stomach demonstrated the robustness and bioadhesion ability of LCS under severe conditions. The findings suggested that these versatile microcapsules are unlikely to be digested in the gastrointestinal tract (GIT). The administration of DIC-loaded LCS was found to play a potential protective role in regulating DIC-induced substantially increased serum levels of transaminases, alkaline phosphatase, total bilirubin, and pro-inflammatory cytokines. In addition, DIC-loaded LCS restored the antioxidant enzymes, DNA damage, and liver histological architecture abnormalities caused by DIC. Microencapsulation of DIC into pollen-derived biomaterials could be employed as an efficient platform with enough safety coverage on rat liver, pending further clinical studies.

Multifaceted roles of pollen in the management of cancer

Oral drug delivery of microparticles demonstrates shortcomings like aggregation, decreased loading capacity and batch-to-batch variation, which limits its scale-up. Later, porous structures gained attention because of their large surface-to-volume ratio, high loading capacity and ability to carry biomacromolecules, which undergo degradation in GIT. But there are pitfalls like non-uniform particle size distribution, the impact of porogen properties, and harsh chemicals. To circumvent these drawbacks, natural carriers like pollen are explored in drug delivery, which withstands harsh environments. This property helps to subdue the acid-sensitive drug in GIT. It shows uniform particle size distribution within the species. On the other side, they contain phytoconstituents like flavonoids and polysaccharides, which possess various pharmacological applications. Therefore, pollen has the capability as a carrier system and therapeutic agent. This review focuses on pollen's microstructure, composition and utility in cancer management. The extraction strategies, characterisation techniques and chemical structure of sporopollenin exine capsule, its use in the oral delivery of antineoplastic drugs, and emerging cancer treatments like photothermal therapy, immunotherapy and microrobots have been highlighted. We have mentioned a note on the anticancer activity of pollen extract. Further, we have summarised the regulatory perspective, bottlenecks and way forward associated with pollen.

Fabrication of Sacha Inchi Oil-Loaded Microcapsules Employing Natural-Templated Lycopodium clavatum Spores and Their Pressure-Stimuli Release Behavior

Polymeric particles have attracted vast attention for use in various fields, especially as drug carriers and cosmetics, due to their excellent ability to protect active ingredients from the environment until reaching a target site. However, these materials are commonly produced from conventional synthetic polymers, which impose adverse effects on the environment due to their non-degradable nature, leading to waste accumulation and pollution in the ecosystem. This work aims to utilize naturally occurring Lycopodium clavatum spores to encapsulate sacha inchi oil (SIO), which contains active compounds with antioxidant activity, by applying a facile passive loading/solvent diffusion-assisted method. Sequential chemical treatments by acetone, potassium hydroxide, and phosphoric acid were employed to remove native biomolecules from the spores before encapsulation effectively. These are mild and facile processes compared to other synthetic polymeric materials. Scanning electron microscopy and Fourier-transform infrared spectroscopy revealed the clean, intact, and ready-to-use microcapsule spores. After the treatments, the structural morphology of the treated spores remained significantly unchanged compared to the untreated counterparts. With an oil/spore ratio of 0.75:1.00 (SIO@spore-0.75), high encapsulation efficiency and capacity loading values of 51.2 and 29.3%, respectively, were obtained. Using antioxidant assay (DPPH), the IC₅₀ of SIO@spore-0.75 was 5.25 ± 3.04 mg/mL, similar to that of pure SIO (5.51 ± 0.31 mg/mL). Under pressure stimuli (1990 N/cm³, equivalent to a gentle press), a high amount of SIO was released (82%) from the microcapsules within 3 min. At an incubation time of 24 h, cytotoxicity tests showed a high cell viability of 88% at the highest concentration of the microcapsules (10 mg/mL), reflecting biocompatibility. The prepared microcapsules have a high potential for cosmetic applications, especially as functional scrub beads in facial washing products.

Extraordinary microcarriers derived from spores and pollens

Spores and pollens refer to the reproductive cells of seed plants and asexually reproducing sporophytes, exhibiting a natural core-shell structure and exquisite surface morphology. They possess extraordinary dimensional homogeneity, porosity, amphiphilicity and adhesion. Their sporopollenin exine layer endows them with chemically stable, UV resistant, and biocompatible properties, which can also be facilely functionalized due to sufficient groups on the surface. The unique characteristics of spores and pollens have facilitated a wide range of applications in drug carriers, biological imaging, food science, microrobotics, environmental purification, flexible electronics, cell scaffolds, 3D printing materials and biological detection. This review showcases the common structural composition and physicochemical properties of spores and pollens, describes the extraction and processing methods, and summarizes the recent research on their applications in various fields. Following these sections, this review analyzes the existing challenges in spores and pollen research and provides a future outlook.

Patterns of Phenolic Compounds in Betula and Pinus Pollen

In this study, phenolic compounds and their antioxidant activity in the pollen of anemophilous Betula and Pinus were determined. Spectrophotometric, high-performance thin-layer and liquid chromatography methods were applied. Free phenolic compounds (free PC) and phenolic compounds bound to the cell wall (bound PC) were analysed in the pollen extracts. Regardless of the pollen species, their content was 20% higher than that in bound PC extracts. Pinus pollen extracts contained 2.5 times less phenolic compounds compared to Betula. Free PC extraction from the deeper layers of Pinus pollen was minimal; the same content of phenolic compounds was obtained in both types of extracts. The bioactivity of pollen (p < 0.05) is related to the content of phenolic compounds and flavonoids in Betula free PC and in bound PC, and only in free PC extracts of Pinus. Rutin, chlorogenic and trans-ferulic acids were characterised by antioxidant activity. Phenolic acids accounted for 70−94%, while rutin constituted 2−3% of the total amount in the extracts. One of the dominant phenolic acids was trans-ferulic acid in all the Betula and Pinus samples. The specific compounds were vanillic and chlorogenic acids of Betula pollen extracts, while Pinus extracts contained gallic acid. The data obtained for the phenolic profiles and antioxidant activity of Betula and Pinus pollen can be useful for modelling food chains in ecosystems.

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 vivo^99mTc 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.

Pollen-derived microcapsules for aspirin microencapsulation: in vitro release and physico-chemical studies

Aspirin, also known as acetylsalicylic acid (ASA), is one of the most crucial therapies needed and/or used in a basic health system. Using biocompatible materials to encapsulate ASA would improve its therapeutic efficacy and reduce its side effects via controlled release in physiological environments. Consequently, we explore in this study the feasibility of encapsulation of ASA into robust Lycopodium clavatum L. sporopollenin (LCS) microcapsules. After extracting sporopollenin from their natural micrometer-sized raw spores, the physico-chemical features of the extracted sporopollenin, pure ASA, and sporopollenin loaded with ASA were characterised using various methods, including optical microscopy, Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-vis.) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Additionally, we demonstrate the in vitro release profile of ASA in a triggered gastrointestinal environment utilizing kinetics analysis to investigate the mechanism of release. The LCS microcapsules were found to be excellent encapsulants for the crucial ASA drug and achieved controlled in vitro release, that would enable further investigations to rationally design versatile controlled delivery platforms.

Biobased Spore Microcapsules for Asphalt Self-Healing

Asphalt pavements and bituminous composites are majorly damaged by bitumen aging and fatigue cracking by traffic load. To add, maintenance and reparation of asphalt pavements is expensive and also releases significant amounts of greenhouse gases. These issues can be mitigated by promoting asphalt self-healing mechanisms with encapsulated rejuvenators. The ability of the required microcapsules to be resilient against high temperatures, oxidation, and mechanical stress is essential to promote such self-healing behavior without compromising the field performance of the asphalt pavement. This work proposes, for the first time, the use of extremely resistant biobased spores for the encapsulation of recycled oil-based rejuvenators to produce more resilient self-healing pavements. Spore encapsulants were obtained from natural spores (Lycopodium clavatum) by applying different chemical treatments, which enabled the selection of the best morphologically intact and clean spore encapsulant. The physical, morphological, and physicochemical changes were examined using fluorescence images, ATR-FTIR, SEM, size distribution, XRD, TGA and DSC analyses. Sunflower oil was used as the encapsulated rejuvenator with an optimal sol colloidal mixture for sporopollenin-oil of 1:5 (gram-to-gram). Vacuum, passive, and centrifugal encapsulation techniques were tested for loading the rejuvenator inside the clean spores and for selecting the best encapsulation technology. The encapsulation efficiency and the profiles of the accelerated release of the rejuvenator from the loaded spores over time were studied, and these processes were visualized with optical and inverted fluorescence microscopy. Vacuum encapsulation was identified as the best loading technique with an encapsulation efficiency of 93.02 ± 3.71%. The rejuvenator was successfully encapsulated into the clean spores, as observed by optical and SEM morphologies. In agreement with the TGA and DSC, the microcapsules were stable up to 204 °C. Finally, a self-healing test was conducted through fluorescence tests to demonstrate how these biobased spore microcapsules completely heal a crack into an aged bitumen sample in 50 min.

Sporopollenin based materials as a versatile choice for the detoxification of environmental pollutants - A review

Before making the transfer to land, plants survive in water for millions of years to avoid the severe circumstances that prevail on lands, such as drought and UV radiation. All land plant spores are coated in sporopollenin, a substance that has developed to endow pollen and spore shells with exceptional, one-of-a-kind qualities. In a nutshell, sporopollenin-coated spores are a unique invention only seen in land plants. Sporopollenin, discovered in the outer exine layer of pollen walls, is a lipid and phenolic-based polymer with high carbon, hydrogen, and oxygen cross-linking. Products based on sporopollenin can remediate toxic pollutant contamination in the aquatic environment. This research and development are now underway. In this review, we show how sporopollenin-based adsorbents act in environmental challenges and their immense promise for this application via remarkable physical and chemical characteristics. A comparison is made of the benefits of various sporopollenin-modified structures. This strategy will further our understanding of how a biopolymer's structure can be accommodated to address emerging environmental challenges, revealing more about sporopollenin's dynamical nature.

A biological nanofoam: The wall of coniferous bisaccate pollen

The outer layer of the pollen grain, the exine, plays a key role in the survival of terrestrial plant life. However, the exine structure in different groups of plants remains enigmatic. Here, modern and fossil coniferous bisaccate pollen were examined to investigate the detailed three-dimensional structure and properties of the pollen wall. X-ray nanotomography and volume electron microscopy are used to provide high-resolution imagery, revealing a solid nanofoam structure. Atomic force microscopy measurements were used to compare the pollen wall with other natural and synthetic foams and to demonstrate that the mechanical properties of the wall in this type of pollen are retained for millions of years in fossil specimens. The microscopic structure of this robust biological material has potential applications in materials sciences and also contributes to our understanding of the evolutionary success of conifers and other plants over geological time.

Eudragit-Coated Sporopollenin Exine Microcapsules (SEMC) of Phoenix dactylifera L. of 5-Fluorouracil for Colon-Specific Drug Delivery

In this study, 5-fluorouracil (5-FU)-loaded pollens of Phoenix dactylifera and their coating with ERS was done and evaluated for the colon-targeted delivery of 5-FU to treat colon cancer. Sporopollenin exine microcapsules (SEMC) from the pollens of Phoenix dactylifera were extracted by the reflux method and 5-FU into SEMC was encapsulated by the vacuum-assisted loading method. 5-FU loaded SEMC was coated with Eudragit^® RS-100 (ERS) by the organic solvent-evaporation technique under vacuum to avoid the discharge of 5-FU in the stomach and small intestine. Morphological and physicochemical characterization of drug-loaded SEMC (coated/uncoated) was performed by scanning electron microscopy (SEM), FTIR, XRD, and DSC. The encapsulation and drug loading were determined by the direct method, and an in vitro release study was performed in simulated gastric and intestinal fluids (SGF/SIF). The colon-specific delivery of 5-FU from the SEMC was assessed in terms of pharmacokinetics and gastrointestinal tract distribution after oral administration in rats. The successful encapsulation and loading of 5-FU into SEMC by a vacuum-assisted loading technique and its coating with ERS by a solvent-evaporation technique were achieved. SEM images of uncoated SEMC have shown porous structures, and coating with ERS reserved their morphology with a smooth surface and discrete microstructures and the 5% w/v ERS acetone solution. ERS-coated SEMC sustained the release of 5-FU until 24 h in SIF, while it was up to 12 h only from uncoated SEMC. The maximum plasma concentration (Cmax) of 5-FU from uncoated SEMC was 102.82 μg/mL after 1 h, indicating a rapid release of 5-FU in the upper gastrointestinal tract. This concentration decreased quickly with a half-life of 4 h, AUC0-t was 264.1 μg/mL.h, and MRT0-inf was 5.2 h. The Cmax of 5-FU from ERS-coated SEMC was 19.47 μg/mL at 16 h. The Cmax of 5-FU in small intestines was 406.2 μg/g at 1 h from uncoated SEMC and 1271.5 μg/g at 12 h from coated SEMC. Conclusively, a 249.9-fold higher relative bioavailability of 5-FU was achieved with the ERS-coated SEMC in colon tissues than that from uncoated SEMC.

Pollens in therapeutic/diagnostic systems and immune system targeting

Pollen is an excellent natural substance that plays an essential role in the reproduction of plants. In this review, we explain the structure, compositions, and characteristics of pollens. We consider pollen as a multifunctional tool that can be used in therapeutic/diagnostic systems. This microcapsule can be used in the forms of the hollow microcapsule, microgel, and composite, and also can be a tool for the synthesis of micro/nanostructures in various medical applications and used for the production of genetically modified plants that affect human health. In addition, we investigate the capability of this multifunctional tool in the immune system targeting that acts as an immunomodulator. In all applications and capabilities, we explain the potential of using nanostructures as parts of these systems and as auxiliary tools for promoting the applications of pollen. It is expected that soon, with the help of pollen-based therapeutic/diagnostic systems with the ability to immune system targeting, we will achieve effective and targeted therapeutic systems for the treatment of inflammatory and autoimmune diseases. In this paper, we suggest some ideas that may be a new step for future researches.

Encapsulation of folic acid (vitamin B9) into sporopollenin microcapsules: Physico-chemical characterisation, in vitro controlled release and photoprotection study

Folic acid (FA) is a crucial vitamin for all living creatures. However, it is susceptible to degradation under pH, heat, ultraviolet (UV) and day sunlight conditions, resulting in lowering its bioavailability. Therefore, a versatile protective encapsulation system for FA is highly required to overcome its inherent instability. We report the use of the robust Lycopodium clavatum sporopollenin (LCS) microcapsules, extracted from their natural micrometer-sized raw spores, for FA microencapsulation. The physico-chemical characterisation of the LCS microcapsules are comprehensively investigated before and after the microencapsulation using SEM, elemental, CLSM, FTIR, TGA/DTG and XRD analyses, revealing a successful FA encapsulation within the LCS in an amorphous form. The phenylpropanoid acids, responsible for the UV protection and the autofluorescence of the LCS, were found in the LCS as evidenced by FTIR analysis. TGA/DTG results revealed that the hemi-cellulose and cellulose are the major component of the LCS. A controlled and sustained release of FA from FA-loaded LCS were achieved where the release profile of FA-loaded LCS was found to be pH-dependent. The percentages of cumulative FA released after 10 h at 37 ± 0.5 °C were 45.5% and 76.1% in pH 1.2 and 7.4, respectively, ensuring controlled and slow release in simulated physiological conditions. The FA release kinetic studies indicated the prevalence of the Fickian diffusion mechanism in pH 1.2, while anomalous non-Fickian transport was ascribed for FA release in pH 7.4. The in vitro cytotoxicity assay revealed that the obtained formulations were biocompatible against the human skin fibroblast (HSF) cell line. The versatile LCS microcapsules exhibited intriguing photostability for FA under UV or sunlight irradiation. Concretely, the obtained FA sustained delivery and photoprotection properties of these LCS microcapsules validate their multifunctional characteristics, opening up intriguing applications in oral and topical drug delivery as well as in food industry.

Sustained In Vitro and In Vivo Delivery of Metformin from Plant Pollen-Derived Composite Microcapsules

We developed a dual microencapsulation platform for the type 2 diabetes drug metformin (MTF), which is aimed to increase its bioavailability. We report the use of Lycopodium clavatum sporopollenin (LCS), derived from their natural spores, and raw Phoenix dactylifera L. (date palm) pollens (DPP) for MTF microencapsulation. MTF was loaded into LCS and DPP via a vacuum and a novel method of hydration-induced swelling. The loading capacity (LC) and encapsulation efficiency (EE) percentages for MTF-loaded LCS and MTF-loaded DPP microcapsules were 14.9% ± 0.7, 29.8 ± 0.8, and 15.2% ± 0.7, 30.3 ± 1.0, respectively. The release of MTF from MTF-loaded LCS microcapsules was additionally controlled by re-encapsulating the loaded microcapsules into calcium alginate (ALG) microbeads via ionotropic gelation, where the release of MTF was found to be significantly slower and pH-dependent. The pharmacokinetic parameters, obtained from the in vivo study, revealed that the relative bioavailability of the MTF-loaded LCS-ALG beads was 1.215 times higher compared to pure MTF, following oral administration of a single dose equivalent to 25 mg/kg body weight MTF to streptozotocin (STZ)-induced diabetic male Sprague-Dawley rats. Significant hypoglycemic effect was obtained for STZ-induced diabetic rats orally treated with MTF-loaded LCS-ALG beads compared to control diabetic rats. Over a period of 29 days, the STZ-induced diabetic rats treated with MTF-loaded LCS-ALG beads showed a decrease in the aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglycerides, cholesterol, and low-density lipoprotein-cholesterol (LDL-C) levels, as well as an increase in glutathione peroxidase (GPx) and a recovery in the oxidative stress biomarker, lipid peroxidation (LPx). In addition, histopathological studies of liver, pancreas, kidney, and testes suggested that MTF-loaded LCS-ALG beads improved the degenerative changes in organs of diabetic rats. The LCS-ALG platform for dual encapsulation of MTF achieved sustained MTF delivery and enhancement of bioavailability, as well as the improved biochemical and histopathological characteristics in in vivo studies, opening many other intriguing applications in sustained drug delivery.

Plant Pollen Grains: A Move Towards Green Drug and Vaccine Delivery Systems

Pollen grains and plant spores have emerged as innovative biomaterials for various applications such as drug/vaccine delivery, catalyst support, and the removal of heavy metals. The natural microcapsules comprising spore shells and pollen grain are designed for protecting the genetic materials of plants from exterior impairments. Two layers make up the shell, the outer layer (exine) that comprised largely of sporopollenin, and the inner layer (intine) that built chiefly of cellulose. These microcapsule shells, namely hollow sporopollenin exine capsules have some salient features such as homogeneity in size, non-toxic nature, resilience to both alkalis and acids, and the potential to withstand at elevated temperatures; they have displayed promising potential for the microencapsulation and the controlled drug delivery/release. The important attribute of mucoadhesion to intestinal tissues can prolong the interaction of sporopollenin with the intestinal mucosa directing to an augmented effectiveness of nutraceutical or drug delivery. Here, current trends and prospects related to the application of plant pollen grains for the delivery of vaccines and drugs and vaccine are discussed.

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.

Pollen grains as a low-cost, green, alternative sorbent for hydrophilic solid-phase extraction

Many natural products have demonstrated functionality as novel, green sorbents for organic compounds. However, only limited reports exist on the use of such green materials as solid-phase extraction (SPE) sorbents for select organic acids. In this study, we employed pollen grains as a hydrophilic sorbent and investigated the influence of various extraction parameters using a series of experimental designs. The chemical structure and surface properties of the prepared sorbent were investigated by Fourier-transform infrared spectroscopy and scanning electron microscopy. The Plackett-Burman design was used to experimentally screen for parameters that significantly influenced the extraction performance. Three selected parameters were then statistically optimized by applying a central composite design combined with a response surface methodology. Phenolic acid residues were determined and quantified using high performance liquid chromatography with ultraviolet detection; a mass spectrometric detector in the selected ion monitoring mode was also used for identification. As a practical example, phenolic acids in the soil were successfully separated by the developed pollen sorbent. These results therefore indicate that pollen grains can be considered as a sustainable, green, and safe alternative to bare silica for extraction and separation applications.

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.

Apitherapy for Age-Related Skeletal Muscle Dysfunction (Sarcopenia): A Review on the Effects of Royal Jelly, Propolis, and Bee Pollen

The global pandemic of sarcopenia, skeletal muscle loss and weakness, which prevails in up to 50% of older adults is increasing worldwide due to the expansion of aging populations. It is now striking young and midlife adults as well because of sedentary lifestyle and increased intake of unhealthy food (e.g., western diet). The lockdown measures and economic turndown associated with the current outbreak of Coronavirus Disease 2019 (COVID-19) are likely to increase the prevalence of sarcopenia by promoting sedentarism and unhealthy patterns of eating. Sarcopenia has multiple detrimental effects including falls, hospitalization, disability, and institutionalization. Although a few pharmacological agents (e.g., bimagrumab, sarconeos, and exercise mimetics) are being explored in different stages of trials, not a single drug has been approved for sarcopenia treatment. Hence, research has focused on testing the effect of nutraceuticals, such as bee products, as safe treatments to prevent and/or treat sarcopenia. Royal jelly, propolis, and bee pollen are common bee products that are rich in highly potent antioxidants such as flavonoids, phenols, and amino acids. These products, in order, stimulate larval development into queen bees, promote defenses of the bee hive against microbial and environmental threats, and increase royal jelly production by nurse bees. Thanks to their versatile pharmacological activities (e.g., anti-aging, anti-inflammatory, anticarcinogenic, antimicrobial, etc.), these products have been used to treat multiple chronic conditions that predispose to muscle wasting such as hypertension, diabetes mellitus, cardiovascular disorder, and cancer, to name a few. They were also used in some evolving studies to treat sarcopenia in laboratory animals and, to a limited degree, in humans. However, a collective understanding of the effect and mechanism of action of these products in skeletal muscle is not well-developed. Therefore, this review examines the literature for possible effects of royal jelly, bee pollen, and propolis on skeletal muscle in aged experimental models, muscle cell cultures, and humans. Collectively, data from reviewed studies denote varying levels of positive effects of bee products on muscle mass, strength, and function. The likely underlying mechanisms include amelioration of inflammation and oxidative damages, promotion of metabolic regulation, enhancement of satellite stem cell responsiveness, improvement of muscular blood supply, inhibition of catabolic genes, and promotion of peripheral neuronal regeneration. This review offers suggestions for other mechanisms to be explored and provides guidance for future trials investigating the effects of bee products among people with sarcopenia.

Comparison of the Micromorphology and Ultrastructure of Pollen Grains of Selected Rubus idaeus L. Cultivars Grown in Commercial Plantation

The genus Rubus is one of the largest taxonomically diverse and complex genera in the family Rosaceae. Morphology of pollen grains (equatorial and polar axes length, shape and size, aperture position, exine sculpture, perforations) is regarded as one of its main diagnostic features for identification of species and varieties. An attempt was made to fill the gap concerning the pollen micromorphology and ultrastructure of R. idaeus L. using light, scanning, and electron transmission microscopy. This study is a comparative analysis of micromorphological and ultrastructural traits of pollen from six raspberry cultivars. The pollen grains were classified as small or medium of shape prolato-spheroids. The parallel striae in the equatorial view in the exine sculpture were sometimes branched dichotomously in ‘Glen Ample’, ‘Polka’, and ‘Polana’, arcuate in ‘Laszka’ and ‘Pokusa’, or irregularly overlapping in ‘Radziejowa’. The width of exine striae of biennial fruiting cultivars was much larger than in repeated fruiting cultivars. In terms of the increasing number of perforations per unit area of the exine surface, the cultivars were ranked as follows: ‘Pokusa’ < ‘Glen Ample’ < ‘Laszka’ < ‘Polka’ < ‘Polana’ < ‘Radziejowa’. The thickest tectum, the highest and thickest columellae with the largest distances between them, and the thicker foot layer were demonstrated in ‘Glen Ample’. The ectoexine constituted on average ca. 78–90% of the exine thickness. The findings may constitute auxiliary traits i.a. for identification of related taxa, interpretation of phylogenetic relationships, and pollination biology.

Juglans Sporopollenin for High-Performance Supercapacitor Electrode Design

Recently, plant pollen has been used as a source of activated carbon to produce carbon-containing supercapacitor electrodes. However, in this study, pollen was used as a biotemplate with a completely different approach. As a biotemplate, pollen offers a wide range of varieties in terms of exterior, porosity, shape, and size. An electrode formed by the use of metal oxide grown on the pollen exine layer (sporopollenin microcapsules) as the active substance will inevitably exhibit good electrochemical capacitive properties. Juglans male flowers have been distinguished by dissection from anthers. Isolation of pollen grains from anthers was carried out using sieving from suitable sieves (45-200 μm). Juglans sporopollenin exine microcapsules (SECs) were separated from the intine and protoplasm by acetolysis in combination with reflux. The solution containing SECs, metal ions, and Ni foam was put into a Teflon-lined hydrothermal container, and then, it was reacted at 120 °C for 15 h. The resulting precipitate, as well as the Ni foam, was heat-treated at 300 and 360 °C for 3 h in air. The raw pollen, chemically treated pollen, and cobalt-coated SEC (CoSEC) and CoSEC/Ni foam were characterized using scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, thermogravimetric analysis, and X-ray diffraction techniques. Two different types of supercapacitor electrode designs, with the use of exine microcapsules of Juglans sporopollenin, were performed for the first time. The maximum specific capacitance was up to 1691 F g^-1 at 5 A g^-1.

Fe-functionalized paramagnetic sporopollenin from pollen grains: one-pot synthesis using ionic liquids

The preparation of Fe-decorated sporopollenins was achieved using pollen grains and an ionic liquid as solvent and functionalizing agent. The integrity of the organic capsules was ascertained through scanning electron microscopy studies. The presence of Fe in the capsule was investigated using FT-IR, X-ray photoemission spectroscopy and energy-dispersive X-ray spectroscopy. Electron paramagnetic resonance and magnetization measurements allowed us to demonstrate the paramagnetic behavior of our Fe-functionalized sporopollenin. A few potential applications of pollen-based systems functionalized with magnetic metal ions via ionic liquids are discussed.

Actuation and locomotion driven by moisture in paper made with natural pollen

Much progress has been made in developing bioinspired sensors and actuators based on engineered synthetic materials, although there remains a critical need to incorporate cost-effective and eco-friendly materials. Here naturally abundant pollen grains are used as a material template to produce paper that sensitively and reversibly responds as an actuator to variations in environmental humidity. The actuating properties of the all-natural paper are readily tuned by material characteristics, such as sheet thickness and surface roughness. We demonstrate self-actuation of the pollen-based paper by mimicking flower blooming. The results presented here point to pathways for the creation of self-propelled robots, flexible electronics, and multifunctional devices. They also offer the potential for digital printing and fabrication of complex and programmable natural actuators.

Here we describe the development of a humidity-responsive sheet of paper that is derived solely from natural pollen. Adaptive soft material components of the paper exhibit diverse and well-integrated responses to humidity that promote shape reconfiguration, actuation, and locomotion. This mechanically versatile and nonallergenic paper can generate a cyclically high contractile stress upon water absorption and desorption, and the rapid exchange of water drives locomotion due to hydrodynamic effects. Such dynamic behavior can be finely tuned by adjusting the structure and properties of the paper, including thickness, surface roughness, and processing conditions, analogous to those of classical soapmaking. We demonstrate that humidity-responsive paper-like actuators can mimic the blooming of the Michelia flower and perform self-propelled motion. Harnessing the material properties of bioinspired systems such as pollen paper opens the door to a wide range of sustainable, eco-friendly, and biocompatible material innovation platforms for applications in sensing, actuation, and locomotion.

Plant exine capsules based encapsulation strategy: A high loading and long-term effective delivery system for nobiletin

The properties of high loading capacity and long-term absorption are of great significance in the field of nutraceuticals or drugs delivery. Herein, we developed an innovative method to achieve these expected effects using plant exine capsules, a kind of natural pollen grains, which could provide large internal cavities for loading and robust exine against harsh conditions. In our work, we firstly made a soluble mixture of glycerol monostearate (GM) and nobiletin (NOB) inside the cavities of plant exine capsules by ultrasound with high temperature to obtain a supersaturated state of NOB, which could be characterized by XRD, DSC and FTIR. After that, the loaded capsules were cooled to room temperature. Alginate hydrogels were then selected for encapsulating and further controlling NOB release in simulated gastric and intestinal conditions. As a result, it demonstrated that our approach was able to reach an extremely high NOB loading capacity of 770 ± 40 mg/g using sunflower pollen grains (SPGs). Meanwhile, the existence of GM, SPGs and alginate hydrogels all retarded the release of the NOB synergistically, thus taking a slow release effect in the stomach while a long-term effective absorption in the intestine. Taken together, our processing method of encapsulating hydrophobic nutraceuticals provides an important insight for broadening the applications of nutraceutical or drug encapsulation and delivery.

A natural solution to photoprotection and isolation of the potent polyene antibiotic, marinomycin A

The photoprotection and isolation of marinomycin A using sporopollenin exine capsules (SpECs) derived from the spores of the plant Lycopodium clavatum is described. The marinomycins have a particularly short half-life in natural light, which severely impacts their potential biological utility given that they display potent antibiotic and anticancer activity. The SpEC encapsulation of the marinomycin A dramatically increases the half-life of the polyene macrodiolide to the direct exposure to UV radiation by several orders of magnitude, thereby making this a potentially useful strategy for other light sensitive bioactive agents. In addition, we report that the SpECs can also be used to selectively extract culture broths that contain the marinomycins, which provides a significantly higher recovery than with conventional XAD resins and provides concomitant photoprotection.

Carboxymethylpachymaran entrapped plant-based hollow microcapsules for delivery and stabilization of β-galactosidase

β-Galactosidase (β-Gal) as a dietary supplement can alleviate symptoms of lactose intolerance. However, β-Gal is deactivated due to the highly acidic conditions and proteases in the digestive tract. In this work, β-Gal was encapsulated into L. clavatum sporopollenin exine capsules (SECs) to fabricate an oral-controlled release system and increase the stability of β-Gal in the digestive tract. The SEC extraction process was optimized. A 3-hour vacuum loading was determined as the optimal loading time. Five different initial ratios of SECs : β-Gal were optimized with the maximum enzyme retention rate reaching 79.40 ± 1.96%. Furthermore, β-Gal-loaded SECs entrapped in carboxymethylpachymaran (CMP) could control the release of β-Gal under simulated gastrointestinal conditions (SGC). The optimal enzyme retention rate reached 65.33 ± 1.46% within 24 h under SGC. Collectively, these results indicated that the entrapped SECs could be used as an effective oral delivery vehicle of β-Gal to improve its performance as a dietary supplement in the digestion of lactose.

Nanoparticle Encapsulation Strategy: Leveraging Plant Exine Capsules Used as Secondary Capping for Oral Delivery

Protein-based nanoparticles (NPs) with favorable properties including enhanced absorptivity and low toxicity still suffer a major challenge for rapid nutraceutical or drug release after oral administration. Hence, we introduced a secondary encapsulation for unstable factor to attain a controlled-release effect in a gastrointestinal environment. In this work, assembled nanoparticles engineered by nobiletin (NOB), zein, and tannin acid (TA) were first reported for drug delivery systems. The TA added was capable of obtaining further assembly to stabilize nobiletin in comparison with NOB-loaded zein NPs only. Sunflower pollens (SPGs) were selected as carriers for further oral delivery, while zein was chosen as a coating material for capping SPGs absolutely. As a result, the NOB/zein/TA NPs (NZT NPs) obtained had a stable size of 100 nm after 48 h. Besides, they could improve the chemical stability of NOB for at least 120 days at 4 °C compared with zein NPs (ZT NPs). Owing to the secondary capping by SPGs, the final system was able to release selectively via an oral route, that is, achieving no release in a gastric environment and slow release in an intestine environment. Generally, our research proposed a secondary protection model to prevent drug-loaded NPs from resolving after oral administration, which provided a new perspective for nutraceutical or drug encapsulation and controlled-release delivery.

Species-Specific Biodegradation of Sporopollenin-Based Microcapsules

Sporoderms, the outer layers of plant spores and pollen grains, are some of the most robust biomaterials in nature. In order to evaluate the potential of sporoderms in biomedical applications, we studied the biodegradation in simulated gastrointestinal fluid of sporoderm microcapsules (SDMCs) derived from four different plant species: lycopodium (Lycopodium clavatum L.), camellia (Camellia sinensis L.), cattail (Typha angustifolia L.), and dandelion (Taraxacum officinale L.). Dynamic image particle analysis (DIPA) and field-emission scanning electron microscopy (FE-SEM) were used to investigate the morphological characteristics of the capsules, and Fourier-transform infrared (FTIR) spectroscopy was used to evaluate their chemical properties. We found that SDMCs undergo bulk degradation in a species-dependent manner, with camellia SDMCs undergoing the most extensive degradation, and dandelion and lycopodium SDMCs being the most robust.

Investigation of the Fate of Proteins and Hydrophilicity/Hydrophobicity of Lycopodium clavatum Spores after Organic Solvent-Base-Acid Treatment

Microcapsules extracted from lycopodium ( Lycopodium clavatum) spores have been increasingly used as an oral therapeutic carrier. A series of sequential treatments involving acetone, KOH, and H₃PO₄ are used to extract a protein-free hollow microcapsule. This study focuses on two critical aspects of lycopodium spores: the fate of native proteins and the wettability of the spores after a chemical treatment. Protein-free spores are desired to prevent an allergic reaction, whereas the wettability is critical for the formulation development. Although the chemically treated lycopodium spores are generally regarded as protein free, the studies that have reported this have not gone into significant depths to understand the nature of residual nitrogen observed even in spores thought to be protein free. Wettability of spores has not received any significant attention. Accordingly, in this study, we performed a comprehensive analysis of natural spores and spores after each chemical treatment step. We show that natural lycopodium spores are hydrophobic and contain low-molecular-weight proteins (∼10 kD). Acetone treatment partially solubilizes unsaturated phospholipids from the spores. Nevertheless, the acetone-treated spores retain native proteins and are still hydrophobic. KOH treatment, however, removes a significant amount of proteins and partially hydrolyzes esters to carboxylic acid salts and results in a hydrophilic spore with a good wettability. Finally, we show that the H₃PO₄ treatment removes residual proteins, hydrolyzes remaining esters to carboxylic acids, and dissolves carbohydrates. H₃PO₄ treatment temperature controls carbohydrate dissolution, which in turn affects the hydroxyl functional groups and hydrophilicity (wettability) of the treated spores. Spores treated at 60 °C as opposed to 160 °C are amphiphilic in nature due to the abundance of hydroxyl functional groups on the surface. In conclusion, this study confirms the removal of native proteins from treated spores and sheds light on the chemical changes that the spores undergo after chemical treatment and correlates these changes to their wettability.

Controlled generation of spiky microparticles by ionic cross-linking within an aqueous two-phase system

Microparticles are used in a variety of different fields, such as drug delivery. Recently, non-spherical microparticle generation has become desirable. The high surface-to-volume ratio of non-spherical microparticles allows for enhanced targeting, and attachment to cells and tissue. Current non-spherical microparticle generation techniques require complicated setup, and utilizing natural micrograins, such as pollen grains, as non-spherical delivery vehicles, requires extensive post-processing. Here, we describe a unique and facile chemical synthesis approach, for controlled generation of pollen-like microparticles, based on ionic cross-linking of alginate and calcium chloride (CaCl2), within an all-biocompatible aqueous two-phase system (ATPS) of dextran (DEX) and polyethylene glycol (PEG). Our technique controls the length of spikes that emerge on the surface of these microparticles. We anticipate that these pollen-like spiky microparticles may be used as drug delivery vehicles, and this new chemical synthesis approach may be used for generating other biomaterials.

Multifunctional Hierarchically-Assembled Hydrogel Particles with Pollen Grains via Pickering Suspension Polymerization

Hierarchical assembly of heterogeneous particles is of great importance to interface and colloid science. In this work, a facile but powerful approach for the large-scale production of multifunctional hydrogel particles armored with biological colloidal species is developed by combining Pickering stabilization and photopolymerization. Biocompatible hollow pollen grains extracted from naturally occurring pollen species with an average diameter of ∼32 μm serve as universal solid emulsifiers dispersed in an oil phase and are self-assembled at the interface between an oil phase and a photo-cross-linkable hydrogel to make water-in-oil (W/O) emulsion droplets. While droplets are solidified into hydrogel particles by UV-induced free-radical polymerization, self-assembled hollow pollen grains are transformed to a robust shell on hydrogel particles with supracolloidal structures. The physically adsorbed hollow pollen grains on the hydrogel core can be released by a hydration-induced swelling of hollow pollen grains, leading to a transient floating behavior of core-shell particles. The size of the resultant core-shell particles is easily controlled by tailoring the process parameters such as a liquid volume or a loading mass of hollow pollen grains. The incorporation of magnetic or upconverting luminescent nanoparticles into a hydrogel core successfully expands the functionality of core-shell particles that can provide new design opportunities for floating drug delivery or ecofriendly proppants.

Pollen grains as a novel microcarrier for oral delivery of proteins

Oral delivery of proteins and peptides is a challenge due to their degradation in the stomach. To overcome this challenge, ragweed (Ambrosia elatior) pollen grains were engineered to serve as protective microcapsules. A matrix comprising of Eudragit L100-55, an enteric polymer was deposited on the inner surfaces of ragweed pollens to protect the encapsulated protein from gastric degradation and to achieve pH-dependent release in the intestine. The Eudragit L100-55 matrix was formed without use of organic solvents so that solvent-induced damage to protein molecules could be prevented. To demonstrate the concept, bovine serum albumin (BSA) a model protein was used. A matrix of Eudragit L100-55 embedded with BSA was prepared in ragweed pollens by optimizing their respective concentrations for maximizing BSA loading in the matrix. The ability of this optimized formulation to protect BSA in simulated gastric acid fluid was evaluated. Release studies in simulated gastric fluid (pH 1.2) showed minimal BSA release from the ragweed-Eudragit L100-55 formulation. Analysis of BSA retained in the formulation after its exposure to gastric fluid confirmed that the residual BSA had not denatured. Release studies in the simulated intestinal fluid (pH 6.8) showed that ragweed pollen offered additional controlled release mechanism within the first few hours of release by virtue of their solid wall. In conclusion, upon use of a protein-friendly solvent for Eudragit L100-55, proteins could be encapsulated in ragweed pollen without denaturing them, and the resulting formulation exhibited selective release of the proteins at intestinal pH suggesting that the ragweed pollen grain-based formulation could be promising for oral delivery of proteins.

Observation of Mie ripples in the synchrotron Fourier transform infrared spectra of spheroidal pollen grains

Conceptually, biological cells are dielectric, photonic resonators that are expected to show a rich variety of shape resonances when exposed to electromagnetic radiation. For spheroidal cells, these shape resonances may be predicted and analyzed using the Mie theory of dielectric spheres, which predicts that a special class of resonances, i.e., whispering gallery modes (WGMs), causes ripples in the absorbance spectra of spheroidal cells. Indeed, the first tentative indication of the presence of Mie ripples in the synchrotron Fourier transform infrared (SFTIR) absorbance spectra of Juniperus chinensis pollen has already been reported [Analyst140, 3273 (2015)ANLYAG0365-488510.1039/C5AN00401B]. To show that this observation is no isolated incidence, but a generic spectral feature that can be expected to occur in all spheroidal biological cells, we measured and analyzed the SFTIR absorbance spectra of Cunninghamia lanceolata, Juniperus chinensis, Juniperus communis, and Juniperus excelsa. All four pollen species show Mie ripples. Since the WGMs causing the ripples are surface modes, we propose ripple spectroscopy as a powerful tool for studying the surface properties of spheroidal biological cells. In addition, our paper draws attention to the fact that shape resonances need to be taken into account when analyzing (S)FTIR spectra of isolated biological cells since shape resonances may distort the shape or mimic the presence of chemical absorption bands.

The atypically high modulus of pollen exine

Sporopollenin, the polymer comprising the exine (outer solid shell) of pollen, is recognized as one of the most chemically and mechanically stable naturally occurring organic substances. The elastic modulus of sporopollenin is of great importance to understanding the adhesion, transport and protective functions of pollen grains. In addition, this fundamental mechanical property is of significant interest in using pollen exine as a material for drug delivery, reinforcing fillers, sensors and adhesives. Yet, the literature reports of the elastic modulus of sporopollenin are very limited. We provide the first report of the elastic modulus of sporopollenin from direct indentation of pollen particles of three plant species: ragweed (Ambrosia artemisiifolia), pecan (Carya illinoinensis) and Kentucky bluegrass (Poa pratensis). The modulus was determined with atomic force microscopy by using direct nanomechanical mapping of the pollen shell surface. The moduli were atypically high for non-crystalline organic biomaterials, with average values of 16 ± 2.5 GPa (ragweed), 9.5 ± 2.3 GPa (pecan) and 16 ± 4.0 GPa (Kentucky bluegrass). The amorphous pollen exine has a modulus exceeding known non-crystalline biomaterials, such as lignin (6.7 GPa) and actin (1.8 GPa). In addition to native pollen, we have investigated the effects of exposure to a common preparative base-acid chemical treatment and elevated humidity on the modulus. Base-acid treatment reduced the ragweed modulus by up to 58% and water vapour exposure at 90% relative humidity reduced the modulus by 54% (pecan) and 72% (Kentucky bluegrass). These results are in agreement with recently published estimates of the modulus of base-acid-treated ragweed pollen of 8 GPa from fitting to mechanical properties of ragweed pollen-epoxy composites.

Macromolecular Microencapsulation Using Pine Pollen: Loading Optimization and Controlled Release with Natural Materials

Pine pollen offers an all-natural multicavity structure with dual hollow air sacs, providing ample cargo capacity available for compound loading. However, the pollen exhibits reduced permeability because of the presence of a thin natural water-proofing layer of lipidic compounds. Herein, we explore the potential for compound loading within pine pollen and the potential for developing all-natural formulations for targeted delivery to the intestinal tract. Removal of the surface-adhered lipidic compounds is shown to improve surface wetting, expose nanochannel structures in the outer pollen shell and enhance water uptake throughout the whole pollen structure. Optimization of loading parameters enabled effective compound loading within the outer pollen shell sexine structure, with bovine serum albumin (BSA) serving as a representative protein. All-natural oral delivery formulations for targeted intestinal delivery are developed based on tableting of BSA-loaded defatted pine pollen, with the incorporation of xanthan gum as a natural binder, or ionotropically cross-linked sodium alginate as an enteric coating. Looking forward, the large cargo capacity, ease of compound loading, competitive cost, abundant availability, and extensive historical usage as food and medicine make pine pollen an attractive microencapsulant for a wide range of potential applications.

A chemical treatment method for obtaining clean and intact pollen shells of different species

Pollen grains and plant spores have emerged as a novel biomaterial for a broad range of applications including oral drug and vaccine delivery, catalyst support, and removal of heavy metals. However, before pollens can be used, their intrinsic biomolecules, which occupy a large part of the pollen inner cavity must be removed not only to create empty space but because they have potential to cause allergies when used in vivo. These intrinsic materials in the pollen core can be extracted through a chemical treatment to generate clean pollen shells. The commonly used method involves a series of sequential treatments with organic solvents, alkalis, and acids to remove the native pollen biomolecules. This method, though successful for treating lycopodium (Lycopodium clavatum) spores, fails for other species of pollens such as common ragweed (Ambrosia elatior) and thus prevents widespread investigation of different pollens. Herein, we report a new chemical treatment for obtaining clean pollen shells from multiple plant species. This new method involves sequential treatment with acetone, phosphoric acid, and potassium hydroxide. Scanning electron micrographs and protein quantification have shown that the new method can successfully produce clean, intact, and hollow shells from many pollen species including ragweed, sunflower, black alder, and lamb's quarters. These results demonstrate the broad applicability of this method to clean pollens of different species, and paves the way to start investigating them for various applications.

Microwave assisted one-pot green synthesis of cinnoline derivatives inside natural sporopollenin microcapsules

We present a green and efficient approach for the synthesis of novel cinnoline derivatives inside natural Lycopodium clavatum sporopollenin (LCS) microcapsules via a one-pot microwave (MW) assisted reaction for the first time. We also propose the concept that the robust micrometre-sized sporopollenin microcapsules can act as MW microreactors. We demonstrate the feasibility of this concept by in situ synthesising 8-hydroxy-7-nitro-6-(3-nitrophenyl)-3-oxo-2-(p-tolyl)-2,3,5,6-tetrahydrocinnoline-4-carbonitrile inside the LCS microcapsules via a microwave (MW) assisted reaction of ethyl 5-cyano-4-methyl-6-oxo-1-(p-tolyl)-1,6-dihydropyridazine-3-carboxylate with 1-nitro-2-phenylethylene in the presence of piperidine as a base at 100 °C for 20 minutes. The LCS microparticles are extensively characterised before and after the MW induced reaction using several techniques. The formation of the cinnoline compound inside the LCS microcapsules is confirmed by laser scanning confocal microscopy (LSCM), X-ray diffraction (XRD) and fourier-transform infrared spectroscopy (FTIR) analyses. Using liquid chromatography-mass spectrometry (LCMS) analyses, we show that the structural integrity of the cinnoline compound, recovered from the cinnoline loaded (cinn-loaded) LCS, is preserved. The pure cinnoline is found to show promising optical properties with two λ_max absorption peaks at 310 and 610 nm. Both the pure cinnoline and cinn-loaded LCS show promising antibacterial activity against Pseudomonas aeruginosa (Gram-negative) and Bacillus cereus (Gram-negative) human pathogenic bacterial strains. The successful MW induced reaction of the prominent cinnoline derivative inside the biocompatible LCS microreactors can open up intriguing applications in materials and pharmaceutical sciences.

We have achieved in situ microwave assisted green syntheses of a novel cinnoline derivative inside natural sporopollenin microreactors.

Encapsulation of erythromycin and bacitracin antibiotics into natural sporopollenin microcapsules: antibacterial, cytotoxicity, in vitro and in vivo release studies for enhanced bioavailability

Nature produces large quantities of superbly complex and highly reliable microcapsules. The micrometre-sized Lycopodium clavatum spores are one example of these robust capsules. The encapsulation of erythromycin (EM) and bacitracin (BAC) antibiotics into the Lycopodium clavatum sporopollenin (LCS) extracted from these spore species is explored for the first time. The LCS microparticles are extensively characterised before and after loading using SEM, CLSM, TGA and FTIR techniques. The loading capacity and entrapping efficiency of EM were 16.2 and 32.4%, respectively. The antibacterial activities of pure antibiotics, empty LCS and the antibiotic-loaded LCS were evaluated against Staphylococcus aureus (Gram-positive), Pseudomonas aeruginosa (Gram-negative), and Klebsiella pneumoniae (Gram-negative) human pathogenic bacterial strains. A remarkable increase in the antibacterial fold activity of both EM- and BAC-loaded LCS compared to that of the pure antibiotics is observed. Crucial for drug delivery applications, empty LCS, EM- and BAC-loaded LCS were found to be nontoxic against human epithelial colorectal adenocarcinoma cells Caco-2 as revealed by the cytotoxicity evaluation. The in vitro release mechanism of EM in pH 7.4 showed a deviation from Fick's law. In vivo release of EM from EM-loaded LCS (an oral dose of 50 mg kg⁻¹) revealed high values of the area under the plasma concentration–time curve (AUC_{0–6 h} and AUC_0–∞ were 1620 and 2147 μg h L⁻¹, respectively) indicative of the enhanced EM bioavailability. The successful loading of antibiotics into the nontoxic LCS and the enhanced bioavailability can open up intriguing applications in oral and topical drug delivery strategies.

Antibacterial activity and bioavailability of antibiotics are enhanced after a successful loading into nontoxic natural Lycopodium clavatum sporopollenin microcapsules.

Ragweed pollen as an oral vaccine delivery system: Mechanistic insights

We have recently developed pollen grains (PGs) as a unique method to deliver vaccines orally. Extensive chemical processing ensures allergen-free pollen microcapsules that can be loaded with vaccine antigens. Successful oral vaccine delivery has been previously demonstrated by us in a mouse model. However, the underlying mechanisms that help the processed PGs to achieve this goal were not fully understood. In this study, we wanted to understand the effects of chemically processed ragweed pollen (Ambrosia elatior) on the innate immune system. Intestinal epithelial cells, macrophages, and dendritic cells all bridge the innate and adaptive immunity. This study has shown that in response to ragweed pollen all these cells release inflammatory cytokines and chemokines. Scanning electron microscopy imaging revealed that macrophages can engulf ragweed pollen. In addition, in the presence of ragweed, mouse dendritic cells upregulated their activation markers, that is, CD40, CD80, CD86, and MHC class II molecules. Ragweed pollens did not cause significant cell membrane damage as compared to similarly sized poly (lactic-co-glycolic acid) particles. Moreover, ragweed did not affect the integrity of the intestinal epithelial cells. Ragweed pollens were also found in the subepithelial region of the small intestine 24h after pollens were gavaged to mice. Our current findings lead to the conclusion that besides transporting the vaccine cargo, ragweed pollen shells have additional immunomodulatory properties that help the orally delivered antigen to effectively induce an immune response.