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

Abstract

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. "Image missing"

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

“…It was reported that natural raw pollens of Lycopodium clavatum and date palm have been used in traditional herbal therapy since they contain promising phytochemicals [ 61 , 62 , 75 ]. In addition, it was shown that both raw pollens and their extracts, that constitute the allergens, did not cause oral hyposensitization in allergic subjects, suggesting the safety of raw pollens [ 55 , 76 ]. Interestingly, it was revealed that sporopollenin of Lycopodium clavatum formulated with ovalbumin, a model antigen, stimulated a “systemic and a mucosal immune response” following oral administration to mice [ 76 ].…”

“…Here, we explore their feasibility in improving MTF sustainable and targeted in vitro and in vivo delivery, thus enhancing its pharmacokinetic properties and bioavailability. Natural sporopollenin microcapsules, the outer shells derived from raw pollens such as Lycopodium clavatum, have recently emerged as an alternative efficacious encapsulation platform for drugs [ 52 , 53 , 54 , 55 ], live cells [ 56 ], probiotics [ 57 ], pollen microgels [ 58 ], proteins [ 59 ], and vaccines [ 60 ]. Being natural biomaterials, these cost-effective sporopollenin microcapsules demonstrated several properties such as robustness, chemical resilience, unique surface ornaments, size uniformity, abundancy, and biocompatibility.…”

Magnetic bio-hybrid micro actuators

“…Derivatives of cellwalled organisms such as plants and fungi have been used to fabricate actuators because of their renewability, low harvest cost, thermal stability, and diverse structural morphology. 84,85 For example, Liu et al manufactured a porous magnetic micromotor based on Kapok fibers, hollow tubular structures. 51 The motor's manganese dioxide coating allowed for hydrogen peroxide fuelled actuation, while iron/aluminum metal oxides permitted guidance by an external magnetic field to remove organic pollutants from water.…”

Plant‐Actuated Micro–Nanorobotics Platforms: Structural Designs, Functional Prospects, and Biomedical Applications

“…The hollow sporopollenin exine shells provide some notable features, such as homogenous size, nontoxic nature, high resistance to alkalis and acids, and ability to withstand elevated temperatures, which are beneficial for microencapsulation and controlled drug delivery and release. [ 109 ]…”