Purification of Hollow Sporopollenin Microcapsules from Sunflower and Chamomile Pollen Grains.

Jose Manuel Ageitos,Jose Manuel Ageitos,Noemi Csaba,Marcos Garcia-Fuentes,Sandra Robla,Sandra Robla,Lorena Valverde-Fraga,Lorena Valverde-Fraga

doi:10.3390/polym13132094

Abstract

Pollen grains are natural microcapsules comprised of the biopolymer sporopollenin. The uniformity and special tridimensional architecture of these sporopollenin structures confer them attractive properties such as high resistance and improved bioadhesion. However, natural pollen can be a source of allergens, hindering its biomedical applicability. Several methods have been developed to remove internal components and allergenic compounds, usually involving long and laborious processes, which often cannot be extended to other pollen types. In this work, we propose an abridged protocol to produce stable and pristine hollow pollen microcapsules, together with a complete physicochemical and morphological characterization of the intermediate and final products. The optimized procedure has been validated for different pollen samples, also producing sporopollenin microcapsules from Matricaria species for the first time. Pollen microcapsules obtained through this protocol presented low protein content (4.4%), preserved ornamented morphology with a nanoporous surface, and low product density (0.14 g/cm3). These features make them interesting candidates from a pharmaceutical perspective due to the versatility of this biomaterial as a drug delivery platform.

Highlights

Pollen grains are protective microcapsules of the male gametes of seed plants, involved in dispersion and adhesion, as well as recognition, during pollination and fertilization processes [1]
Sunflower pollen grains are composed by a multilayer structure covered by an external layer named pollenkitt
To study the components removed on each step, both the purification extracts and pollen were studied by SEM and Fourier Transform Infrared Spectroscopy (FTIR) analyses (Figure 2E), techniques widely employed for the identification of pollen species and biomaterials [30,31,32]

Summary

Introduction

Pollen grains are protective microcapsules of the male gametes of seed plants, involved in dispersion and adhesion, as well as recognition, during pollination and fertilization processes [1]. These natural microcapsules are composed by several layers of different lipidic and polymeric materials that confer them unique, plant-specific morphologies [2]. The exine is mainly composed by sporopollenin, one of the most resistant biopolymers found in nature, still part of 500-million-year-old sedimentary rocks [5,6] This biomaterial is considered a keystone in the adaptation of early aquatic plant gametes to terrestrial life [7]. In addition to its unique chemical composition, pollen exine has a complex tridimensional structure with ornaments and nanopores, naturally designed for interacting with different biological surfaces, such as insect cuticula, animals, and plant tissues

Methods

Results

Conclusion