Investigating human IgE antibody interactions with pollen-derived sporopollenin biopolymers: immunoreactivity profiling for the rational design of structurally robust and biocompatible biomaterials

Pollen grains are being explored as innovative biomaterials for different applications, ranging from oral drug delivery to encapsulation of food additives, with the production of pollen-based building blocks standing on its robust, chemically inert, and mechanically durable sporopollenin wall. Yet, concerns remain regarding the safety of sporopollenin microcapsules (SMCs) or derivatized sporopollenin materials purified from pollen grains, traditionally linked to allergies. Herein, we address the critical question of whether sporopollenin shells purified from bee pollen may cause allergic reactions by evaluating their interaction with human immunoglobulin E (IgE) antibodies in sera from patients with and without allergic sensitization to pollen of specific species. Clean SMCs from<i>Castanea sativa</i>, Amaranthaceae (<i>Chenopodium album</i>), and<i>Olea europaea</i>pollen grains were successfully produced using a species-independent chemical treatment and characterized. The Covaris Adaptive Focused Acoustics™ (AFA) technology was employed for protein extraction from the bee pollen and the SMCs, yielding 0.72-1.25 ng and 0.026 ng-0.028 ng of protein per pollen grain, respectively. X-ray photoelectron spectroscopy (XPS) analysis also confirmed that the surface nitrogen content of the SMCs was minimal, ranging from 0.9% to 2.7%. SDS-PAGE, followed by immunoblotting analysis, showed that proteins extracted from bee pollen strongly reacted with IgE antibodies in human sera, whereas SMCs did not trigger allergic sensitization. Overall, our findings suggest that while bee pollen proteins could elicit allergic reactions in sensitive patients, SMCs do not, highlighting their potential as safe biomaterials for various applications and offering valuable insights into the allergenic potential of bee pollen.