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.