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% AlCl 3 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.
There
are multiple obstacles for the storage and digestion of orally
administered bioactive macromolecules. This study developed a low-cost
and sustained-release delivery system (sporopollenin exine capsules
with zein/tannic acid modification) of proteins with excellent storage
stability, and at the same time provided insights into the sustained-release
mechanism through exploring the interaction between zein and tannic
acid (TA). β-Galactosidase (β-Gal) was utilized as a model
protein and loaded into sporopollenin exine capsules (SECs), which
were then coated with the zein/TA system. Under the optimized zein/TA
conditions, the zein/TA system showed better performance than the
zein alone system in the sustained release of β-Gal, with the
residual activity of about 70.26% after 24 h of simulated digestion.
Evaluation of the storage stability demonstrated a β-Gal residual
activity of nearly 90% for 28 days at 25 °C. Additionally, FTIR
analysis demonstrated that the stability of the zein/TA system depends
on both hydrogen bonding and certain covalent bonding through the
Schiff-base reaction, and the sustained release is regulated by the
bonding strength.
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