Therapeutic potential of zein-based nanoparticles

Resumen

The project of this doctoral thesis was focused on the development, characterization, and evaluation of nanoparticles made of a vegetal protein intended for the oral delivery of biomacromolecules. The project was divided in 4 scientific chapters. The first chapter was focused on the development and characterization of empty nanoparticles with a mucus-diffusive behavior. For that purpose, bare nanoparticles were decorated with a hydrophilic polymer at different ratios. The main physico-chemical properties of the resulting nanoparticles were evaluated, as well as their capability to diffuse in pig intestinal mucus and their biodistribution following oral administration. The second chapter aimed to evaluate the potential hypoglycemic effect of the empty nanoparticles. For that purpose, empty nanoparticles, either naked or coated with the hydrophilic polymer, were orally administered to two different animal models: C. elegans and healthy rats. In C. elegans, the supplementation of the growth medium with empty nanoparticles induced a decrease in the fat accumulation inside the worm, which is closely related to the glucose metabolism. In healthy rats, the oral administration nanoparticles induced a hypoglycemic effect, which was demonstrated to be caused by an increase in the secretion of insulin and incretins. The objective of the third chapter was to evaluate whether the hypoglycemic effect observed for orally administered empty nanoparticles could lead to some health benefits in two animal models: C. elegans and the senescence accelerated mouse prone-8 (SAMP8 mice). The supplementation of the growth medium of C. elegans with empty nanoparticles induced a significant increase in the lifespan of the worms. In SAMP8 mice, an animal model used for the study of dementia and Alzheimer s Disease, the oral administration of the empty nanoparticles every two days did not induce a cognitive or behavioral improvement. Interestingly, animals receiving a suspension of bare nanoparticles, but not coated nanoparticles, experienced a significant expansion on the lifespan. The last chapter of the project was focused on the evaluation of mucoadhesive and mucus-permeating nanoparticles as oral carriers for insulin delivery. Insulin was loaded in the nanoparticles and the main physico-chemical properties, as well as the insulin payloads and release profiles, of the resulting formulations were evaluated. The cytotoxicity of the systems were evaluated against two different cellular lines: Caco-2 and HT29-MTX. Finally, the efficacy of the formulations was evaluated in C. elegans and diabetic rats. The encapsulation of insulin increased the size and slightly decreased the surface zeta potential of the resulting nanoparticles. The coating of insulin-loaded nanoparticles with the polymer did not significantly alter the surface zeta potential or the release profiles of the resulting nanoparticles. The safety of the formulations, assessed in the cellular models, showed no toxicity of the systems. Finally, the oral administration of insulin-loaded nanoparticles induced a hypoglycemic effect that lasted for at least 6 hours. Nevertheless, insulin-loaded nanoparticles coated with the hydrophilic polymer induced a more potent hypoglycemic effect and a better oral bioavailability of insulin than bare nanoparticles. In summary, nanoparticles can be formulated using a vegetal protein and coated with a hydrophilic polymer to increase their mucus diffusivity and to modify their behavior upon oral administration. Hence, these formulations could become a suitable device for oral administration of therapeutic biomacromolecules. In addition, empty nanoparticles showed promising health benefits in laboratory animals, what could make of them a therapeutic tool.