Zein nanoparticles as low-cost, safe, and effective carriers to improve the oral bioavailability of resveratrol.

The clinical translation of the multiple pharmacological effects of resveratrol (RSV) found in preclinical studies has been impaired by its poor bioavailability, due to poor solubility and rapid metabolism and elimination. The inclusion of this molecule in medicines or functional food products will be ineffective unless suitable systems are developed. Zein protein may constitute an inexpensive, safe, and effective choice to produce nanoparticles (NPs) to incorporate hydrophobic molecules and overcome the bioavailability issues of RSV. In this work, we loaded RSV into zein NPs by using a nanoprecipitation method. Unloaded and RSV-loaded NPs presented average diameter values in the range of 120-180 nm, narrow size distribution (polydispersity index < 0.150), and zeta potential of around + 20 mV. The association efficiency of the drug was equal to or greater than 77% for different initial drug loads. Scanning electron microscopy imaging revealed that zein NPs were round-shaped and presented a smooth surface. Aqueous suspensions of zein NPs were stable for at least 1 month when stored at 4 °C. The freeze-drying of zein NPs using sucrose as cryoprotectant allowed an easy re-suspension of NPs in water without significantly changing the initial colloidal properties. RSV-loaded NPs presented low cytotoxicity to the human colorectal Caco-2 and HT29-MTX cell lines. Finally, permeability studies of RSV across Caco-2 and Caco-2/HT29-MTX evidenced some ability of zein NPs to protect RSV from metabolism events. However, further investigation is needed in order to confirm the possible role of zein NPs in the metabolic stability of RSV. Overall, zein NPs may present the potential to circumvent bioavailability issues of RSV. Graphical abstract.