Design and characterization of ellagic acid-loaded zein nanoparticles and their effect on the antioxidant and antibacterial activities

Ellagic acid (EA) has demonstrated remarkable antioxidant and antimicrobial activities. The corn protein zein is a natural biopolymer whose biological and functional properties encourage its use to improve therapeutic nano drug delivery systems. In this study, we aimed to design and characterize EA-loaded zein nanoparticles and to evaluate the impact of nanoencapsulation in the antioxidant and antibacterial properties. The nanoparticles were produced by nanoprecipitation and evaluated in terms of morphology, size, polydispersity, zeta potential, encapsulation efficiency and drug loading. The chemical interactions between EA and zein were studied by FTIR, 1H STD-NMR and Fluorescence spectroscopy. Antioxidant activity was quantified using the DPPH and ABTS radical scavenging methods, while antimicrobial activity was determined in terms of inhibitory, bactericide and antibiofilm assays against Staphylococcus aureus and Pseudomonas aeruginosa. EA-loaded zein nanoparticles were spherical, non-aggregated, below 370 nm and positively charged. Selected nanoparticles showed relevant inhibitory and bactericide activity against S. aureus and P. aeruginosa (MIC < 72 µg/mL). The antioxidant activity (IC50) for the nanoencapsulated EA were 56.02 µg/mL and 136.6 µg/mL in the DPPH and ABTS assays, respectively. Furthermore, EA nanoparticles were found to be efficient in reducing S. aureus and P. aeruginosa biofilms by 60 and 30%, respectively. The 1H STD-NMR, FTIR and Fluorescence combined analyses confirmed the interaction between EA and zein, which could explain the enhancement found in the biological activities studied, as the active phenolic groups of this molecule are likely to become more accessible after the entrapment of EA in the formed zein nanoparticles. From this we can conclude that nanoencapsulation of EA boosted its antioxidant and antibacterial activities; this offers a potential strategy against free radicals as well as preventive and treatment option for infections related to Gram-positive and Gram-negative bacteria.