Effects of Sophorolipids on the Structure and Properties of Zein-Quercetin Nanoparticles

In this study, zein-quercetin (Zein-Q) nanoparticles were prepared and the effects of sophorolipids (SL) on the structure of Zein-Q nanoparticles were evaluated based on the combination of scanning electron microscopy, Fourier infrared spectroscopy and fluorescence spectroscopy. Their antioxidant and antibacterial properties were analyzed as well. The results showed that Zein-Q nanoparticles were spherical with an average particle size of 128 nm, the encapsulation efficiency and loading capacity were separately 25.8%±1.28% and 3.98%±0.24%, respectively, and its scavenging ability on DPPH· and ABTS⁺· were 76.8%±0.9% and 65.4%±1.2%. The addition of sophorolipids resulted in forming nanoparticles with good dispersion. The structural characteration results showed that sophorolipids were coated with the outer layer of zein-quercetin nanoparticles driven by the interaction of hydrogen bonding and electrostatic interaction, forming a spherical core-cell structure with a larger particle size. At Zein-Q:SL=3:4, the encapsulation efficiency and loading capacity of composite Zein-Q-SL nanoparticles were increased to 73.6%±1.80% and 7.98%±0.41%, respectively. The antioxidant activity of zein-quercetin nanoparticles was enhanced, which showed that the scavenging ability of composite Zein-Q-SL nanoparticles on DPPH· and ABTS⁺· reached 88.8%±1.0% and 78.6%±1.5%, respectively. In addition, the composite Zein-Q-SL nanoparticles showed a good inhibitory activity against Escherichia coli and Staphylococcus aureus. Thus, it can be concluded that biosurfactant sophorolipids have potential to be excellent modifier for enhancing the structural stability and activity of zein-quercetin nanoparticles.