Multi-frequency ultrasound-assisted dialysis modulates the self-assembly of alcohol-free zein-sodium caseinate to encapsulate curcumin and fabricate composite nanoparticles

Abstract Developing a number of zein distribution mechanisms that encapsulate hydrophobic nutraceuticals has become a hot topic in food industry. In this study, the multi-frequency ultrasound-assisted dialysis method was used to fabricate stable nanoparticles. The ultrasound working mode and sodium caseinate modulated physicochemical properties, molecular interactions and microstructure of the nanoparticles system. The optimal ultrasonic frequency of 20/40 kHz resulted in Zein-sodium caseinate particle size, zeta potential and PDI values of 225.94 ± 3.84 nm, - 29.97 ± 1.49 mv, and the 0.19 ± 0.08, respectively. Additionally, ultrasound and Sodium Caseinate have a synergistic effect in improving the storage stability of nanoparticles. The results of fluorescence and CD demonstrated that ultrasound promoted the interaction between Sodium Caseinate and zein, by changing the local microenvironment and structure of the protein. FTIR results showed that the dominant driving force in the formation of hybrid nanoparticles was hydrophobic interaction, hydrogen bond and electrostatic interaction. Ultrasound-assisted dialysis was an effective strategy to encapsulate curcumin. XRD showed that curcumin was successfully encapsulated, and the 20/40 kHz ultrasound frequency combination improved encapsulation rate by 90.19 ± 0.33% as well as thermal stability, storage stability and antioxidant activity of curcumin (86.91 ± 0.72%). AFM and SEM showed uniform and regular spherical structure of composite nanoparticles. The findings revealed not only the multi-mode ultrasound assisted dialysis could be utilized to encapsulate hydrophobic bioactive compounds, which constructed delivery system, but also it provided a controlled release under simulated gastrointestinal conditions, and a better protection and desirable sustained-release of hydrophobic nutraceuticals.