Fabrication of zein and rhamnolipid complex nanoparticles to enhance the stability and in vitro release of curcumin

In this work, zein/rhamnolipid complex nanoparticles were successfully fabricated by anti-solvent co-precipitation method to deliver curcumin (Cur). The results showed that the mean size and zeta-potential of Cur-loaded zein/rhamnolipid complex nanoparticles (Cur-Z/R) were obviously influenced by the mass ratio of zein to rhamnolipid. As expected, the presence of rhamnolipid greatly increased the encapsulation efficiency (EE) of Cur, from 17.64% in zein nanoparticles to 98.05% in zein/rhamnolipid complex nanoparticles at the mass ratio of 1:2. Both Cur-Z and Cur-Z/R nanoparticles exhibited spherical shapes as observed by scanning electron microscopy. Furthermore, the thermal and UV irradiation stability of Cur was also improved after the addition of rhamnolipid. The retention rate of Cur in Cur-Z/R 1:2 complex nanoparticles was enhanced about 5.89 and 2.76 folds after heat treatment at 95 °C for 30 min and UV exposure for 90 min, respectively, compared with free Cur. Moreover, Cur-Z/R complex nanoparticles also significantly improved the in vitro release of Cur in simulated gastrointestinal tract. The results of Fourier transform infrared spectroscopy and fluorescence spectrum revealed that electrostatic attraction, hydrogen bonding, and hydrophobic effects were the dominant driving forces for the formation of complex nanoparticles. These findings interpreted that zein/rhamnolipid complex nanoparticles might be an efficient and promising delivery system to encapsulate and protect hydrophobic bioactive compounds.