Development and application of nanoparticles synthesized with folic acid conjugated soy protein

In this study, soy protein isolate (SPI) was conjugated with folic acid (FA) to prepare nanoparticles for target-specific drug delivery. Successful conjugation was evidenced by UV spectrophotometry and primary amino group analysis. An increase in count rate by at least 142% was observed in FA-SPI nanoparticles compared to the nonconjugated ones, whereas the particle size was decreased upon FA conjugation. This was probably attributed to the substitution of positively charged lysine residues by the FA backbone. The ζ-potential ranged from -36 to -42 mV depending on the conjugation degree, indicating desirable dispersion stability. Curcumin as a model drug was encapsulated successfully into FA-SPI nanoparticles, evidenced by X-ray diffraction study. The highest encapsulation and loading efficiencies were around 92.7% and 5.4%, respectively, which were significantly higher (P < 0.05) than those with nonconjugated SPI nanoparticles. In addition, a faster and more complete release of curcumin was observed for FA-SPI nanoparticles in PBS/Tween 20 buffer. Cell culture study showed that conjugation of FA resulted in an increase in cellular uptake by at most 93% in Caco-2 cells. These results suggested that FA-SPI is a potential wall material for encapsulation and enhanced delivery of anticancer drugs.