Carboxymethyl chitosan-soy protein complex nanoparticles for the encapsulation and controlled release of vitamin D₃

In this study, complex nanoparticles were developed from carboxymethyl chitosan (CMCS) and soy protein isolate (SPI) by a simple ionic gelation method. The effect of Ca(2+) concentration, pH and CMCS/SPI mass ratio on the formation of nanoparticles was systematically investigated. Vitamin D3 (VD), a hydrophobic micronutrient, was successfully incorporated into the polymeric complex, forming particles with sizes between 162 and 243 nm and zeta potentials ranging from -10 to -20 mV. In comparison with CMCS, the CMCS/SPI complex required a lower concentration of Ca(2+), and it showed better particle forming capability over a broad range of pH. These features resulted in an increased loading efficiency to 6.06%. In addition, the complex nanoparticles achieved significantly higher encapsulation efficiency (up to 96.8%), possibly due to their compact structure and high capability of hydrogen bonding evidenced by Fourier transform infrared spectroscopy (FTIR). In contrast to the ones prepared with SPI, the complex nanoparticles exhibited a reduced (42.3% compared to 86.1%) release of VD in simulated gastric fluid and an increased (36.0% compared to 8.2%) release under simulated intestinal condition. These characteristics made the CMCS/SPI complex nanoparticles an attractive candidate for the encapsulation and controlled release of hydrophobic nutraceuticals and bioactives.