Ultrasound-assisted pH-shifting remodels egg-yolk low-density lipoprotein to enable construction of a stable aqueous solution of vitamin D(3)

Egg-yolk low-density lipoprotein (LDL) has a natural liposome structure. Using ultrasound-assisted pH-shifting (pH 12), a naturally safe and stable aqueous solution of vitamin D(3) (VD(3)) was constructed employing LDL as the carrier. Images from electron microscopy showed that pH-shifting remodeled LDL molecules, resulting in a dramatic reduction in particle size (∼50%) and an increase in specific surface area, which reduced the turbidity (27.7%) and provided new interfaces for VD(3) loading. Fluorescence analyses showed that the binding of VD(3) to LDL under pH-shifting was strong, involved quenching, and the binding constant was 6.19 × 10(4) M(−1). Thermogravimetric analysis and Fourier transform-infrared spectroscopy showed that pH-shifting hydrolyzed the esters in LDL to fatty acid salts, and the maximum weight loss of LDL occurred from 381.9 °C to 457.0 °C. Ultrasonic treatment enhanced the binding of LDL and VD(3) (binding constant increased to 2.56 × 10(7) M(−1)), reduced the particle size, and increased the ζ-potential of the complex between LDL and VD(3), thereby resulting in the improvement of solution stability and storage stability of VD(3). Ultrasound-assisted pH-shifting could remodel LDL to construct a stable aqueous solution of VD(3), which showed the potential of LDL as a carrier for lipid-soluble components.