Solubilization of Hydrophobic Astaxanthin in Water by Physical Association with Phytoglycogen Nanoparticles

Phytoglycogen (PG) is a soft glucose-based dendrimer produced as compact nanoparticles in the kernels of sweet corn. Its softness and deformability, combined with its biocompatibility, non-toxicity and digestibility, make it an attractive choice for biomedical applications such as bioactive delivery. This is a challenge since most bioactives are hydrophobic. In the present study, we demonstrate that PG can be used as an effective solubilizing agent for the hydrophobic carotenoid astaxanthin (AXT), which has reported health benefits. We have developed a procedure that results in a strong physical association of AXT to PG without using chemicals such as surfactants. By combining AXT dissolved in acetone with PG dispersed in water, evaporating the acetone, and removing the water, we obtain a dry powder of AXT-PG that can be easily redispersed in water, increasing the effective solubility of AXT in water by more than a factor of 10¹² relative to that calculated for AXT in water. Aqueous dispersions of AXT-PG are stable for several months, as measured using UV-Vis spectroscopy. UV-Vis measurements also allowed us to quantify the aggregation state of AXT on the surface of the PG particles. Our results demonstrate the promise of using PG as an effective solubilizing and stabilizing agent for hydrophobic compounds in water.