Protein Nanoparticles for Enhanced Oral Delivery of Coenzyme-Q10: in Vitro and in Silico Studies.

Coenzyme-Q10 (CoQ10) is a hydrophobic benzoquinone with antioxidant and anti-inflammatory properties. It is known to reduce oxidative stress in various health conditions. However, due to the low solubility, permeability, stability, and poor oral bioavailability, the oral dose of CoQ10 required for the desired therapeutic effect is very high. In the present study, CoQ10 is encapsulated into two milk derived proteins β-lactoglobulin and lactoferrin (BLG and LF) to produce self-assembled nanostructures of around 100-300 nm with high encapsulation efficiency (5-10% w/w). Both CoQ10-BLG and CoQ10-LF nanoparticles (NPs) significantly improved the aqueous solubility of CoQ10 60-fold and 300-fold, compared to CoQ10 alone, which hardly dissolves in water. Insight into the difference in solubility enhancement between BLG and LF was obtained using in silico modeling, which predicted that LF possesses multiple prospective CoQ10 binding sites, potentially enabling greater loading of CoQ10 on LF compared to BLG, which was predicted to be less capable of binding CoQ10. At pH 7.4, CoQ10-LF NPs showed a burst release between 30 min and 2 h then plateaued at 12 h with 30% of the total drug released over 48 h. However, pure CoQ10-BLG and pure CoQ10 had a significantly lower release rate with less than 15% and 8% cumulative release in 48 h, respectively. Most importantly, both BLG and LF NPs significantly improved CoQ10 permeability compared to the pre-dissolved drug across the Caco-2 monolayer with up to 2.5-fold apparent permeability enhancement for CoQ10-LF─further confirming the utility of this nanoencapsulation approach. Finally, in murine macrophage cells (J774A.1), CoQ10-LF NPs displayed significantly higher anti-ROS properties compared to CoQ10 (predissolved in DMSO) without affecting the cell viability. This study paves the way in improving oral bioavailability of poorly soluble drugs and nutraceuticals using milk-based self-assembled nanoparticles.