Experimental Assessment, Quantum Computation (DFT, ELF, and LOL), and Integrative Nutriology Insights on Lactoferrin/Luteolin Nanocomplex Self-Assembly via pH-Driven Method

Abstract

As the limited water solubility and stability severely restrict the food application of luteolin, a deep knowledge of luteolin is required to understand the reactivity in complex formation. In the present study, the formation mechanism between lactoferrin and luteolin via a pH-driven method was systematically explored to confirm the application in hydrophilic nutraceutical delivery. The physicochemical properties of lactoferrin-luteolin nanocomplexation were investigated through particle size, PDI, ζ-potential, encapsulation efficiency, and loading amount assays. Observation of complexation behaviors revealed the pH-driven method effectively incorporated luteolin into the cores of lactoferrin with pH-dependent solubility characteristics. The improved thermal stability resulted in a stable nanocomplex formation with a zeta potential near − 15 mV. Furthermore, multi-spectroscopy (FTIR and fluorescence spectroscopy) demonstrated that luteolin-lactoferrin nanocomplexation was a spontaneous process together with secondary structure alterations during acidification. Fascinating biological applications of luteolin inspire to do quantum chemical calculations in order to confirm its bioactivities. In-depth investigations of electronic structure (MEP), topology characteristic (ELF, and LOL), and frontier molecular orbital (HOMO and LUMO, energy gap) help confirm the nucleophilic and electrophilic regions of luteolin, which play a crucial role in recognition between luteolin and lactoferrin. Consistent with the observed behavior in vitro, molecular docking further elucidated that hydrophobic contact and hydrogen bonding dominated the location of luteolin into the hydrophobic and deprotonated pocket of lactoferrin, especially at pH 4. From the integrative nutriology perspective, the synergistically biological mechanism of lactoferrin-luteolin nanocomplexation possessed multi-target and multi-pathway properties in preventing oxidative stress-related diseases. In conclusion, experimental and theoretical studies demonstrate great potential in using the pH-driven method for manufacturing luteolin-lactoferrin nanocomplexation with better physical and biological characteristics for delivery of hydrophobic nutraceuticals in the food sector.