Lignin nanoparticles as a promising nanomaterial for encapsulation of Rose damascene essential oil: Physicochemical, structural, antimicrobial and in-vitro release properties

Abstract

Lignin is the second most abundant biopolymer, suitable for use as a raw material in various industries due to its low cost and inherent properties. The development of lignin nanoparticles (LNPs) can provide an innovative way to utilize lignin for high-value applications. The food industry is seeking to utilize LNPs for various purposes such as dietary supplements, carriers, and preservatives due to their exceptional biodegradability and biocompatibility. This study aimed to prepare LNPs for the encapsulation of Rosa damascena essential oil (REO) to enhance the protection of this bioactive compound under storage conditions and control its release in contact with foodstuff conditions. Alkali lignin was used for the preparation of LNPs through an anti-solvent method and no chemical modification approach was used for their stabilization. The effect of the REO:LNP mass ratio on the physicochemical and structural properties of the encapsulated essential oil (REO-LNPs) was investigated. The REO-LNP sample with a mass ratio of 0.2:1.0 showed excellent physical properties with a zeta potential of −45 mV, a diameter of 119.7 ± 1.4 nm, moderate polydispersity (0.087 ± 0.014) and high encapsulation efficiency (99.63%). The stability assay of REO-LNP demonstrated enhanced protection of the entrapped REO under storage conditions. Subsequently, the morphological, thermal, antioxidant, antimicrobial, and in vitro release properties of the REO-LNP were determined. The thermogravimetric analysis (TGA) showed that the REO-LNP has a significantly higher thermal stability than free REO. The inclusion of REO in LNPs led to an enhancement of the antioxidant activity of REO. Compared to REO, REO-LNPs exhibited improved antibacterial properties against both S. aureus and E. coli. The REO-LNP demonstrated lower release in aqueous food simulant, and the Ritger-Peppas model showed that the Fickian diffusion mechanism occurred, which was caused by the poor swelling degree and presence of oils at the surface of nano-capsules. In vitro cell viability evaluation showed that the prepared samples had no cytotoxicity and excellent biocompatibility with normal human fibroblast cells. Overall, LNPs can be proposed as renewable nanocarriers for the protection and controlled release of natural antioxidants/antibacterials such as REO in multifunctional applications.