Nanoencapsulation of Phenolics and Antioxidants in Solid Lipid Nanoparticles
SLNs can be applied for designing nanoencapsulation systems of phenolic compounds and antioxidants. Indeed, these bioactive compounds are incorporated into a solid lipid matrix and are surrounded by surfactants. There are a number of review studies that provide main information about formulation, preparation, and characterization of SLNs (Mueller, Maeder, & Gohla, 2000; Muller & Lucks, 1996; Muller, Radtke & Wissing, 2002).
SLNs have more advantages such as controlled release, higher encapsulation efficiency, and the large-scale production without using organic solvents, in comparison to other lipid-based vehicles such as nanoliposomes and nanoemulsions (Muller & Lucks, 1996). Therefore, SLNs can be a good candidate for nanoencapsulation of phenolics and antioxidants. As shown in Fig. 2.2, bioactive compounds can be incorporated into SLNs in three forms: enriched matrix, enriched shell, and enriched core.
The loaded phenolic compounds and antioxidants into SLNs are more bioavailable compared with their free form. For example, curcumin as a valuable phenolic compound has many advantages such as antioxidant and anticancer properties. However, its application is restricted due to its poor solubility and stability in aqueous systems, as well as its rapid metabolism and systemic elimination (Anand, Kunnumakkara, Newman, & Aggarwal, 2007). Several studies have shown that these restrictions can be eliminated by loading curcumin into SLNs (Kakkar, Singh, Singla, & Kaur, 2011; Sun et al., 2013). In a study by Jose et al. (2014), RSV was loaded into SLNs formulated with Tween 80 or a combination of Tween 80 and polyvinyl alcohol (PVA) as surfactants. The diameter and zeta potential of produced particles were 248.30 nm and —25.49 mV, respectively. Their results showed that the RSV-loaded SLNs provided a sustained release and were promising therapeutic systems to treat neoplastic diseases located in the brain tissue (Jose et al., 2014).
Li et al. (2009a) incorporated quercetin into SLNs with an active encapsulation efficiency of 91.1% and 155.3 nm in mean particle diameter. The quercetin-SLN was composed of glyceryl monostearate, soya lecithin, Tween 80, and PEG 400 with emulsification and low-temperature solidification method. The results revealed that SLNs were the best delivery system to enhance the oral absorption of poorly water-soluble phenolics, like the quercetin.
Enzymatic antioxidants can also be protected from proteolysis by incorporating them into SLNs. Qi, Chen, Huang, Jin, and Wang (2012) loaded CAT as an enzymatic antioxidant in SLNs prepared with high-purity soybean phosphatidylcholine (SPC). They showed that these formulated SLNs can protect CAT against proteolysis, suggesting the potential application of SPC in delivery and protection of functional food enzymes.