## 3 Some Key Issues on the Use of SLNs and NLCs as Oral Nanovehicles for Nutraceuticals or Bioactives
### Bioactive Absorption and Intestinal Transport
The nanoencapsulation of these poorly soluble bioactive components in lipid-based nanoparticles has been confirmed to be one of the most effective strategies for improving their availability [53]. Great progress has been made in the development of such lipid nanovehicles for curcumin over the past 10 years (see the below), due in large part, perhaps, to the following reasons: (i) curcumin is a golden bioactive, with many promising beneficial effects on human health [60; 61]; (ii) lipid nanoparticles have been confirmed to act as effective nanovehicles for the delivery of drugs [17; 62]. In this section, we have provided a critical review about the development of SLNs and/or NLCs as nanovehicles for many liposoluble nutraceuticals, with an emphasis on carotenoids with different structural and physicochemical properties, e.g., \(\beta\)-carotene, astaxanthin, lutein, lycopene, and bixin (Table 1). Then, advances in the utilization of SLNs and/or NLCs as potential nanovehicles for improving the water dispersibility, stability, and bioaccessibility (or bioavailability) of many poorly soluble bioactive components, e.g., curcumin and phytosterols, were comprehensively reviewed. Herein, issues regarding fabrication strategies for SLNs and NLCs, the stability and release behavior of encapsulated bioactives, as well as their in vivo health effects, were also fully discussed. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Liposoluble** & **Type of Lipid** & **Formulation** & **Liposidents** & **E/DL** & **Main Results** & **References** \\
**Naturzeticals** & **Nanoparticles** & **Ingredients** & **Processing Technique** & **E/DL** & **Main Results** & **References** \\ \hline \multicolumn{6}{c}{Caronechs} \\ \hline \(\beta\)-carotene (10\% in sunflower oil) & NLCs & \begin{tabular}{c} Propylene glycol \\ monosterate; sunflower oil; Tween 80 \\ \end{tabular} & Hot HPH & \(>\) 0.35\% & The dispersions of \(\beta\)-carotene NLCs were & \\  & & & & stable at +8 °C after 30 weeks; the & recrystallization of solid lipids occurred & [49] \\  & & & & completely; the oxidative degradation of & \\  & & & & encapsulated \(\beta\)-carotene was enhanced by & \\  & & & & the dilution in water. & & \\ \hline \(\beta\)-carotene & SLNs & \begin{tabular}{c} Tripalmitric; lecithin or \\ Tween 60 or 80 \\ \end{tabular} & Hot HPH & \(>\) 0.1\% & \begin{tabular}{c} The crystallization of solid lipids was \\ affected by the type of surfactants; the use \\ of high melting surfactant (leithin) in \\ SLSNs provided a better protection against \\ chemical degradation of encapsulated \\ \(\beta\)-carotene. \\ \end{tabular} & \begin{tabular}{c} \\ \(\beta\)-carotene. \\ \end{tabular} & \begin{tabular}{c} \\ \(\beta\)-carotene. \\ \end{tabular} & \begin{tabular}{c} \\ \(\beta\)-carotene. \\ \end{tabular} & \begin{tabular}{c} \\ \(\beta\)-carotene. \\ \end{tabular} & \begin{tabular}{c} \\ \(\beta\)-carotene. \\ \end{tabular} & \begin{tabular}{c} \\ \(\beta\)-carotene. \\ \end{tabular} & \begin{tabular}{c} \\ \(\beta\)-carotene. \\ \end{tabular} & \begin{tabular}{c} with the \\ aim to achieve the small particle size and \\ high \(\beta\)-carotene \\ spherical in morphology \\ \end{tabular} & [63] \\ \hline \(\beta\)-carotene & NLCs & Milk fat; Tween 80 & \begin{tabular}{c} Hot shear \\ homogenization + phase- \\ inversion-temperature \\ \end{tabular} & \(>\) & \begin{tabular}{c} A kind of transparent \(\beta\)-carotene-NLCs \\ disproves were successfully fabricated; \\ the NLCs showed stability against dilution, \\ storage, and chemical degradation. \\ \end{tabular} & [64] \\ \hline \(\beta\)-carotene & SLNs & \
\begin{tabular}{c} Hydrogenerated palm oil, \\ cocoa butter; Tween 20 \\ \end{tabular} & Hot HPH & \(>\) -0.5\% &
\begin{tabular}{c} The SLNs had better stability to droplet \\ aggregation but lower \(\beta\)-carotene oxidation \\ than liquid liquid nanoparticles; the \\ impaired stability was attributed to the \\ \(\beta\)-carotene exclusion from the crystallized lipids. \\ \end{tabular} & [51] \\ \hline \end{tabular}
\end{table}