## 3 Some Key Issues on the Use of SLNs and NLCs as Oral Nanovehicles for Nutraceuticals or Bioactives
### Liposoluble Nntraceuticalticals
#### 4.1.2 Fat-Soluble Vitamins
The incorporation of the vitamin D in the NLCs remarkably improved its stability over long-term storage and during simulated gastric digestion, as well as its release behavior during digestion [80]. The stability of vitamin D\({}_{3}\)-loaded NLC dispersion was more related to the choice of emulsifier than the use of different carrier oils [82]. The vitamin D-loaded NLCs, or lipid nanocapsules, were very compatible with food formulations, e.g., milk beverages [102; 105], thus representing great potential in food applications. As expected, the incorporation of vitamin D\({}_{3}\) in the NLCs enhanced its in vivo absorption upon oral administration [81]. In addition to the enhanced bioavailability, the incorporation of vitamin D in NLCs can provide a colon-targeted delivery via oral administration. [PERSON] and colleagues [106] confirmed that, when orally administrated to mice, vitamin D\({}_{3}\) in the NLCs was delivered to the colon, and remained in the colonic tract at a high concentration for a long period. More interestingly, the oral administration of vitamin D\({}_{3}\)-NLCs showed multiple effects on the suppression of symptoms of colitis induced by dextran sodium sulfate (DSS) [106]. In a more recent work, it was reported that the oral administration of a vitamin D\({}_{3}\)-NLC ameliorated the non-alcoholic steatohepatitis progression in mice via enhanced intestinal barrier support and suppressed inflammation and fibrosis in the liver [107]. In concurrent administration with doxorubicin (an anticancer agent), the application of vitamin D\({}_{3}\)-loaded NLC was shown to greatly elevate the efficacy of the anticancer activities of doxorubicin in breast cancer [108]. Vitamin E is another important liposoluble vitamin that occurs naturally in vegetable oils and deodorizer distillates. This vitamin is well recognized for its role as an antioxidant, scavenging lipid peroxyl radicals or acting as a synergistic with other antioxidants [109]. Vitamin E is, in fact, a group, consisting of eight different tool compounds, including top-phenyls and tocotrienols. In addition to the direct oxidative protection, vitamin E exhibits a variety of oxidative stress-related health-benefitting effects on cardiovascular diseases, cancer, immune response, inflammatory diseases, neurological disorders, cataracts, and age-related macular degeneration [110, 111]. Despite these beneficial effects, all tocoperlojs and tocotrienols are difficult to incorporate in food formulations, due to their insolubility in water. A few works have reported that the incorporation of vitamin E in SLNs or NLCs not only facilitated its application in food formulations, but also increased its oral bioavailability and storage stability [83, 84, 85]. In these works, both the SLNs and NLCs were fabricated using the melt-emulsification process (e.g., hot HPH), using poloxamer as the emulsifier, alone or in combination with lecithin. The EE and LC also considerably varied with the type and composition of lipid nanoparticles and homogenization conditions (Table 1).