Solid lipid nanoparticles for phytosterols delivery: The acyl chain number of the glyceride matrix affects the arrangement, stability, and release.

The lipid matrix plays a key role in solid lipid nanoparticles (SLNs) embedding active ingredients. To investigate the influence of lipid matrix structure on arrangement, release, and stability of solid lipid nanoparticles, three phytosterols formulations with different carrier glycerides [glycerol monostearate (GMS), glycerol distearate (GDS), and glycerol tristearate (GTS)] were prepared and evaluated. X-ray diffraction and differential scanning calorimetry revealed the lowest crystallinity of phytosterols in the GMS matrix, corresponding to the maximum bioaccessibility (40.2%) in vitro experiments. Sustained release and better stability were observed from GDS and GTS matrices, which could be attributed to strong molecular interactions or a core-rich structure inside the nanoparticles. Molecular dynamics simulations demonstrated that the affinity between phytosterols and glycerides decreased in the order GDS > GTS > GMS, as well as explaining the release and storage capacities of the three nanoparticles. This study would facilitate the rational design of SLNs in functional foods.

Enzymatic synthesis of hydrophilic phytosterol polyol esters and assessment of their bioaccessibility and uptake using an in vitro digestion/Caco-2 cell model.

A novel enzyme-catalyzed method was developed for the synthesis of phytosterol polyol esters from ß-sitosterol and polyols (sorbitol, mannitol and xylitol) by two-step transesterification using divinyl adipate (DVA) as a link. A high conversion (exceeding 94%) of ß-sitosterol with a vinyl group was achieved, in the presence of Candida rugosa lipase (CRL), at low temperature (35 °C) within 30 min. Subsequently, the maximum conversion of phytosterol polyol esters (>94%) was obtained using alkaline protease from Bacillus subtilis at 65 °C. Phytosterol polyol esters had enhanced thermal stability (up to an above 355 °C) and excellent water solubility (4.6-7.9 mM at 35 °C). Moreover, obvious increases in the bioaccessibility (41.5-63.6%) and intestinal uptake (5.2-6.5%) were observed using a simulated gastrointestinal digestion/Caco-2 cell model. These results highlighted the key role of hydrophilic structural modifications on physicochemical properties and absorption of phytosterols.