Nanostructured Lipid Carriers

Lacatusu et al. (2013) fabricated nanostructured lipid carriers (NLCs) for the nanoencapsulation of lutein by utilizing w-3 fatty acids as liquid oil and car- nauba wax and glycerol stearate as solid state lipids. They concluded that the particle sizes and entrapment efficiency of the formulation were under 200 nm and 89%, respectively (Lacatusu et al., 2013). The oxygen absorbance potential of lutein-loaded NLCs was estimated to be nearly 98%. The in vitro release assay revealed that the designed NLCs manifested a prolonged release behavior of lutein when compared with the commonly used nanoemulsions. Hence, this novel nanostructure can be employed in the production of functional food stuff in regard to its exclusive advantages mentioned before. In another study by Hentschel et al. (2008), NLCs were fabricated by using hydrophobic (3-carotene in an aqueous phase. Subsequently, photon correlation spectroscopy (PCS) and laser diffraction (LD) runs were carried out to determine the physical stability and particle size of the NLC suspensions by exposure to two different storage temperatures. All the fabricated particles with adequate levels of emulsifier were smaller than 1 pm (LD diameter 100%) and the average particle size was around 0.3 pm (LD) for 9 weeks at 20°C and a minimum period of 30 weeks at 4—8°C. Differential scanning calorimetry (DSC) was also implemented to assess the required heat for the crystallization (phase conversion of the applied lipids) in both propylene glycol monostearate (PGMS) plus the NLC particles. PGMS being introduced into the NLC was actually recrystallized up to 98% during storage phase. Besides, no polymorph transitions were noticed during the 7-month storage span.

Curcumin-loaded NLCs (Cur-NLCs) were developed by Fang et al. (2012) to be directly administered into the stomach of laboratory rats. This research explored the pharmacokinetics, nanostructure diffusion in tissues, and approximate bioavailability of curcumin in rats after the rats were fed with the prepared formulation. Regarding the tissue distribution tests, curcu- min was identified within heart, spleen, liver, lungs, and brain. Cur-NLCs enhanced the residence time of curcumin in the prementioned organs, particularly in the brain. They concluded that NLCs are capable of improving the oral absorption of water-insoluble bioactives, such as curcumin.

Hejri, Khosravi, Gharanjig, and Hejazi (2013) optimized (3-carotene- loaded NLCs using the solvent diffusion method. The results depicted that the lipid phase concentration along with the surface-active agents level had a direct impact on the particle size of NLCs. Also, the liquid lipid contribution to the degradation of (3-carotene was much higher in relation to the whole lipid ratio. Mathematical models were established and fitted to obtain the optimum formulations, subsequently they were experimentally tested and the resultant values were in agreement with the predicted measurements (least particle size of 8—15 nm and low (3-carotene degradation of 0—3%). In a similar study, (3-carotene was also successfully incorporated into an NLC matrix, composed of anhydrous milk fat (AMF) as the solid lipid and Tween 80 as the surface active agent through the phase inversion temperature (PIT) method (Zhang, Hayes, Chen, & Zhong, 2013). The authors noted that the advantages of PIT over the high-pressure homogenization method include the formation of transparent yield and being economical. They studied thermal processing circumstances, salinity, and the proportion of surfactant to oil in the formed NLCs and the related parameters affecting the turbidity of the emulsions. Altogether, this study supported that PIT method can be applied to fabricate stable and transparent NLCs for encapsulation of various lipophilic bioactive compounds in food and beverage systems.

NLCs have been developed for nanoencapsulation of quercetin (QT) by Ni, Sun, Zhao, and Xia (2015). The QT-NLC specimens were produced by applying the high-pressure homogenization method. The optimized QT-NLC presented a high encapsulation efficiency of about 93.50%. In addition, the formulated QT-NLCs were highly stable at the room temperature. In vitro antioxidant activity experiments demonstrated the elevated antioxidant performance of QT-NLC to uncoated QT. Furthermore, Fourier transform infrared spectroscopy report represented no chemical interaction between QT and lipid matrix as well as the successful encapsulation process. The gastrointestinal tract model approved the enhanced bioavailability obtained by encapsulation. They introduced QT-NLC as practical additives to enrich soft beverages. Similarly, Liu et al. (2014) developed a new model of quercetin-loaded cationic NLC (QT-CNLC) and analyzed its biodistribution in vivo after oral delivery. To sum up, the prepared QT-CNLC had a prolonged release and is an effective alternative to free QT as it would lead to the accumulation in several organs, such as lung, liver, and kidney following oral administration. Barras et al. (2009) implemented the phase inversion technique to prepare lipid nanocapsules (LNCs) involving two bioactive ingredients (quercetin and epigallocatechin gallate). Initially, the bioactives were mixed in the oil phase; afterwards soybean lecithin, NaCl, surfactant, and distilled water were added to the mixture and heated. The formulated combination was cooled and distilled cold water (0°C) was added under stirring to O/W nanocapsules. By using this method, it is possible to control the size of formed LNC and therefore the formulation needs to be accurately designed according to our purpose. The obtained results of this experiment exhibited the enhanced rate of nanostructure solubility by a factor of 100 as well as being stable during storage.

In another study, astaxanthin-loaded NLCs were prepared by Tamjidi, Shahedi, Varshosaz, and Nasirpour (2014). Tween 80 and lecithin were the chosen emulsifiers and oleic acid together with glyceryl behenate was the utilized lipid. Astaxanthin-NLCs were fabricated by melt emulsification soni- cation method and stored at 19°C during 25 days. The ideal formulation of astaxanthin-NLC (with OCL: 22.4% and LTR: 1.8) had dominant properties against the free astaxanthin. X-ray diffraction and thermal identifications suggested a novel crystalline structure presenting lower crystallinity for the ideal composition in comparison to glyceryl behenate (Tamjidi, et al. 2014).

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