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Vitamin C (ascorbic acid, VC), a water soluble antioxidant, is an essential nutrient involved in a variety of physiological functions. However, VC is unstable, can be easily oxidized and hardly transport to skin due to the barrier of the stratum corneum. This work was based on our previous research about VC nanoliposomes, used high methoxyl pectin (HMP) or low methoxyl pectin (LMP) to coat VC nanoliposomes (NL), in order to enhance the liposomal physicochemical stability and storage stability, and to overcome the conventional liposome only can deliver drugs to upper layer of the stratum corneum. The preparation, physicochemical properties, stability and bioavailability of pectin-coated VC nanoliposomes were investigated. Results showed that pectin-coated VC nanoliposomes could significantly improve storage stability and bioavailability, especially the LMP-NL could be used as a promising drug delivery system.The preparation of pectin-coated VC nanoliposomes:based on the average diameter, zeta potential and entrapment efficiency, the optimized formular of pectin-coated VC nanoliposomes was obtained. The coating method was selected by NL adding to pectin solutions. Similar entrapment efficiency of liposomes (48.57±3.72%～50.23±4.21%) were evident for various concentrations of pectin, both HMP-NL and LMP-NL. However, the average diameter of liposomes generally increased with increasing concentration of pectin, while the zeta potential values of liposomes decreased. When the concentration of pectin was more than0.3%, the average diameter of liposomes increased, but the zeta potential of vesicles were not changed. Hence, the appropriate concentration of pectin for the following study was0.3%, both HMP-NL and LMP-NL.The physicochemical properties of pectin-coated VC nanoliposomes:the physicochemical properties of HMP-NL and LMP-NL were investigated, respectively. At the appropriate concentration of pectin (0.3%, w/v), the entrapment efficiency, average diameter, and zeta potential of HMP-NL and LMP-NL were about49.32%(49.58%),117.28nm (129.62nm), and-23.86mV (-35.53mV), respectively, while the NL showed48.81%,66.91nm, and-2.31mV. The increase in average diameter, decrease in zeta potential, chain-like structure formed in TEM and AFM, and signal changes of characteristic peaks (C=O and PO2-) in FTIR, which confirmed that pectin has been successfully coated on the surface of NL, instead of influence on the interior of the bilayer.The stability of pectin-coated VC nanoliposomes:the HMP-NL, LMP-NL and NL were stored at4℃and25℃for10weeks, and the change of appearance, particle size, zeta potential, pH value, malondialdehyde value, and leakage of VC were investigated. It can be concluded that all these liposomal formulations had favorable physicochemical stability with no sedimentation and little oxidation at4℃. However, the stability of NL was much poorer than HMP-NL and LMP-NL at25℃, occurred aggregation, fusion, leakage, and oxidation. Results indicated HMP-NL and LMP-NL could significantly improve storage stability, with lower aggregation, oxidation of lipid and leakage ratio of VC, and LMP-NL showed better physicochemical stability than HMP-NLThe bioavailability of pectin-coated VC nanoliposomes:in vitro skin permeation study showed HMP-NL and LMP-NL improved the skin permeation of VC1.68-fold and2.09-fold after24h, respectively, in comparison with NL. Additionally, it is important to note that the combination of pectin-coated VC nanoliposomes with orange juice could improve its storage stability, and showed microbiological stability after pasteurization and storage at4℃for30days.
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