Skin Transport of Hydrophilic Compound-Loaded PEGylated Lipid Nanocarriers: Comparative Study of Liposomes, Niosomes, and Solid Lipid Nanoparticles

The effect of surface grafting with N-(carbonyl-methoxypolyethylene glycol-2000)-1,2-distearoyl-snglycero-3-phosphoethanolamine (PEG2000-DSPE) onto three types of lipid nanocarriers, liposomes, niosomes and solid lipid nanoparticles (SLNs) on the skin penetration of sodium fluorescein (NaFI) was investigated. Confocal laser scanning microscopy (CLSM) was used to visualize the penetration pathways. Fourier transform infrared spectroscopy (FT-IR) was used to determine the skin hydration. The results showed that the physicochemical properties of each nanocarrier were modified after PEG grafting. In the skin penetration study, PEG grafting increased the flux of NaFI-loaded PEGylated liposomes and significantly decreased the flux of NaFI-loaded PEGylated niosomes and NaFI-loaded PEGylated SLNs. The skin deposition study and CLSM images showed that the intact liposome vesicles permeated into the skin. The niosomes and SLNs had little or no vesicles in the skin, suggesting that NaFI may have been released from these nanocarriers before permeation. Additionally, the fluorescent CLSM images of the SLNs showed that NaFI deposited along the length of hair follicles inside the skin, indicating that the skin penetration route may be through the transfollicular pathway. For the PEGylated nanocarriers, the PEGylated liposomes had higher fluorescence intensities than the non-PEGylated liposomes, indicating higher NaFI concentrations. The PEGylated niosomes and PEGylated SLNs had lower fluorescence intensities than those of the non-PEG modified niosomes and SLNs. For FT-IR results, PEGylated liposomes increased the skin hydration, while the grafting PEG onto niosomes and SLN surfaces decreased the skin hydration. This study showed that the surface grafting of PEG onto various nanocarriers affected the skin transport of NaFI.