Influence Of Liposomal Charge On Transdermal Delivery Efficacy Using Quantum Dots As A Fluorescent Probe

Liposome is composed of phospholipids and cholesterol to form a bilayer membrane. As phospholipids are amphiphilic, thus are capable to capsulate both water-soluble substances and fat-soluble substances. With its good biocompatibility and drug loading efficiency, liposomes are widely used in drug delivery system, including transdermal drug delivery system. Stratum corneum acts as the major permeability barrier of the human skin in the transdermal drug delivery process, inhibiting the penetration efficiency of both carriers and loaded drugs. The properties of the liposome itself also influence the transdermal drug delivery efficiency. In this study, we combined phosphatidylcholine (PC) with cholesterol analogues, either with cationic charge,4-cholesterocarbonyl-4’-(N,N,N-triethylamine butyloxyl bromide) azobenzene (CAB), or neutral charge,4-cholesterocarbonyl-4’-(N,N-diethylamine butyloxyl) azobenzene (ACB) in liposomal membranes respectively, with CdTe quantum dots (QDs) as the fluorescence probe. Neutrally charged liposome PC-QDs and CdTe QDs were as the control. Firstly, we studied the interactions between liposomes and NIH3T3cells to confirm if charged liposomes could influence the intracellular drug delivery capacity. And then, we applied the liposomes onto the nude mouse dorsal skin. The influence of charged liposomes on transdermal drug delivery efficiency was studied by tracking the distribution of QDs probe within different skin layers.The results indicated that cationic liposome CAB-QDs facilitated the internalization of loaded QDs into cells and distributed in cytoplasm area within1h incubation; otherwise, neutrally charged liposome was incapable to achieve the result. Moreover, on contrary to neutrally charged liposomes, i.e., ACB-QDs and PC-QDs, cationic liposome forcefully promoted transdermal delivery of loaded QDs into the skin. In2h, cationic liposome delivered loaded QDs to the upper epidermis, while QDs loaded in neutrally charged liposome still stayed on the skin surface which had no obvious facilitation. The neutrally charged liposomes loaded QDs could reach to epidermis after8h, which was similar to the naked QDs. On the other hand, the cationic liposome performed transdermal delivery efficiency by accelerating the diffusion of loaded QDs to vascular dermis at12h.In conclusion, this study established cationic liposomal drug delivery system, and confirmed its enhancement in both cellular and transdermal drug delivery efficiency, in comparison with neutrally charged liposomes.