Improved skin permeation of methotrexate via nanosized ultradeformable liposomes

Abstract

The aim of this study is to investigate methotrexate-entrapped ultradeformable liposomes (MTX-UDLs) for potential transdermal application. MTX-UDLs were prepared by extrusion method with phosphatidylcholine as a bilayer matrix and sodium cholate or Tween 80 as an edge activator. The physicochemical properties of MTX-UDLs were determined in terms of particle size, polydispersity index, zeta potential, and entrapment efficiency. The deformability of MTX-UDLs was compared with that of methotrexate-entrapped conventional liposomes (MTX-CLs) using a steel pressure filter device. The skin permeation of MTX-UDLs was investigated using Franz diffusion cell, and the skin penetration depth of rhodamine 6G-entrapped UDLs was determined by confocal laser scanning microscopy. MTX-UDLs showed a narrow size distribution, with the particle size of ~100 nm. The deformability of MTX-UDLs was two to five times greater than that of MTX-CLs. The skin permeation of MTX-UDLs was significantly improved compared with MTX-CLs and free MTX solution. The optimized UDLs (phosphatidylcholine: Tween 80 =7:3, w/w) showed a higher fluorescence intensity than conventional liposomes at every increment of skin depth. Thus, the optimized UDLs could be promising nanocarriers for systemic delivery of MTX across skin.

Keywords: deformability; methotrexate; skin permeation; transdermal delivery; ultradeformable liposomes.

Figure 1

Diagrammatic illustration of MTX-UDLs (A) and mechanism of MTX-UDLs transport in skin permeation (B). Note: During skin permeation, the vesicular structure of UDLs is maintained via deformation and reformation. Abbreviation: MTX-UDLs, methotrexate-entrapped ultradeformable liposomes.

Figure 2

Particle size distribution (A) and TEM image (B) of MTX-UDLs. Abbreviations: TEM, transmission electron microscopy; MTX-UDLs, methotrexate-entrapped ultradeformable liposomes.

Figure 3

Deformability of MTX-UDLs with different types and amounts of edge activators. Notes: The deformability of MTX-UDLs was compared with that of MTX-CLs. Data are expressed as mean ± SD (n=3). *P<0.01 versus MTX-CLs. Abbreviations: MTX-UDLs, methotrexate-entrapped ultradeformable liposomes; MTX-CLs, methotrexate-entrapped conventional liposomes; SD, standard deviation.

Figure 4

Skin permeation profiles of MTX-UDLs, MTX-CLs, and MTX solution across rat skin for 24 hours. Note: Data are expressed as mean ± SD (n=3). Abbreviations: MTX-UDLs, methotrexate-entrapped ultradeformable liposomes; MTX-CLs, methotrexate-entrapped conventional liposomes; SD, standard deviation; h, hours.

Figure 5

Confocal laser scanning photomicrographs with different depths of rat skin after 4 hour treatments with R6G-UDLs, R6G-CLs, and R6G solution. Abbreviations: R6G, rhodamine 6G; UDLs, ultradeformable liposomes; CLs, conventional liposomes.

Figure 6

Fluorescent intensity versus skin permeation depth profiles of R6G-UDLs-T3, R6G-CLs, and R6G solution. Note: Data are expressed as mean ± SD (n=3). Abbreviations: R6G, rhodamine 6G; UDLs, ultradeformable liposomes; CLs, conventional liposomes; SD, standard deviation.

Figure 7

DSC thermograms (A) and FTIR spectra (B) of MTX-UDLs-T3-treated and untreated epidermis from rat skin. Abbreviations: DSC, differential scanning calorimetry; FTIR, Fourier transform infrared spectroscopy; MTX-UDLs, methotrexate-entrapped ultradeformable liposomes.