Topically applied methotrexate is rapidly delivered into skin by fractional laser ablation

Abstract

Objectives: Methotrexate (MTX) is a chemotherapeutic and anti-inflammatory drug that may cause systemic adverse effects. This study investigated kinetics and biodistribution of MTX delivered topically by ablative fractional laser (AFXL).

Methods: In vitro passive diffusion of 10 mg/ml MTX (1 w/v%) was measured from 0.25 to 24 h through AFXL-processed and intact porcine skin in Franz Cells (n = 46). A 2,940 nm fractional Erbium Yttrium Aluminium Garnet laser generated mid-dermal microchannels at 2.4% density, and 256 mJ/microchannel. HPLC quantified MTX-concentrations in extracts from mid-dermal skin sections, donor and receiver compartments. Fluorescence microscopy of UVC-activated MTX-fluorescence and desorption electro-spray ionization mass spectrometry imaging (DESI-MSI) evaluated MTX biodistribution.

Results: AFXL-processed skin facilitated rapid MTX delivery through cone-shaped microchannels of 690 µm ablation depth, lined by the 47 µm thermal coagulation zone (CZ). Quantitatively, MTX was detectable by HPLC in mid-dermis after 15 min, significantly exceeded deposition in intact skin after 1.5 h, and saturated skin after 7 h at a 10-fold increased MTX-deposition versus intact skin (3.08 vs 0.30 mg/cm³, p = 0.002). Transdermal permeation was < 1.5% of applied MTX before skin saturation, and increased up to 8.0% after 24 h. Qualitatively, MTX distributed into CZ within 15 min (p = 0.015) and further into surrounding dermal tissue after 1.5 h (p = 0.004). After skin saturation at 7 h, MTX fluorescence intensities in CZ and tissue were similar and DESI-MSI confirmed MTX biodistribution throughout the mid-dermal skin section.

Conclusions: MTX absorbs rapidly into mid-dermis of AFXL-processed skin with minimal transdermal permeation until skin saturation, suggesting a possible alternative to systemic MTX for some skin disorders.

Keywords:

• desorption electro-spray ionization mass spectrometry imaging
• fluorescence microscopy
• fractional erbium laser
• franz skin permeability cells
• high performance liquid chromatography
• laser-assisted drug delivery

Acknowledgements

The authors wish to thank Georg Larsen from Bio-science Aps, Denmark, for supporting development of the fluorescence microscopy technique and photographer Nis Kentorp for helping with illustrations for the article. Data has been presented at American Society of Lasers in Medicine and Surgery in Phoenix at April 3 – 6, 2014.

Declaration of interest

M Haedersdal received a research grant from Pantec Biosolutions AG, Ruggell, Liechtenstein. The company had no influence on collection, interpretation or presentation of data. Bispebjerg University Hospital is acknowledged for financial support. All other authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

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