MALDI mass spectrometry imaging as a complementary analytical method for improved skin distribution analysis of drug molecule and excipients

In cutaneous drug delivery, it is widely accepted that the choice of excipients affects the delivery of a drug molecule to the skin. MALDI mass spectrometry imaging (MALDI-MSI) is an imaging technique which enables the simultaneous detection of multiple compounds. MALDI-MSI was applied to study the penetration of tofacitinib and excipients in porcine skin from two formulations with sodium lauryl sulphate (SLS) and dexpanthenol (DXP) using Franz diffusion cells. Further, the receptor media was collected for analysis of the permeated amounts of tofacitinib and excipients. The MALDI images showed DXP to be co-localized with tofacitinib in the epidermal and deep dermal region while SLS was distributed in the entire skin compartment. The permeation of tofacitinib for the two formulations was similar after 24 h, whereas, the percentage of permeated DXP was higher than for SLS. This study provided an overview of the skin penetration and permeation of drug molecule and excipients. MALDI-MSI showed differences in the DXP and SLS distribution. This indicates that the excipients interact with the skin through different mechanisms. Compound-specific imaging methods such as MALDI-MSI are potential tools to increase the understanding of the complex interplay between skin, excipients and the drug molecule for optimized cutaneous drug delivery.