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Updated: Mar 10, 2026
Single Molecule Analysis of Laser Localized Psoralen Adducts
Published on: April 20, 2017
A method for the quantification of 8-methoxypsoralen by mass spectrometry for offline extracorporeal photopheresis
Viola Hähnel1, Frauke Dormann1, Athanasios Nitsopoulos2
1Institute for Clinical Chemistry and Laboratory Medicine, Transfusion Medicine, University Hospital Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany. norbert.ahrens@ukr.de.
Background:
Extracorporeal photopheresis (ECP) is an efficient method to treat various autoimmune diseases, cutaneous T-cell lymphoma, and graft-versus-host disease. It is based on the ex vivo inactivation of lymphocytes by 8-methoxypsoralen (8-MOP)/UV light treatment. Despite the adhesive, lipophilic nature of 8-MOP, no quality control is established for the ECP procedure.
Methods:
We developed a sensitive high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) assay to monitor residual 8-MOP concentration after UVA irradiation in the whole blood supernatant after acetonitrile precipitation.
Results:
The preanalytical stability of 8-MOP exceeded 7 days, allowing batch mode analysis. Linearity was determined with R2 above 0.99. The 8-MOP concentrations decreased exponentially after UV exposure, with decay constants of 0.0259 in plasma and 0.0528 in saline. The recovery of 8-MOP in photopheresates was about 68%, indicating binding to DNA as well as to plastic structures. UVA induced no 8-MOP fragmentation, but caused self-adducts under extreme conditions (10-fold UV dosage).
Conclusions:
Detection of 8-MOP proved to be feasible and demonstrated that the doses were in the pharmaceutically active range.
