FP496
CHARACTERIZATION OF DIALYZER MEMBRANES BY MALDI MASS SPECTROMETRIC IMAGING TECHNIQUES

Introduction and Aims: Dialyzer polymer membranes are grossly classified as cellulose-based and synthetically produced membranes. Although cellulose membrane’s clearance and mechanical properties qualify it for use in dialyzer membranes, hydroxyl groups of these membranes lead to strong activation of the complement system. Therefore, recent membranes are manufactured from synthetic polymers.

For physical and chemical characterization of these materials of dialyzer a wide range of analytical methods is available. Techniques like NMR and x-ray are often combined for a detailed characterization of polymers used in medical applications. Over the last few years, MALDI mass-spectrometry has been developed as a powerful tool for space-resolved analysis, not least because of its mass accuracy and high sensitivity. MALDI imaging techniques combine the potential of mass-spectrometric analysis with imaging as additional spatial information with relevance for biocompatibility of the dialyzer membranes. MALDI imaging enables the visualization of localization and distribution of biomolecules, chemical compounds and other molecules on different surfaces.

Methods: In this study, surfaces of polymeric dialyzer membranes, consisting of polysulfone (PS) and polyvinylpyrrolidone (PVP) were investigated, regarding to chemical structure and compound’s distribution. Flat membranes as well as hollow fiber membranes were analyzed by MALDI imaging.

Results: First, analysis parameters like laser intensity and laser raster step size (spatial resolution in resulting image) were established in accordance with polymer’s characteristics. According to the manufacturing process luminal and abluminal membrane surfaces are characterized by differences in chemical composition and physical characteristics. The MALDI imaging demonstrated that the abluminal membrane surface is more consisting of polysulfone than polyvinylpyrrolidone, the luminal membrane surface displayed more PVP than PS. The addition of PVP as hydrophilic modifier to polysulfone-based membranes increases the biocompatibility of the dialysis membranes. The analysis of polymer distribution is a relevant feature for characterization of dialysis membranes.

Conclusions: In conclusion, MALDI imaging is a powerful technique for polymer membrane analysis, regarding not only detection and identification of polymers but also localization and distribution in membrane surfaces, which has strong impact on the biocompatibility of the dialyzer membranes.