Aim:This study aims at developing a nondestructive way for investigating protein adsorption on surfaces such as biomaterials using mass spectrometry.Methods:Ventricular cerebrospinal fluid in contact with poly carbonate membranes were used as adsorption templates and on-surface enzymatic digestion was applied to desorb proteins and cleave them into peptides. Mass spectrometric analysis provided both protein identification and determination of protein specific adsorption behavior.Results:In general, the adsorption increased with incubation time but also protein-specific time-resolved adsorption patterns from the complex protein solution were discovered.Conclusion:The method developed is a promising tool for the characterization of biofouling, which sometimes causes rejection and encapsulation of implants and can be used as complement to other surface analytical techniques.

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This study investigates if deeper understanding is achieved when combining nonlinear and linear chromatographic column characterization methods. As test systems, two hybrid columns (Phenomenex Gemini-NX C18 and Kromasil Eternity C18) and one classic one (Kromasil-C18) were selected. The nonlinear methods were based on firm adsorption theory and involved determination of adsorption isotherms followed by calculations with a new numerical tool, adsorption energy distribution, on probe components at different pH values. The linear methods involved the hydrophobic subtraction model and selected probe components retention factors as a function of pH. The combined analysis indicated that both complementary and confirmative information can be achieved regarding the actual model systems.

This study describes our efforts to study some of the mechanistic aspects of the earlier established on-surface enzymatic digestion (oSED) method. In a multitude of application areas, it has become important to be able to fully characterize and understand selective protein adsorption to biomaterial surfaces for various applications, including biomedicine (implants), nanotechnology (microchip surfaces and sensors) and materials sciences. Herein, the investigation of the mechanistic aspects was based on microdialysis catheter tubes that were flushed with controlled protein solutions mimicking the extracellular fluid of the brain. The protein adsorption properties were monitored using high-resolution liquid chromatography tandem mass spectrometry (LC-MS/MS) with a targeted method. The temporally resolved results show that most proteins stay adsorbed onto the surface during the entire digestion process and are only cut away piece by piece, whereas smaller proteins and peptides seem to desorb rather easily from the surface. This information will simplify the interpretation of data generated using the oSED method and can also be used for the characterization of the physicochemical properties controlling the adsorption of individual proteins to specific surfaces.