Search

Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) has been used for over a decade for the determination of purity and accurate molecular masses of macromolecular analytes, such as proteins, in solution. In the last few years the technique has been adapted to become a new surface analysis method with unique capabilities that complement established biomaterial surface analysis methods such as XPS and ToF-SSIMS. These new MALDI variant methods, which we shall collectively summarize as Surface-MALDI-MS, are capable of desorbing adsorbed macromolecules from biomaterial surfaces and detecting their molecular ions with high mass resolution and at levels much below monolayer coverage. Thus, Surface-MALDI-MS offers unique means of addressing biomaterial surface analysis needs, such as identification of the proteins and lipids that adsorb from multicomponent biological solutions in vitro and in vivo, the study of interactions between biomaterial surfaces and biomolecules, and identification of surface-enriched additives and contaminants. Surface-MALDI-MS is rapid, experimentally convenient, overcomes limitations in mass resolution and sensitivity of established biochemical techniques such as SDS-PAGE, and can in some circumstances be used for the quantitative analysis of adsorbed protein amounts. At this early stage of development, however, limitations exist: in some cases proteins are not detectable, which appears to be related to tight surface binding. This review summarizes ways in which Surface-MALDI-MS methods have been applied to the study of a range of issues in biomaterials surfaces research. [Copyright &y& Elsevier]

Abstract: Coated layers of biologically active molecules on synthetic biomaterials and biomedical devices can promote a variety of desirable biological reactions by the host body or the biological medium, such as cell and tissue attachment or deterring bacterial biofilm formation. Such coated layers should be immobilised covalently in order to avoid competitive displacement phenomena, and the use of surface-activating plasmas or plasma polymer interlayers with suitable chemical surface groups has proved to be very convenient means of grafting bioactive molecules onto solid materials surfaces. We review selected work on the covalent immobilisation of proteins and peptides onto solid biomaterial surfaces and describe efforts towards plasma methods that allow biomolecules to be covalently captured in a single step. After reviewing a number of approaches, we discuss in more detail the use of plasma polymer interlayers that possess aldehyde or epoxide surface groups; these groups react readily with amine groups on proteins and peptides without undesirable side reactions, and avoid other issues such as crosslinking. We also emphasise the importance of detailed surface analysis to verify that covalent grafting has indeed taken place, and to assess the surface density of grafted molecules. With suitably chosen peptides or proteins, such covalently grafted layers can support the surface attachment of delicate cells, or combat bacterial biofilm formation. [Copyright &y& Elsevier]