MALDI-MS Profiling of Intact Blood Proteins without the Need for Freezing - Dried Serum Spots as Future Clinical Tools for Patient Screening

To open new ways for MALDI-MS-based patient screening, blood serum is the most preferred specimen because of its richness in patho-physiological information and due to ease of collection. To overcome deleterious freeze / thaw cycles and to reduce high costs for shipping and storage, we sought to develop a procedure which enables MALDI-MS protein profiling of blood serum proteins without the need for serum freezing. MALDI mass spectra from either (p)FFS or (p)DSS preparations showed on average 25 strong ion signals (mass range m/z 6000 to m/z 10,000) from intact serum proteins (apolipoproteins, complement proteins, transthyretin and hemoglobin) and from proteolytic processing products. Semi-quantitative analysis of three ion pairs: m/z 6433 and 6631, m/z 8205 and 8916, as well as m/z 9275 and 9422 indicated that the mass spectra from either (p)FFS or (p)DSS contained the same protein composition information. A workflow that avoids the conventional cold-chain and yet enables to investigate intact serum proteins and/or serum proteolysis products by MALDI-MS profiling was developed. The here described protocol tremendously broadens clinical application of MALDI-MS and simultaneously allows to reduce the costs for storage and shipping of serum samples.