Mass spectrometry has long been recognized as one of the leading analytical tools for the rapid characterization of biological macromolecules. The imaging function of mass spectrometry combines the capabilities of quantitative and qualitative identification with information on the location of an analyte within a sample. To achieve the maximum yield of information, it is necessary to optimize spatial resolution and mass spectral quality. Usually the optimization of one of these factors is detrimental to the other.
In this report, we describe the use of a dry sublimation device, which enabled us to perform spatial resolution of 10 µm, resolving individual cells within tissues.
To optimize sample preparation, we have investigated various approaches of applying the MALDI matrix to prepared slides. The general trend with these techniques is tht the “drier” the preparation, the smaller the matrix crystal size and consequent improvement in resolution. By employing sublimation, we avoid the use of solvents completely, resulting in improved spatial resolution, especially suited for the assessment of the limits of the instrument performance.
With large crystal no longer a limiting factor, it was possible to examine the role of minimum laser focus diameter and the precision of the sample stage movement in determining the limitations of spatial resolution by analyzing phospholipids, which desorb quite well from sublimed matrix.
As an experimental tissue, we selected rat cerebellum and testis. The choice was based upon the diversity and dimension of architectural features within these tissues.