Workpackage 1: Sample Preparation |
Workpackage 1 reviews the choice and the characterization of several chemical compounds which will be utilized along the program as references for (ME-) SIMS and MALDI mass spectrometry and mass spectrometry imaging. The objective is to enhance the performance of MALDI and SIMS mass spectrometry towards their imaging capabilities. Peptides, proteins, lipids, polymers and oligosaccharides are mapped with MALDI with the help of MALDI matrices, while lipids are mapped with SIMS with and without coating. In all the cases these compounds can be used either as calibrants or to adjust the mass spectrometer parameters. The compounds are separated in six classes:
All these compounds, as well as the reference spectra, are available all along the duration of the project to characterize and test the ion desorption methods, instrument performances in terms of sensitivity, mass resolution and/or spatial resolution. The second deliverable reviews the choice and the characterization of reference biological samples which will be utilized along the program as references for SIMS and/or MALDI mass spectrometry and mass spectrometry imaging, as well as their most utilized samples supports, sample preparation methods, sample storage, etc…One important accomplishment is that silicon wafers have been agreed by all the involved partners to become the reference sample support for the future of the project. This material brings together several important and necessary features, flatness, conductivity, purity, adhesion of samples, as well as a moderate price and an excellent reproducibility. Nevertheless, some of the other sample supports, which were previously utilized by the different partners, will still continued to be utilized for particular cases (e.g. optiTOF plates for the fixation of whole-body tissue sections). Concerning the standard samples, a general agreement has been found during the meeting held in Gif-sur-Yvette in December 2006 for rat brain tissue sections and several well known and well characterized cell lines. Characteristic spectra and images of the reference biological samples are provided In a report. Some examples are given below: Different sample treatments protocols utilized by the partners are described and discussed. The aim of these treatments is to obtain, for molecular imaging, and in both MALDI and SIMS, the best sensitivity, with the lowest spatial delocalization of the compounds. In MALDI, the application of a matrix at the surface of the sample is mandatory, and different methods are now supplanting the original method in which the tissue surface was manually coated with an air sprayer. Some of these methods can also be transposed to SIMS in which the addition of a matrix on the surface is not always utilized. At CNRS-Gif, a prototype of an automatic spotter has been developed in collaboration with a French company (Siliflow). The droplets are delivered by a patented piezoelectric ejector, having different nozzle diameters (80 & 150 µm), with different ejected droplet volume (1 & 6 nL, respectively). The ejector is connected to a syringe pump and all the sucking, ejection and rinsing steps are fully automated and computer controlled. The precise positioning of the droplet on the sample is performed by a computer controlled plate. This system is presently able to deposit several droplets of ~400 µm diameter (depending on the tissue, the sample support, etc) at the same position.
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