Imaging Spray coating

Another approach to matrix application is to robotically deposit small (pL to nL) droplets of matrix on discrete areas of the sample surface. When the droplets are deposited as arrays over the entire tissue surface, mass spectra can be acquired at each matrix spot and reconstructed into an image. In this case, potential analyte delocalization is limited to the area under the matrix spot, typically -100-250 pm with commercially available spotters (e.g., Portrait 630 by Labcyte [23], ChIP by Shimadzu, TM iD by LEAP Technologies). This approach is fundamentally a trade-off between spatial integrity and resolution, because what limits resolution in most cases is the diameter of the laser beam, which is typically much smaller than the diameter of the matrix spot (on the order of 30-50 pm). Samples prepared by spray-coating, either manually or robotically, may be imaged at the diameter of the laser beam, but may not have maintained analyte localization throughout the spray process. 

The SECM has been applied to image holes and humps obtained on a gold surface spray-coated with carbon (37,38). Compared to the gold, the... 

Microstructural analysis of suspension plasma sprayed Ti02 coatings by Raman spectroscopy and transmission electron microscopy correlated well with results obtained by XRD. The anatase content in the coatings varied between 10 and 22 mass%, dependent on spraying parameters. Raman spectroscopy enabled the imaging of the spatial 2D-distribution of the rutile and anatase (Podlesak et al., 2008). Transmission electron microscope enabled to visualise the contact areas between the lamellae inside sprayed coatings as well as the columnar growth of crystal inside the lamellae. 

Figure 6.2 shows cross-sectional SEM images of coating type I with maximum surface roughness (a), type II with maximum porosity (b) and type III with maximum tensile adhesion strength (c). The (crystalline) phase contents of the as-sprayed coatings are shown in Table 6.5. Coating type I has a maximum hydroxyapatite content of 66 3 mass%, followed by type III with 61 3 mass%. The... 

Figure 7.19 Cathodoluminescence images of an as-sprayed hydroxyapatite coating cross-section (a) and CL images of coatings immersed in Hank s Balance Salt Solution (HBSS) for 7 days (b) and 28days (c).

Figure 7.21 Cathodoluminescence images of Mn2+-doped hydroxyapatite powder (top), an as-sprayed coating (a), and coatings incubated in r-SBF (SBF-H, Table 7.8) for 1 day (b),...

Deshpande, S., Kulkarni, A., Sampath, S., and Herman, H. (2004) Application of image analysis for characterization of porosity in thermal spray coatings and correlation with small angle neutron scattering. Surf. Coat. Technol., 187, 6-16. 

To date, several reports have been published using MALDI imaging MS on whole-body (rat and mouse) tissue sections. Images of peptides, proteins, drugs, and metabolites have been presented. All of the published reports have used spray coating for application of matrix, but otherwise, they have differed in application and methodology. The earliest detailed report... 

Spray Coating. Although very thin and uniform coatings are possible with this method, its use in resist imaging has been limited due to concerns about waste caused by overspray. 

Flame spray coatings for metals Developer compositions for electrostatic images... 

Robotic droplet ejection holds several advantages over spray coating for matrix deposition including quality sample preparation and data reproducibility for mass spectrometric imaging. The small discrete droplets can be sampled hundreds of... 

Han and Schey [71] used a special matrix coating method in processing the bovine lenses sections (30 10 pm) for MS imaging. The tissue sections were first sprayed with an acetonitrile-water (50 50, vol/vol) solution resulting in a tightly bound section. After drying, the tissue sections were coated with a thin layer matrix of S A at 15 mg/mL in ethanol-water (50 50, vol/vol). After it was dried, the tissue sections were finally sprayed with several cycles of SA matrix solution at 15 mg/mL in ethanol-water-formic acid (44 44 12, vol/vol/vol). 

Stoeckli et al. [155] reported the whole-body imaging by MALDI. Three HLA-B27 transgenic mice were dosed intravenously with 0.5 mL of a saline solution of (5-peptide at 2 mg/mL. A fourth mouse was dosed with 0.5 mL of a saline solution of the Rheuma a-peptide at 2 mg/mL as a control. Mice treated with P-peptide were sacrificed at 5 min, 1 h, and 24 h postdose (one mouse per time point). Matrix coating was obtained by spraying 4 mL per plate of a solution of 10 mg/mL CHCA in acetonitrile-water (50 50) using a TLC sprayer. 

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