MALDI Imaging
The adoption of MALDI-TOF MS for imaging applications is a major recent development in the MALDI market. Such applications are leading to the rise in demand for sample preparation and data analysis software that are specific to MALDI imaging. Applications lie squarely in the life sciences area, primarily in histopathology. The market for MALDI imaging products already accounts for a significant and rapidly growing portion of the aftermarket for MALDI-TOF MS. MALDI-TOF MS is amenable to tissue imaging applications because it is a straightforward process. Samples are prepared using a microtome and are then coated with matrix for direct analysis via a MALDI interface, which allows the retention of spatial information. Commercial products that provide the accoutrements for MALDI-TOF imaging, primarily software and sample preparation equipment, became widely available within the past five years. Early on, scientists were preparing samples by manually coating tissue sections with matrix. While manual sample preparation is inexpensive, it requires skill and is not easily reproducible. Over the past several years, a number of automated sample preparation systems have been introduced that automatically apply a spray or spot matrix onto the sample, reducing the required expertise and improving reproducibility. New software applications developed for all major makes of MALDI-TOF instruments now make it possible to view color-coded spatial maps of the sample that indicate how compounds of interest are distributed. One of the biggest advantages of MALDI-TOF imaging over other imaging techniques is that dying and tagging is generally not required, making the MALDI-TOF method simpler and relatively inexpensive. Applications for MALDI-TOF are primarily histological and pathological in nature. Both plant and animal tissue sections can be analyzed for the distribution of specific drug compounds and their metabolites, which is currently the largest application area. MALDI-TOF imaging can also be used to identify the distribution of proteins and biomarkers. Products for MALDI-TOF imaging primarily include spotting and spraying sample preparation equipment and software. The combined market for such products amounted to less than $10 million in 2007, excluding the mass spectrometers themselves, but accounted for 15%–20% of the total aftermarket, as well as a small percentage of initial systems. The rapid growth of MALDI imaging products is also responsible for the growth of the aftermarket for MALDI-TOF MS. Applied Biosystems was one of the first MALDI-TOF vendors to introduce products specifically for MALDI imaging. More recently, MALDI-TOF market leader Bruker introduced its own automated MALDI imaging sample preparation system, as have Labcyte and LEAP Technologies. In 2007, Shimadzu adapted its CHIP-1000 MALDI sample preparation system to support imaging applications.