Metabolite imaging by mass spectrometry: A new discovery tool

Mass spectrometry imaging is a rapidly emerging, powerful technique which not only allows the analysis of molecules such as lipids or peptides but also allows the spatial distribution of those metabolites to be mapped within flat biological tissue sections. It allows both targeted and untargeted imaging of thousands of metabolites with little or no preparation of the sample and negates the need for any complex chemical labeling. This makes it particularly useful for characterization of biological samples such as plant and mammalian tissues. Mass Spectrometry Imaging (MSI) utilizes several different sample introduction techniques however this review will concentrate mainly on matrix-assisted laser desorption/ionization mass spectrometry (MALDI) along with desorption electrospray ionization mass spectrometry (DESI) as these techniques are more widely used and well characterized.