While this conventional procedure might be fully automated, a direct surface sampling, ionization, and analysis method by mass spectrometry of such thin tissue sections, including the same tissues used for WBA study, would save time and other resources by shortening the sampling and extraction steps of a quick first pass look for drug and metabolite distributions.Ĭurrently, the most widely used technique for molecular identification of drug related materials directly from animal thin tissue sections is matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). (3-5) While this technique continues to mature, some lingering limitations are apparent. First, MALDI-MS requires the careful coating of the tissue with a matrix compound prior to the MS analysis. (4) This may be because phase II metabolites, like glucuronides and glutathione conjugates, are relatively fragile and do not survive the laser desorption/ionization process intact.Īlso second, most MALDI-MS analyses report detection of parent drug and some phase I metabolites, but apparently only rarely are phase II metabolites reported. ![]() Newer atmospheric pressure surface sampling/ionization techniques, (6-8) like desorption electrospray ionization (DESI)-MS, (9) have also been demonstrated for determining drug related materials in thin tissue sections. ![]() (10) This technique does not require a matrix coating, but initial reports from the analysis of tissue from drug dosed animals indicate that overall sensitivity may need improvement and detection of glucuronides known to be present in the tissue have so far been unsuccessful.
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