ABSTRACT
A new quantitation method for mass spectrometry imaging (MSI) with matrix-assisted laser desorption/ionization (MALDI) has been developed. In this method, drug concentrations were determined by tissue homogenization of five 10 µm tissue sections adjacent to those analyzed by MSI. Drug levels in tissue extracts were measured by liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS). The integrated MSI response was correlated to the LC/MS/MS drug concentrations to determine the amount of drug detected per MSI ion count. The study reported here evaluates olanzapine in liver tissue. Tissue samples containing a range of concentrations were created from liver harvested from rats administered a single dose of olanzapine at 0, 1, 4, 8, 16, 30, or 100 mg/kg. The liver samples were then analyzed by MALDI-MSI and LC/MS/MS. The MALDI-MSI and LC/MS/MS correlation was determined for tissue concentrations of ~300 to 60,000 ng/g and yielded a linear relationship over two orders of magnitude (R(2) = 0.9792). From this correlation, a conversion factor of 6.3 ± 0.23 fg/ion count was used to quantitate MSI responses at the pixel level (100 µm). The details of the method, its importance in pharmaceutical analysis, and the considerations necessary when implementing it are presented.
Subject(s)
Histocytochemistry/methods , Molecular Imaging/methods , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods , Animals , Benzodiazepines/administration & dosage , Benzodiazepines/pharmacokinetics , Chromatography, Liquid , Linear Models , Liver/chemistry , Liver/metabolism , Male , Olanzapine , Rats , Rats, Sprague-Dawley , Tandem Mass Spectrometry , Tissue DistributionABSTRACT
We have developed an NMR chemical shift prediction system that enables high throughput automatic grading of NMR spectra. In support of high throughput synthetic efforts for our drug discovery program, a rapid and accurate analysis for identity was needed. The system was designed and implemented to take advantage of the NMR assignments that had been tabulated on internally generated research compounds. The system has been operational for four years and has been used in conjunction with an internally written grading program to successfully analyze several hundred thousand samples based only on their 1D 1H spectrum. A focused test of the system's accuracy on 1006 molecules demonstrated the ability to estimate the proton chemical shift with an average error of +/-0.16 ppm. This level of chemical shift accuracy allows for reliable structure confirmation by automated analysis using only proton NMR.
Subject(s)
Magnetic Resonance Spectroscopy/methods , Magnetic Resonance Spectroscopy/standards , Protons , Reference Standards , SoftwareABSTRACT
Experiments were performed to demonstrate the potential of counter-current chromatography (CCC) for the isolation of drugs and their metabolites from biological matrices relevant to the metabolism studies of pharmaceutical research. Examples of typical drugs are spiked into biological media ex vivo to provide test samples for analysis. A mass spectrometer hyphenated to a CCC allows for the detection of small molecule drugs within the matrix through selected ion monitoring, and fraction collection can provide material for further structural elucidation by NMR.
