MALDI-Mass spectrometry imaging (MALDI-MSI) was performed in positive
ion mode on a MALDI LTQ Orbitrap XL mass spectrometer (Thermo Scientific,
Waltham, MA, USA) equipped with a N2 laser. LTQ Tune software (Thermo
Scientific) was used to select the imaging region and step size, and Xcaliber
(Thermo Scientific, Waltham) was used to select the instrument parameters.
Imaging was performed on three control mice and three mice dosed with the
Gd-NM600 compound at 75 μm raster step size, from 130–2000 mass to
charge ratio (m/z) at 60K resolution. Two microscans were averaged at each
pixel. ImageQuest software (Thermo Scientific) was used to view raw data and
export the raw data to an imzML format. MSiReader software (1 (link)) was used to generate images unique to mice dosed
with the compound (experimental mice). Briefly, m/z elements that were present
in at least 10% of the interrogated zone (experimental mice) and in less than 5%
of the reference zone (control mice) or in over 5% of the reference zone with a
ratio greater than 2 were selected. Images for these m/z were then identified
and manually inspected.
For MALDI mass spectra of Gd-DOTA, and Gd-BOPTA (MultiHance), a mixture
of these compounds formulated at 1 μmol in distilled water and
2,5-dihydroxybenzoic acid (DHB, Acros Organics) matrix (40 mg/mL) was used to
obtain the MALDI mass spectra.
ion mode on a MALDI LTQ Orbitrap XL mass spectrometer (Thermo Scientific,
Waltham, MA, USA) equipped with a N2 laser. LTQ Tune software (Thermo
Scientific) was used to select the imaging region and step size, and Xcaliber
(Thermo Scientific, Waltham) was used to select the instrument parameters.
Imaging was performed on three control mice and three mice dosed with the
Gd-NM600 compound at 75 μm raster step size, from 130–2000 mass to
charge ratio (m/z) at 60K resolution. Two microscans were averaged at each
pixel. ImageQuest software (Thermo Scientific) was used to view raw data and
export the raw data to an imzML format. MSiReader software (1 (link)) was used to generate images unique to mice dosed
with the compound (experimental mice). Briefly, m/z elements that were present
in at least 10% of the interrogated zone (experimental mice) and in less than 5%
of the reference zone (control mice) or in over 5% of the reference zone with a
ratio greater than 2 were selected. Images for these m/z were then identified
and manually inspected.
For MALDI mass spectra of Gd-DOTA, and Gd-BOPTA (MultiHance), a mixture
of these compounds formulated at 1 μmol in distilled water and
2,5-dihydroxybenzoic acid (DHB, Acros Organics) matrix (40 mg/mL) was used to
obtain the MALDI mass spectra.