Quantitative MALDI Tandem Mass Spectrometric Imaging of Cocaine from Brain Tissue with a Deuterated Internal Standard

Abstract

Mass spectrometric imaging (MSI) is an analytical technique used to determine the distribution of individual analytes within a given sample. A wide array of analytes and samples can be investigated by MSI, including drug distribution in rats, lipid analysis from brain tissue, protein differentiation in tumors, and plant metabolite distributions. Matrix-assisted laser desorption/ionization (MALDI) is a soft ionization technique capable of desorbing and ionizing a large range of compounds, and it is the most common ionization source used in MSI. MALDI mass spectrometry (MS) is generally considered to be a qualitative analytical technique because of significant ion-signal variability. Consequently, MSI is also thought to be a qualitative technique because of the quantitative limitations of MALDI coupled with the homogeneity of tissue sections inherent in an MSI experiment. Thus, conclusions based on MS images are often limited by the inability to correlate ion signal increases with actual concentration increases. Here, we report a quantitative MSI method for the analysis of cocaine (COC) from brain tissue using a deuterated internal standard (COC-d(3)) combined with wide-isolation MS/MS for analysis of the tissue extracts with scan-by-scan COC-to-COC-d(3) normalization. This resulted in significant improvements in signal reproducibility and calibration curve linearity. Quantitative results from the MSI experiments were compared with quantitative results from liquid chromatography (LC)-MS/MS results from brain tissue extracts. Two different quantitative MSI techniques (standard addition and external calibration) produced quantitative results comparable to LC-MS/MS data. Tissue extracts were also analyzed by MALDI wide-isolation MS/MS, and quantitative results were nearly identical to those from LC-MS/MS. These results clearly demonstrate the necessity for an internal standard for quantitative MSI experiments.

Quantification of Candesartan in Mouse Plasma by MALDI-TOFMS and in Tissue Sections by MALDI-Imaging Using the Stable-Isotope Dilution Technique

“…Pirman et al reported some studies in which the contents of small molecules in brain tissue sections were determined by quantitative MALDI-MS/MS imaging using the same stable isotope dilution technique and discussed about the origin of a false-positive signal. 10,11) It concluded that the similar false-positive signal in the tissue section was the non-labeled target drug with no significant contribution from impurity of the stable isotopic standard. Similarly in our case, the false-positive blank signal in the mouse blood vessel and kidney sections was partially derived from an impurity of deuterated CAD in the same manner, although it was not the same as MALDI matrix in their study.…”

“…Recently, some groups demonstrated that the quantitative analysis by MALDI imaging MS/MS using a stable isotopic internal standard enabled us to determine contents of small DOI: 10.5702/massspectrometry.A0021 molecules in animal tissue sections. [10][11][12] By the incorporation of a uniformly applied internal standard coupled with the specificity of MS/MS technique and scan-by-scan ionsignal normalization, the quantitative MALDI imaging was improved in a tissue section.…”

Quantification of Small Molecule Drugs in Biological Tissue Sections by Imaging Mass Spectrometry Using Surrogate Tissue-Based Calibration Standards

“…On the other hand, a stable isotope-labeled version of the target drug is considered ideal for the normalization of ion suppression. 24) In this study, we used S-777469-d 10 , a deuterium-labeled version of S-777469, as an internal standard to maximize the quantitative capability of MALDI-IMS, and uniformly coated S-777469-d 10 solution over the sections to allow pixel-by-pixel normalization (Figs. 3c and f).…”

“…[22][23][24] e preparation of analyte calibration standards is also a key factor for successful quanti cation because analyte extraction from tissue sections into the matrix solution should be considered. 16) Several studies on MALDI-IMS method development for the quanti cation of small molecule drugs have been reported in the past few years.…”

Partial synthesis of ganglioside and lysoganglioside lipoforms as internal standards for MS quantification

“…In addition to ganglioside classes, which are defi ned by the carbohydrate head group, MS also allows profi ling of ganglioside lipoforms ( 15 ) with different structure of acyl chain and sphingoid base. Ganglioside quantifi cation is applied to ganglioside pattern investigation ( 16 ) in food analyses ( 17,18 ), but is also used in the analysis of lysosomal storage diseases ( 19 ) and in quantitative imaging MS ( 20 ). Lysogangliosides play a role in the pathogenesis of gangliosidoses.…”