Advances in Bioanalytics and Biomarkers

Label Free High-Throughput ESI-MS: A Novel Sampling Interface for ADME and HTS

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  Hui Zhang, PhD

  Senior Principal Scientist
  Pfizer Inc.

Label-free LC/MS based screening technology is routinely used in pharmaceutical industries for hit discovery and various ADME profiling applications. Although the current analysis speed of less than 30 seconds per sample is quite promising, it still cannot match the throughput provided by plate-reader based HTS platforms. In this study direct injection is coupled with an open-port probe (OPP) for direct sampling into a standard ESI ion source. Screening speeds of <2 seconds-per-sample were demonstrated with high sensitivity (attomole loading), good quantitation capability (>3 orders of magnitude), and broad compound coverage (from small molecule pharmaceuticals to peptides and antibodies).
The use of a “classic” ESI ion source for MS analysis yielded a perfectly Gaussian-shaped signal peak with baseline width of 0.8 - 1.5 seconds. High sensitivity and reproducibility were demonstrated for this approach, showing linearity over three orders of magnitude, and sensitivity (attomole loading for small molecules, and sub-femtomole loading for intact antibody). The continuous-flow of carrier solvent for the OPP maintained ionization stability and actively cleaned the entire flow system resulting in no observed carry-over. The advantages of this integrated system approach were demonstrated with a Drug-Drug Interaction (DDI) assay, where various substrates/metabolites were monitored and compared to conventional analysis.