Targeted and nontargeted metabolomics has the potential
to evaluate
and detect global metabolite changes in biological systems. Direct
infusion mass spectrometric analysis enables detection of all ionizable
small molecules, thus simultaneously providing information on both
metabolites and lipids in chemically complex samples. However, to
unravel the heterogeneity of the metabolic status of cells in culture
and tissue a low number of cells per sample should be analyzed with
high sensitivity, which requires low sample volumes. Here, we present
the design and characterization of the direct infusion probe, DIP.
The DIP is simple to build and position directly in front of a mass
spectrometer for rapid metabolomics of chemically complex biological
samples using pneumatically assisted electrospray ionization at 1
μL/min flow rate. The resulting data is acquired in a square
wave profile with minimal carryover between samples that enhances
throughput and enables several minutes of uniform MS signal from 5
μL sample volumes. The DIP was applied to study the intracellular
metabolism of insulin secreting INS-1 cells and the results show that
exposure to 20 mM glucose for 15 min significantly alters the abundance
of several small metabolites, amino acids, and lipids.