Ambient Nanoelectrospray Ionization with In-Line Microdialysis for Spatially Resolved Transient Biochemical Monitoring within Cell Culture Environments

摘要

We have developed a new mass spectrometry (MS) based approach for continuous, spatially resolved in vitro biochemical detection and demonstrated its utility in a 3-D cell culture system. Extracellular liquid is passively extracted at a low flow rate (approx10 nL/s) through a small bore silica capillary (ID 50 (mu)m); inline microdialysis (MD) removes ions that would interfere with mass spectrometric analysis, and the sample is ionized by nanoelectrospray ionization (nano-ESI) and mass analyzed in a time-of-flight mass spectrometer. The system successfully detects low-volume, low-concentration releases of a small protein (8 (mu)L of 5 (mu)M cytochrome-c, molecular mass approx12 kDa) and exhibits approx1 min temporal resolution. The system also displays sensitivity to probe proximity to the sample release point. Due to the sensitivity of ESI-MS and its ability to simultaneously detect and identify multiple unanticipated biochemicals, this approach shows considerable potential as a biomarker discovery tool.