Simultaneous LC-MS determination of glucose regulatory peptides secreted by stem cell-derived islet organoids

For studying stem cell-derived islet organoids (SC-islets) in an organ-on-chip platform, we have developed a reversed phase liquid chromatography tandem mass spectrometry (RPLC-MS/MS) method allowing for simultaneous determination of insulin, somatostatin-14, and glucagon, with improved matrix robustness compared to earlier methodology. Combining phenyl/hexyl-C18 separations using 2.1 mm inner diameter LC columns and triple quadrupole mass spectrometry, identification and quantification were secured with negligible variance in retention time and quantifier/qualifier ratios, negligible levels of carry-over (< 2%), and sufficient precision (± 10% RSD) and accuracy (± 15% relative error) with and without use of internal standard. The here developed RPLC-MS/MS method showed that the SC-islets have an insulin response dependent on glucose concentration, and the SC-islets produce and release somatostatin-14 and glucagon. The RPLC-MS/MS method for these peptide hormones was compatible with an unfiltered off-line sample collection from SC-islets cultivated on a pump-less, recirculating organ-on-chip (rOoC) platform. The SC-islets background secretion of insulin was not significantly different on the rOoC device compared to a standard cell culture well-plate. Taken together, RPLC-MS/MS is well suited for multi-hormone measurements of SC-islets on an organ-on-chip platform.