Abstract
Tumor cells exhibit prominent metabolic alterations through which they acclimatize to their stressful microenvironment. These cells have a high rate of glutaminolysis and release ammonia (NH(3)) as a byproduct, which may function as a diffusible signal among cancer cells and can reveal cellular heterogeneity. E7, a nematic liquid crystal (LC), is doped with 4-pentyl-4'-biphenyl carboxylic acid (PBA) and encapsulated in polymeric microcapsules (P-E7(PBA)), which are then immobilized on cells in a microfluidic channel. Normal human umbilical vein endothelial cells (HUVECs) and myeloma, human primary glioblastoma (U87), human colon carcinoma (Caco-2), and human breast adenocarcinoma (MCF-7) cells are investigated for the release of NH(3). The P-E7(PBA) is able to visualize NH(3) release from the cell via a radial-to-bipolar (R-B) orientation change, observed through a polarized optical microscope. The various cell lines significantly differ in their response time required for an R-B change. The mean response times for Caco-2, U87, and MCF-7 cells are 277, 155, and 121 s, respectively. NH(3) release from a single cell captured in a microwell flow chip shows a similar R-B change. The P-E7(PBA) droplets technology could be applied to other multiple targets by functionalizing LCs with different probes.