Time-Resolved Non-Invasive Metabolomic Monitoring of a Single Cancer Spheroid by Microfluidic NMR

We present a quantitative NMR study comparing the metabolic activity in a spheroid and a monolayer of the same number of MCF-7 cells. Both cultures were carried out under hypoxic conditions on microfluidic devices with 2.5 µL sample volume. NMR spectra were obtained by periodically inserting the devices into a dedicated micro-NMR probe. The results demonstrate that quantitative, non-invasive metabolomic monitoring of microfluidic cultures with as few as 1250 individual cells is possible. Metabolite concentrations in the cultures were found to change linearly with time. The consumption rates of D-Glucose and the production rates of L-Lactic acid were approximately 2.5 times larger in the monolayer than in the spheroid. In contrast to the spheroids,
monolayers exhibited significant production of L-Alanine and L-Glutamine. Due to its non-invasive nature, metabolic monitoring by NMR can complement destructive fluorescent-based assays that are commonly used for read-out in microfluidic cultures.