Time-resolved non-invasive metabolomic monitoring of a single cancer spheroid by microfluidic NMR

We present a quantitative study of the metabolic activity of a single spheroid culture of human cancer cells. NMR (nuclear magnetic resonance) spectroscopy is an ideal tool for observation of live systems due to its non-invasive nature. However, limited sensitivity has so far hindered its application in microfluidic culture systems. We have used an optimised micro-NMR platform to observe metabolic changes from a single spheroid. NMR spectra were obtained by directly inserting microfluidic devices containing spheroids ranging from 150 mu m to 300 mu m in diameter in 2.5 mu L of culture medium into a dedicated NMR probe. Metabolite concentrations were found to change linearly with time, with rates approximately proportional to the number of cells in the spheroid. The results demonstrate that quantitative monitoring of a single spheroid with <= 2500 cells is possible. A change in spheroid size by 600 cells leads to a clearly detectable change in the l-Lactic acid production rate (p=3.5x10-3). The consumption of d-Glucose and production of l-Lactic acid were approximately 2.5 times slower in spheroids compared to monolayer culture of the same number of cells. Moreover, while cells in monolayer culture were found to produce l-Alanine and l-Glutamine, spheroids showed slight consumption in both cases.

Automated summary

The study utilized a micro-NMR platform to observe metabolic changes in a single spheroid culture of human cancer cells, revealing interesting findings such as linear monitoring of cell numbers and differences in metabolic rates between spheroids and monolayer cultures.