Label-free and time-resolved measurements of cell volume changes by surface plasmon resonance (SPR) spectroscopy

Cell volume and its regulation is one of the key players for cellular integrity and a strong indicator for several cell pathologies. But time-resolved volume measurements of adherently grown mammalian cells using established methods, such as extracellular impedance analysis or light microscopy, are complex and time-consuming. In this study, we demonstrate that surface plasmon resonance spectroscopy (SPR) is a powerful transducer device capable of reporting volume changes of cells that are directly grown on the SPR sensor surface. The approach is label-free, non-invasive and provides an outstanding time resolution. In proof-of-principle studies we recorded the volume change of confluent MDCK II cells induced by hypo- or hypertonic stimulation in a time-resolved manner. Comparison of the SPR-based experiments reported here with more recent studies using different approaches suggests a direct correlation between SPR signal shift and cell volume changes.