Cell movement monitoring using microcavity Mach-Zehnder interferometer

Real-time, label-free monitoring of cell dynamics in the cell culture is pivotal for advancing biomedical research. This particularly concerns studies on endothelial cells forming complex biological barriers like the blood-brain barrier (BBB). In this work, we report the application of a microcavity in-line Mach-Zehnder interferometer (μIMZI) fabricated in a single-mode optical fiber as a novel tool for high-sensitivity, non-invasive, real-time cell movement monitoring. The finite-difference time-domain (FDTD) method has been used to identify interactions between the electromagnetic field and cellular structures within the μIMZI. Next, the simulations considering local refractive index variations within the cavity provided a predictive framework for interpreting experimentally achieved μIMZI optical responses to cellular movements. By correlating simulated field distributions with experimental spectral features, this study demonstrates how numerical modeling enhances the understanding of dynamic processes such as cell adhesion, morphology changes, proliferation, and cell layer integrity. This method allows for efficient monitoring of changes in the several micrometers thick cell layer, which is typical for endothelial cells. Following endothelial cell behavior in real-time using μIMZI opens the possibility of in vitro modeling of more complex processes within the human body, such as the formation and functioning of the BBB.