Refractive Index Morphology Imaging Microscope System Utilizing Polarization Multiplexing for Label-Free Single Living Cells

Detections of internal substances and morphologies for label-free living cells are crucial for revealing malignant diseases. With the phase serving as a coupling of refractive index (RI) (marker for substances) and thickness (morphology), existing decoupling methods mainly rely on complex integrated systems or extensive optical field information. Developing simple and rapid decoupling methods remains a challenge. This study introduces a refractive index morphology imaging microscope (RIMIM) system utilizing polarization multiplexing for label-free single living cells. By simultaneous degree of circular polarization (DOCP) imaging and noninterferometric quantitative phase imaging (QPI), the intracellular refractive index distribution (IRID) and morphology can be decoupled. The optical thickness calculated from the phase is input into the circular depolarization decay model (CDDM) of degree of circular polarization to retrieve IRID. Subsequently, the thickness can be decoupled from phase result using retrieved IRID. Experiments conducted on mouse forestomach carcinoma (MFC) cells and human kidney-2 cells (HK-2) demonstrated the RIMIM system’s ability to retrieve IRID and decouple fine morphology. Additionally, the RIMIM system effectively detected membrane damage and changes in erastin-induced ferroptotic HK-2 cells, with average and root-mean-square of surface folds 65.5% and 70.0% higher than those of normal HK-2 cells. Overall, the RIMIM system provides a simple and rapid method for decoupling RI and fine morphology, showing great potential for label-free live cells’ cytopathology detection.