Real-Time Sensing of Cell Morphology by Infrared Waveguide Spectroscopy

We demonstrate that a live epithelial cell monolayer can act as a planar waveguide. Our infrared reflectivity measurements show that highly differentiated simple epithelial cells, which maintain tight intercellular connectivity, support efficient waveguiding of the infrared light in the spectral region of 1.4–2.5 µm and 3.5–4 µm. The wavelength and the magnitude of the waveguide mode resonances disclose quantitative dynamic information on cell height and cell-cell connectivity. To demonstrate this we show two experiments. In the first one we trace in real-time the kinetics of the disruption of cell-cell contacts induced by calcium depletion. In the second one we show that cell treatment with the PI3-kinase inhibitor LY294002 results in a progressive decrease in cell height without affecting intercellular connectivity. Our data suggest that infrared waveguide spectroscopy can be used as a novel bio-sensing approach for studying the morphology of epithelial cell sheets in real-time, label-free manner and with high spatial-temporal resolution.

本研究证实，活上皮细胞单层可作为平面光波导（planar waveguide）。我们通过红外反射率测量发现，维持紧密细胞间连接的高度分化单层上皮细胞，可在1.4–2.5 微米与3.5–4 微米的光谱区域内实现红外光的高效波导。波导模式共振的波长与幅值，可揭示细胞高度及细胞间连接的定量动态信息。为验证这一结论，我们开展了两项实验：其一，实时追踪钙耗竭诱导的细胞间接触破坏的动力学过程；其二，证实采用磷脂酰肌醇3-激酶（PI3-kinase）抑制剂LY294002处理细胞，可使细胞高度逐渐降低，且不影响细胞间连接。本研究数据表明，红外光波导光谱学可作为一种新型生物传感手段，能够以实时、无标记且高时空分辨率的方式研究上皮细胞层的形态学特征。