Low-coherence reflectometry for cell refractive index sensing

We demonstrate the use of near infra-red low-coherence reflectometry combined with low-cost, rectangular glass micro-capillaries for label-free refractive index sensing of non-homogenous fluids. To test the capability of the proposed method to investigate highly diffusing media, we estimate the average refractive index (RI) of whole milk and Red Blood Cells (RBC) inserted in rectangular glass capillaries with channel depth equal to 100 μm and 50 μm, respectively. Then, as an example of interest, we estimate the RI of hematological and epithelial cells in normal and malignant condition gently confined in capillaries with channel depth and walls thickness equal to 50 μm. The non-contact, remote optical readout was performed by means of a tungsten lamp emitting in the near infrared, thus with minimum invasiveness for biological tissues.