A mid infrared LED-photodiode based sensor for cell analysis

We report on the development of a novel LED-photodiode based mid-infrared absorbance sensor system for label-free cell analysis. Compared to common techniques to distinguish healthy from malignant cells our sensor system does not require specific labeling or staining, or the use of expensive liquid nitrogen cooled IR spectrometers. The detection principle comprises a four-wavelength based absorbance measurement to determine the lipid CH₂-symmetric/CH₂-antisymmetric stretch ratio (3.51 and 3.42 ¿m, respectively). The other two wavelengths (3.33 and 3.57 ¿m) are used as reference points to derive a baseline for determination of the functional absorbance values at 3.51 and 3.42 ¿m. Our sensor experiments show significant differences in CH₂ stretch ratio of healthy and malignant epithelial kidney cells. The developed sensor has the potential for fast, low cost and label-free screening of suspicious biopsy samples.