A label-free sensor system for chemotherapeutic drug screening

Here we report on the design and realisation of a measurement method and sensor system for the label-free determination of chemotherapeutic drug effectiveness. The measurement method is based on the CH₂-symmetric and CH₂-antisymmetric stretches of tumour cells. These CH₂-stretches in cells can visualize the formation of tight packed phospholipid, which are formed while the cells are being in apoptosis. The sensor system records IR absorbance of the CH₂-symmetric and CH₂-antisymmetric stretch at wavelengths 3.51μm and 3.42 μm, respectively. In addition, the IR absorbance at two reference wavelengths is determined to compensate for variations in the sample thickness and water content. By taken the ratio of the two stretches the CH₂-stretch ratio is obtained independent on sample thickness and confluency. The main components of the sensor system are mid-IR emitting LEDs, a photodiode, and narrow band-pass filters. Experiments on melanoma cell lines exposed to cisplatin show a significant decrease in CH₂-stretch ratio indicating that the proposed label-free sensing system has great potential for investigating the effectiveness of chemotherapeutic drugs on tumour cells.