Absorbance measurement for interdisciplinary educational experiment on cytotoxicity

Abstract We propose a multidisciplinary educational experiment, linking knowledge and skills in physics, biology and information technology through the training and application of the research method by students. From a physics point of view, the experiment consists in light absorption measurement, and in terms of biology, it demonstrates the process of cytotoxicity evaluation by means of the colorimetric method neutral red uptake in vitro test. The test allows to determine the concentration of a test drug at which 50% cytotoxicity (CC 50 values) of the cells is observed. After initial exposure to the tested drug, neutral red (NR) is added to the cell culture medium, it is absorbed by the living cells and subsequently released in a desorb buffer. The cell culture medium becomes coloured, and the more intensive colour corresponds to higher cell viability, while more transparent solution corresponds to lower number of living cells. The NR concentration in the solution is estimated by the absorbance value. We measure the absorbance of NR by utilizing a very affordable educational-grade spectrometer and compare its output with that of a professional microplate reader. We show that the educational spectrometer gives a result on the CC 50 value that is in agreement with the acceptable values of the official protocol. We include a comment on the results when performing this laboratory exercise in one class of 18 year old students (in their last year of secondary education). The experiment can be also successfully applied in the laboratory practicum of first year university study.