Understanding MTT–Graphene Oxide Interactions for Accurate Viability Measurements

Abstract

Large surface enriched with oxygen-containing groups, enabling interactions with various molecules, makes graphene oxide (GO) valuable in sensing, imaging, and therapy but complicates cytotoxicity assessment using standard colorimetric assays. In this study we examined adsorption of tetrazolium (MTT) ion, used as a dye in colorimetric assay, on GO. Using a cell-free system, adsorption behavior was modelled with Freundlich, Langmuir, and Langmuir Freundlich (Sips) isotherms. Satisfactory fits were obtained by all models. However, the Sips model provided the best nonlinear regression performance, while Langmuir fit best under linear regression. π–π interactions between MTT and the GO aromatic rings were discussed as the most probable driving force for the adsorption. Interactions between GO and components of the culture medium (DMEM) and serum (FBS) were indirectly observed by comparing MTT monolayer capacity values with the values obtained in aqueous MTT solutions. The results confirm that GO interactions with MTT, responsible for the interferences, can be described quantitatively in the presence of cell supporting medium and that corrective adjustments of the colorimetric assay  results may be required, yet the question remains whether such corrections can be applied in practice. The present study provides an initial foundation for assessing their feasibility.