Application of CCK-8 kit in the evaluation of the interaction between bacteria and black nanoparticles

Blanka Emődy-Kiss, János Fent and Susan Lakatos

Institute for Epidemiological and Scientific Research, Medical Centre of HDF
H-1134, Róbert Károly krt. 44., Budapest, Hungary

The CCK-8 kit is recommended by the manufacturer for measuring the viability of eukaryotic cells. Its use is based on the conversion of the colorless WST-8 molecule into colored, water-soluble formazan in the presence of NADH, produced by living cells. We wanted to find out whether this kit was suited to the evaluation of bacterial systems containing black nanoparticles.

Staphylococcus aureus samples were studied in the presence of single-walled carbon nanotubes. Changes in the CCK-8 signal at 450 nm, characteristic of bacterial metabolism, were measured. Simultaneously, the turbidity of the samples was measured at 650 nm, which is characteristic of bacterial growth.

The presence of single-walled carbon nanotubes in the samples resulted in a reduction of the CCK-8 signal compared to the control sample. This may suggest a decrease in NADH availability as a consequence of a possible decrease in the metabolic activity of the bacteria. However, the turbidity, characteristic of bacterial growth varied equally in the treated and the control samples. A decrease in the CCK-8 signal in a bacterial system is not necessarily proportional to the decrease in the number of living bacteria in the system.



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