Study of fluorescence quenching by bilirubin of carbocyanine dye in complex with DNA. Effect of Cu<SUP>2+</SUP> additives

The effect of bilirubin on the spectral fluorescence properties of the cationic thiacarbocyanine dye Cyan 2 in the presence of DNA was studied. The Cyan 2 dye forms a non-covalent complex with DNA, which leads to an increase in the fluorescence of the dye. Interaction with bilirubin leads to effective quenching of dye fluorescence in complex with DNA (static mechanism), which can be used to construct a spectral-fluorescent sensor for bilirubin. The results of in vitro experiments are illustrated by in silico molecular docking experiments. The effect of Cu2+ ion additives can further enhance the quenching of dye fluorescence by bilirubin. Effective quenching constants and detection limits of bilirubin using the Cyan 2–DNA system (LOD and LOQ) are determined.