Fluorescence quenching of bioactive molecules by nanodiamonds

In this work, the fluorescence quenching of two types of bioactive molecules - of the protein lysozyme and of the drug doxorubicin - by carboxylated detonation nanodiamonds in the result of their interaction has been studied. It was demonstrated that nanodiamonds effectively quench the fluorescence of lysozyme and doxorubicin but by different mechanisms. It was found that the fluorescence quenching of lysozyme by nanodiamonds is caused only by a static type of quenching while the fluorescence quenching of doxorubicin by nanodiamonds is caused by both static and dynamic types of quenching. We propose a hypothesis that the surface groups of nanodiamonds are the quenchers of the fluorescence and the variety of surface groups with which a fluorescent molecule interacts determines the fluorescence quenching mechanism. The accounting of our results will provide the insight in the nanodiamonds' visualization as well as the possible way to track the loading and subsequent unloading of drugs from the nanodiamonds' surface.