Spectral Properties of an Indotricarbocyanine Dye upon Complexation by Detonation Nanodiamonds and Blood Serum Proteins

Spectral properties of an indotricarbocyanine dye upon complexation with nanodiamonds in aqueous solutions were studied. Complexation was accompanied by disappearance of the H*-aggregate absorption band at 514 nm and a bathochromic shift of long-wavelength absorption maxima from 706 to 718 nm. The dye emission spectrum was almost unchanged. The fluorescence excitation peak shifted from 706 to 710 nm. The dye carboxyl groups played an important role in the complexation of the dye to nanodiamonds based on an analysis of the IR absorption spectra. The complexes broke down and the dye molecules bonded to serum proteins in the presence of human blood serum. This was confirmed by significant increases in the fluorescence lifetime and anisotropy. The obtained complexes could be used as a basis for fluorescent biosensors.