Substitution reactions in carbocyanine dyes are used to determine nucleophilic compounds. The interaction of a chlorine-containing carbocyanine dye with a number of medicinal substances is studied. It is shown that, in the reaction with isoniazid in the presence of a surfactant, this dye selectively changes color from yellow-green to violet. The formation of a product of the substitution of chlorine for isoniazid is proven by chromatography–mass spectrometry. The reaction proceeds in 20 min in the presence of 1 mM cetyltrimethylammonium bromide. The limit of detection for isoniazid in water by the photometric method is 10 μg/mL and in diluted artificial urine using fluorimetry, 0.3 μg/mL. The procedure does not use full-spectrum equipment, which simplifies the determination.

For the purpose of imaging hydrophilic drugs, aggregates of gentamicin and vinorelbine with carbocyanine dyes fluorescing in the near-infrared region of the spectrum and a laurate ion as a counterion are obtained. To isolate the aggregates, precipitation from an aqueous solution of components is used. The size of the aggregates with gentamicin range from 200 to 600 nm; with vinorelbine, from 400 to 1000 nm; the surface ζ potential varies in the range of –15…–5 mV. The aggregates are sorbed by the subcutaneous fatty tissue, muscle, bone, and endothelial tissues of chickens. In the future, the resulting aggregates can be used to visualize drug delivery to the tissues of living organisms.

A method for the synthesis of a series of symmetric and asymmetric conformationally fixed tricarbocyanines was developed based on benzоindolenine containing ethyl phosphonate and diethyl phosphonate groups in the linker at the quaternary nitrogen atom of the indolenine fragment. The polymethine chain meso position was modified by nucleophilic substitution of chlorine with O- and N-nucleophiles. Their absorption and fluorescence spectra were recorded, the possibility of further use of phosphonate-substituted tricarbocyanines as biomarkers was demonstrated. The dark cytotoxicity of synthesized compounds was studied, the possibility of their accumulation in HCT116, MCF7 cancer cells was shown.

New tricarbocyanine dyes with phosphonate groups (2, 3) were synthesized and their binding constants to bovine serum albumin (BSA) were determined. The binding constants of the synthesized tricarbocyanines and cardiogreen (1) (K b ~ 105 M–1) are similar, indicating an insignificant contribution of the Coulomb interaction to the complex formation, which is determined by the polymethine chain interaction with BSA. The fluorescence lifetimes attest to the formation of two types of complexes: the lifetime of the dye complex with BSA with a major contribution (~80%) is 740–800 ps, and a lifetime of ~210 ps corresponds to the complex of dye aggregates with BSA.