Indotricarbocyanine Dye Research Articles

Photophysical Properties of Indotricarbocyanine Dyes Complexed with Lipid-Transfer Protein Ns-LTP1

Photophysical Properties of Indotricarbocyanine Dyes Complexed with Lipid-Transfer Protein Ns-LTP1

Singlet Oxygen Generation by an Indotricarbocyanine Dye with Bulky Substituents

Singlet Oxygen Generation by an Indotricarbocyanine Dye with Bulky Substituents

Indotricarbocyanine dyes relevant for photodynamic therapy and their radicals: Substituent effects studied by optical and electrochemical methods

Photodynamic therapy is an effective and minimally invasive treatment method for cancer. A deeper understanding of the photocytotoxicity mechanism of cyanine dyes is necessary for the development of more efficient photosensitizers. We combine electrochemistry, optical and ESR spectroscopy, and quantum chemical calculations to study indotricarbocyanine dyes relevant for photodynamic therapy. The incorporation of 4-meso-chloride and a 3,5-o-phenylene bridge into the polymethine chain results in a hypsochromic shift of the absorption spectrum by ca. 30 nm and in a downward shift of the frontier orbitals energy levels by 0.1–0.3 eV. In addition, such substitution imparts stability to the electrogenerated radical dications of the dyes. The presence of 4-meso-chloride and a 3,5-trimethylene bridge in the polymethine chain causes the absorption spectrum to shift bathochromically by almost 40 nm and the HOMO–LUMO energy gap to decrease by ca. 0.1 eV. The radical dication of the dye with such substitution is particularly stable and exhibits improved electron delocalization. The radical dication of the dye with an unsubstituted polymethine chain is unstable due to its propensity to form dimers. The substituents at the nitrogen atoms are shown to have almost no influence on the optical and electrochemical properties of the indotricarbocyanine dyes. The radical dications of the dyes with an o-phenylene bridge can oxidize bromide ions, unlike the radical dications of the dyes with an unsubstituted polymethine chain or with a trimethylene bridge. The reported data can be used to develop new indotricarbocyanine dyes with desired characteristics.

SYNTHESIS AND ABSORPTION SPECTRA OF INDOTRICARBOCYANINE DYES WITH ELECTRON-DONATING GROUPS IN THE MESO-POSITION OF THE POLYMETHINE CHAIN

Recently, a large number of studies have been dedicated to chemistry and physical stu­dies of polymethine dyes, especially to the functio­na­lized symmetrical heptamethinecyanines based on the indole derivatives. Due to their unique and versatile spectral properties, which lie in the near infrared region (NIR), meso-substituted indotricarbocyanine dyes are widely used in various physical and biological fields. In the present work, we have developed methods of synthesis of a series of indotricarbocyanine dyes with di- and trimethylene bridging groups in the γ,γ'-positions and donor substituents in the meso-position of the polymethine chromophore and studied their effects on the spectral properties of the dyes. The obtained data indicated that the change of the substituent in the meso-position of the chromophore and the presence of a poly­me­thylene bridging groups allow to vary signi­ficantly the absorption maxima of the synthesized indoheptamethinecyanine dyes without altering the length of the polymethine chain. It was shown that the electron-donating nitrogen-containing substituents lead, according to the Forster-Dewar-Knott rule, to a hypsochromic shifts of the absorption maxima. However, it was found that the methoxy group in the meso-position of the polymethine chromophore in some cases exhibited unexpected "acceptor" properties due to a certain steric hindrance, resulting in a red shift of the absorption band, in contrast to the other donor substituents. Additionally, the effects of the insertion of di- and trimethylene bridging groups to the polymethine chain of the cyanine dyes on their spectral properties were studied. The synthesized meso-substituted indotricarbocyanines demonstrated significant solvatochromism and spectral properties that lie in the red and near-infrared regions.

Photophysical Properties of Indotricarbocyanine Dyes During Complexation with Serum Albumin

Photophysical Properties of Indotricarbocyanine Dyes During Complexation with Serum Albumin

PHOTOPHYSICAL PROPERTIES OF INDOTRICARBOCYANINE DYES DURING COMPLEXATION WITH SERUM ALBUMIN

The photophysical properties of indotricarbocyanine dyes upon complexation with serum albumin have been studied, and the technique for controlling their formation using electrophoresis has been optimized. In connection with the degradation of dye molecules under the action of acids, the search for the area of localization of the dye under study on the surface of the gel plate was carried out by recording the fluorescence spectra of the dye before protein fixation and visualization followed by the completion of the protocol for obtaining electrophoregrams. To minimize the possible influence of the luminescence of the gel components, the excitation was carried out by the radiation of a semiconductor laser with a wavelength of 684 nm, which initiates the fluorescence of the studied dyes. It was established that the position of the maxima and the half-width of the fluorescence spectra of dyes with an orthophenylene bridge in the conjugation chain in the regions of the electropherogram corresponding to the localization of albumin coincide with the characteristics of the emission of dyes in initial solutions with albumin, which makes it possible to reveal the formation of covalently bound complexes of dye molecules with albumin.

Spectroelectrochemical and ESR investigation of free radicals derived from indotricarbocyanine dyes for photodynamic therapy

Cyclic voltammetry, UV–Vis absorption spectroscopy, and electron spin resonance are applied to study the properties of indotricarbocyanine dyes and their radicals formed during electrooxidation. We use electrochemistry to generate relatively stable free radicals of the dyes under controlled conditions. The dyes undergo electrooxidation during the chronoamperometric electrolysis at 1.1 V (versus saturated calomel electrode) yielding radical dications. The radicals exhibit an absorption band that is blue-shifted relative to the parent dye (561 nm versus 714 nm). In acetonitrile solutions, the radicals are characterized by a lifetime of ca. 20 min and a g factor of 2.002. The oxidation potential of the dyes is slightly greater than that of bromide ions allowing the radicals of the dyes to interact with bromide ions. The ability of the indotricarbocyanine dyes to sensitize generation of highly reactive bromine radicals might play an important role in their photodynamic activity.

Regularities of complexation of indotricarbocyanine dyes with human blood serum proteins

The interaction of indotricarbocyanine dyes with human blood serum proteins was studied. The spectral and fluorescent properties of dyes in butanol, Dulbecco’s sodium and potassium phosphate buffer (0.14 mol/L) with pH 7.4, and human blood serum solutions were determined. It was shown that the spectral properties of dyes in butanol differ significantly from the spectral properties in solutions of Dulbecco’s sodium and potassium phosphate buffer and human blood serum, and that butanol effectively extracts the molecules of the studied dyes that do not form covalently bound complexes with blood serum components. By analysing the extraction products, the proportion of covalent complexes of dyes with protein molecules was determined. It has been established that indotricarbocyanine dyes with a chlorine-substituted orthophenylene bridge in the conjugation chain are partially passes into butanol, the degree of extraction depends on the ratio of dye and protein concentrations. Thus, at a concentration of 10 mmol/L in 5 % human serum, the degree of extraction of these dyes is ~50 – 60 % respectively, the proportion of dye molecules in strong covalently bound complexes with blood serum components is ~ 40 –50 %. On the contrary, the dye with a free polymethine chain is extracted almost completely (91.4 % extraction rate). The indotricarbocyanine dyes are promising for use as a photosensitisers for photodynamic therapy.

H*- and J-Aggregates of an Indotricarbocyanine Dye: Steady-State Spectral Properties and Excited-State Dynamics

H*-aggregates are a rarely observed type of molecular aggregates, with many of their properties yet to be investigated. The indotricarbocyanine dye under study is the first known compound able to produce both H*- and J-aggregates. Steady-state spectral properties, morphology, photoelectrochemical response, and excited-state dynamics of the H*-aggregates are investigated for the first time. Under 400 nm pumping, the deactivation of electronic excitations in the H*-aggregates follows two paths involving the top and bottom of the exciton band. This is consistent with the presence of a fast 3 ps and a slow 33 ps component in the decay trace of the ground-state bleaching. Under 800 nm pumping, the H*-aggregates are promoted to the bottom of the exciton band. Consequently, only the slow component is present in the decay trace of the ground-state bleaching. For the J-aggregates, the ground-state bleaching follows biexponential decay with the time constants of 1 and 20 ps under both 400 and 800 nm pumping. The relaxation involves only the bottom of the exciton band. The faster deactivation of electronic excitations in the J-aggregates is probably due to greater exciton delocalization: 9 molecules in the J-aggregates versus 4 molecules in the H*-aggregates. The obtained results can be used to create photonic devices containing the H*-aggregates.

Optical and Electrochemical Properties of Indotricarbocyanine Dyes for Photodynamic Therapy

Optical and Electrochemical Properties of Indotricarbocyanine Dyes for Photodynamic Therapy

Spectral properties of indotricarbocyanine dye in tissues of experimental animals

The paper presents the results of studies of the spectral properties of a photosensitizer based on indotricarbocyanine dye when accumulating in tissues of experimental animals. Using laser fluorescence spectroscopy, the in vivo and ex vivo fluorescence spectra of tissue-localized indotricarbocyanine dye were obtained for different time counts after intravenous administration. The profile of the pharmacokinetics of its accumulation and withdrawal was determined from the change in the intensity of fluorescence in the tumor and healthy muscle tissues of the photosensitizer. A monotonic deformation of its fluorescence spectrum was revealed in the tissues of tumor nodes and muscles of the thigh when registered through the skin over time after intravenous administration. The achievement of the maximum accumulation of the photosensitizer in the tumor correlates with the stabilization of the shape of its in vivo fluorescence spectrum. Thus, the maximum shift can be used as a diagnostic indicator of the maximum accumulation of indotricarbocyanine photosensitizer in the tumor tissues. The results were confirmed for two groups of animals: the first one – black mice of the C57Bl/6 line with an inoculated tumor of Clone M3 melanoma, the second – white mice of the ICR line with an inoculated tumor of Ehrlich ascites carcinoma. The analysis of the shape of the fluorescence spectrum of the photosensitizer during registration through the skin for animals with different colors has been carried out.

Spectral Properties of Indotricarbocyanine Dye during Self-Assembly of Its H*- and J-Aggregates

The results of studying the self-assembly of H*- and J-aggregates of indotricarbocyanine dye in a phosphate-buffered saline are given. The formation of nonluminescent H*-aggregates with an absorption band at 516 nm and a full width at half maximum of 35 nm (1303 cm–1) is observed for the dye under study at pH 7.0, while J-aggregates are practically absent. At pH 7.4, H*-aggregates of the dye are not formed, but the self-assembly of J-aggregates with an absorption band at 777 nm and a full width at half maximum (FWHM) of 30 nm (497 cm–1) is observed; their photoluminescence quantum yield does not exceed 10–6. It was found that a change in the solution temperature from 20 to 31°C reduces the time of self-assembly of H*‑aggregates by a factor of 25. An increase in the solution temperature from 20 to 80°C leads to the decomposition of both H*- and J-aggregates; the temperature, at which the absorbance at the band maximum decreases by half, is 37°C for the bands of H*-aggregates and 32°C for the band of J-aggregates. It is shown that the absorption bands that appear in the spectral range of 400–480 nm are attributed to electronic transitions to high excited states of dye aggregates.

Ultrafast Excited-State Dynamics in Molecular Aggregates of an Indotricarbocyanine Dye

The dynamics of the transient absorption spectra of H*- and J-aggregates of an indotricarbocyanine dye was studied using femtosecond pump-probe spectroscopy. Relaxation of the induced transmission of the H*-aggregates occurs with time constants of ~3 and ~30 ps with radiation pumping at λmax = 400 nm and ~30 ps with pumping at λmax = 800 nm. For J aggregates biexponential relaxation with time constants of ~1 and ~20 ps is observed in both cases. The fast component of the kinetics of transmission of the band of the H* aggregates with pumping at λmax =400 nm is due to the possibility of direct transition from the upper edge of the exciton band of the aggregate to the ground state, while the slow component is present as a result of concurrent fast transition from the upper edge of the exciton band to the lower edge and subsequent relaxation from this to the ground state. The fast component of the kinetics of transmission of the band of the J aggregates is determined by the possibility of transition from the unthermalized exciton state to the ground state, while the slow component is due to transition to the ground state after relaxation within the limits of the exciton band. The greater length of delocalization of the excitons in the J aggregates (nine molecules) compared with the H* aggregates (four molecules) appears not only as decrease of the half-width of the stationary absorption band but also as more rapid quenching of the excited states. It was shown that the H* aggregates have a narrow stationary absorption band at 514 nm and weak absorption with a maximum at 756 nm. With pumping at λmax = 800 nm there is a bathochromic shift of the maxima of the transmission band of the system as a result of the appearance of nonuniform broadening.

Spectrophotometrical purity and stability testing of a photosensitizer based on an indotricarbocyanine dye

The express method for testing purity and stability of an indotricarbocyanine dye based photosensitizer for photodynamic therapy was developed. Storage of the hydrophilic photosensitizer under unfavorable conditions resulted in contamination with a hydrophobic dye. The absorption spectrum of the hydrophobic dye was characterized by a new band at 514 nm that was absent in the absorption spectrum of the photosensitizer. There was no spectral overlap between this absorption band and the absorbance of the photosensitizer. Therefore, presence of the band at 514 nm allowed us to detect contamination of the photosensitizer substance with the hydrophobic dye. It was established that the optimal photosensitizer concentration for purity testing is ca. 0.8 mmol/L, when as little as 0.6 wt. % of the impurity can be detected. The developed method is not time consuming and requires accessible equipment only. Data obtained with this method was verified with the aid of liquid chromatography-mass spectrometry.

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.

Controlling H*- and J-aggregation of an indotricarbocyanine dye in aqueous solutions of inorganic salts

Aggregation process of a symmetrical cationic indotricarbocyanine dye in aqueous medium was studied. It was shown that self-assembled H*-aggregates with an absorption peak at 514 nm as well as J-aggregates with an absorption peak at 777 nm can be obtained. Both of the aggregate types are non-fluorescent. High concentration of a desired aggregate type can be obtained and stabilized by changing ionic strength and pH of the solution. At ionic strength of 170 mmol/L and pH 7.4 J-aggregates are stable. Decreasing pH as well as ionic strength leads to demise of J-aggregates and concomitant formation of H*-aggregates. Increasing temperature leads to a faster H*-aggregate formation. The type of aggregates can be changed by heating and subsequent cooling of the solution. An organic compound forming both H*- and J-aggregates has never been observed before. The fact that the H*- and J-bands are narrow, the shift between them is significant, the J-band is located in the far-red spectral region, and the type of aggregates can be controlled makes these objects promising for future applications.

Спектральные свойства индотрикарбоцианинового красителя в процессе самоорганизации его H-=SUP=-*-=/SUP=-- и J-агрегатов

Self-assembly of H*- and J-aggregates of an indotricarbocyanine dye in phosphate buffered saline was investigated. At pH value of 7.0 the dye studied was shown to form non-luminescent H*-aggregates with the absorption band peaked at 516 nm, its FWHM being 35 nm (1303 cm-1), whereas, J-aggregates are absent. At pH value of 7.4 the H*-aggregates are not formed, whereas, the J-aggregates are observed. The absorption band of the J-aggregates is peaked at 777 nm, its FWHM being 30 nm (497 cm-1). Photoluminescence quantum yield of the J-aggregates does not exceed 10-6. An increase in the solution temperature from 20 to 31oC results in a 25-fold decrease in the self-assembly time of the H*-aggregates. An increase in the solution temperature from 20 to 80oC is followed by a reversible decay of both the H*- and J-aggregates. The H*-aggregate (J-aggregate) absorption band is reduced two-fold at the solution temperature of 37oC (32oC). Thansitions of the dye aggregates to high-lying electronic excited states were evidenced in the steady-state absorption in the spectral range between 400 and 480 nm.

Spectral and Luminescent Properties and Morphology of Self-Assembled Nanostructures of an Indotricarbocyanine Dye

Spectral and luminescent properties of an indotricarbocyanine dye are studied in solutions and after deposition on quartz or silicon substrates. It is found that the dye molecules self-assemble in aqueous EtOH solutions to form H*-aggregates. The absorption band of the H*-aggregates shows a hypsochromic shift of 192 nm (5291 cm–1) relative to the absorption maximum of dye monomers (706 nm) and has a full width at half maximum of 21 nm (797 cm–1). The morphology of the H*-aggregates of the indotricarbocyanine dye is studied for the first time. It is found that the aggregates are rod-like species ~10 nm high, 100 nm wide, and several micrometers long. H-aggregates with a fluorescence maximum at 560 nm and Stokes shift of 325 cm–1 in addition to non-fluorescent H*-aggregates form in aqueous EtOH solutions and are nanoparticles with a height of 1–3 nm and lateral dimensions of ~100 nm.

Synthesis and characterization of novel zwitterionic heptamethine indocyanine fluorophores

Two novel electroneutral indotricarbocyanine dyes with two sulfo groups have been synthesized. They possess higher photo and thermal stability as compared to known analogue and were conjugated with aminoallyl-dUTP for enzymatic labeling of DNA by polymerase chain reaction.

Complex formation of albumin with tricarbocyanine dyes containing phosphonate groups.

The spectral characteristics, binding constants with bovine (BSA) and human serum albumin (HSA) and lifetimes of fluorescence in PBS and EtOH solutions and in the presence of BSA in PBS were measured for novel indotricarbocyanine dyes bearing remote phosphonate groups. These parameters are close to those for indocyanine green (ICG) indicating that the Coulomb interaction does not play a significant role in complex formation, and the binding is determined by the interaction of the dye polymethine chain with albumin. The fluorescence lifetimes of the complexes with BSA strongly indicate the formation of complexes of two types with different lifetimes. The complex with a longer fluorescence lifetime (740-800 ps) and major contribution (up to 88%) is bound to the more hydrophobic site and that with a shorter fluorescence lifetime (300-340 ps) to the more hydrophilic site.