New Cysteine-Containing PEG-Glycerolipid Increases the Bloodstream Circulation Time of Upconverting Nanoparticles.

Upconverting nanoparticles have unique spectral and photophysical properties that make them suitable for development of theranostics for imaging and treating large and deep-seated tumors. Nanoparticles based on NaYF4 crystals doped with lanthanides Yb3+ and Er3+ were obtained by the high-temperature decomposition of trifluoroacetates in oleic acid and 1-octadecene. Such particles have pronounced hydrophobic properties. Therefore, to obtain stable dispersions in aqueous media for the study of their properties in vivo and in vitro, the polyethylene glycol (PEG)-glycerolipids of various structures were obtained. To increase the circulation time of PEG-lipid coated nanoparticles in the bloodstream, long-chain substituents are needed to be attached to the glycerol backbone using ether bonds. To prevent nanoparticle aggregation, an L-cysteine-derived negatively charged carboxy group should be included in the lipid molecule.

A novel bacteriochlorin-styrylnaphthalimide conjugate for simultaneous photodynamic therapy and fluorescence imaging.

Propargyl-152,173-dimethoxy-131-amide of bacteriochlorin e (BChl) and a 4-(4-N,N-dimethylaminostyryl)-N-alkyl-1,8-naphthalimide bearing azide group in the N-alkyl fragment were conjugated by the copper(i)-catalyzed 1,3-dipolar cycloaddition to produce a novel dyad compound BChl-NI for anticancer photodynamic therapy (PDT) combining the modalities of a photosensitizer (PS) and a fluorescence imaging agent. A precise photophysical investigation of the conjugate in solution using steady-state and time-resolved optical spectroscopy revealed that the presence of the naphthalimide (NI) fragment does not decrease the photosensitizing ability of the bacteriochlorin (BChl) core as compared with BChl; however, the fluorescence of naphthalimide is completely quenched due to resonance energy transfer (RET) to BChl. It has been shown that the BChl-NI conjugate penetrates into human lung adenocarcinoma A549 cells, and accumulates in the cytoplasm where it has a mixed granular-diffuse distribution. Both NI and BChl fluorescence in vitro provides registration of bright images showing perfectly intracellular distribution of BChl-NI. The ability of NI to emit light upon excitation in imaging experiments has been found to be due to hampering of RET as a result of photodestruction of the energy acceptor BChl unit. Phototoxicity studies have shown that the BChl-NI conjugate is not toxic for A549 cells at tested concentrations (<8 µM) without light-induced activation. At the same time, the concentration-dependent killing of cells is observed upon the excitation of the bacteriochlorin moiety with red light that occurs due to reactive oxygen species formation. The presented data demonstrate that the BChl-NI conjugate is a promissing dual function agent for cancer diagnostics and therapy.

Pharmacokinetics of Chlorin e6-Cobalt Bis(Dicarbollide) Conjugate in Balb/c Mice with Engrafted Carcinoma.

The necessary precondition for efficient boron neutron capture therapy (BNCT) is control over the content of isotope 10B in the tumor and normal tissues. In the case of boron-containing porphyrins, the fluorescent part of molecule can be used for quantitative assessment of the boron content. Study Objective: We performed a study of the biodistribution of the chlorin e6-Cobalt bis(dicarbollide) conjugate in carcinoma-bearing Balb/c mice using ex vivo fluorescence imaging, and developed a mathematical model describing boron accumulation and release based on the obtained experimental data. Materials and Methods: The study was performed on Balb/c tumor-bearing mice (CT-26 tumor model). A solution of the chlorin e6-Cobalt bis(dicarbollide) conjugate (CCDC) was injected into the blood at a dose of 10 mg/kg of the animal's weight. Analysis of the fluorescence signal intensity was performed at several time points by spectrofluorimetry in blood and by laser scanning microscopy in muscle, liver, and tumor tissues. The boron content in the same samples was determined by mass spectroscopy with inductively coupled plasma. Results: Analysis of a linear approximation between the fluorescence intensity and boron content in the tissues demonstrated a satisfactory value of approximation reliability with a Spearman's rank correlation coefficient of r = 0.938, p < 0.01. The dynamics of the boron concentration change in various organs, calculated on the basis of the fluorescence intensity, enabled the development of a model describing the accumulation of the studied compound and its distribution in tissues. The obtained results reveal a high level of correspondence between the model and experimental data.

Chlorin e6 fused with a cobalt-bis(dicarbollide) nanoparticle provides efficient boron delivery and photoinduced cytotoxicity in cancer cells.

Further development of boron neutron capture therapy (BNCT) requires new neutronsensitizers with improved ability to deliver (10)B isotopes in cancer cells. Conjugation of boron nanoparticles with porphyrin derivatives is an attractive and recognized strategy to solve this task. We report on breakthroughs in the structural optimization of conjugates of chlorin e6 derivative with cobalt-bis(dicarbollide) nanoparticles resulting in the creation of dimethyl ester 13-carbomoylchlorin e6 [N-hexylamine-N'-ethoxyethoxy]-cobalt-bis(dicarbollide) (conjugate 1). Conjugate 1 is able to accumulate quickly and efficiently (distribution factor of 80) in cancer cells, thus delivering more than 10(9) boron atoms per cell when its extracellular concentration is more than 1 µmol L(-1). Also 1 is an active photosensitizer and is phototoxic towards human lung adenocarcinoma A549 cells at 80 nmol L(-1) (50% cell death). Photoinduced cytotoxicity of 1 is associated with lipid peroxidation, lysosome rupture and protease activity enhancement. Conjugate 1 fluoresces in the red region (670 nm), which is useful to monitor its accumulation and distribution in vivo. It is not toxic to cells without activation by neutrons or photons. Structural features that improve the functional properties of 1 are discussed. The properties of 1 warrant its preclinical evaluation as a multifunctional agent for BNCT, photodynamic therapy and fluorescent tumor diagnosis.

Cobalt bis(dicarbollide) versus closo-dodecaborate in boronated chlorin e(6) conjugates: implications for photodynamic and boron-neutron capture therapy.

Conjugation of boron nanoparticles with porphyrins is an attractive way to create dual agents for anticancer boron neutron capture therapy (BNCT) and photodynamic therapy (PDT). Properties of chlorin e(6) conjugated with two cobalt bis(dicarbollide) nanoparticles (1) or with a closo-dodecaborate nanoparticle (2) are reported. Fluorescent dianionic conjugates 1 and 2 penetrate in A549 human lung adenocarcinoma cells, stain cytoplasm diffusely and accumulate highly in lysosomes but are not toxic themselves for cells. Average cytoplasmic concentration of boron atoms (B) achieves 270 µM (ca. 2 × 10(8) B/cell) and 27 µM (ca. 2 × 10(7) B/cell) at the 1.5 µM extracellular concentration of 1 and 2, respectively, that makes conjugate 1 especially suitable for BNCT. Conjugate 2 causes photoinduced cell death at micromolar concentrations and can be considered also as a photosensitizer for PDT. Conjugates 1 and 2 have high quantum yields of singlet oxygen generation (0.55 and 0.85 in solution, respectively), identical intracellular localization and similar lipid-like microenvironment but conjugate 1 possesses no photoinduced cytotoxicity. A presence of cobalt complexes in conjugate 1 is supposed to be a reason of the observed antioxidative effect in cellular environment, but an exact mechanism of this intriguing phenomenon is unclear. Due to increased intracellular accumulation and absence of photoinduced cytotoxicity conjugate 1 is promising for fluorescence diagnostics of cancer.

Photodiagnosis and photodynamic effects of bacteriochlorin-naphthalimide conjugates on tumor cells and mouse model.

Photo-induced cytotoxicity and antitumor activity of a series of dual function agents for photodynamic therapy (PDT) and fluorescent imaging based on bacteriochlorin photosensitizer conjugated with various naphthalimide fluorophores was studied in vitro using murine tumor cells of S37 sarcoma and in vivo on mice bearing murine S37 sarcoma. Upon irradiation at the absorption maximum of the photosensitizer, the activity of conjugates was as high as in the case of individual bacteriochlorin, while an additional excitation of the naphthalimide fragment led to an increase in the PDT efficacy due to resonance energy transfer from the fluorophore to photosensitizer. The fluorescence contrast and specific cytotoxic activity measurements indicate that the conjugate of bacteriochlorin with 3,4-dimethoxestyrene-substituted naphthalimide is the most promising agent for the application as theranostic in PDT.

Highly Purified Conjugates of Natural Chlorin with Cobalt Bis(dicarbollide) Nanoclusters for PDT and BNCT Therapy of Cancer.

To combine the neutron-capturing and photodynamic properties of boron nanoclusters and derivatives of natural chlorins, respectively, in one molecule, conjugate of chlorin e6 methyl ester with cyclen and dioxane and nitrile derivatives of cobalt bis(dicarbollide) were synthesized. The conditions for the purification of compounds by HPLC were selected since the work with natural compounds is complicated by the production of closely related impurities.

Novel Cationic Meso-Arylporphyrins and Their Antiviral Activity against HSV-1.

This work is devoted to the search for new antiherpes simplex virus type 1 (HSV-1) drugs among synthetic tetrapyrroles and to an investigation of their antiviral properties under nonphotodynamic conditions. In this study, novel amphiphilic 5,10,15,20-tetrakis(4-(3-pyridyl-n-propanoyl)oxyphenyl)porphyrin tetrabromide (3a), 5,10,15,20-tetrakis(4-(6-pyridyl-n-hexanoyl)oxyphenyl)porphyrin tetrabromide (3b) and known 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetraiodide (TMePyP) were synthesized, and their dark antiviral activity in vitro against HSV-1 was studied. The influence of porphyrin's nanosized delivery vehicles based on Pluronic F127 on anti-HSV-1 activity was estimated. All the received compounds 3a, 3b and TMePyP showed virucidal efficiency and had an effect on viral replication stages. The new compound 3b showed the highest antiviral activity, close to 100%, with the lowest concentration, while the maximum TMePyP activity was observed with a high concentration; porphyrin 3a was the least active. The inclusion of the synthesized compounds in Pluronic F-127 polymeric micelles had a noticeable effect on antiviral activity only at higher porphyrin concentrations. Action of the received compounds differs by influence on the early or later reproduction stages. While 3a and TMePyP acted on all stages of the viral replication cycle, porphyrin 3b inhibited viral replication during the early stages of infection. The resulting compounds are promising for the development of utilitarian antiviral agents and, possibly, medical antiviral drugs.

Conjugate of chlorin е6 with iron bis(dicarbollide) nanocluster: synthesis and biological properties.

Background: Efficiency of both photodynamic and boron-neutron capture anticancer therapies (BNCT) depends on the properties of the used photo- and neutronsensitizer. We report on the synthesis and properties of the advanced photo- and neutronsensitizer designed as a conjugate of chlorin e6 with iron bis(dicarbollide) nanocluster. Results: The conjugate is shown to accumulate efficiently in rat glioblastoma C6 cells delivering >109 boron atoms per cell and thus meeting requirements for BNCT agents, to provide photoinduced 50% death of C6 cells at 35 ± 3 nM, to be not toxic for cells without activating stimulus. Conclusions: The conjugate is a prospective theranostic agent for photodynamic, BNCT and fluorescent diagnostics of tumors.

New Derivatives of Bacteriopurpurin with Thiolated Au (I) Complexes: Dual Darkand Light Activated Antitumor Potency.

BACKGROUND: Conventional antitumor Photosensitizers (PS) are normally low toxic in the dark whereas light activation triggers massive cell death (photodynamic therapy, PDT). OBJECTIVE: To expand the therapeutic potential of PS to dual potency cytocidal agents, taking advantage of the use of bacteriopurpurin for a deeper tissue penetration of light, and suitability of the tetrapyrrolic macrocycle for chemical modifications at its periphery. METHODS: Conjugation of a pro-oxidant thiolate Au (I) moiety to the bacteriopurpurin core and evaluation of cytotoxicity in cell culture and in vivo. RESULTS: New water-soluble derivatives showed micromolar cytotoxicity for cultured human tumor cell lines in the dark, including the subline with an altered drug response due to p53 inactivation. Cellular PDT with the selected conjugate, thiolate Au (I)-dipropoxybacteriopurpurinimide (compound 6) with two triphenylphosphine Au fragments, triggered rapid (within minutes) cell death. Damage to the plasma membrane (necrosis) was a hallmark of cell death by compound 6 both in the dark and upon light activation. Furthermore, one single i.v. injection of compound 6 caused retardation of transplanted syngeneic tumors at the tolerable dose. Illumination of tumors that accumulated compound 6 significantly synergized with the effect of 6 in the dark. CONCLUSION: Complexes of virtually non-toxic, photoactivatable bacteriopurpurin with the gold-containing organic moiety are considered the dual potency antitumor agents, tentatively applicable for intractable tumors.

Targeting cancer cells by novel engineered modular transporters.

A major problem in the treatment of cancer is the specific targeting of drugs to these abnormal cells. Ideally, such a drug should act over short distances to minimize damage to healthy cells and target subcellular compartments that have the highest sensitivity to the drug. We describe the novel approach of using modular recombinant transporters to target photosensitizers to the nucleus, where their action is most pronounced, of cancer cells overexpressing ErbB1 receptors. We have produced a new generation of the transporters consisting of (a) epidermal growth factor as the internalizable ligand module to ErbB1 receptors, (b) the optimized nuclear localization sequence of SV40 large T-antigen, (c) a translocation domain of diphtheria toxin as an endosomolytic module, and (d) the Escherichia coli hemoglobin-like protein HMP as a carrier module. The modules retained their functions within the transporter chimera: they showed high-affinity interactions with ErbB1 receptors and alpha/beta-importin dimers and formed holes in lipid bilayers at endosomal pH. A photosensitizer conjugated with the transporter produced singlet oxygen and (*)OH radicals similar to the free photosensitizer. Photosensitizers-transporter conjugates have >3,000 times greater efficacy than free photosensitizers for target cells and were not photocytotoxic at these concentrations for cells expressing a few ErbB1 receptors per cell, in contrast to free photosensitizers. The different modules of the transporters, which are highly expressed and easily purified to retain full activity of each of the modules, are interchangeable, meaning that they can be tailored for particular applications.

Synthesis and Investigation of Photophysical and Biological Properties of Novel S-Containing Bacteriopurpurinimides.

Novel hybrid molecule containing 2-mercaptoethylamine was synthesized starting from O-propyloxime-N-propoxy bacteriopurpurinimide (dipropoxy-BPI), which was readily oxidized in oxygen atmosphere yielding the corresponding disulfide analogue (disulfide-BPI). Spectral, photophysical, photodynamic, and biological properties of compound were properly evaluated. Compounds bearing disulfide moiety can directly interact with glutathione (GSH), thereby reducing its intracellular concentration. Indeed, mice sarcoma S37 cell line was treated in vitro with disulfide-BPI, yielding a CC50 value of 0.05 ± 0.005 µM. A relatively high level of singlet oxygen was detected. It was demonstrated (by fluorescence) that the PS was rapidly accumulated in a cancer nest (S37) at a relatively high level after 2 h upon intravenous administration. After 24 h, no traces of the molecule were detected in the tumor mass. Moreover, high photodynamic efficiency was demonstrated at doses of 150-300 J/cm2 against two different in vivo tumor models, achieving 100% regression of cancer growth.

Cycloimide bacteriochlorin p derivatives: photodynamic properties and cellular and tissue distribution.

Reactive oxygen species generated by photosensitizers are efficacious remedy for tumor eradication. Eleven cycloimide derivatives of bacteriochlorin p (CIBCs) with different N-substituents at the fused imide ring and various substituents replacing the 3-acetyl group were evaluated as photosensitizers with special emphasis on structure-activity relationships. The studied CIBCs absorb light within a tissue transparency window (780-830 nm) and possess high photostability at prolonged light irradiation. The most active derivatives are 300-fold more phototoxic toward HeLa and A549 cells than the clinically used photosensitizer Photogem due to the substituents that improve intracellular accumulation (distribution ratio of 8-13) and provide efficient photoinduced singlet oxygen generation (quantum yields of 0.54-0.57). The substituents predefine selective CIBC targeting to lipid droplets, Golgi apparatus, and lysosomes or provide mixed lipid droplets and Golgi apparatus localization in cancer cells. Lipid droplets and Golgi apparatus are critically sensitive to photoinduced damage. The average lethal dose of CIBC-generated singlet oxygen per volume unit of cell was estimated to be 0.22 mM. Confocal fluorescence analysis of tissue sections of tumor-bearing mice revealed the features of tissue distribution of selected CIBCs and, in particular, their ability to accumulate in tumor nodules and surrounding connective tissues. Considering the short-range action of singlet oxygen, these properties of CIBCs are prerequisite to efficient antitumor photodynamic therapy.

Recombinant modular transporters for cell-specific nuclear delivery of locally acting drugs enhance photosensitizer activity.

The search for new pharmaceuticals that are specific for diseased rather than normal cells in the case of cancer and viral disease has raised interest in locally acting drugs that act over short distances within the cell and for which different cell compartments have distinct sensitivities. Thus, photosensitizers (PSs) used in anti-cancer therapy should ideally be transported to the most sensitive subcellular compartments in order for their action to be most pronounced. Here we describe the design, production, and characterization of the effects of bacterially expressed modular recombinant transporters for PSs comprising 1) alpha-melanocyte-stimulating hormone as an internalizable, cell-specific ligand; 2) an optimized nuclear localization sequence of the SV40 large T-antigen; 3) an Escherichia coli hemoglobin-like protein as a carrier; and 4) an endosomolytic amphipathic polypeptide, the translocation domain of diphtheria toxin. These modular transporters delivered PSs into the nuclei, the most vulnerable sites for the action of PSs, of murine melanoma cells, but not non-MSH receptor-overexpressing cells, to result in cytotoxic effects several orders of magnitude greater than those of nonmodified PSs. The modular fusion proteins described here for the first time, capable of cell-specific targeting to particular subcellular compartments to increase drug efficacy, represent new pharmaceuticals with general application.

Spectroscopical study of bacteriopurpurinimide-naphthalimide conjugates for fluorescent diagnostics and photodynamic therapy.

Two novel bis(chromophoric) dyads ABPI-NI1 and ABPI-NI2 containing 1,8-naphthalimide and bacteriopurpurinimide units linked by p-phenylene-methylene (ABPI-NI1) and pentamethylene (ABPI-NI2) spacers were prepared to test their ability to be used in the design of effective agents for both photodynamic therapy (PDT) and fluorescent tumor imaging. Photophysical studies revealed that the emission from the naphthalimide chromophore in both conjugates was partially quenched due to resonance energy transfer between the photoactive components. Compound ABPI-NI2 with more sterically flexible oligomethylene group demonstrated higher fluorescence intensity as compared with that for ABPI-NI1.