Efficient synthesis and photodynamic activity of porphyrin-saccharide conjugates: targeting and incapacitating cancer cells

A new trick (hydroxyl radical generation) of an old vitamin (B2) for near-infrared-triggered photodynamic therapy

A new NIR-light-triggered PDT method has been developed using an old vitamin (vitamin B₂) integrated with the upconversion nanotechnology.

Carbohydrates in Supramolecular Chemistry

Carbohydrates are involved in a variety of biological processes. The ability of sugars to form a large number of hydrogen bonds has made them important components for supramolecular chemistry. We discuss recent advances in the use of carbohydrates in supramolecular chemistry and reveal that carbohydrates are useful building blocks for the stabilization of complex architectures. Systems are presented according to the scaffold that supports the glyco-conjugate: organic macrocycles, dendrimers, nanomaterials, and polymers are considered. Glyco-conjugates can form host-guest complexes, and can self-assemble by using carbohydrate-carbohydrate interactions and other weak interactions such as π-π interactions. Finally, complex supramolecular architectures based on carbohydrate-protein interactions are discussed.

Photodynamic Efficiency: From Molecular Photochemistry to Cell Death

Photodynamic therapy (PDT) is a clinical modality used to treat cancer and infectious diseases. The main agent is the photosensitizer (PS), which is excited by light and converted to a triplet excited state. This latter species leads to the formation of singlet oxygen and radicals that oxidize biomolecules. The main motivation for this review is to suggest alternatives for achieving high-efficiency PDT protocols, by taking advantage of knowledge on the chemical and biological processes taking place during and after photosensitization. We defend that in order to obtain specific mechanisms of cell death and maximize PDT efficiency, PSes should oxidize specific molecular targets. We consider the role of subcellular localization, how PS photochemistry and photophysics can change according to its nanoenvironment, and how can all these trigger specific cell death mechanisms. We propose that in order to develop PSes that will cause a breakthrough enhancement in the efficiency of PDT, researchers should first consider tissue and intracellular localization, instead of trying to maximize singlet oxygen quantum yields in in vitro tests. In addition to this, we also indicate many open questions and challenges remaining in this field, hoping to encourage future research.

Synthesis of 2-nitro-3-(pyrrol-1-yl)-5,10,15,20-tetraarylporphyrins via a Clauson-Kaas reaction and the study of their electronic properties

Versatile synthesis of new porphyrin building blocks, 2-nitro-3-(pyrrol-1-yl)-5,10,15,20-tetraarylporphyrins is described. These porphyrins demonstrate red shifted absorption bands and S₂ emission.

Synthesis and in vitro bioactivity evaluation of new glucose and xylitol ester derivatives of 5-aminosalicylic acid

Synthesis,in vitroanti-bacterial, anti-inflammatory and anti-cancer activity evaluations andin silicostudy of monosaccharide derivatives of mesalazine in comparison with parent drug.

Synthesis, characterization and biomolecule-binding properties of novel tetra-platinum(ii)-thiopyridylporphyrins

New tetra-platinum(ii)-thiopyridylporphyrin complexes and their DNA binding studies.

Synthesis and cell phototoxicity of a triply bridged fused diporphyrin appended with six thioglucose units

A triply bridged fused diporphyrin appended with six thioglucose units is reported. This new, chemically and photochemically stable amphiphilic compound is taken up by breast cancer cells and causes cell death upon light exposure. Photophysical studies reveal absorption bands in the near IR region, and photosensitized formation of singlet oxygen in high quantum yields.

Synthesis and in vitro evaluation of BBB permeability, tumor cell uptake, and cytotoxicity of a series of carboranylporphyrin conjugates

A series of tri[(p-carboranylmethylthio)tetrafluorophenyl]porphyrin conjugates of linear and branched polyamines, glucose, arginine, tri(ethylene glycol), and Tyr-D-Arg-Phe-β-Ala (YRFA) peptide were synthesized. These conjugates were investigated for their BBB permeability in human hCMEC/D3 brain endothelial cells, and their cytotoxicity and uptake were assessed using human glioma T98G cells. For comparison purposes, a symmetric tetra[(p-carboranylmethylthio)tetrafluorophenyl]porphyrin was also synthesized, and its crystal structure was obtained. All porphyrin conjugates show low dark cytotoxicity (IC50>400 μM) and low phototoxicity (IC50>100 μM at 1.5 J/cm2) toward T98G cells. All conjugates were efficiently taken up by T98G cells, particularly the cationic polyamine and arginine conjugates, and were localized in multiple cellular organelles, including mitochondria and lysosomes. All compounds showed relatively low in vitro BBB permeability compared with that of lucifer yellow because of their higher molecular weight, hydrophobicity, and tendency for aggregation in solution. Within this series, the branched polyamine and YRFA conjugates showed the highest permeability coefficient, whereas the glucose conjugate showed the lowest permeability coefficient.

Ytterbium(III) porpholactones: β-lactonization of porphyrin ligands enhances sensitization efficiency of lanthanide near-infrared luminescence

The near-infrared (NIR) luminescence efficiency of lanthanide complexes is largely dependent on the electronic and photophysical properties of antenna ligands. Although porphyrin ligands are efficient sensitizers of lanthanide NIR luminescence, non-pyrrolic porphyrin analogues, which have unusual symmetry and electronic states, have been much less studied. In this work, we used porpholactones, a class of β-pyrrolic-modified porphyrins, as ligands and investigated the photophysical properties of lanthanide porpholactones Yb-1 a-5 a. Compared with Yb porphyrin complexes, the porpholactone complexes displayed remarkable enhancement of NIR emission (50-120 %). Estimating the triplet-state levels of porphyrin and porpholactone in Gd complexes revealed that β-lactonization of porphyrinic ligands lowers the ligand T1 state and results in a narrow energy gap between this state and the lowest excited state of Yb(3+) . Transient absorption spectra showed that Yb(III) porpholactone has a longer transient decay lifetime at the Soret band than the porphyrin analogue (30.8 versus 17.0 μs). Thus, the narrower energy gap and longer lifetime arising from β-lactonization are assumed to enhance NIR emission of Yb porpholactones. To demonstrate the potential applications of Yb porpholactone, a water-soluble Yb bioprobe was constructed by conjugating glucose to Yb-1 a. Interestingly, the NIR emission of this Yb porpholactone could be specifically switched on in the presence of glucose oxidase and then switched off by addition of glucose. This is the first demonstration that non-pyrrolic porphyrin ligands enhance the sensitization efficiency of lanthanide luminescence and also display switchable NIR emission in the region of biological analytes (800-1400 nm).

Small molecule phosphorescent probes for O2imaging in 3D tissue models

PtPFPP-carbohydrate conjugates are promising O₂probes for 3D PLIM imaging of live spheroids and brain explants.

Photophysics of glycosylated derivatives of a chlorin, isobacteriochlorin and bacteriochlorin for photodynamic theragnostics: discovery of a two-photon-absorbing photosensitizer

The photophysical properties of a chlorin, isobacteriochlorin and bacteriochlorin built on a core tetrapentafluorophenylporphyrin (TPPF20 ) and the nonhydrolyzable para thioglycosylated conjugates of these chromophores are presented. The photophysical characterization of these compounds was done in three different solvents to correlate with different environments in cells and tissues. Compared with TPPF20 other dyes have greater absorption in the red region of the visible spectrum and greater fluorescence quantum yields. The excited state lifetimes are from 3 to 11 ns. The radiative and nonradiative rate constants for deactivation of the excited state were estimated from the fluorescence quantum yield and excited state lifetime. The data indicate that the bacteriochlorin has strong absorption bands near 730 nm and efficiently enters the triplet manifold. The isobacteriochlorin has a 40-70% fluorescence quantum yield depending on solvent, so it may be a good fluorescent tag. The isobacteriochlorins also display enhanced two-photon absorption, thereby allowing the use of 860 nm light to excite the compound. While the two-photon cross section of 25 GM units is not large, excitation of low chromophore concentrations can induce apoptosis. The glycosylated compounds accumulate in cancer cells and a head and neck squamous carcinoma xenograft tumor model in mice. These compounds are robust to photobleaching.

Comparative photodynamic inactivation of antibiotic resistant bacteria by first and second generation cationic photosensitizers

Photodynamic inactivation (PDI) is an efficient approach against a wide range of microorganisms and can be viewed as an alternative for the treatment of microbial infections. In this work we synthesized "first" and "second" generation photosensitizers (PSs), the tetra-cationic porphyrin and the new penta-cationic chlorin , respectively, and evaluated their efficiency against two antibiotic resistant bacterial strains, Staphylococcus aureus and Pseudomonas aeruginosa. The PS was obtained in very good yield by an easy synthesis method. The PDI studies were performed in parallel with 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetra-iodide (), a widely studied PS in PDI, and the obtained results were compared. Two different light ranges were used: white light (400-800 nm) and red light (530-800 nm) delivered at a fluence rate of 150 mW cm(-2). The results show that both strains, even though antibiotic resistant, were efficiently inactivated by the three PSs, chlorin being the most effective. For the Gram positive bacterium S. aureus a 7.0 log reduction was observed after 5-10 min of irradiation, at a concentration of 0.5 μM, whereas for the Gram negative P. aeruginosa, similar photoinactivation occurred at a higher PS concentration (10 μM) and after a longer irradiation period (30 min). The synthetic chlorin can be regarded as promising for the treatment of bacterial infections under red light, which penetrates deeper in living tissues. The results of this study open the possibility to prepare a new series of chlorin-type derivatives to efficiently photoinactivate Gram (+) and (-) antibiotic resistant bacteria. The efficient PDI with the chlorin indicates high potential for the use of a scaffold in the preparation of new generation PSs based on cationic chlorin derivatives.

"Click chemistry" in the synthesis of the first glycoconjugates of bacteriochlorin series

A regioselective synthesis of glycoconjugates based on bacteriochlorophyll a and lactose derivatives has been carried out. The conjugation was achieved via 1,3-dipolar cycloaddition of bacteriochlorins containing a terminal triple bond and a lactose azide derivative. The conjugates obtained in this way had one or two disaccharide fragments attached to pyrrol A, the exocyclic imide ring of the tetrapyrrolyc macrocycle, or to both positions. Exhaustive NMR analysis by 1D and 2D NMR experiments ( 1H-1H COSY, TOCSY, ROESY, 1H-13C HSQC, HMBC, and 1H-15N HMBC) allowed us to determine the structures and configurations of the glycoconjugates obtained. A bioassay of the glycoconjugates using the Hep2 cell line showed that the highest efficiency was observed for the glycosylated bacteriopurpurinimide containing a lactose residue at pyrrole ring A.

Unique diagnostic and therapeutic roles of porphyrins and phthalocyanines in photodynamic therapy, imaging and theranostics

Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types. Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms. The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review.

The effect of the number of carbohydrate moieties on the azaphthalocyanine properties

A series of azaphthalocyanines (AzaPc) bearing one, two, four or eight isopropylidene-protected galactosyl units was prepared by azide-alkyne click reaction or by classical Pc template cyclotetramerization of the corresponding dicyanopyrazine and AzaPc properties important for photodynamic therapy were compared. All compounds absorbed at long wavelengths (above 650 nm) and belonged to strong singlet oxygen producers (Φ(Δ) = 0.58-0.64) retaining significant fluorescence emission (Φ(F) = 0.026-0.23). The only exception was the compound with four isopropyliden-protected galactosyl units where partial aggregation was observed. Removal of protecting groups increased the polar character of all AzaPc. However, only AzaPc bearing eight galactoses was found to be water-soluble (105 mg mL(-1)) but noticeably aggregated in water as well as in organic solvents (DMF, DMSO). Amphiphilic AzaPc bearing one deprotected galactose was incorporated into the lipidic bilayer of liposomes in a nonaggregated form. Liposomes may therefore be a suitable delivery system for this amphiphilic photosensitizer.

Cationic β-vinyl substitutedmeso-tetraphenylporphyrins: synthesis and non-covalent interactions with a short poly(dGdC) duplex

Several cationic beta-vinyl-pyridinium and beta-vinyl-quinolinium-meso-tetraphenylporphyrin derivatives were synthesized starting from 2-formyl-meso-tetraphenylporphyrin, and the corresponding Zn(II) complex, and different N-alkyl derivatives of 2- and 4-methylpyridine and 2- and 4-methylquinoline. The new compounds were obtained in a one-step process via base catalyzed aldol-type condensation reactions. Electrospray ionization mass spectrometry (ESI-MS) and ultraviolet-visible (UV-vis) spectroscopy were used to investigate the binding mode of the synthesized cationic beta-vinyl-pyridinium and beta-vinyl-quinolinium-meso-tetraphenylporphyrin derivatives with a short GC duplex oligonucleotide. Analysis of the obtained mass spectrometry results indicates the probable occurrence of outside binding. UV-vis spectroscopy data also points to non-intercalation. The potential photosensitizing capacity of these compounds was also ascertained from preliminary photophysical studies.

5,10,15,20-tetrakis(pentafluorophenyl)porphyrin: a versatile platform to novel porphyrinic materials

5,10,15,20-tetrakis(pentafluorophenyl)porphyrin reacts with a range of nucleophiles (amines, alcohols, thiols, nitrogen heterocycles, and others) resulting in the nucleophilic aromatic substitution of the para-F atoms of the pentafluorophenyl groups. This reaction, which was fortuitously discovered by Kadish and collaborators in 1990, is now being extensively used to synthesize porphyrins bearing electron-donating substituents in the para-position of their meso-aryl groups. This mini-review highlights the methods of synthesis of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin, the use of its metal complexes in catalysis and its reaction with nucleophiles to yield new monomeric porphyrins, porphyrins supported in polymers or new polymeric porphyrin matrices useful for heterogeneous catalysis.

Photodynamic therapy in urology: what can we do now and where are we heading?

BACKGROUND

Photodynamic therapy (PDT) is an innovative technique in oncologic urology. Its application appears increasingly realistic to all kind of cancers with technological progress made in treatment planning and light delivery associated with the emergence of novel photosensitizers. The aim of this study is to review applications of this technique in urology.

MATERIALS AND METHODS

We reviewed the literature on PDT for urological malignancies with the following key words: photodynamic therapy, prostate cancer, kidney cancer, urothelial cancer, penile cancer and then by cross-referencing from previously identified studies.

RESULTS

Focal therapy of prostate cancer is an application of PDT. Clinical studies are ongoing to determine PDT efficacy and safety. PDT as salvage treatment after radiotherapy has been tested. Oncologic results were promising but important side effects were reported. Individual dosimetric planning is necessary to avoid toxicity. PDT was tested to treat superficial bladder carcinoma with promising oncologic results. Serious side effects have limited use of first photosensitizers generation. Second generation of photosensitizer allowed reducing morbidity. For upper urinary tract carcinoma and urethra, data are limited. Few studies described PDT application in penile oncology for conservative management of carcinoma in situ and premalignant lesions. For renal cancer, PDT was only tested on preclinical model despite of its potential application. No data is available concerning PDT application for testicular cancer.

CONCLUSION

PDT clinical applications in urology have proved a kind of efficiency balanced with an important morbidity. Development of new photosensitizer generations and improvement in illumination protocols should permit to decrease side effects.

Synthesis and characterization of 1,8(11),15(18),22(25)-tetraglycosylated zinc(II) phthalocyanines

In continuation of our work on glycosylated phthalocyanines, a new series of 1,8(11),15(18),22(25)-tetraglycosylated zinc(II) phthalocyanines (PcZns) have been synthesized and characterized. 3-glycosylated phthalonitriles were synthesized through nitrite displacement in 3-nitrophthalonitrile with anomerically deprotected glycoses. The anomerically glycosylated phthalonitriles were then treated with hexamethyldisilazane (HMDS), trimethylsilyltriflate (TMSOTf) and zinc salt in DMF to form the corresponding acetyl-protected PcZns, followed by deprotection of acetyl groups by NaOMe in methanol/DMSO mixture. The formed unprotected tetraglycosylated PcZns are highly soluble in water, which is a necessary condition for potential biological applications.

A novel water-soluble near-infrared glucose-conjugated porphyrin: synthesis, properties and its optical imaging effect

A simple novel near-infrared water-soluble glucose-conjugated porphyrin, 5,15-bis-[(trimethylsilyl)ethynyl]-10,20-bis[4-β-D-glucopyranosyl)phenyl]porphyrin, with good optical stability and high emission ability in near-infrared region, was synthesized. And Optical Imaging in vivo with this compound as probe was performed on liver tumor-bearing nude mice. The result shows that this glucose-conjugated porphyrin could display information in vivo more than 1 cm in depth, which implies its potential application as optical probe in cancer diagnosis.

Synthesis of new glycoporphyrin derivatives through carbohydrate-substituted α-diazoacetates

The reaction of carbohydrate-substituted α-diazoacetates with meso-tetrakis(pentafluorophenyl)porphyrinatozin(II) allows the synthesis of new glyco-hydroporphyrin derivatives.

High-dose rapamycin induces apoptosis in human cancer cells by dissociating mTOR complex 1 and suppressing phosphorylation of 4E-BP1

mTOR, the mammalian target of rapamycin, has been widely implicated in signals that promote cell cycle progression and survival in cancer cells. Rapamycin, which inhibits mTOR with high specificity, has consequently attracted much attention as an anti-cancer therapeutic. Rapamycin suppresses phosphorylation of S6 kinase at nano-molar concentrations, however at higher micro-molar doses, rapamycin induces apoptosis in several human cancer cell lines. While much is known about the effect of low dose rapamycin treatment, the mechanistic basis for the apoptotic effects of high-dose rapamycin treatment is not understood. We report here that the apoptotic effects of high-dose rapamycin treatment correlate with suppressing phosphorylation of the mTOR complex 1 substrate, eukaryotic initiation factor 4E (eIF4E) binding protein-1 (4E-BP1). Consistent with this observation, ablation of eIF4E also resulted in apoptorsis in MDA-MB 231 breast cancer cells. We also provide evidence that the differential dose effects of rapamycin are correlated with partial and complete dissociation of Raptor from mTORC1 at low and high doses, respectively. In contrast with MDA-MB-231 cells, MCF-7 breast cancer cells survived rapamycin-induced suppression of 4E-BP1 phosphorylation. We show that survival correlated with a hyper-phosphorylation of Akt at S473 at high rapamycin doses, the suppression of which conferred rapamycin sensitivity. This study reveals that the apoptotic effect of rapamycin requires doses that completely dissociate Raptor from mTORC1 and suppress that phosphorylation of 4E-BP1 and inhibit eIF4E.

Synthesis and photophysics of an octathioglycosylated zinc(II) phthalocyanine

A water soluble zinc(II) phthalocyanine symmetrically appended with eight thioglucose units was synthesized from commercially available hexadecafluorophthalocyaninatozinc(II) by controlled nucleophilic substitution of the peripheral fluoro groups. The photophysical properties and cancer cell uptake studies of this nonhydrolyzable thioglycosylated phthalocyanine are reported. The new compound has amphiphilic character, is chemically stable, and can potentially be used as a photosensitizer in photodynamic therapy.