Singlet Oxygen Production Ability Research Articles

A New Boron 2‐(2′‐pyridyl) Imidazole Complex as a Candidate Photosensitizer for Photodynamic Therapy

A photosensitive molecule is one of the main components required in photodynamic therapy (PDT), and one of the essential specifications is its ability to produce singlet oxygen under appropriate light. In this study, boron 2-(2′-pyridyl) imidazole (BOPIM) core, which has many advantages compared to existing many photosensitizers, was functionalized with phenyl group from pyridine side for the first time, and its potential to be as a good photosensitizer candidate for PDT was revealed by its singlet oxygen production ability.

The molecule-level photoreactor: accurate embedded iodine-substituted boron dipyrromethene dye within zeolitic imidazolate framework-8 for highly efficient oxidization of sulfides under visible light

Using porous metal–organic frameworks (MOFs) as supports for immobilizing dyes as photocatalysts is an important strategy to construct a molecule-level photoreactor. Rational assembly of a heterogeneous photoreactor (photosensitizer + porosity + catalysis) requires individually tailoring based on the structure and function of the dyes and MOFs. Herein we report a facile, one-pot, room-temperature (RT) aqueous solution method to precisely embed an iodine-substituted boron dipyrromethene (I2-BODIPY) photosensitizer within zeolitic imidazolate framework-8 (ZIF-8) cavity. The resultant I2-BODIPY@ZIF-8 composite not only maintained the nanoporous cavity and outstanding stability inherited from ZIF-8 material but also possessed excellent visible-light harvesting property and high singlet oxygen production ability originated from I2-BODIPY dye. Combining the advantages of ZIF-8 material and I2-BODIPY dye, the composite is highly active as a visible light–driven photocatalyst for selective oxidization of aryl sulfides and a sulfur mustard simulant, 2-chloroethyl ethyl sulfide, at RT without overoxidation. Owing to its heterogeneous nature, the composite can be readily recycled at least five times for the oxidization without obvious loss of the catalytic activity.

Halogenated cyanine dyes for synergistic photodynamic and photothermal therapy

Cyanine dyes are widely used in the field of tumor phototherapy due to their excellent photophysical properties. To explore the heavy atoms effects on the photothermal and photodynamic performance of phototherapeutic agents, chlorine, bromine, and iodine were introduced to synthesize a series of cyanine dyes (IR6, IR7, and IR8). We have found that all halogenated cyanine dyes exhibited high excitation wavelength (around 800 nm) and low dark toxicity. Among them, IR8 behaved the best singlet oxygen production ability in the three dyes. For photothermal performance, IR8 exhibited the best photothermal conversion rate (46.6%), photothermal stability, and excellent therapy efficiency (half-maximal inhibitory concentration, IC50 = 16.2 μg/mL). IR7 behaved a greater enhancement of the photothermal conversion rate (43.4%) than IR6 (42.3%). In conclusion, the heavy atoms effects on the photothermal and photodynamic properties of cyanine dyes are positively correlated with the increase of the atomic number of the halogen atom, and the iodine atom may be the most worthy of consideration in the all halogen atoms.

Cyclometalated Iridium(III) Complexes as Mitochondria-targeting Photosensitizers against Cisplatin-resistant Cells.

Four iridium (III) complexes Ir1-Ir4 were synthesized and characterized. Possessing high singlet oxygen production ability and specific mitochondria-localization, Ir1 was developed as a mitochondria-targeting photosensitizer. Ir1 exhibited strong phototoxicity against cancer cell line A549 and its corresponding cisplatin-resistant one A549R. In contrast, Ir1 showed low cytotoxicity toward normal cell HLF. This selectivity resulted from the different uptake amount. With 405 nm irradiation, Ir1 induced mitochondria-mediated cell death in A549R cells, achieving the overcome of drug-resistant.

In vitro phototherapeutic effects of indolenine-based mono- and dithiosquaraine cyanine dyes against Caco-2 and HepG2 human cancer cell lines.

Photodynamic therapy is a noninvasive approach for the treatment of oncological and nononcological diseases which has attempted to address the shortcomings and disadvantages of conventional cancer therapies. Given the scarcity of photosensitizers that exhibit desirable characteristics for its potential application in this therapeutic strategy, the main aims of this work were the study of the photophysical and photochemical properties, and the in vitro photobiological activity of several squaraine cyanine dyes. Thus, herein, the synthesis of indolenine-based N-methyl and N-ethyl mono- and dithiosquaraine dyes, the study of their spectroscopical properties, aggregation behavior, photodegradation and singlet oxygen production ability, and the further application of the previously synthesized dyes in colorectal adenocarninoma and hepatocellular carcinoma cell lines to evaluate their phototherapeutic effects, are described. Thionation significantly favored the ability to singlet oxygen production, and moderate photostability was observed for squaraine and monothionated dyes. Squaraine and monothiosquaraine cyanine dyes showed high promise within the tested concentration range regarding their potential application as cancer photodynamic therapy photosensitizers. Squaraine dyes' monothionation resulted in the preparation of compounds with poor photocytotoxicity, which was an undesirable effect on their phototherapeutic application.

Red and Near-Infrared Absorbing DicyanomethyleneSquaraine Cyanine Dyes: PhotophysicochemicalProperties and Anti-Tumor Photosensitizing Effects.

Photodynamic therapy is a medical modality developed for the treatment of several diseases of oncological and non-oncological etiology that requires the presence of a photosensitizer, light and molecular oxygen, which combined will trigger physicochemical reactions responsible for reactive oxygen species production. Given the scarcity of photosensitizers that exhibit desirable characteristics for its potential application in this therapeutic strategy, the main aims of this work were the study of the photophysical and photochemical properties and the photobiological activity of several dicyanomethylene squaraine cyanine dyes. Thus, herein, the study of their aggregation character, photobleaching and singlet oxygen production ability, and the further application of the previously synthesized dyes in Caco-2 and HepG2 cancer cell lines, to evaluate their phototherapeutic effects, are described. Dicyanomethylene squaraine dyes exhibited moderate light-stability and, despite the low singlet oxygen quantum yields, were a core of dyes that exhibited relevant in vitro photodynamic activity, as there was an evident increase in the toxicity of some of the tested dyes exclusive to radiation treatments.

Designing a highly stable coordination-driven metallacycle for imaging-guided photodynamic cancer theranostics.

Coordination-driven self-assembly features good predictability and directionality in the construction of discrete metallacycles and metallacages with well-defined sizes and shapes, but their medicinal application has been limited by their low stability and solubility. Herein, we have designed and synthesized a highly stable coordination-driven metallacycle with desired functionality derived from a perylene-diimide ligand via a spontaneous deprotonation self-assembly process. Brilliant chemical stability and singlet oxygen production ability of this emissive octanuclear organopalladium macrocycle make it a good candidate toward biological studies. After cellular uptake by endocytosis, the metallacycle exhibits potent fluorescence cell imaging properties and cancer photodynamic therapeutic ability through enhancing ROS production, with high biocompatibility and safety. This study not only provides a rational design strategy for highly stable luminescent organopalladium metallacycles, but also sheds light on their application in imaging-guided photodynamic cancer therapy.

Photophysicochemical Properties and In Vitro Phototherapeutic Effects of Iodoquinoline- and Benzothiazole-Derived Unsymmetrical Squaraine Cyanine Dyes

The search to replace conventional cancer treatment therapies, such as chemotherapy, radiotherapy and surgery has led over the last ten years, to a substantial effort in the development of several classes of photodynamic therapy photosensitizers with desired photophysicochemical and photobiological properties. Herein we report the synthesis of 6-iodoquinoline- and benzothiazole-based unsymmetrical squaraine cyanine dyes functionalized with amine groups located in the four-membered central ring. Their photodegradation and singlet oxygen production ability, as well as their in vitro photocytotoxicity against Caco-2 and HepG2 cell lines using a 630.8 ± 0.8 nm centered light-emitting diode system, were also investigated. All photosensitizer candidates displayed strong absorption within the tissue transparency spectral region (650–850 nm). The synthesized dyes were found to have moderate light stability. The potential of these compounds is evidenced by their cytotoxic activity against both tumor cell lines, highlighting the zwitterionic unsubstituted dye, which showed more intense photodynamic activity. Although the singlet oxygen quantum yields of these iodinated derivatives are considered low, it could be concluded that their introduction into the quinoline heterocycle was highly advantageous as it played a role in increasing selective cytotoxicity in the presence of light. Thus, the novel synthesized dyes present photophysicochemical and in vitro photobiological properties that make them excellent photosensitizer candidates for photodynamic therapy.

Synthesis and photophysical properties of near infra-red absorbing BODIPy derivatives and their nanoaggregates

A facile synthesis of 1,3,5,7-tetraaryl (thienyl and pyrenyl) substituted BODIPy derivatives from tetramethyl BODIPy and aryl aldehydes via one-pot Knoevenagel reaction conditions has been carried out to yield extensively conjugated BODIPy (1,2). Drastic bathochromic shift of more than 200 nm was observed in absorption (∼up to 700 nm) and emission (up to ∼740 nm) maxima of 1,2 as compared to classical BODIPy (∼500 nm). Nano-aggregates of 1,2 were prepared by re-precipitation method in aqueous medium and are characterized by absorption, emission, transient lifetime, DLS and SEM measurements. These studies revealed the aggregation formation through BODIPy core which is further strengthen by peripheral aryl substituents. Furthermore singlet oxygen production ability of 1,2 and their nano-aggregates were studied. Importantly, the nano-aggregates reveal superior singlet oxygen production ability in the aqueous phase as compared to their monomers in the biologically advantageous near-IR region.

Complexing Methylene Blue with Phosphorus Dendrimers to Increase Photodynamic Activity.

The efficiency of photodynamic therapy is limited mainly due to low selectivity, unfavorable biodistribution of photosensitizers, and long-lasting skin sensitivity to light. However, drug delivery systems based on nanoparticles may overcome the limitations mentioned above. Among others, dendrimers are particularly attractive as carriers, because of their globular architecture and high loading capacity. The goal of the study was to check whether an anionic phosphorus dendrimer is suitable as a carrier of a photosensitizer—methylene blue (MB). As a biological model, basal cell carcinoma cell lines were used. We checked the influence of the MB complexation on its singlet oxygen production ability using a commercial fluorescence probe. Next, cellular uptake, phototoxicity, reactive oxygen species (ROS) generation, and cell death were investigated. The MB-anionic dendrimer complex (MB-1an) was found to generate less singlet oxygen; however, the complex showed higher cellular uptake and phototoxicity against basal cell carcinoma cell lines, which was accompanied with enhanced ROS production. Owing to the obtained results, we conclude that the photodynamic activity of MB complexed with an anionic dendrimer is higher than free MB against basal cell carcinoma cell lines.

Novel nanostructured smart, photodynamic hydrogels based on poly(N-isopropylacrylamide) bearing porphyrin units in their crosslink chains: A potential sensitizer system in cancer therapy

Novel nanostructure, pH-thermo dual responsive photodynamic hydrogels based on poly(N-isopropylacrylamide) were successfully synthesized by in situ dispersion polymerization of NIPAAm with 5,10, 15, 20-tetrakis(4-N-carbonylacrylic aminophenyl)porphyrin (2% and 4% w/w) in the presence of methylene-bis-acrylamide (MBA) in water. 5, 10, 15, 20-tetrakis (4-N-carbonylacrylic aminophenyl)porphyrin (CAA-TPP) was designed and synthesized for the first time via reaction of tetrakis(4-aminophenyl)porphyrin (NH2-TPP) with maleic anhydrid and was applied as a crosslinker. The structure of the 5, 10, 15, 20-tetrakis(4-N-carbonylacrylic aminophenyl) porphyrin and hydrogels was thoroughly studied by a variety of techniques such as NMR, FT-IR and UV–visible spectrophotometer. The surface morphology of freeze-dried hydrogels using SEM showed one-dimensional nanostructured with uniform morphology of self-assembled interconnected nanofibers. Rheological measurement results were showed that the incorporation of porphyrin onto polymer structure can provide hydrogels without the loss of thermoresponsive viscoelastic properties. The lower critical solution temperatures (LCST) of P[NIPAAm-co-CAA-TPP] hydrogels in water were measured by the cloud point (CP) method. The LCST of P[NIPAAm-co-CAA-TPP (2%)] and P[NIPAAm-co-CAA-TPP (4%)] were at about 40 °C and 43 °C, respectively. The results showed that an increase in porphyrin content makes the LCSTs of the hydrogels increase. Swelling measurements of hydrogels indicated sensitivity to temperature and pH, suggesting that the P[NIPAAm-co-CAA-TPP]s were temperature/pH dual stimulus-responsive hydrogels. In this work, the efficiency of P[NIPAAm-co-CAA-TPP (2%)] and P[NIPAAm-co-CAA-TPP (4%)] as photodynamic therapy (PDT) systems were investigated. The production of reactive singlet oxygen, cytotoxity and phototoxicity of them were assessed. The study showed that the singlet oxygen production ability of P[NIPAAm-co-CAA-TPP (2%)] can be well controlled by irradiation time compared with free porphyrin. We tested these two hydrogels on A453 cells to compare their effectiveness. P[NIPAAm-co-CAA-TPP (2%)] and P[NIPAAm-co-CAA-TPP (4%)] exhibited cell viability over 97% and good photocytotoxity, indicating they are promising photodynamic systems for cancer therapy.

Iron oxide nanoparticles functionalized with novel hydrophobic and hydrophilic porphyrins as potential agents for photodynamic therapy

The preparation of novel porphyrin derivatives and their immobilization onto iron oxide nanoparticles to build up suitable nanotools for potential use in photodynamic therapy (PDT) has been explored. To achieve this purpose, a zinc porphyrin derivative, ZnPR-COOH, has been synthesized, characterized at the molecular level and immobilized onto previously synthesized iron oxide nanoparticles covered with oleylamine. The novel nanosystem (ZnPR-IONP) has been thoroughly characterized by a variety of techniques such as UV–Vis absorption spectroscopy, fluorescence spectroscopy, X-ray photoloectron spectroscopy (XPS) and transmission electron microscopy (TEM). In order to probe the capability of the photosensitizer for PDT, the singlet oxygen production of both ZnPR-IONP and the free ligand ZnPR-COOH have been quantified by measuring the decay in absorption of the anthracene derivative 9,10-anthracenedipropionic acid (ADPA), showing an important increase on singlet oxygen production when the porphyrin is incorporated onto the IONP (ZnPR-IONP).On the other hand, the porphyrin derivative PR-TRIS3OH, incorporating several polar groups (TRIS), was synthesized and immobilized with the intention of obtaining water soluble nanosystems (PR-TRIS-IONP). When the singlet oxygen production ability was evaluated, the values obtained were similar to ZnPR-COOH/ZnPR-IONP, again much higher in the case of the nanoparticles PR-TRIS-IONP, with more than a twofold increase. The efficient singlet oxygen production of PR-TRIS-IONP together with their water solubility, points to the great promise that these new nanotools represent for PDT.

Maximizing the thiol-activated photodynamic and fluorescence imaging functionalities of theranostic reagents by modularization of Bodipy-based dyad triplet photosensitizers.

To maximize both the activatable singlet oxygen (1O2) production and fluorescence of theranostic photodynamic (PDT) reagents, herein we propose a modularized molecular structural profile, i.e. the intersystem crossing (ISC) and fluorescence functionalities were accomplished with different modules in a dyad, thus enabling the activated 1O2 production yield (ΦΔ, PDT) and the fluorescence yield (ΦF) to both approach 100%. The PDT and the fluorescence were caged with a thiol-cleavable disulfide bond (-S-S-) linker and an electron trap (2,4-dinitrobenzenesulfide, DNBS). This new molecular structural profile is different from that of conventional theranostic PDT reagents, which are based on a single chromophore for both PDT and fluorescence; thus, the limitation of ΦΔ + ΦF = 100% exists for only half of our new molecular profile. To this end, six Bodipy dyads were prepared. The photophysical properties of the dyads were studied with steady state absorption, fluorescence and nanosecond transient absorption spectroscopy. The dyads show weak PDT and luminescence, due to the caging effect. In the presence of thiols (GSH or Cys), cleavage of the disulfide linker and DNBS occurs, and the PDT and fluorescence modules are activated simultaneously (ΦF: 1.3% → 47.6%; ΦΔ: 16.7% → 71.5%). These results are useful in designing activatable PDT/fluorescence imaging theranostic reagents.

Redox Behavior and Reactions of Cobalt Porphycene Derivatives

Tetrapyrrole compounds are very important for the biological system, and these are pigments of life. Heme protein has an iron porphyrin, and chlorophyll contains a magnesium porphyrin derivative. And vitamin B12 has a cobalt corrin. These tetrapyrrole compounds have various functions.1 Inspired by the significance of the porphyrins, a new research direction has emerged that is devoted to the preparation and study of non-porphyrin tetrapyrrolic macrocycles. In this symposium, we will present photochemical and electrochemical reactions of porphycene derivative, which is a porpyrin isomer.We prepared various brominated porphycenes.2 The singlet oxygen production ability via energy transfer from the triplet state of the porphycene was controlled by the number of bromine. And then, the porphycene having an ionic liquid tag was synthesized and the photo-oxidation reaction in ionic liquid was investigated.3 Tetrapropyl porphycene (H2TPrPc) was synthesized according to the reported procedure.4 A hydrogenated porphycene was obtained by a hydrogenation of H2TPrPc in the presence of zinc and hydrochloric acid.5 Cobalt complexes (cobalt porphycene and cobalt dihydroporphycene) were synthesized by the reaction with [CoII(acac)2] as a metal source. Redox properties were examined by cyclic voltammetry and controlled potential electrolysis. UV-vis spectra of controlled-potential electrolysis revealed that spectra of cobalt porphycene and cobalt dihydroporphycene were quite different in the reduced conditions. These data indicate that the cobalt porphycene was reduced to form a ligand reduced anionradical, but cobalt dihydroporphycene was reduced to form Co(I) species. It suggests the ligand hydrogenation can change the redox behavior.It is known that cobalt porphyrin can form a Co-C bond by the oxidative addition with Co(I) species and an alkyl halide. Cobalt porphycene is not reduced to form the corresponding Co(I) species unlike cobalt porphyrin. We found that Co-C bond formation is mediated by the reduced ligand of cobalt porphycene. This new reaction, “redox-active ligand-mediated Co-C bond formation of porphycene”, will be reported. Reference (1) Hisaeda, Y.; Tahara, K.; Shimakoshi, H.; Masuko, T. Pure Appl. Chem., 2013, 85, 1415.(2) Shimakoshi, H.; Baba, T.; Iseki, Y.; Aritome, I.; Endo, A.; Adachi, C.; Hisaeda, Y. Chem. Commun., 2008, 2882.(3) Shimakoshi, H.; Sasaki, K.; Iseki, Y.; Hisaeda Y. J. Porphyrins Phthalocyanines, 2012, 16, 530.(4) Vogel, E.; Balci, M.; Pramod, K.; Koch, P.; Lex, J.; Ermer, O. Angew. Chem. Int. Ed. Engl., 1987, 26, 928.(5) Okawara, T.; Hashimoto, K.; Abe, M.; Shimakoshi, H.; Hisaeda, Y. Chem. Commun., 2012, 48, 5413.

Synthesis and photodynamic properties of maltohexaose-conjugated porphyrins

A series of porphyrin derivatives with one to four maltohexaose moieties in their meso positions have been synthesized. Zinc or free-base m-THPP (5,10,15,20-tetrakis(m-hydroxyphenyl)-porphyrin) was used as the porphyrin platform. The reaction of m-THPP with 3-iodopropyl nonadecaacetylmaltohexaoside afforded a mixture of all possible combinations of glycoconjugated porphyrins having one to four maltohexaose moieties; monoglycosylated (Ac-1), bisglycosylated (Ac-cis-2 and Ac-trans-2), triglycosylated (Ac-3), and tetraglycosylated (Ac-4) porphyrins were obtained in 11–26% yield. Removal of acetyl groups at maltohexaose moiety afforded highly water-soluble glycoconjugated porphyrins 1–4. Zinc derivatives were synthesized in a similar manner. These maltohexaose-linked porphyrins exhibit remarkable water-solublity (530 mg/mL for 4). The singlet oxygen production ability upon visible light irradiation is not affected by the maltohexaose substitution. Photo- and dark cytotoxicities of the maltohexaose-conjugated porphyrins 1–4 and Zn-1–4 were examined against a HeLa cell line, which showed that the mono-maltohexaosylated derivative (1 and Zn-1) was the most effective photosensitizer for PDT.

Banana-shaped biphotonic quadrupolar chromophores: from fluorophores to biphotonic photosensitizers

This study aims at designing dual-role biphotonic chromophores that could be used for photodynamic therapy (PDT) while maintaining some fluorescence in order to locate them, thus allowing selective irradiation of cancer cells when combined with targeting. Quadrupolar two-photon absorbing fluorophores were synthesized from the symmetrical functionalization of a fluorene core bearing elongated conjugated rods made from arylene–vinylene or arylene–ethynylene building blocks in order to test modifications which could increase singlet oxygen production ability while retaining some fluorescence and high two-photon absorption (TPA) cross-sections in the biological spectral range of interest. All chromophores show a polar emissive excited state whose dipole moment is highly dependent on the nature of the conjugated linker. Interestingly, the largest TPA responses in the NIR region as well as singlet oxygen quantum yield are correlated with the smallest dipole moment of the emissive excited-state. The molecular optimization study led to a multifunctional biphotonic chromophore combining high TPA cross-sections in the whole spectral range of interest (700–900 nm), reasonable singlet oxygen production efficiency, significant remaining fluorescence, and alcohol end-groups for further covalent grafting. This compound offers thus interesting potentialities for highly selective spatially-resolved two-photon PDT by incorporation in nanostructures.

Methylene Blue‐Conjugated Hydrogel Nanoparticles and Tumor‐Cell Targeted Photodynamic Therapy

Methylene blue-conjugated polyacrylamide nanoparticles are prepared through a microemulsion polymerization, after conjugation of the dye with a monomer. The nanoparticles have a 50-60 nm diameter in solution. This conjugation method enables a large increase in loading of methylene blue per nanoparticle and also minimizes dye leaching out of the nanoparticle. Furthermore, the dye content can be controlled by variation of the dye amount, enabling a more refined control of the singlet oxygen production ability. The nanoparticles are coated with F3 peptides, which give specific targeting to selected tumor cells, 9L, MDA-MB-435, and F98, in vitro. In addition, MTT assays reveal that the nanoparticles have no dark toxicity but excellent PDT efficacy increasing with the nanoparticle dose and irradiation time.

Photophysical and photosensitizing properties of brominated porphycenes

A heavy atom, bromine, was directly substituted into the porphycene macrocycle to promote intersystem crossing by way of spin-orbit coupling. The singlet oxygen production ability of the porphycene is dramatically enhanced, and the highest value of 0.95 for the quantum yield of singlet oxygen generation (PhiDelta) was obtained for the dibrominated porphycene by visible light excitation.