Peripheral and axial substitution of phthalocyanines with solketal groups: synthesis and in vitro evaluation for photodynamic therapy

Spectroscopic and photophysicochemical properties of zinc(II) phthalocyanine substituted with benzenesulfonamide units containing schiff base

In this study, compounds (E)-4-((5-bromo-2-hydroxy-3-methoxybenzylidene)amino)-N-(pyridin-2-yl)benzenesul-fonamide 1, (E)-4-((5-bromo-2-(3,4-dicyanophenoxy)-3-methoxybenzylidene)amino)-N-(pyridin-2-yl)benzenesulfonamide 2 and, complex 2(3),9(10),16(17),23(24)-tetra-[(E)-4-((5-bromo-3-methoxy-2-(λ 1-oxidanyl)benzylidene)amino)-N-(pyridine-2-yl)benzenesulfonamide]phthalocyaninato zinc(II) 3 were synthesized for the first time. Their structures (1 –3) were characterized by spectroscopic methods such as FTIR, 1H NMR,13C NMR, UV–vis, MALDI-TOF mass spectra and elemental analysis. The spectroscopic, aggregation, photophysical and photochemical properties of zinc(II) phthalocyanine 3 in dimethyl sulfoxide were investigated and the effects on the above-mentioned properties were reported as a result of the presence of benzenesulfonamide derivatives containing different bioactive groups, in their peripheral positions. In addition, its above-mentioned properties were also reported by comparing different species with those of their substituted and/or unsubstituted counterparts. The zinc(II) phthalocyanine 3 can be a potential photosensitizer candidate in photodynamic therapy, which is an effective alternative therapy in cancer treatment, due to its good solubility in commonly known solvents and monomeric species, as well as its adequate and favorable fluorescence, singlet oxygen production and photostability.

Anticancer and Biological Properties of New Axially Disubstituted Silicon Phthalocyanines

This study reports the synthesis of three novel axially disubstituted silicon phthalocyanines (1-3-Si) and their quaternized phthalocyanines (1-3-QSi). The resulting compounds were characterized by applying spectroscopic techniques including 1H NMR,...

Methoxypolyethylene Glycol-Substituted Zinc Phthalocyanines for Multiple Tumor-Selective Fluorescence Imaging and Photodynamic Therapy

Highly tumor-tissue-selective drugs are a prerequisite for accurate diagnosis and efficient photodynamic therapy (PDT) of tumors, but the currently used fluorescent dyes and photosensitizers generally lack the ability for high accumulation and precise localization in tumor tissues. Here we report that monomethoxy polyethylene glycol (MPEG)-modified zinc phthalocyanine (ZnPc) can be selectively accumulated in multiple tumor tissues, and that the selectivity is controlled by the chain length of MPEG. MPEG-monosubstituted ZnPcs with different chain lengths were synthesized, among which the shorter chain (mw < 2k)-modified ZnPc did not show tumor tissue selectivity, while MPEG2k-5k-substituted ZnPc could be rapidly and selectively accumulated in H22 tumor tissues in mice after intravenous injection. Especially, MPEG4k-Pc showed the best tumor tissue selectivity with a tumor/liver (T/L) ratio of 1.7-2.2 in HepG2, MDA-MB231, AGS, and HT-29 tumor-bearing mice. It also exhibited potent photodynamic therapy effects after one PDT treatment, and tumor growth was significantly inhibited in H22-bearing mice with an inhibition rate over 98% and no obvious toxicity. Consequently, MPEG-modified ZnPc could serve as a potential platform for selective fluorescence imaging and photodynamic therapy of multiple tumors.

Symmetrically Substituted Zn and Al Phthalocyanines and Polymers for Photodynamic Therapy Application

N4 macrocyclic complexes of Al and Zn phthalocyanines with symmetrical imine and imidazole moiety at the periphery were synthesized. The synthesized ligands, complexes, and polymers were purified and characterized to study the structure of the molecule. These synthesized complexes were used for photodynamic therapy application as the diamagnetic Zn and Al have the ability to produce and stabilize singlet oxygen species. The synthesized N4 molecules of aluminum iminomethoxy phenyl phthalocyanine and aluminum ethyl phenyl benzimidazolephthalocyanine showed better activity against MCF-7 cells. These results suggest that this assay may be used as an early biomarker of clinical response.

Silicon phthalocyanines: synthesis and resurgent applications

Their unique axial bonds and NIR optical properties have made silicon phthalocyanines (SiPcs) valuable compounds. Herein, we present key synthetic strategies and emerging applications of SiPcs over the past decade.

Naphthalonitriles featuring efficient emission in solution and in the solid state

In this work, a series of γ-substituted diphenylnaphthalonitriles were synthesized and characterized. They show efficient emission in solution and in the aggregated state and their environment responsiveness is based on having variable substituents at the para-position of the two phenyl moieties. The excited state properties were fully investigated in tetrahydrofuran (THF) solutions and in THF/H₂O mixtures. The size of the aggregates in aqueous media were measured by dynamic light scattering (DLS). The steady-state and time-resolved photoluminescence spectroscopy studies revealed that all the molecules show intense fluorescence both in solution and in the aggregated state. In THF solutions, a blue emission was observed for the unsubstituted (H), methyl- (Me) and tert-butyl- (t-Bu) substituted γ-diphenylnaphthalonitriles, which can be attributed to a weak π-donor capability of these groups. On the other hand, the methoxy- (OMe), methylsulfanyl- (SMe) and dimethylamino- (NMe₂) substituted compounds exhibit a progressive red-shift in emission compared to H, Me and t-Bu due to a growing π-electron donating capability. Interestingly, upon aggregation in water-containing media, H, Me and t-Bu show a slight red-shift of the emission and a blue-shift is observed for OMe, SMe and NMe₂. The crystal structure of Me allowed a detailed discussion of the structure–property relationship. Clearly, N-containing substituents such as NMe₂ possess more electron-donating ability than the S-based moieties such as SMe. Moreover, it was found that NMe₂ showed higher luminescence quantum yields (Φ_F) in comparison to SMe, indicating that N-substituted groups could enhance the fluorescence intensity. Therefore, the π-donor nature of the substituents on the phenyl ring constitutes the main parameter that influences the photophysical properties, such as excited state lifetimes and photoluminescence quantum yields. Hence, a series of highly luminescent materials from deep blue to red emission depending on substitution and environment is reported with potential applications in sensing, bioimaging and optoelectronics.

Octa-substituted metallophthalocyanines bearing (2,3-dihydrobenzo-1,4-benzodioxin-2-yl)methoxy and chloro groups: Synthesis, characterization and photophysicochemical studies

In this study, the synthesis and characterization of novel 4-chloro-5-((2,3-dihydrobenzo-1,4-benzodioxin-2-yl)methoxy)phthalonitrile (1) and its peripherally octa-substituted Zn(II) (Pc-Zn), In(III) (PcInCI) and Mg(II) (Pc-Mg) phthalocyanine (Pc) derivatives are reported for the first time. FT-IR, elemental analysis, UV-vis, NMR and MS techniques were used for characterization studies of the compounds. Aggregation properties of the compounds were evaluated in DMF, DMSO and THF solvents in different concentrations, and the compounds did not tend to aggregate in these solvents. In addition, photophysicochemical properties such as fluorescence, photodegradation and singlet oxygen quantum yield of the compounds were examined in DMSO, DMF and THF solvents to show the potential use of these novel compounds as photosensitizers for photodynamic therapy (PDT). The effects of zinc, indium and magnesium metals, octa substitutions in peripheral positions and different types of solvents on photophysicochemical properties were investigated. The singlet oxygen quantum yield values of compounds ranged from 0.27 to 0.77 in different solvents. As a result of the photophysicochemical properties, these compounds can be considered as potential candidates for PDT, applications.

Amphiphilic phthalocyanines in polymeric micelles: a supramolecular approach toward efficient third-generation photosensitizers

In this paper we describe a straightforward supramolecular strategy to encapsulate silicon phthalocyanine (SiPc) photosensitizers (PS) in polymeric micelles made of poly(ε-caprolactone)-b-methoxypoly(ethylene glycol) (PCL-PEG) block copolymers. While PCL-PEG micelles are promising nanocarriers based on their biocompatibility and biodegradability, the design of our new PS favors their encapsulation. In particular, they combine two axial benzoyl substituents, each of them carrying either three hydrophilic methoxy(triethylenoxy) chains (1), three hydrophobic dodecyloxy chains (3), or both kinds of chains (2). The SiPc derivatives 1 and 2 are therefore amphiphilic, with the SiPc unit contributing to the hydrophobic core, while lipophilicity increases along the series, making it possible to correlate the loading efficacy in PCL-PEG micelles with the hydrophobic/hydrophilic balance of the PS structure. This has led to a new kind of third-generation nano-PS that efficiently photogenerates ¹O₂, while preliminary in vitro experiments demonstrate an excellent cellular uptake and a promising PDT activity.

Porphyrinoid-based photosensitizers for diagnostic and therapeutic applications: An update

Porphyrin-based molecules are actively studied as dual function theranostics: fluorescence-based imaging for diagnostics and fluorescence-guided therapeutic treatment of cancers. The intrinsic fluorescent and photodynamic properties of the bimodal molecules allows for these theranostic approaches. Several porphyrinoids bearing both hydrophilic and/or hydrophobic units at their periphery have been developed for the aforementioned applications, but better tumor selectivity and high efficacy to destroy tumor cells is always a key setback for their use. Another issue related to their effective clinical use is that, most of these chromophores form aggregates under physiological conditions. Nanomaterials that are known to possess incredible properties that cannot be achieved from their bulk systems can serve as carriers for these chromophores. Porphyrinoids, when conjugated with nanomaterials, can be enabled to perform as multifunctional nanomedicine devices. The integrated properties of these porphyrinoid-nanomaterial conjugated systems make them useful for selective drug delivery, theranostic capabilities, and multimodal bioimaging. This review highlights the use of porphyrins, chlorins, bacteriochlorins, phthalocyanines and naphthalocyanines as well as their multifunctional nanodevices in various biomedical theranostic platforms.

Effectiveness of ZnPc and of an amine derivative to inactivate Glioblastoma cells by Photodynamic Therapy: an in vitro comparative study

Glioblastoma multiforme is considered to be one of the most aggressive types of tumors of the central nervous system, with a poor prognosis and short survival periods of ~ one year. The current protocol for glioblastoma treatment includes the surgical excision of the primary tumor followed by radio and chemotherapy. Photodynamic therapy (PDT) is considered a promising strategy for the treatment of several types of tumors. Phthalocyanines (Pcs) are good photosensitizers (PSs) for PDT because they induce cell death in several cellular models. ZnPc (Zn(II)phthalocyanine) is a well-known Pc, extensively tested in different cells and tumor models, but its evaluation on a glioblastoma model has been poorly studied. Herein, we compare the capacity of ZnPc and one of its derivatives, Zn(II)tetraminephthalocyanine (TAZnPc), to photoinactivate glioblastoma cells (T98G, MO59, LN229 and U87-MG) in culture. We measured the cellular uptake, the toxicity in the dark and the subcellular localization of the different Pcs, as well as the clonogenic capacity of surviving cells after PDT. The mechanism of cell death induced after PDT was determined by measuring caspase 3 activation, DNA fragmentation, phosphatidylserine externalization, mitochondrial morphological changes and loss of mitochondrial membrane potential as well as lysosomal membrane integrity. Overall, ZnPc and TAZnPc present good properties to be used as PSs with photoinactivation capacity on glioblastoma cells.

Potent peptide-conjugated silicon phthalocyanines for tumor photodynamic therapy

Phthalocyanines (Pcs) are a group of promising photosensitizers for use in photodynamic therapy (PDT). However, their extremely low solubility and their strong tendency to aggregate in aqueous solution greatly restrict their application. Conjugation of Pc macrocycles with peptide ligands could be a very useful strategy to optimize the physical properties of Pcs not only by increasing their water solubility and reducing their aggregation but also by endowing the conjugates with a tumor-targeting capability. To develop highly potent photosensitizers for tumor PDT, we prepared new peptide-conjugated photosensitizers using silicon Pc (SiPc), which has much higher photodynamic activity than zinc Pcs, as the light activation moiety and the cRGDfK peptide (or simply cRGD) as the peptide moiety. A polyethylene glycol linker and an extra carboxylic acid group were also tested for introduction into the conjugates to optimize the conjugate structure. The conjugates' photophysical and photodynamic behaviors were then carefully evaluated and compared using in vitro and in vivo experiments. One of the prepared conjugates, RGD-(Linker)₂-Glu-SiPc, showed excellent physical properties and photodynamic activity, with an EC₅₀ (half maximal effective concentration) of 10-20 nM toward various cancer cells. This conjugate eradicated human glioblastoma U87-MG tumors in a xenograft murine tumor model after only one dose of photodynamic treatment, with no tumor regrowth during observation for up to 35 days. The conjugate RGD-(Linker)₂-Glu-SiPc thus showed highly promising potential for use in tumor treatment.

Photophysical and photochemical properties of novel peripherally triethyleneoxysulfanyl substituted monomeric and Si–Si bonded dimeric silicon phthalocyanines

Monomeric and Si–Si bonded dimeric silicon(IV) phthalocyanines bearing 4[Formula: see text],7[Formula: see text],10[Formula: see text]-trioxaundecylsulfanyl groups were synthesized. These novel phthalocyanine derivatives were characterized by general analysis methods such as FT-IR, MALDI-TOF or HRMS, 1H NMR and UV-vis electronic absorption. Their aggregation behaviors were described in dimethyl sulfoxide (DMSO). In addition, the photophysical and photochemical properties of these phthalocyanines were also investigated in DMSO to determine potential of these phthalocyanines to acts as photosensitizer for photodynamic therapy (PDT) of cancer. Their high singlet oxygen generation demonstrated their suitability for PDT applications. These peripherally 4[Formula: see text],7[Formula: see text],10[Formula: see text]-trioxaundecylsulfanyl substituted silicon(IV) phthalocyanines are promising Type II photosensitizers owing to their favorable singlet oxygen generation capability. In addition, their fluorescence quenching behavior by 1,4-benzoquinone were also studied in DMSO.

Photodynamic antimicrobial chemotherapy with cationic phthalocyanines against Escherichia coli planktonic and biofilm cultures

Cationic phthalocyanines (Pcs) combine with photodynamic antimicrobial chemotherapy (PACT) presents excellent antibacterial activity to Gram-negative bacteriaE. coli.

Study of the coordination of quinuclidine to a chiral zinc phthalocyanine dimer

We attempted the calculation of an accurate equilibrium constant for the dimerization process of enantiomerically pure Zn-1 using UV-vis dilution experiments. At millimolar concentration Zn-1 is involved in a chemical exchange process between its monomeric and dimeric state that is slow on the 1H NMR timescale. We performed variable-temperature 1H NMR experiments in CDCl3 solution to determine the dimerization constant value at different temperatures and performed a van’t Hoff plot to derive the thermodynamic parameters of the process. The calculated thermodynamic data revealed that the dimerization process is entropy-driven and enthalpically opposed. We also probed the coordination of quinuclidine, 1-azabicyclo[2.2.2]octane, 2, to the Zn-1 using UV-vis and 1H NMR titrations in CDCl3 solution. At micromolar concentration the Zn-1 exclusively exists in solution as a monomer and forms a simple 1:1, [Formula: see text], complex with quinuclidine having a stability constant of [Formula: see text]([Formula: see text]) [Formula: see text] 106 M[Formula: see text]. On the other hand, the 1H NMR titrations carried out at 298 K and at millimolar concentration showed that Zn-1 was present in solution as the dimer and formed 1:2, [Formula: see text], and 2:2, [Formula: see text] complexes by coordination to 2. In addition, the 1:1 complex, [Formula: see text] showed a reduced dimerization constant compared to the uncoordinated parent monomer Zn-1. At high quinuclidine concentration, the 1:1 complex, [Formula: see text], derived from the coordinated dimer dissociation was also detected. The 1H NMR spectra of the titrations displayed separate signals for some hydrogen atoms of the Zn-phthalocyanine in each one of the four species. Remarkably, the chemical exchange processes involving free and bound quinuclidine in the monomeric and dimeric complexes showed different kinetics on the NMR timescale.

Synthesis, Photophysical and Photochemical Properties of a Set of Silicon Phthalocyanines Bearing Anti-Inflammatory Groups

In this study, a series of novel silicon (IV) phthalocyanines conjugated axially with anti-inflammatory (sulindac) and triethylene glycol groups has been synthesized. Different synthetic strategies were attempted to obtain the targeted molecules in high yield. The compounds were fully characterized by using different analyses techniques. Our objectives were to generate a system with sulindac group which enhances the singlet oxygen generation and exhibits anti-cancer effect. Therefore, photophysical and photochemical properties of these compounds were investigated in different solvents. The substituent effect on fluorescence quantum yield and singlet oxygen generation was evaluated for efficiency in photodynamic therapy (PDT) as photosensitizer. The molecules exhibited no aggregation tendency, solubility in common organic solvents, high singlet oxygen quantum yield and high photostability in DMSO so these favourable properties make them good candidates as photosensitizer for PDT. In addition, their stabilities were investigated in DMSO, THF, acetonitrile and DMF.

Recent applications of phthalocyanines and naphthalocyanines for imaging and therapy

With high extinction coefficients and long absorption wavelengths in the near infrared region, phthalocyanines (Pcs) and naphthalocyanines (Ncs) are well-suited for optical imaging and phototherapies in biological tissues. Pcs and Ncs have been used in a range of theranostic applications. Peripheral and axial substituents can be introduced to Pcs and Ncs for chemical modification. Seamless metal chelation of Pcs or Ncs can expand their possibilities as medical therapeutic and imaging agents. Nanoparticulate approaches enable unique ways to deliver Pcs and Ncs to target tissues and improve their solubility, biocompatibility, biodistribution and stability. Herein, we highlight some recent Pc or Nc nanoscale systems for theranostic applications. WIREs Nanomed Nanobiotechnol 2017, 9:e1420. doi: 10.1002/wnan.1420 For further resources related to this article, please visit the WIREs website.

Dicyanobenzene and dicyanopyrazine derived X-shaped charge-transfer chromophores: comparative and structure-property relationship study

A series of novel X-shaped push-pull compounds based on benzene-1,2-dicarbonitrile has been designed, synthesized and further investigated by X-ray analysis, electrochemistry, absorption and emission spectra, SHG experiment and quantum-chemical calculations. The obtained data were compared with those for isolobal 5,6-disubstituted pyrazine-2,3-dicarbonitriles. Structure-property relationships were elucidated. The extension, composition and planarization of the π-linker used as well as the electron-withdrawing ability of both dicyano-substituted acceptor units affect the linear and nonlinear properties of the target charge-transfer chromophores most significantly.

Cholesteryl oleate-appended phthalocyanines as potential photosensitizers in the treatment of leishmaniasis

Two phthalocyanines (Pcs) with either a zinc or a ruthenium metal at the center of the macrocycle have been functionalized by a cholesteryl oleate moiety. The potential photosensitizers (PSs) for the treatment of cutaneous leishmaniasis have been studied on their photophysical properties and their ability to generate singlet oxygen. These experiments corroborate that solvent mixtures containing variable ratios of THF and water impact the excited state deactivation. The compounds were used preloaded into LDL particles and their phototoxic activity was evaluated in a preliminary way.

Generation-dependent templated self-assembly of biohybrid protein nanoparticles around photosensitizer dendrimers

In this article, we show the great potential of dendrimers for driving the self-assembly of biohybrid protein nanoparticles. Dendrimers are periodically branched macromolecules with a perfectly defined and monodisperse structure. Moreover, they allow the possibility to incorporate functional units at predetermined sites, either at their core, branches, or surface. On these bases, we have designed and synthesized negatively charged phthalocyanine (Pc) dendrimers that behave as photosensitizers for the activation of molecular oxygen into singlet oxygen, one of the main reactive species in photodynamic therapy (PDT). The number of surface negative charges depends on dendrimer generation, whereas Pc aggregation can be tuned through the appropriate choice of the Pc metal center and its availability for axial substitution. Remarkably, both parameters determine the outcome and efficiency of the templated self-assembly process by which a virus protein forms 18 nm virus-like particles around these dendritic chromophores. Protein-dendrimer biohybrid nanoparticles of potential interest for therapeutic delivery purposes are obtained in this way. Biohybrid assemblies of this kind will have a central role in future nanomedical and nanotechnology applications.

Inverted methoxypyridinium phthalocyanines for PDI of pathogenic bacteria

New tetra- and octa-methoxypyridinium phthalocyanines and their efficiency to photoinactivate Escherichia coli.

π-π Stacking induced enhanced molecular solubilization, singlet oxygen production, and retention of a photosensitizer loaded in thermosensitive polymeric micelles

Cancer photodynamic therapy (PDT) by photosensitizers (PS)-loaded polymeric micelles (PM) is hampered by the tendency of PS to aggregate in PM and/or by premature release of PS in the blood circulation. In the present study, aromatic thermosensitive PM, characterized by π-π stacking interaction, are used to encapsulate an axially solketal-substituted silicon phthalocyanine (Si(sol)2 Pc) with enhanced loading capacity, smaller size, and significantly improved retention of Si(sol)2 Pc compared with systems based on thermosensitive PM lacking aromatic groups. Interestingly, Si(sol)2 Pc is much less prone to aggregation in the aromatic PM, i.e., the amount of Si(sol)2 Pc that could be encapsulated without aggregation is 330 times higher in the aromatic PM than in the nonaromatic PM. Furthermore, Si(sol)2 Pc in the aromatic PM in a molecularly dissolved (non-aggregated) form displays three times more efficient singlet oxygen production than Si(sol)2 Pc aggregated in the non-aromatic PM. As a result, the photocytotoxicity of Si(sol)2 Pc-loaded aromatic PM to B16F10 cells is increased, compared with that of the non-aromatic PM, while no significant cytotoxicity is observed in the dark. Fluorescence-activated cell sorting (FACS) and confocal laser scanning microscopy (CLSM) analysis shows cell uptake of Si(sol)2 Pc loaded in the aromatic PM, and the Si(sol)2 Pc is taken up by the cells together with the micelles. The efficient singlet oxygen production of Si(sol)2 Pc dissolved in the aromatic PM makes it an interesting formulation for cancer PDT.