Improved photodynamic efficacy of Zn(II) phthalocyanines via glycerol substitution

NIR-activated multifunctional agents for the combined application in cancer imaging and therapy

Anticancer therapies that combine both diagnostic and therapeutic capabilities hold significant promise for enhancing treatment efficacy and patient outcomes. Among these, agents responsive to near-infrared (NIR) photons are of particular interest due to their negligible toxicity and multifunctionality. These compounds are not only effective in photodynamic therapy (PDT), but also serve as contrast agents in various imaging modalities, including fluorescence and photoacoustic imaging. In this review, we explore the photophysical and photochemical properties of NIR-activated porphyrin, cyanine, and phthalocyanines derivatives as well as aggregation-induced emission compounds, highlighting their application in synergistic detection, diagnosis, and therapy. Special attention is given to the design and optimization of these agents to achieve high photostability, efficient NIR absorption, and significant yields of fluorescence, heat, or reactive oxygen species (ROS) generation depending on the application. Additionally, we discuss the incorporation of these compounds into nanocarriers to enhance their solubility, stability, and target specificity. Such nanoparticle-based systems exhibit improved pharmacokinetics and pharmacodynamics, facilitating more effective tumor targeting and broadening the application range to photoacoustic imaging and photothermal therapy. Furthermore, we summarize the application of these NIR-responsive agents in multimodal imaging techniques, which combine the advantages of fluorescence and photoacoustic imaging to provide comprehensive diagnostic information. Finally, we address the current challenges and limitations of photodiagnosis and phototherapy and highlight some critical barriers to their clinical implementation. These include issues related to their phototoxicity, limited tissue penetration, and potential off-target effects. The review concludes by highlighting future research directions aimed at overcoming these obstacles, with a focus on the development of next-generation agents and platforms that offer enhanced therapeutic efficacy and imaging capabilities in the field of cancer treatment.

Synthesis, Photo-Characterizations, and Pre-Clinical Studies on Advanced Cellular and Animal Models of Zinc(II) and Platinum(II) Sulfonyl-Substituted Phthalocyanines for Enhanced Vascular-Targeted Photodynamic Therapy

Two phthalocyanine derivatives tetra-peripherally substituted with tert-butylsulfonyl groups and coordinating either zinc(II) or platinum(II) ions have been synthesized and subsequently investigated in terms of their optical and photochemical properties, as well as biological activity in cellular, tissue-engineered, and animal models. Our research has revealed that both synthesized phthalocyanines are effective generators of reactive oxygen species (ROS). PtSO2tBu demonstrated an outstanding ability to generate singlet oxygen (ΦΔ = 0.87-0.99), while ZnSO2tBu in addition to 1O2 (ΦΔ = 0.45-0.48) generated efficiently other ROS, in particular ·OH. Considering future biomedical applications, the affinity of the tested phthalocyanines for biological membranes (partition coefficient; log Pow) and their primary interaction with serum albumin were also determined. To facilitate their biological administration, a water-dispersible formulation of these phthalocyanines was developed using Pluronic triblock copolymers to prevent self-aggregation and improve their delivery to cancer cells and tissues. The results showed a significant increase in cellular uptake and phototoxicity when phthalocyanines were incorporated into the customizable polymeric micelles. Moreover, the improved distribution in the body and photodynamic efficacy of the encapsulated phthalocyanines were investigated in hiPSC-delivered organoids and BALB/c mice bearing CT26 tumors. Both photosensitizers exhibit strong antitumor activity. Notably, vascular-targeted photodynamic therapy (V-PDT) led to complete tumor eradication in 84% of ZnSO2tBu and 100% of PtSO2tBu-treated mice, and no recurrence has so far been observed for up to five months after treatment. In the case of PtSO2tBu, the effect was significantly stronger, offering a wider range of light doses suitable for achieving effective PDT.

Catalytic and Selective Red Light-Triggered Photodegradation of a G-Quadruplex DNA by a Zinc (II) Phthalocyanine

Water-soluble phthalocyanine (Pc) derivatives have been regarded as potential G-quadruplex (G4) nucleic acid-targeting ligands for anticancer therapy and have been extensively studied as effective photosensitizers for photodynamic therapy (PDT). Understanding how photosensitizers interact with nucleic acids and the subsequent photolytic reactions is essential for deciphering the initial steps of PDT, thereby aiding in the development of new photosensitizing agents. In this study, we found that red-light irradiation of a mixture of a Zn(II) Pc derivative and an all-parallel G4 DNA leads to catalytic and selective photodegradation of the DNA by reactive oxygen species (ROS) generated from the Zn(II) Pc derivative bound to DNA through a reaction mechanism similar to that of an enzyme reaction. This finding provides a novel insight into the molecular design of a photosensitizer to enhance its PDT efficacy.

Photodynamic Therapy: A Novel Approach for Head and Neck Cancer Treatment with Focusing on Oral Cavity

Oral cancers, specifically oral squamous cell carcinoma (OSCC), pose a significant global health challenge, with high incidence and mortality rates. Conventional treatments such as surgery, radiotherapy, and chemotherapy have limited effectiveness and can result in adverse reactions. However, as an alternative, photodynamic therapy (PDT) has emerged as a promising option for treating oral cancers. PDT involves using photosensitizing agents in conjunction with specific light to target and destroy cancer cells selectively. The photosensitizers accumulate in the cancer cells and generate reactive oxygen species (ROS) upon exposure to the activating light, leading to cellular damage and ultimately cell death. PDT offers several advantages, including its non-invasive nature, absence of known long-term side effects when administered correctly, and cost-effectiveness. It can be employed as a primary treatment for early-stage oral cancers or in combination with other therapies for more advanced cases. Nonetheless, it is important to note that PDT is most effective for superficial or localized cancers and may not be suitable for larger or deeply infiltrating tumors. Light sensitivity and temporary side effects may occur but can be managed with appropriate care. Ongoing research endeavors aim to expand the applications of PDT and develop novel photosensitizers to further enhance its efficacy in oral cancer treatment. This review aims to evaluate the effectiveness of PDT in treating oral cancers by analyzing a combination of preclinical and clinical studies.

A Photochemical Study of Photo-Induced Electron Transfer from DNAs to a Cationic Phthalocyanine Derivative

Water-soluble cationic gallium(III)-Pc complex (GaPc) is capable of photogenerating ROSs but does not exhibit photocytotoxicity in vivo. GaPc binds selectively, through a π-π stacking interaction, to the 5'-terminal G-quartet of a G-quadruplex DNA. The photo-excited state of GaPc of the complex is effectively quenched through electron transfer (ET) from the ground state of DNA guanine (G) bases to the photo-excited state of GaPc (ET(G-GaPc)). Hence the loss of the photocytotoxicity of GaPc in vivo is most likely to be due to the effective quenching of its photo-excited state through ET(G-GaPc). In this study, we investigated the photochemical properties of GaPc in the presence of duplex DNAs formed from a series of sequences to elucidate the nature of ET(G-GaPc). We found that ET(G-GaPc) is allowed in electrostatic complexes between GaPc and G-containing duplex DNAs and that the rate of ET(G-GaPc) (kET(G-GaPc)) can be reasonably interpreted in terms of the distance between Pc moiety of GaPc and DNA G base in the complex. We also found that the quantum yields of singlet oxygen (1O2) generation (ΦΔs) determined for the GaPc-duplex DNA complexes were similar to the value reported for free GaPc (Fujishiro R, Sonoyama H, Ide Y, et al (2019) J Inorg Biochem 192:7-16), indicating that ET(G-GaPc) in the complex is rather limited. These results clearly demonstrated that photocytotoxicity of GaPc is crucially affected by ET(G-GaPc). Thus elucidation of interaction of a photosensitizer with biomolecules, i.e., an initial process in PDT, would be helpful to understand its subsequent photochemical processes.

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.

Dicoma anomala Enhances Phthalocyanine Mediated Photodynamic Therapy in MCF-7 Breast Cancer Cells

Breast cancer is one of the most common types of cancer in women, and it is regarded as the second leading cause of cancer-related deaths worldwide. The present study investigated phytochemical profiling, in vitro anticancer effects of Dicoma anomala methanol root extract and its enhancing effects in phthalocyanine mediated PDT on MCF-7 (ATCC^® HTB-22™) breast cancer cells. Ultra-high performance liquid chromatography coupled to electrospray ionization quadrupole-time of flight mass spectrometry (UHPLC-qTOF-MS²) was used to identify the secondary metabolites in the crude extract. The 50% inhibitory concentration (IC₅₀) of the two experimental models was established from dose response studies 24 h post-treatment with D. anomala methanol root extract (25, 50, and 100 μg/ml) and ZnPcS₄ (5, 10, 20, 40, and 60 μM) mediated PDT. The inverted microscope was used to analyze morphological changes, trypan blue exclusion assay for viability, and Annexin V-fluorescein isothiocyanate (FITC)-propidium iodide (PI) for cell death mechanisms. Immunofluorescence analysis was used to investigate the qualitative expression of the Bax, p53, and caspase 3 apoptotic proteins. Experiments were performed 4 times (n = 4) and SPSS version 27 software was used to analyze statistical significances. D. anomala methanol root extract induced cell death in MCF-7 cells by decreasing cell viability. The combination of D. anomala methanol root extract and ZnPcS₄ mediated PDT led to a significant increase in apoptotic activities, expression of Bax, and p53 with significant decrease in cell viability. These findings pinpoint the possibility of D. anomala methanol root extract of being employed as a natural antiproliferative agent in the treatment of various cancers.

Phototherapeutic anticancer strategies with first-row transition metal complexes: a critical review

Photodynamic therapy (PDT) and photoactivated chemotherapy (PACT) are therapeutic techniques based on a photosensitizer (PS) and light. These techniques allow the spatial and temporal control of the activation of drugs with light. Transition metal complexes are attractive compounds as photoactivatable prodrugs since their excited states can be appropriately designed by subtle modifications of the ligands, the metal centre, or the oxidation state. However, most metal-based PSs contain heavy metals such as Ru, Os, Ir, Pt or Au, which are expensive and non-earth-abundant, contrary to first-row transition metals. In this context, the exploration of the photochemical properties of complexes based on first-row transition metals appears to be extremely promising. This did encourage several groups to develop promising PSs based on these metals. This review presents up-to-date state-of-the-art information on first-row-transition metal complexes, from titanium to zinc in regard to their application as PSs for phototherapeutic applications.

A novel, dual action chimera comprising DNA methylating agent and near-IR xanthene-cyanine photosensitizer for combined anticancer therapy

A facile synthesis, biological evaluation and photodynamic properties of novel activatable anticancer molecular hybrids (chimeras) Ch and I-Ch are described. The chimeras consist of DNA methylating methyl triazene moiety and fluorogenic xanthene-cyanine (XCy) or iodinated xanthene-cyanine (I-XCy) photosensitizer. These two anticancer core structures are bound by means of a self-immolative 4-aminobenzyl alcohol linker. The hydrolytic cleavage of the carbamate protecting group promotes activation of both DNA methylating monomethyl triazene and phototoxic xanthene-cyanine dye providing, in addition, a near-IR emission signal for detection of the drug activation events. Preliminary antiproliferative assay demonstrates that the developed chimeras exhibit higher antitumor activity in the breast cancer cell line upon near-IR light irradiation compared to their structural constituents, xanthene-cyanine photosensitizer and monomethyl triazene substance.

Pyrrole-based photosensitizers for photodynamic therapy — a Thomas Dougherty award paper

Photodynamic therapy (PDT) is a therapeutic modality that uses light to treat malignant or benign diseases. A photosensitizer, light, and oxygen are the three main components needed to generate a cytotoxic effect. Pyrrole-based photosensitizers have been widely used for PDT. Many of the photosensitizers within this class are macrocyclic. This is particularly true for systems that have received regulatory approval or been the subject of clinical trials. However, in recent years, a number of boron dipyrromethanes (BODIPY) have been studied as photosensitizers. Herein, we review examples of some of the most relevant pyrrole-based photosensitizers.

Positively charged styryl pyridine substituted Zn(II) phthalocyanines for photodynamic therapy and photoantimicrobial chemotherapy: effect of the number of charges

Cationic Zn phthalocyanine complexes were synthesized using Knoevenagel reaction starting from a Zn(ii) tetrakis(2-formylphenoxy)phthalocyanine (1) to form Zn(ii) tetrakis(1-butyl-4-(4-(tetraphenoxy)styryl)pyridin-1-ium) phthalocyanine (2) and Zn(ii) tetrakis(4-(4-(tetraphenoxy)styryl)-1-(4-(triphenylphosphonio)butyl)pyridin-1-ium)phthalocyanine (3). The photophysicochemical behaviours of the Pc complexes were assessed. The cationic complexes display high water-solubility and gave moderate singlet oxygen quantum yield in water. The cationic Pcs demonstrate good cellular uptake and photodynamic activity against MCF-7 cells with IC50 values of 8.2 and 4.9 μM for 2 and 3, respectively. The cationic Pcs also demonstrate high photoantimicrobial activity against Escherichia coli with log reductions of 5.3 and 6.0 for 2 and 3, respectively.

Attritional evaluation of lipophilic and hydrophilic metallated phthalocyanines for oncological photodynamic therapy

BACKGROUND AND AIM

Oncological photodynamic therapy (PDT) relies on photosensitizers (PSs) to photo-oxidatively destroy tumor cells. Currently approved PSs yield satisfactory results in superficial and easy-to-access tumors but are less suited for solid cancers in internal organs such as the biliary system and the pancreas. For these malignancies, second-generation PSs such as metallated phthalocyanines are more appropriate. Presently it is not known which of the commonly employed metallated phtahlocyanines, namely aluminum phthalocyanine (AlPC) and zinc phthalocyanine (ZnPC) as well as their tetrasulfonated derivatives AlPCS4 and ZnPCS4, is most cytotoxic to tumor cells. This study therefore employed an attritional approach to ascertain the best metallated phthalocyanine for oncological PDT in a head-to-head comparative analysis and standardized experimental design.

METHODS

ZnPC and AlPC were encapsulated in PEGylated liposomes. Analyses were performed in cultured A431 cells as a template for tumor cells with a dysfunctional P53 tumor suppressor gene and EGFR overexpression. First, dark toxicity was assessed as a function of PS concentration using the WST-1 and sulforhodamine B assay. Second, time-dependent uptake and intracellular distribution were determined by flow cytometry and confocal microscopy, respectively, using the intrinsic fluorescence of the PSs. Third, the LC₅₀ values were established for each PS at 671 nm and a radiant exposure of 15 J/cm² following 1-h PS exposure. Finally, the mode of cell death as a function of post-PDT time and cell cycle arrest at 24 h after PDT were analyzed.

RESULTS

In the absence of illumination, AlPC and ZnPC were not toxic to cells up to a 1.5-μM PS concentration and exposure for up to 72 h. Dark toxicity was noted for AlPCS4 at 5 μM and ZnPCS4 at 2.5 μM. Uptake of all PSs was observed as early as 1 min after PS addition to cells and increased in amplitude during a 2-h incubation period. After 60 min, the entire non-nuclear space of the cell was photosensitized, with PS accumulation in multiple subcellular structures, especially in case of AlPC and AlPCS4. PDT of cells photosensitized with ZnPC, AlPC, and AlPCS4 yielded LC₅₀ values of 0.13 μM, 0.04 μM, and 0.81 μM, respectively, 24 h post-PDT (based on sulforhodamine B assay). ZnPCS4 did not induce notable phototoxicity, which was echoed in the mode of cell death and cell cycle arrest data. At 4 h post-PDT, the mode of cell death comprised mainly apoptosis for ZnPC and AlPC, the extent of which was gradually exacerbated in AlPC-photosensitized cells during 8 h. ZnPC-treated cells seemed to recover at 8 h post-PDT compared to 4 h post-PDT, which had been observed before in another cell line. AlPCS4 induced considerable necrosis in addition to apoptosis, whereby most of the cell death had already manifested at 2 h after PDT. During the course of 8 h, necrotic cell death transitioned into mainly late apoptotic cell death. Cell death signaling coincided with a reduction in cells in the G₀/G₁ phase (ZnPC, AlPC, AlPCS4) and cell cycle arrest in the S-phase (ZnPC, AlPC, AlPCS4) and G₂ phase (ZnPC and AlPC). Cell cycle arrest was most profound in cells that had been photosensitized with AlPC and subjected to PDT.

CONCLUSIONS

Liposomal AlPC is the most potent PS for oncological PDT, whereas ZnPCS4 was photodynamically inert in A431 cells. AlPC did not induce dark toxicity at PS concentrations of up to 1.5 μM, i.e., > 37 times the LC₅₀ value, which is favorable in terms of clinical phototoxicity issues. AlPC photosensitized multiple intracellular loci, which was associated with extensive, irreversible cell death signaling that is expected to benefit treatment efficacy and possibly immunological long-term tumor control, granted that sufficient AlPC will reach the tumor in vivo. Given the differential pharmacokinetics, intracellular distribution, and cell death dynamics, liposomal AlPC may be combined with AlPCS4 in a PS cocktail to further improve PDT efficacy.

Synthesis, characterization, photophysics, and photochemistry of peripherally substituted tetrakis(quinolinylethylenephenoxy)-substituted zinc(ii) phthalocyanines

Quinoline substituted zinc phthalocyanine derivatives were synthesized and characterized, and their photophysical and photochemical properties were investigated.

The unique features and promises of phthalocyanines as advanced photosensitisers for photodynamic therapy of cancer

Phthalocyanines exhibit superior photoproperties that make them a surely attractive class of photosensitisers for photodynamic therapy of cancer. Several derivatives are at various phases of clinical trials, and efforts have been put continuously to improve their photodynamic efficacy. To this end, various strategies have been applied to develop advanced phthalocyanines with optimised photoproperties, dual therapeutic actions, tumour-targeting properties and/or specific activation at tumour sites. The advantageous properties and potential of phthalocyanines as advanced photosensitisers for photodynamic therapy of cancer are highlighted in this tutorial review.

Zinc(II) phthalocyanines as photosensitizers for antitumor photodynamic therapy

Photodynamic therapy (PDT) is a highly specific and clinically approved method for cancer treatment in which a nontoxic drug known as photosensitizer (PS) is administered to a patient. After selective tumor irradiation, an almost complete eradication of the tumor can be reached as a consequence of reactive oxygen species (ROS) generation, which not only damage tumor cells, but also lead to tumor-associated vasculature occlusion and the induction of an immune response. Despite exhaustive investigation and encouraging results, zinc(II) phthalocyanines (ZnPcs) have not been approved as PSs for clinical use yet. This review presents an overview on the physicochemical properties of ZnPcs and biological results obtained both in vitro and in more complex models, such as 3D cell cultures, chicken chorioallantoic membranes and tumor-bearing mice. Cell death pathways induced after PDT treatment with ZnPcs are discussed in each case. Finally, combined therapeutic strategies including ZnPcs and the currently available clinical trials are mentioned.

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.

Double stimuli-responsive polysaccharide block copolymers as green macrosurfactants for near-infrared photodynamic therapy

The NIR absorbing photosensitizer phthalocyanine zinc (PC(Zn)) was stabilized in aqueous media as water-dispersible nanoparticles with a reduction- and pH-responsive full polysaccharide block copolymer. A cellular uptake and also photo switchable intracellular activity of the cargo upon irradiation at wavelengths in the near infrared region were shown. The block copolymer was synthesized by applying a copper-free click strategy based on a thiol exchange reaction, creating an amphiphilic double-stimuli-responsive mixed disulfide. The dual-sensitive polysaccharide micelles represent a non-toxic and biodegradable green macrosurfactant for the delivery of phthalocyanine zinc. By encapsulation into micellar nanoparticles, the bioavailability of PC(Zn) increased significantly, enabling smart photodynamic therapy for future applications in cancer-related diseases.

Triphenylphosphonium-substituted phthalocyanine: Design, synthetic strategy, photoproperties and photodynamic activity

In line with current efforts to direct PDT photosensitizers to specific organelles such as mitochondria, a triphenylphosphonium-tetrasubstituted Zn phthalocyanine was designed, taking into account synthetic constraints. Triphenylphosphonium moieties were successfully introduced on alkyl bromide substituents on a pre-formed phthalocyanine. Photophysical and photochemical measurements showed that the photoproperties of the Zn phthalocyanine core were not affected by the triphenylphosphonium groups. Biological investigations demonstrated the dark innocuousness of the phthalocyanine up to 1 [Formula: see text]M, a concentration that exhibited a powerful phototoxicity. Cell death was confirmed to be photodynamically induced thanks to reactive oxygen species detection experiments. Nonetheless, the triphenylphosphonium moieties did not promote the accumulation of the phthalocyanine in mitochondria as significantly as expected.

Synthesis of axially disubstituted silicon phthalocyanines and investigation of photodynamic effects on HCT-116 colorectal cancer cell line

Photodynamic therapy is one of the hot topics in cancer studies. Photosensitizing chemical substrates are stimulated by light having a specific wavelength to cause fatal effect on different kinds of targets. In this study, axially 4-{[(1E)-2-furylmethylene]amino}phenol, 4-{[(1E)-2-thienylmethylene]amino}phenol and 4-{[(1E)-(4-nitro-2-thienyl)methylene]amino}phenol disubstituted silicon phthalocyanines were synthesized as Photosensitizers for photodynamic therapy in cancer treatment. The structural characterizations of these novel compounds were performed by a combination of FT-IR, ¹H-NMR, UV-vis and mass. All these newly prepared compounds did not show aggregation at the concentration range of 2 × 10^-6-12 × 10^-6 M in tetrahydrofurane and also did not show aggregation in different organic solvents at 2 × 10^-6 M concentration. Phthalocyanines synthesized in this study were tested on HCT-116 colorectal cancer cells and stimulated by light has wavelength of 680 nm. The toxic effects on cancer cells which are caused by different concentrations of photosensitizing molecules have been examined and compared with the toxic effects on cancer cells that were kept in the dark. It is confirmed that these molecules caused toxic effects on colorectal cancer cells when they were stimulated by light but there was no toxic effect in the dark.

Axially Decorated SiIV -phthalocyanines Bearing Mannose- or Ammonium-conjugated Siloxanes: Comparative Bacterial Labeling and Photodynamic Inactivation<sup/>

Herein, we present a comparative study about the photoinactivation of Staphylococcus aureus (Gram-positive model) and Escherichia coli (Gram-negative model) employing a neutral and a dicationic axially functionalized Si^IV -phthalocyanine. Depending on the charge of the siloxane moiety (neutral monosaccharide or cationic ammonium salt), different interactions with the bacteria were observed, and a differential photoinactivation was facilitated. The intensity of the fluorescence labeling correlated with the photoinactivation of the two types of bacteria: While the neutral species only significantly affected the Gram-positive cells, we observed that the positively charged photosensitizer interacted both with the Gram-positive and with the Gram-negative models. The dicationic photosensitizer labeled both models with a characteristic deep-red fluorescence and photoinactivated both classes of prokaryotes. In general, our study clearly demonstrates that axially ammoniumsiloxane-functionalized Si(IV) phthalocyaninates constitute excellent photosensitizers due to their weak aggregation in aqueous environments. In particular, we also show that charge-based targeting with axial ammonium groups leads toward broad-spectrum Si^IV -phthalocyanines for photodynamic inactivation of bacteria.

Zinc phthalocyanine encapsulated in polymer micelles as a potent photosensitizer for the photodynamic therapy of osteosarcoma

Zinc phthalocyanine (ZnPc) is a highly potent second-generation photosensitizer for cancer photodynamic therapy (PDT) with attractive photo-physical and photo-chemical properties. However, poor solubility and strong trend of crystallization prevent it from loading in most of drug delivery systems and hamper its further application. Herein, to overcome this problem, an amphiphilic block copolymer poly(ethylene glycol)-poly[2-(methylacryloyl)ethylnicotinate] (PEG-PMAN) with aromatic nicotinate is used to load ZnPc for their π-π interactions. The formed PEG-PMAN/ZnPc nanoparticle (PPZ) dramatically increases reactive oxygen species production in osteosarcoma cells after light irradiation, causes mitochondrial injury and promotes cell cycle arrest at G2/M, leading to a 100-fold cytotoxicity improvement comparing with free ZnPc. The excellent therapeutic effectiveness and safety of PPZ are also proved by in vivo experiments operating on osteosarcoma model. The finding above indicates that PPZ has promising clinical applications as a next-generation photosensitizer in PDT of osteosarcoma.

Simulations of a Graphene Nanoflake as a Nanovector To Improve ZnPc Phototherapy Toxicity: From Vacuum to Cell Membrane

We propose a new approach to improving photodynamic therapy (PDT) by transporting zinc phthalocyanine (ZnPc) in biological systems via a graphene nanoflake, to increase its targeting. Indeed, by means of time-dependent density functional theory simulations, we show that the ZnPc molecule in interaction with a graphene nanoflake preserves its optical properties not only in a vacuum but also in water. Moreover, molecular dynamic simulations demonstrate that the graphene nanoflake/ZnPc association, as a carrier, permits one to stabilize the ZnPc/graphene nanoflake system on the cellular membrane, which was not possible when using ZnPc alone. We finally conclude that the graphene nanoflake is a good candidate to transport and stabilize the ZnPc molecule near the cell membrane for a longer time than the isolated ZnPc molecule. In this way, the choice of the graphene nanoflake as a nanovector paves the way to ZnPc PDT improvement.

Properties of halogenated and sulfonated porphyrins relevant for the selection of photosensitizers in anticancer and antimicrobial therapies

The impact of substituents on the photochemical and biological properties of tetraphenylporphyrin-based photosensitizers for photodynamic therapy of cancer (PDT) as well as photodynamic inactivation of microorganisms (PDI) was examined. Spectroscopic and physicochemical properties were related with therapeutic efficacy in PDT of cancer and PDI of microbial cells in vitro. Less polar halogenated, sulfonamide porphyrins were most readily taken up by cells compared to hydrophilic and anionic porphyrins. The uptake and PDT of a hydrophilic porphyrin was significantly enhanced with incorporation in polymeric micelles (Pluronic L121). Photodynamic inactivation studies were performed against Gram-positive (S. aureus, E. faecalis), Gram-negative bacteria (E. coli, P. aeruginosa, S. marcescens) and fungal yeast (C. albicans). We observed a 6 logs reduction of S. aureus after irradiation (10 J/cm²) in the presence of 20 μM of hydrophilic porphyrin, but this was not improved with incorporation in Pluronic L121. A 2–3 logs reduction was obtained for E. coli using similar doses, and a decrease of 3–4 logs was achieved for C. albicans. Rational substitution of tetraphenylporphyrins improves their photodynamic properties and informs on strategies to obtain photosensitizers for efficient PDT and PDI. However, the design of the photosensitizers must be accompanied by the development of tailored drug formulations.

Modulation of singlet oxygen generation and amphiphilic properties of trihydroxylated monohalogenated porphyrins

Two of the properties important for photodynamic therapy applications are systematically investigated on a trihydroxylated monohalogenated porphyrin core. Singlet oxygen generation can be increased thanks to the heavy atom effect, frequently provided by the introduction of halogen atoms on the photosensitizer. We compare the effect of the presence of the four halogen atoms with the analogous halogen-free porphyrin. Cell uptake is crucial as well for successful photodynamic outcome and is directly related to the amphiphilicity of the molecule. The five derivatives bearing H, F, Cl, Br or I atoms are compared in this regard. The presence of iodine atom induces a sharp difference in singlet oxygen generation compared to all the other derivatives investigated, but increases its lipophilicity, still in the limits suitable for biomedical applications.

Design of an amphiphilic porphyrin exhibiting high in vitro photocytotoxicity

A promising photosensitiser, which exhibits extremely suitable properties for photodynamic applications is described.

Aggregation–disaggregation pattern of photodynamically active ZnPcS4 and its interaction with DNA alkylating quinone: effect of micellar compactness and central metal ion

The graphical abstract shows the aggregation–disaggregation pattern of ZnPcS₄ in neutral and different cationic micelles and its enhanced interaction with a DNA alkylating quinone in a TTAB micellar medium.

Methylsulfonyl Zn phthalocyanine: A polyvalent and powerful hydrophobic photosensitizer with a wide spectrum of photodynamic applications

BACKGROUND

The biomedical photodynamic principle is based on the light-induced and photosensitizer-mediated killing of unwanted or harmful cells by overproduction of reactive oxygen species. Motivated by the success of photodynamic therapy (PDT) against several types of tumors, further applications of this approach are constantly identified which require the design and synthesis of novel photosensitizers with specifically tailored properties for a particular clinical application.

METHODS

Hydrophobic photosensitizers are currently gaining attention and hence a tetramethylsulfonyl Zn(II) phthalocyanine (2) was designed with respect to the desired photoproperties. The photodynamic potential of 2 was assessed by the determination of its photophysical and photochemical properties, and by a large range of biological tests including its phototoxicity against cancer cells and Gram(+) bacteria. Unsubstituted ZnPc was used as a reference compound for comparison purposes.

RESULTS

Phthalocyanine 2 has a better oxygen generation and is more photostable than ZnPc. 2 is a polyvalent and powerful hydrophobic photosensitizer with a wide spectrum of photodynamic applications against cancer (tested on A431 cells) and for Gram(+) PDI. Against Staphylococcus aureus, a maximum photokilling efficiency of more than 6 log10 steps was induced by a 5μM concentration of 2, outperforming the 3 log10 criterion for an antimicrobial effect (according to the recommendation of the American Society for Microbiology) by more than three orders of magnitude.

CONCLUSIONS

Phthalocyanine 2 has attractive photophysical and -chemical characteristics. Initial evaluation of its application in anti-tumor PDT and PDI suggest potential for further pre-clinical and clinical development of this compound.