Preparation and In Vitro Photodynamic Activity of Glucosylated Zinc(II) Phthalocyanines as Underlying Targeting Photosensitizers

In Vitro and In Vivo Antipsoriatic Efficacy of Protected and Unprotected Sugar-Zinc Phthalocyanine Conjugates

Psoriasis, a chronic immune-mediated skin disorder affecting over 125 million people globally, is characterized by abnormal keratinocyte proliferation and immune cell infiltration. Photodynamic therapy (PDT) remains underutilized in the treatment of psoriasis despite its potential as a promising and effective therapeutic approach. This study aimed to explore the efficacy of zinc phthalocyanine (ZnPc) and its sugar conjugates as potential antipsoriatic agents. We successfully synthesized protected and unprotected sugar-conjugated zinc phthalocyanines and evaluated their potential against cytokine-stimulated HaCaT keratinocytes, as well as an established IMQ psoriasis-like in vivo model. Tetrasubstituted protected glucose-ZnPc (Glu-4-ZnPc-P) demonstrated superior phototoxicity (IC50 = 2.55 µM) compared to unprotected glucose conjugate (IC50 = 22.7 µM), protected galactose-ZnPc (IC50 = 7.13 µM), and free ZnPc in cytokine-stimulated HaCaT cells (IC50 = 5.84 µM). Cellular uptake analysis revealed that IL-17A, a cytokine that plays a central role in the pathogenesis of psoriasis, enhanced unprotected Glu-4-ZnPc uptake by 56.3%, while GLUT1 inhibitor BAY-876 reduced its accumulation by 23.8%. Intracellular ROS generation following Glu-4-ZnPc-P-PDT was significantly increased after stimulation with IL-17A, correlating with in vitro photocytotoxicity. In vivo PDT using Glu-4-ZnPc-P exhibited significant improvement in Psoriasis Area and Severity Index (PASI), inhibiting splenomegaly and restoring normal skin morphology. This study highlights sugar-conjugated zinc phthalocyanines as potential candidates for targeted PDT in psoriasis, providing a basis for further clinical investigations.

A Novel Boron Dipyrromethene-Erlotinib Conjugate for Precise Photodynamic Therapy against Liver Cancer

Photodynamic Therapy (PDT) is recognized for its exceptional effectiveness as a promising cancer treatment method. However, it is noted that overexposure to the dosage and sunlight in traditional PDT can result in damage to healthy tissues, due to the low tumor selectivity of currently available photosensitizers (PSs). To address this challenge, we introduce herein a new strategy where the small molecule-targeted agent, erlotinib, is integrated into a boron dipyrromethene (BODIPY)-based PS to form conjugate 6 to enhance the precision of PDT. This conjugate demonstrates optical absorption, fluorescence emission, and singlet oxygen generation efficiency comparable to the reference compound 7, which lacks erlotinib. In vitro studies reveal that, after internalization, conjugate 6 predominantly accumulates in the lysosomes of HepG2 cells, exhibiting significant photocytotoxicity with an IC50 value of 3.01 µM. A distinct preference for HepG2 cells over HELF cells is observed with conjugate 6 but not with compound 7. In vivo experiments further confirm that conjugate 6 has a specific affinity for tumor tissues, and the combination treatment of conjugate 6 with laser illumination can effectively eradicate H22 tumors in mice with outstanding biosafety. This study presents a novel and potential PS for achieving precise PDT against cancer.

Synthesis, Cellular Uptake, and Photodynamic Activity of Oligogalactosyl Zinc(II) Phthalocyanines

A series of di-α-substituted zinc(II) phthalocyanines with different number of galactose moieties, ranging from 1 to 8, namely Pc-gal_n (n=1, 2, 4, and 8) were designed and synthesized. The synthesis involved the copper-catalyzed azide-alkyne cycloaddition reaction of a mono- or dialkynyl zinc(II) phthalocyanine with an acetyl-protected galactosyl azide or its dendritic derivative with four acetyl-protected galactosyl groups, followed by removal of the acetyl protecting groups via alkaline hydrolysis. In N,N-dimethylformamide, these oligogalactosyl phthalocyanines were non-aggregated as shown by the strong Q-band absorption and fluorescence emission. Owing to the di-α-substitution, they also behaved as efficient singlet oxygen generators upon light irradiation with a singlet oxygen quantum yield of 0.84. The spectroscopic and photophysical properties were not affected by the number of galactosyl units. In contrast, the compounds became significantly aggregated and quenched in phosphate-buffered saline. Their cellular uptake was then studied using a range of cell lines, which generally followed the order Pc-gal₁ >Pc-gal₂ ≈Pc-gal₄ >Pc-gal₈ . Interestingly, the di-galactosyl analogue exhibited selective uptake against HeLa human cervical carcinoma cells through an energy-dependent pathway instead of the expected asialoglycoprotein receptor. Upon light irradiation, it could effectively kill the cells with a half-maximal inhibitory concentration of 0.58 μM.

Synthesis and characterization of photosensitive gelatin-based hydrogels for photodynamic therapy in HeLa-CCL2 cell line

BACKGROUND

Hydrogel systems are increasingly gaining visibility involving biomedicine, tissue engineering, environmental treatments, and drug delivery systems. These systems have a three-dimensional network composition and high-water absorption capacity, are biocompatible, allowing them to become an option as photosensitizer carriers (PS) for applications in Photodynamic Therapy (PDT) protocols.

METHODS

A nanohydrogel system (NAHI), encapsulated with chloroaluminium phthalocyanine (ClAlPc) was synthesized for drug delivery.. NAHI was synthesized using gelatin as based polymer by the chemical cross-linking technique. The drug was encapsulated by immersing the hydrogel in a 1.0 mg.mL^-1 ClAlPc solution. The external morphology of NAHI was examined by scanning electron microscopy (SEM). The degree of swelling of the synthesized system was evaluated to determine the water absorption potential. The produced nanohydrogel system was characterized by photochemical, photophysical and photobiologial studies.

RESULTS

The images from the SEM analysis showed the presence of three-dimensional networks in the formulation. The swelling test demonstrated that the nanohydrogel freeze-drying process increases its water holding capacity. All spectroscopic results showed excellent photophysical parameters of the drug studied when served in the NAHI system. The incorporation efficiency was 70%. The results of trypan blue exclusion test have shown significant reduction (p < 0.05) in the cell viability for all groups treated with PDT, in all concentrations tested. In HeLa cells, PDT mediated by 0,5 mg.mL^-1 ClAlPc encapsulated in NAHI showed a decrease in survival close to 95%. In the internalization cell study was possible to observe the internalization of phthalocyanine after one hour of incubation, at 37 °C, with the the accumulation of PS in the cytoplasm and inside the nucleus at both concentrations tested.

CONCLUSIONS

Given the peculiar performance of the selected system, the resulting nanohydrogel is a versatile platform and display potential applications as controlled delivery systems of photosensitizer for photodynamic therapy application.

Azides and Porphyrinoids: Synthetic Approaches and Applications. Part 2-Azides, Phthalocyanines, Subphthalocyanines and Porphyrazines

The reaction between organic azides and alkyne derivatives via the Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) is an efficient strategy to combine phthalocyanines and analogues with different materials. As examples of such materials, it can be considered the following ones: graphene oxide, carbon nanotubes, silica nanoparticles, gold nanoparticles, and quantum dots. This approach is also being relevant to conjugate phthalocyanines with carbohydrates and to obtain new sophisticated molecules; in such way, new systems with significant potential applications become available. This review highlights recent developments on the synthesis of phthalocyanine, subphthalocyanine, and porphyrazine derivatives where CuAAC reactions are the key synthetic step.

α- and β-Substituted Metal-Free Phthalocyanines: Synthesis, Photophysical and Electrochemical Properties

Two novel phthalonitrile derivatives, bearing two hexyloxy groups and a benzodioxin (or a naphthodioxin) annulated ring, along with their corresponding metal-free phthalocyanines (H2Pc) were prepared. FT-IR, mass, electronic absorption, 1H NMR, and 13C NMR spectroscopy were employed for the characterization of all compounds. The effect of hexadeca substituents on the photophysical properties of metal-free Pcs was investigated. Photophysical properties of H2Pc were studied in tetrahydrofuran (THF). Fluorescent quantum yields of phthalocyanines (Pcs) were calculated and compared with the unsubstituted phthalocyanine. 1,4-Benzoquinone effectively quenched the fluorescence of these compounds in THF. Cyclic and square wave voltammetry methods were applied to metal-free phthalocyanines and Pc-centered oxidation and reduction processes were obtained.

Encapsulation of Gold Nanorods with Porphyrins for the Potential Treatment of Cancer and Bacterial Diseases: A Critical Review

Cancer and bacterial diseases have been the most incidental diseases to date. According to the World Health Report 2018, at least every family is affected by cancer around the world. In 2012, 14.1 million people were affected by cancer, and that figure is bound to increase to 21.6 million in 2030. Medicine therefore sorts out ways of treatment using conventional methods which have been proven to have many side effects. Researchers developed photothermal and photodynamic methods to treat both cancer and bacterial diseases. These methods pose fewer effects on the biological systems but still no perfect method has been synthesized. The review serves to explore porphyrin and gold nanorods to be used in the treatment of cancer and bacterial diseases: porphyrins as photosensitizers and gold nanorods as delivery agents. In addition, the review delves into ways of incorporating photothermal and photodynamic therapy aimed at producing a less toxic, more efficacious, and specific compound for the treatment.

Novel Hexadeca-Substituted Metal Free and Zinc(II) Phthalocyanines; Design, Synthesis and Photophysicochemical Properties

The syntheses of a novel 1,4,8,11,15,18,22,25-octahexyloxy-2,3,9,10,16,17,23,24-octa-(4-trifluoromethoxyphenyl) phthalocyanine (3a) and its zinc(II) phthalocyanine derivative (3b) have been described and characterized by elemental analysis,¹H NMR, ¹³C NMR, ¹⁹F NMR, mass, UV-Vis and FT-IR. The newly prepared metal-free phthalocyanine and its zinc(II) counterpart are soluble in most organic solvents. The photophysical and photochemical properties such as aggregation, fluorescence, singlet oxygen generation and photodegradation under light irradiation of these phthalocyanines have been investigated in DMF. The hexadeca-substituted phthalocyanines (3a and 3b) showed longer absorption and emission wavelength values when compared to that of reported phthalocyanine derivatives due to substitution of the all possible positions in the phthalocyanine framework. The zinc(II) phthalocyanine derivative does not only have a good singlet oxygen generation but also has other photophysicochemical properties that enables this phthalocyanine to be useful as a photosensitizer for cancer treatment using photodynamic therapy.

Insights into the binding mechanism of BODIPY-based photosensitizers to human serum albumin: A combined experimental and computational study

Photodynamic therapy (PDT) is a noninvasive and effective approach in clinical cancer treatments. Boron-dipyrromethene (BODIPY)-based derivatives have emerged as novel and promising photosensitizers (PSs) in PDT, attributed to their strong near-infrared singlet oxygen luminescence emissions and high photostabilities. However, the binding mechanism of BODIPY derivatives to proteins, key for their therapeutic and biomedical applications is still poorly understood. Here, we investigated the molecular interactions of two 2, 6-diiodo-BODIPY derivatives with human serum albumin (HSA) using combined experimental and computational techniques. Our spectroscopic results showed that both BODIPY derivatives formed stable complexes with HSA. Strikingly, the BODIPY/HSA complexes exhibited notably enhanced water solubility and singlet oxygen generation efficiency with respect to the BODIPY alone. Furthermore, molecular docking, molecular dynamics simulations, and binding free energy calculations provided the structural and energetic insights into the binding mechanism of BODIPY-based derivatives to HSA. Our work demonstrated that conjugation of BODIPYs with HSA may be a promising strategy to enhance the performance of BODIPY-based PSs, and the combination of computational and experimental techniques is expected to play key roles in the design and development of novel PSs with improved bioavailability and biocompatibility for cancer therapeutic applications.

Improved photodynamic efficacy of thiophenyl sulfonated zinc phthalocyanine loaded in lipid nano-carriers for hepatocellular carcinoma cancer cells

BACKGROUND

The aim of the present study was to modify the structural activity of zinc(II)phthalocyanine by combining it with thiophenyl groups then loaded in lipid nano-carriers and evaluate its parameters required for the structure-activity relationship (SAR) for photodynamic therapy (PDT) of cancer.

METHODS

Tetra (4-Thiophenyl) sulfonated phthalocyaninatozinc(II) (PhS·SO₃Na)₄ZnPc 5 was synthesized and characterized by various spectroscopic methods as a test compound. Liver hepatocellular carcinoma (HepG2) cells were treated with the synthesized (PhS·SO₃Na)₄ZnPc 5 derivative loaded in lipid nano carriers to understand the effect of combined compound on liver cancer cells. Furthermore, HepG2 cells were irradiated by visible red light at 60 mW/cm² for 20 min. The phototoxicity of (PhS·SO₃Na)₄ZnPc 5 after being formulated in both (L) and transfersomes (T) was investigated.

RESULTS

Overall, the results indicate that combination of thiophenyl groups substitution, in particular in the structure of sulfonated zinc phthalocyanine is able to improve the photodynamic properties of ZnPc, and (PhS·SO₃Na)₄ZnPc 5 loaded in lipid nano-carriers can be a promising combined PDT treatment strategy for Liver hepatocellular carcinoma (HepG2) cells.

CONCLUSIONS

The new formulation ZnPc-lipid nano-carriers will be beneficial in the upcoming clinical trials and would enhance the inhibition of tumor growth.

Molecular Mechanism of Uptake of Cationic Photoantimicrobial Phthalocyanine across Bacterial Membranes Revealed by Molecular Dynamics Simulations

Phthalocyanines are aromatic macrocyclic compounds, which are structurally related to porphyrins. In clinical practice, phthalocyanines are used in fluorescence imaging and photodynamic therapy of cancer and noncancer lesions. Certain forms of the substituted polycationic metallophthalocyanines have been previously shown to be active in photodynamic inactivation of both Gram-negative and Gram-positive bacteria; one of them is zinc octakis(cholinyl)phthalocyanine (ZnPcChol⁸⁺). However, the molecular details of how these compounds translocate across bacterial membranes still remain unclear. In the present work, we have developed a coarse-grained (CG) molecular model of ZnPcChol⁸⁺ within the framework of the popular MARTINI CG force field. The obtained model was used to probe the solvation behavior of phthalocyanine molecules, which agreed with experimental results. Subsequently, it was used to investigate the molecular details of interactions between phthalocyanines and membranes of various compositions. The results demonstrate that ZnPcChol⁸⁺ has high affinity to both the inner and the outer model membranes of Gram-negative bacteria, although this species does not show noticeable affinity to the 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphatidylcholine membrane. Furthermore, we found out that the process of ZnPcChol⁸⁺ penetration toward the center of the outer bacterial membrane is energetically favorable and leads to its overall disturbance and formation of the aqueous pore. Such intramembrane localization of ZnPcChol⁸⁺ suggests their twofold cytotoxic effect on bacterial cells: (1) via induction of lipid peroxidation by enhanced production of reactive oxygen species (i.e., photodynamic toxicity); (2) via rendering the bacterial membrane more permeable for additional Pc molecules as well as other compounds. We also found that the kinetics of penetration depends on the presence of phospholipid defects in the lipopolysaccharide leaflet of the outer membrane and the type of counterions, which stabilize it. Thus, the results of our simulations provide a detailed molecular view of ZnPcChol⁸⁺ "self-promoted uptake", the pathway previously proposed for some small molecules crossing the outer bacterial membrane.

Trifluoromethyl Boron Dipyrromethene Derivatives as Potential Photosensitizers for Photodynamic Therapy

In this study, two novel boron dipyrromethene-based photosensitizers (BDP3 and BDP6) substituted with three or six trifluoromethyl groups have been synthesized and characterized with various spectroscopic methods, and their photo-physical, photo-chemical, and photo-biological properties have also been explored. The two photosensitizers are highly soluble and remain nonaggregated in N,N-dimethylformamide as shown by the intense and sharp Q-band absorption. Under red light irradiation (λ = 660 nm, 1.5 J/cm²), both photosensitizers show high and comparable cytotoxicity towards HepG2 human hepatocarcinoma and HeLa human cervical carcinoma cells with IC₅₀ values of 0.42–0.49 μM. The high photocytotoxicity of BDP3 and BDP6 can be due to their high cellular uptake and low aggregation tendency in biological media, which result in a high efficiency to generate reactive oxygen species inside the cells. Confocal laser fluorescence microscopic studies indicate that they have superior selective affinities to the mitochondria and lysosomes of HepG2 and HeLa cells. The results show that these two trifluoromethyl boron dipyrromethene derivatives are potential anticancer agents for photodynamic therapy.