A comparative study of the photophysical and phototoxic properties of octakis(decyloxy)phthalocyaninato zinc(ii), incorporated in a hydrophilic polymer, in liposomes and in non-ionic micelles

Silicon(IV) Phthalocyanine-Decorated Cyclodextrin Vesicles as a Self-Assembled Phototherapeutic Agent against MRSA

The host-guest complexation of a tailored Si(IV) phthalocyanine with supramolecular β-cyclodextrin vesicles (CDV) was studied, revealing a reduced aggregation of the photoactive center upon binding to the CDV, even in aqueous environments. For this purpose, a photosensitizing unit axially decorated with one adamantyl group and one pyridinium moiety on the other side was obtained by two successive click reactions on a bis-azido-functionalized derivative of Si(IV) phthalocyanine. To evaluate its potential as a photosensitizer against antibiotic-resistant bacteria, comparative studies of the photophysical properties including absorption and emission spectroscopy, lifetimes as well as fluorescence and singlet oxygen quantum yields were determined for the Si(IV) phthalocyanine alone and upon self-assembly on the CDV surface. In vitro phototoxicity against the methicillin-resistant Staphylococcus aureus (MRSA) USA300 was evaluated, showing an almost complete inactivation.

Strategies for delivering porphyrinoid-based photosensitizers in therapeutic applications

Delivery strategies for porphyrinoid-based photosensitizers for use in therapeutic applications are based on a myriad of factors, which include porphyrinoid structure, solubility and cellular targets. These drug-delivery methods include encapsulation, hydrogels, protein carriers, nanoparticles and polymeric micelles among others. This article reviews the strategies for delivering porphyrinoids published to date and will focus on porphyrins, corroles, chlorins, bacteriochlorins, porphyrazines and phthalocyanines. Highlighted are the most recent and different strategies used for each of the corresponding porphyrinoid-based macrocycles.

Metal based photosensitizers of tetradentate Schiff base: promising role in anti-tumor activity through singlet oxygen generation mechanism

In the present investigation, a Schiff base N'(1),N'(3)-bis[(Z)-(2-hydroxynapthyl)methylidene]benzene-1,3-dicarbodihydrazide (L1) and its Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized as novel photosensitizing agents for photodynamic therapy (PDT). The interaction of these complexes with calf thymus DNA (CT DNA) has been explored using absorption, thermal denaturation and viscometric studies. The experimental results revealed that Co(II) and Ni(II) complexes on binding to CT DNA imply a covalent mode, most possibly involving guanine N7 nitrogen of DNA, with an intrinsic binding constant Kb of 4.5×10(4)M(-1) and 4.2×10(4)M(-1), respectively. However, interestingly, the Cu(II) complex is involved in the surface binding to minor groove via phosphate backbone of DNA double helix with an intrinsic binding constant Kb of 5.7×10(4)M(-1). The Co(II), Ni(II) and Cu(II) complexes are active in cleaving supercoiled (SC) pUC19 DNA on photoexposure to UV-visible light of 365nm, through (1)O2 generation with quantum yields of 0.28, 0.25 and 0.30, respectively. Further, these complexes are cytotoxic in A549 lung cancer cells, showing an enhancement of cytotoxicity upon light irradiation.

Boron-Fluorine Photosensitizers for Photodynamic Therapy

Photodynamic therapy (PDT) has been recognized as a promising treatment for cancers and tumors, in which photosensitizer is one of the most important issues. As a class of excellent fluorescent dyes, boron-fluorine derivatives (typically 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene, BODIPY) have preferable ability of generating singlet oxygen and have been under extensive study for PDT sensitizers. In this review, we summarize the recent progress of design and applications of boron-fluorine-based photosensitizers for PDT.

Photodynamic effects of zinc(II) phthalocyanine-loaded polymeric micelles in human nasopharynx KB carcinoma cells

A major difficulty in photodynamic therapy is the poor solubility of the photosensitizer (PS) under physiological conditions which correlates with low bioavailability. PS aggregation leads to a decrease in the photodynamic efficiency and a more limited activity in vitro and in vivo. To improve the aqueous solubility and reduce the aggregation of 2,9(10),16(17),23(24)-tetrakis[(2-dimethylamino)ethylsulfanyl]phthal-ocyaninatozinc(II) (Pc9), the encapsulation into four poloxamine polymeric micelles (T304, T904, T1107 and T1307) displaying a broad spectrum of molecular weight and hydrophilic-lipophilic balance was investigated. The aqueous solubility of Pc9 was increased up to 30 times. Morphological evaluation showed the formation of Pc9-loaded spherical micelles in the nanosize range. UV/Vis and fluorescence studies indicated that Pc9 is less aggregated upon encapsulation in comparison with Pc9 in water-DMSO 2% and remained photostable. Pc9-loaded micelles generated singlet molecular oxygen in high yields. Photocytotoxicity assays using human nasopharynx KB carcinoma cells confirmed that the encapsulation of Pc9 in T1107 and T1307 increases its photocytotoxicity by 10 times in comparison with the free form in water-DMSO. In addition, Pc9 incorporated into cells was mainly localized in lysosomes.

Photophysical properties of microencapsulated phthalocyanines

Lipophilic substituted zinc(II) phthalocyanines: 2,3,9,10,16,17,23,24-octakis[(N,N-dimethylaminoethylsulfanyl)]phthalocyaninatozinc(II) (S1) and tetrakis(N,N-dibutylaminoethoxy)phthalocyaninatozinc(II) (3) were incorporated into soybean L-α-phosphatidylcholine (SPC) liposomes of 100 nm diameter. Liposomes were characterized by static light scattering (SLS), transmission electronic microscopy (TEM), and differential scanning calorimetry. The fluorescence quantum yield and singlet molecular oxygen production of 3 are Φ F = 0.15 and ΦΔ = 0.24, respectively, whereas the same photophysical parameters for S1 are Φ F = 0.13 and ΦΔ = 0.51. Higher values of Φ F and ΦΔ are obtained in organic solvent for both dyes. Synthesis of compound 3 has also been reported.

A synthetic approach towards novel octa-substituted zinc(II) phthalocyanines with different solubility and photophysical properties

The synthesis and behavior in homogeneous solutions of 2,3,9,10,16,17,23,24-octakis(3-phthalimidopropyloxy)phthalocyaninatozinc(II) (5) and 2,3,9,10,16,17,23,24-octakis(3-aminopropyloxy)phthalocyaninatozinc(II) (6) are reported.

Influence of complex formation with tetraantraquinoporphyrazines and tetrasulphophthalocyanine on thermal stability of bovine serum albumin

Interaction between bovine serum albumin (BSA) and tetraantraquinoporphyrazines (TAP) and tetrasulphophthalocyanine (Pc) aluminum hydroxide was studied by means of electron absorption spectroscopy, IR spectroscopy, fluorescence spectroscopy and differential scanning calorimetry. It was found that the complex formation of BSA with the TAPs results in increase of thermal stability of the protein while Pc does not have remarkable influence on the protein thermal denaturation.

Photophysical behaviour and photodynamic activity of zinc phthalocyanines associated to liposomes

Phthalocyanines are macrocyclic compounds that can be employed as photosensitizers in the treatment of various infections and diseases, as well as in photodynamic therapy. Nevertheless, a disadvantage for the clinical application of these compounds is their strong tendency to form oligomers (especially dimers), a phenomenon that reduces their efficiency as photosensitizers. In the present contribution, we have studied the photophysical and photochemical properties of ZnPc and ZnF(16)Pc in an organic solvent (THF) and liposomal formulations (DMPC, DPPC and DSPC). Our results show that dye incorporation into liposomes decreases its aggregation degree, as revealed by absorption spectra, triplet quantum yield, and singlet oxygen quantum yield measurements. Additionally, we studied the photodynamic activity of both phthalocyanines in liposomal formulation on human cervical carcinoma (HeLa) cells. For ZnF(16)Pc the photophysical behavior and phototoxicity in vitro correlate with the aggregation degree. The dimers are not photoactive and the photochemistry of ZnF(16)Pc depends of the fraction present as monomer. On the other hand, ZnPc aggregation is minimal and its photophysical and photochemical properties are similar in the three liposomes studied. Nevertheless, its phototoxicity in vitro is liposome dependent.

Anaerobic photocleavage of DNA in red light by dicopper(II) complexes of 3,3'-dithiodipropionic acid

Binuclear copper(II) complexes [{(phen)Cu(II)}(2)(mu-dtdp)(2)] (1), [{(dpq)Cu(II)}(2)(mu-dtdp)(2)] (2), [{(phen)Cu(II)}(2)(mu-az)(2)] (3), and [{(dpq)Cu(II)}(2)(mu-az)(2)] (4) and a zinc(II) complex [{(phen)Zn(II)}(2)(mu-dtdp)(2)] (5), having 3,3'-dithiodipropionic acid (H(2)dtdp), azelaic acid (nonanedioic acid), 1,10-phenanthroline (phen), and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), were prepared and characterized by physicochemical methods. Complex 1 has been structurally characterized by X-ray crystallography. The complexes have each metal center bound to a chelating phenanthroline base and two bridging carboxylate ligands giving a square-planar MN(2)O(2) coordination geometry. The molecular structure of complex 1 shows two sterically constrained disulfide moieties of the dtdp ligands. The complexes show good binding propensity to calf thymus DNA in the major groove. The photoinduced DNA cleavage activity of the complexes has been studied using 365 nm UV light and 647.1 nm and >750 nm red light under both aerobic and anaerobic conditions. The phen complex 1, having dtdp ligand, cleaves supercoiled (SC) DNA to its nicked circular (NC) form. The dpq analogue 2 shows formation of a significant quantity of linear DNA resulting from double-strand breaks (dsb) in air. Mechanistic studies reveal the involvement of HO(*) and (1)O(2) as the reactive species under an aerobic medium. The dsb of DNA is rationalized from the docking studies on 2, showing a close proximity of two photosensitizers, namely, the disulfide moiety of dtdp and the quinoxaline ring of dpq to the complementary strands of DNA. The copper(II) complexes of the dtdp ligand cleave SC DNA to its NC form upon exposure to UV or red light under an argon atmosphere. An enhancement of the DNA cleavage activity under argon has been observed upon increasing the concentration of the DMF solvent in the DMF-Tris buffer medium. Theoretical studies suggest the possibility of sulfide anion radical formation from a copper(II)-bound dtdp ligand in >750 nm red light, which further cleaves the DNA. The copper(II) azelate complexes are inactive under similar reaction conditions. The azelate complex of the dpq ligand cleaves DNA in air following the (1)O(2) pathway. The zinc(II) complex of the dtdp ligand (5) does not show any photoinduced DNA cleavage activity in red light.

Metal-Based Netropsin Mimics Showing AT-Selective DNA Binding and DNA Cleavage Activity at Red Light

Copper(II) bis-arginate [Cu(l-arg)2](NO3)2 (1) and [Cu(l-arg)(phen)Cl]Cl (2) as mimics of the minor-groove-binding natural antibiotic netropsin show preferential binding to the AT-rich region of double-stranded DNA. The complexes with a d-d band near 600 nm display oxidative DNA cleavage activity on photoirradiation at UV-A light of 365 nm and at red light of 647.1 nm (Ar-Kr laser) in a metal-assisted photoexcitation process forming singlet oxygen (1O2) species in a type-2 pathway.

Photodynamic ultradeformable liposomes: Design and characterization

Hydrophobic ([tetrakis(2,4-dimetil-3-pentyloxi)-phthalocyaninate]zinc(II)) (ZnPc) and hydrophilic ([tetrakis(N,N,N-trimethylammoniumetoxi)-phthalocyaninate]zinc(II) tetraiodide) (ZnPcMet) phthalocyanines were synthesized and loaded in ultradeformable liposomes (UDL) of soybean phosphatidylcholine and sodium cholate (6:1, w/w, ratio), resulting 100 nm mean size vesicles of negative Zeta potential, with encapsulation efficiencies of 85 and 53%, enthalpy of phase transition of 5.33 and 158 J/mmol for ZnPc and ZnPcMet, respectively, indicating their deep and moderate partition into UD matrices. Matrix elasticity of UDL-phthalocyanines resulted 28-fold greater than that of non-UDL, leaking only 25% of its inner aqueous content after passage through a nanoporous barrier versus 100% leakage for non-UDL. UDL-ZnPc made ZnPc soluble in aqueous buffer while kept the monomeric state, rendering singlet oxygen quantum yield (Phi(Delta)) similar to that obtained in ethanol (0.61), whereas UDL-ZnPcMet had a four-fold higher Phi(Delta) than that of free ZnPcMet (0.21). Free phthalocyanines were non-toxic at 1 and 10 microM, both in dark or upon irradiation at 15 J/cm2 on Vero and J-774 cells (MTT assay). Only liposomal ZnPc at 10 microM was toxic for J-774 cells under both conditions. Additionally, endo-lysosomal confinement of the HPTS dye was kept after irradiation at 15 J/cm2 in the presence of UDL-phtalocyanines. This could lead to improve effects of singlet oxygen against intra-vesicular pathogen targets inside the endo-lysosomal system.

Water soluble distyryl-boradiazaindacenes as efficient photosensitizers for photodynamic therapy

We introduce a novel class of water soluble, extended conjugation boradiazaindacene dyes which are efficient singlet oxygen generators and have spectacular photoinduced cytotoxicity when excited in the "therapeutic window" of the electromagnetic spectrum.