Syntheses and photodynamic activities of novel trisulfonated zinc phthalocyanine derivatives.

The synthesis of water-soluble, unsymmetrical, trisulfonated zinc phthalocyanines (ZnPcS3) as single products of the ring expansion of boron tri(4-sulfo)subphthalocyanine (SubPc) is reported. The novel, water-soluble trisulfo-SubPcB(OH) was prepared via hydrolysis of the tris(4-chlorosulfonyl)SubPcB(Br) which in turn was obtained from the condensation of 4-(chlorosulfonyl)phthalonitrile with BBr3 in 1-chlorobenzene. A number of ZnPcS3 analogues were prepared via the reaction of S3SubPcB (OH) with different diiminoisoindoline derivatives of increasing hydrophobicity. The reaction proceeds at relative low temperature with acceptable yields. Metalation of free base Pc's with zinc acetate dihydrate afforded the corresponding zinc complexes. Photodynamic activities were measured against the EMT-6 mouse mammary tumor cell line and compared to those of the known ZnPcS3 and ZnPcS4. Added (t-Bu)benzo and (t-Bu)naphtho groups increased the in vitro cell photoinactivation efficacy of the ZnPcS3, whereas addition of a fourth sulfobenzo or bulky diphenylpyrazino group decreased the activity of the parent molecule. The (t-Bu)naphthotrisulfobenzoporphyrazine induced the best in vivo photodynamic tumor control which, combined with its good solubility and broad absorption spectrum, renders this compound an interesting dye for photodynamic applications in medicine.

PEG-coated poly(lactic acid) nanoparticles for the delivery of hexadecafluoro zinc phthalocyanine to EMT-6 mouse mammary tumours.

Hexadecafluoro zinc phthalocyanine (ZnPcF16), a second generation sensitizer for the photodynamic therapy of cancer, was incorporated in three vehicles: poly(D,L-lactic acid) (PLA) nanoparticles, polyethylene glycol (PEG)-coated nanoparticles and a Cremophor EL (CRM) oil-water emulsion. Nanoparticles were prepared by the salting-out procedure. Biodistribution of the dye was assessed by fluorescence in EMT-6 mammary tumour bearing mice after intravenous injection of 1 mumol kg-1 ZnPcF16. Plain nanoparticles were rapidly retained by the reticuloendothelial system (RES) as reflected by the low area under the blood concentration-time curve (AUC0-168, 57 micrograms h g-1). Little tumour uptake of the dye was observed with this formulation. In contrast, PEG-coated nanoparticles displayed a reduced RES uptake, leading to significantly higher blood levels over an extended period (t1/2 30 h; AUC 0-168 227 micrograms h g-1) and enhanced tumour uptake. At 48 h post injection, tumour to skin and tumour to muscle concentration ratios reached 3.5 and 10.8, respectively. Blood levels of ZnPcF16 after administration as a CRM emulsion decreased faster than with PEG-coated nanoparticles (t1/2 12 h), but since no early liver uptake was observed, the AUC0-168 and the tumour uptake were only slightly lower. However, with the CRM formulation, a late liver uptake was observed, reaching 51% of the injected dose after 7 days.

Hexadecafluorinated zinc phthalocyanine: photodynamic properties against the EMT-6 tumour in mice and pharmacokinetics using 65Zn as a radiotracer.

Hexadecafluorinated zinc phthalocyanine (ZnPcF16), an analogue of zinc phthalocyanine (ZnPc) in which all hydrogen atoms have been substituted by fluorine, was prepared as a single isomeric product via the condensation of tetrafluorophthalonitrile with zinc acetate. Fluorination renders the ZnPc soluble in most common solvents. The photodynamic properties and pharmacokinetics of the ZnPcF16 were evaluated in EMT-6 tumour-bearing Balb/c mice using 65Zn-radiolabelled analogues. Both dyes, administered i.v. at 1 mumol kg-1 as Cremophor emulsions, revealed good tumour uptake [approximately 8-9 per cent of the injected dose per g tissue (%IDg-1)] at 24 h post injection (p.i.), with the fluorinated dye reaching higher concentrations (approximately 11%IDg-1) at 48 h p.i. and subsequently higher tumour-blood ratios due to rapid blood clearance. ZnPcF16 at a dose of 5 mumol kg-1 (4.3 mg kg-1) induced complete tumour regression after phototherapy (24 h p.i., 650-700 nm band, 360 J cm-2, 200 mW cm-1). At a dose of 2 mumol kg-1 and phototherapy at 24 h p.i., the tumour volume doubling time increased to 11 days vs 6 days for the control tumours. A similar tumour growth delay was observed when phototherapy was conducted at 48 h or 72 h after dye injection implying that tumour response correlates with tumour dye concentrations rather than serum concentrations. As a result of its low solubility, the administered dose of ZnPc was limited to 1 mumol kg-1 and at this drug level significant tumour response was only observed when the dye was solubilised as the pyridinium salt. Isolation of the neoplastic cells after in vivo dye administration and in vitro exposure to red light followed by a colony formation assay showed that the ZnPcF16 exhibited a 1-2 order of magnitude higher potential for direct cell killing as compared with Photofrin and about a five times lower efficiency than ZnPc. However, all three photosensitisers induced complete occlusion of tumour vasculature immediately after PDT, suggesting that tumour regression mainly resulted from vascular stasis. The ZnPcF16 offers several advantages over ZnPc for clinical applications, including improved solubility in most solvents, resulting in facilitated drug formation, favourable pharmacokinetics as well as the potential use in fluorine magnetic resonance (F-MR) imaging.

Photodynamic activities and biodistribution of fluorinated zinc phthalocyanine derivatives in the murine EMT-6 tumour model.

The photodynamic properties and biodistribution pattern of zinc dodecafluoro-4-sulphophthalocyanine (ZnPcF12S1), zinc hexadecafluorophthalocyanine (ZnPcF16) and zinc phthalocyanine (ZnPc) were evaluated in the murine EMT-6 tumour model. All 3 dyes were formulated as a Cremophor oil-water emulsion after initial solubilization in methanol, acetone and pyridine, respectively. Comparison of their phototoxicity after in vitro incubation with EMT-6 cells and exposure to various fluences of red light showed that ZnPcF12S1 is about 50 times more active than ZnPcF16, reflecting better cell-penetrating properties. Solubilisation of ZnPc in 1-methyl-2-pyrrolidinone prior to formulation resulted in loss of photoactivity upon dilution in serum due to precipitation of the dye in the aqueous environment. In contrast, initial solubilisation in pyridine likely forms a ZnPc-pyridinium salt, and this preparation was 6 times more phototoxic than ZnPcF12S1. In vivo comparison of monosulphonated ZnPcF12S1 with perfluorinated ZnPcF16 showed improved pharmacokinetics in mice, including lower liver and spleen retentions and higher tumour-to-non-target tissue ratios. However, photodynamic therapy (PDT) of the EMT-6 tumour in BALB/c mice with red light, 24 or 48 hr post-injection of 1 micromol x kg(-1) of ZnPcF12S1 induced mortality. Lowering the drug and/or light dose or extending the time interval between drug administration and irradiation to 72 hr avoided adverse effects but also resulted in poor tumour response. The best tumour control (25% of animals) was obtained at 0.1 micromol x kg(-1) and a fluence of 400 J x cm(-2) at 24 hr post-injection. In contrast, ZnPcF16 required a 20-fold higher drug dose to induce a similar tumour response. The systemic shock following PDT with the amphiphilic ZnPcF12S1 likely results from extensive cellular effects.

The synthesis and properties of new 2-pyrrolylthiones as chelating agents for transition metals and technetium.

A series of new 2-pyrrolylthiones was synthesized and found to be good chelating agents for transition metals and technetium.

Photodynamic therapy of tumours with hexadecafluoro zinc phthalocynine formulated in PEG-coated poly(lactic acid) nanoparticles.

Hexadecafluoro zinc phthalocyanine (ZnPcF16), a second-generation sensitizer for the photodynamic therapy (PDT) of cancer, was formulated in polyethylene-glycol-coated poly(lactic acid) nanoparticles (PEG-coated PLA-NP) and tested in EMT-6 tumour-bearing mice for its photodynamic activity. The tumour response was compared to that induced by the same dye formulated as a Cremophor EL (CRM) emulsion. Formulation in the biodegradable NP improved PDT response of the tumour while providing prolonged tumour sensitivity towards PDT.