Delivery of a hydrophobic phthalocyanine photosensitizer using PEGylated gold nanoparticle conjugates for the in vivo photodynamic therapy of amelanotic melanoma.

Photodynamic therapy (PDT) is a treatment of cancer whereby tumours are destroyed by reactive oxygen species generated upon photoactivation of a photosensitizer drug. Hydrophobic photosensitizers are known to be ideal for PDT; however, their hydrophobicity necessitates that they are typically administered using emulsions. Here, a delivery vehicle for photodynamic therapy based on the co-self-assembly of both a Zn(ii)-phthalocyanine derivative photosensitizer and a polyethylene glycol (PEG) derivative onto gold nanoparticles is reported. The PEG on the particle surface ensured that the conjugates were water soluble and enhanced their retention in the serum, improving the efficiency of PDT in vivo. The pharmacokinetic behaviour of the nanoparticle conjugates following intravenous injection into C57/BL6 mice bearing a subcutaneous transplanted B78H1 amelanotic melanoma showed a significant increase of retention of the nanoparticles in the tumour. PDT tumour destruction was achieved 3 h following injection of the nanoparticle conjugates leading to a remarkable 40% of the treated mice showing no tumour regrowth and complete survival. These results highlight that dual functionalised nanoparticles exhibit significant potential in PDT of cancer especially for difficult to treat cancers such as amelanotic melanoma.

Photothermal sensitisation and therapeutic properties of a novel far-red absorbing cyanine.

A water-soluble disulfonate cyanine was prepared by chemical synthesis and shown to possess photophysical properties which are particularly favourable for the promotion of photothermally sensitised processes, including a very low (<0.1) quantum yield of fluorescence emission and ultra-short (110 to 400 ps) excited state lifetimes, as well as the presence of intense absorption bands at wavelengths longer than 800 nm. This allows the possibility of high-energy irradiation by means of a Ti:sapphire laser operated in a pulse regime. The cyanine was accumulated in comparable amounts by B78H1 amelanotic melanoma cells and HT1080 transformed fibroblasts, however only the B78H1 cells could be extensively damaged by photothermal sensitisation with the cyanine, which was endocellularly distributed as suggested by observations at the optical microscope; the efficiency of the photoprocess could be enhanced by formation of aggregated intracellular cyanine clusters. On the other hand, only a modest photoinactivation of HT1080 cells was induced by photothermal sensitisation, possibly owing to the localization of the cyanine at the periphery of such cells. The cyanine also exhibited a good selectivity of amelanotic melanoma targeting in C57BL/6 mice, bearing the tumour subcutaneously transplanted in the dorsal area: the ratio of cyanine concentration in the melanoma and the surrounding cutaneous districts was as large as 3.8 at 1 h post-injection. The cyanine underwent a fast clearance from the organism, since only traces of the photosensitiser were observed in all the studied tissues at 3 h after i.v. administration. Thus, irradiations were performed at post-injection times shorter than 1 h. Maximum photothermal sensitisation efficiency was obtained at 10 min after injection with a 50% cure rate. Thus, photothermal therapy (PTT) appears to be a very promising and efficient modality of tumour treatment.

Metallo-naphthalocyanines as photothermal sensitisers for experimental tumours: in vitro and in vivo studies.

BACKGROUND AND OBJECTIVES: Photothermal sensitisation has been recently proposed as a novel approach for the treatment of solid tumours through the development of a therapeutic modality named photothermal therapy (PTT). The technique involves the use of high power pulsed laser irradiation and photosensitising agents with especially short lifetime (in the subnanosecond range) in the electronically excited states. This study aims to investigate the molecular features of the photosensitiser which optimise the photothermal activity. STUDY DESIGN/MATERIALS AND METHODS: Two octabutoxy-naphthalocyanines centrally coordinated with Pd(II) or Pt(II) ions were prepared by chemical synthesis and tested for their affinity and photothermal sensitisation activity toward a selected tumour cell line, namely B78H1 amelanotic melanoma. Irradiations were performed by using a Ti:sapphire laser operated in a pulsed regime (10 Hz, 30 nanosecond pulses, 120 mJ) at 809 nm (Pt) or 826 nm (Pd). The subcellular distribution pattern of the photosensitiser was also assessed by optical microscopy, while the nature of the photoinduced cell damage was determined by scanning electron microscopy. The results thus obtained provided a basis for subsequent in vivo studies, aimed at defining the phototherapeutic efficiency of the two metallo-naphthalocyanines: the photosensitisers were i.v. injected into C57BL/6 mice bearing a subcutaneously transplanted amelanotic melanoma and at 24 hours post-injection the tumour area was irradiated by the Ti:sapphire laser using the same protocol as above detailed. RESULTS: Both naphthalocyanines exhibited a high affinity for the amelanotic melanoma cells. The subcellular distribution pattern was modulated by the incubation time: after 48 hours incubation with 7.7 microM Pd- and Pt derivatives, the naphthalocyanine appeared to localise in specific sites with a gradual formation of aggregated clusters. Subsequent irradiation of the naphthalocyanine-loaded cells caused an extensive cell death; the photoinduced damage, as observed at the scanning electron microscope, mainly consisted in the formation of large endocellular holes consequent to the loss of cytoplasmic material. This scenario is typical of photothermal sensitisation processes. Lastly, both metallo-naphthalocyanines, and in particular the Pd(II) derivative, promoted an important response by the amelanotic melanoma, when the neoplastic tissue was irradiated by the pulsed Ti:sapphire laser. In certain cases, the photothermal treatment appeared to be curative. In all cases, the in vivo photodamage was confined within the tumour area with no detectable involvement of the perilesional tissues. CONCLUSION: PTT appears to act very efficiently at least on subcutaneous tumours. The technique can be used either in combination with photodynamic therapy (PDT) or as an alternative to PDT in those cases where the latter modality displays a limited efficacy, such as in the treatment of pigmented or poorly vascularised tumours.

Photothermal sensitisation as a novel therapeutic approach for tumours: studies at the cellular and animal level.

Irradiation of B78H1 murine amelanotic melanoma cells with 850 nm light emitted from a Ti:sapphire laser, operated in a pulsed mode at high fluence rates and in the presence of Ni(II)-octabutoxy-naphthalocyanine (NiNc), promoted a photothermally sensitised process leading to fast and irreversible cell death. This resulted in the ejection of a consistent mass of cytoplasmic material from the irradiated cells that was detected by scanning electron microscopy. The extensive chemical and mechanical damage was probably caused by the photoinduced generation of an acoustic shock wave. The efficiency of the photoprocess was modulated by intracellular concentration of NiNc and maximally by the formation of aggregated naphthalocyanine clusters in specific subcellular areas. Very similar results were obtained upon irradiation of NiNc-loaded C32 human amelanotic melanoma cells and transformed murine HT-1080 and HaCaT fibroblasts. From these results, photothermal sensitisation appears to be a general phenomenon and preliminary studies with mice bearing subcutaneously transplanted amelanotic melanomas, irradiated with 850 nm light 24 h after intravenous injection of NiNc, suggest that this approach has potential for the therapy of some types of skin tumours.

Polymer nanoparticles with electrostatically loaded multicargo for combined cancer phototherapy.

We have developed a multifunctional polymer-based nanoplatform for bimodal cancer phototherapy. It was achieved by electrostatic entangling of two anionic photoactivable components, a commercial porphyrin and a tailored nitro-aniline derivative, within the cationic shell of polymeric nanoparticles (NPs) based on polymethyl methacrylate. The combination of steady-state and time-resolved spectroscopic and photochemical techniques shows that the two photoresponsive agents do not interfere with each other while being in close proximity in the same polymeric scaffold and can thus operate in parallel under the exclusive control of light stimuli. Specifically, visible light triggers satisfactory red fluorescence emission and generation of singlet oxygen (1O2) from one component and release of nitric oxide (NO) from the other. Fluorescence microscopy analysis provides unambiguous evidence for the internalization of the NPs within B78H1 melanoma cells, where they induce amplified mortality due to a combinatory effect of the two photogenerated cytotoxic species.

Photodynamic inactivation of microbial pathogens: disinfection of water and prevention of water-borne diseases.

Porphyrins have been shown to act as very efficient photosensitizing agents against a broad number of microbial pathogens, including bacteria, fungi, and protozoa. This property has promising applications at a clinical level for the treatment of infectious diseases by photodynamic therapy. Moreover, this technique is also being used to address environmental problems of high significance, such as the decontamination of wastewaters, the disinfection of fish-farming tanks, the protection of animal species (e.g., amphibians and reptiles) that are endangered by pathogens whose life cycle takes place largely in aqueous media, and the control of populations of noxious insects. Such diversified applications take advantage of the availability of a truly large number of porphyrin derivatives with chemical structures that can be tailored to comply with the physical and chemical properties as well as the biological features of several milieus. In addition, the property typical of porphyrins to absorb essentially all of the wavelengths in the sun emission spectrum allows the promotion of processes largely based on natural resources with significant energy savings and low impact on ecosystems.

Photooxidation and Phototoxicity of pi-extended squaraines.

This paper describes the synthesis of pi-extended squaraines and their photooxidation properties and gives an in-depth characterization of these molecules as photosensitizing agents. Squaraines show a strong absorption in the tissue transparency window (600-800 nm), and upon irradiation, they undergo a photooxidation process, leading to the formation of peroxide and hydroperoxide radicals according to a type I radical chain process. Confocal laser microscopy demonstrates that the designed squaraines efficiently internalize in the cytoplasm and not in the nucleus of the cell. In the dark, they are scarcely cytotoxic, but after irradition, they promote a strong dose-dependent phototoxic effect in four different cancer cells. In HeLa and MCF-7 cells, squaraines 4 and 5, thanks to their hydrocarbon tails, associate to the membranes and induce lipid peroxidation, as indicated by a marked increase of malonyldialdehyde after photodynamic treatment, in agreement with in vitro photooxidation studies. FACS, caspase-3/7 assays and time-lapse microscopy demonstrate that the designed squaraines cause cell death primarily by necrosis.

The in vivo efficacy of phthalocyanine-nanoparticle conjugates for the photodynamic therapy of amelanotic melanoma.

The efficiency of a Zn(II)-phthalocyanine disulphide (C11Pc), a compound with both phthalocyanine units bearing seven hexyl chains and a sulphur terminated C11 chain, as a photodynamic therapy (PDT) agent was investigated in C57 mice bearing a sub-cutaneously transplanted amelanotic melanoma. The phthalocyanine was intravenously injected at a dose of 1.5 micromol/kg body weight either free or bound to gold nanoparticles, using a Cremophor emulsion as a delivery vehicle. Biodistribution studies at selected post-injection times showed that the nanoparticle-associated C11Pc was recovered in significantly larger amounts from all the examined tissues and the serum and yielded a greater selectivity of tumour targeting: thus, the ratio between the amount of phthalocyanine recovered from the amelanotic melanoma and the skin (peritumoural tissue) increased from 2.3 to 5.5 from the free to the gold nanoparticle-bound C11Pc at 24 h after injection. PDT studies with the C11Pc-loaded amelanotic melanoma showed a markedly more significant response of the tumour in the mice that had received the nanoparticle-bound photosensitiser; the PDT effect was especially extensive if the irradiation was performed at 3h after C11Pc injection when large phthalocyanine amounts were still present in the serum. This suggests that the PDT promoted by C11Pc predominantly acts via vascular damage at least in this specific animal model. This hypothesis was fully confirmed by electron microscopy observations of tumour specimens obtained at different times after the end of PDT, showing an extensive damage of the blood capillaries and the endothelial cells.

Photothermal sensitisation: evidence for the lack of oxygen effect on the photosensitising activity.

Irradiation of amelanotic melanoma B78H1 cells in the presence of liposome-delivered Ni(II)-octabutoxy-naphthalocyanine with a Q-switched Ti:sapphire laser operated in a pulsed mode (850 nm, 30 ns pulses, 10 Hz, 120 mJ pulse -1) promotes a photothermal sensitization process leading to extensive cell inactivation. The photoprocess occurs with identical efficiency in N2-saturated and air-equilibrated media, indicating that this photosensitization modality does not require the presence of oxygen.