Low Dark Toxicity Research Articles

Photocyanine: A novel and effective phthalocyanine-based photosensitizer for cancer treatment

As one of the three key components of photodynamic therapy (PDT), photosensitizers (PSs) greatly influence the photodynamic efficiency in the treatment of tumors. Photosensitizers with tetrapyrrole structure, such as porphyrins, chlorins and phthalocyanines, have been extensively investigated for PDT and some of them have already received clinical approval. However, only a few of porphyrin-based photosensitizers are available for clinical applications, and PDT has not received wide recognition in clinical practice. In this regard, PSs remain a limiting factor. Our research focuses on the rational design of new PSs. Photocyanine, a Zinc (II) phthalocyanine (ZnPc) type photosensitizer with low dark toxicity and high single oxygen quantum yield, is one of the promising PSs candidates and currently being tested in clinical trials. Here, we present an overview on the development of Photocyanine, including its design, synthesis, purification, characterization and preclinical studies, wishing to contribute to the research of more promising PSs.

Iridium(III) Complex-Derived Polymeric Micelles with Low Dark Toxicity and Strong NIR Excitation for Phototherapy and Chemotherapy.

Iridium(III) complexes are potent candidates for photodynamic therapy. However, their clinical usage is impeded by their poor water solubility, high dark toxicity, and negligible absorption in near-infrared region (NIR region). Here, it is proposed to solve these challenges by developing an iridium(III) complexe-based polymeric micelle system. This system is self-assembled using an iridium(III) complex-containing amphiphilic block polymer. The upconversion nanoparticles are included in the polymeric micelles to permit NIR excitation. Compared with the nonformulated iridium(III) complexes, under NIR stimulation, this polymeric micelle system exhibits higher 1 O2 generation efficiency, negligible dark toxicity, excellent tumor-targeting ability, and synergistic phototherapy-chemotherapy effect both in vitro and in vivo.

Synthesis and Characterization of Ru(II) Complexes with π-Expansive Imidazophen Ligands for the Photokilling of Human Melanoma Cells.

Ru(II) complexes were synthesized with π-expanding (phenyl, fluorenyl, phenanthrenyl, naphthalen-1-yl, naphthalene-2-yl, anthryl and pyrenyl groups) attached at a 1H-imidazo[4,5-f][1,10]phenanthroline ligand and 4,4'-dimethyl-2,2'-bipyridine (4,4'-dmb) coligands. These Ru(II) complexes were characterized by 1D and 2D NMR, and mass spectroscopy, and studied for visible light and dark toxicity to human malignant melanoma SK-MEL-28 cells. In the SK-MEL-28 cells, the Ru(II) complexes are highly phototoxic (EC50 =0.2-0.5µm) and have low dark toxicity (EC50 =58-230µm). The highest phototherapeutic index (PI) of the series was found with the Ru(II) complex bearing the 2-(pyren-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline ligand. This high PI is in part attributed to the π-rich character added by the pyrenyl group, and a possible low-lying and longer-lived 3 IL state due to equilibration with the 3 MLCT state. While this pyrenyl Ru(II) complex possessed a relatively high quantum yield for singlet oxygen formation (Φ∆ =0.84), contributions from type-I processes (oxygen radicals and radical ions) are competitive with the type-II (1 O2 ) process based on effects of added sodium azide and solvent deuteration.

Comparing a thioglycosylated chlorin and phthalocyanine as potential theranostic agents

Herein we describe the design, efficient synthesis, and photophysical properties of two macrocycle dyes for cancer theranostics. This study compares a glycosylated chlorin with a glycosylated phthalocyanine designed to specifically target cancer, wherein the photophysical properties enable both fluorescence imaging and the sensitization of the formation of reactive oxygen species (ROS) for photodynamic therapy. Both the compounds show low darktoxicity (IC50 > 100 μM). The glycosylated phthalocyanine showed low phototoxicity (IC50 > 100 μM) while glycosylated chlorin showed high phototoxicity (IC50 = 1–2 μM). ZnPcGlc8 has low solubility and also form aggregates in aqueous media, thus resulting in minimal uptake in two different human breast cancer cell lines: MDA-MB-231 and MCF-7. The glycosylated chlorin however was efficiently taken up by these two cell lines, thus allows fluorescence imaging in cells and in xenograft tumor model in mice. In this study, we find that the chlorin conjugate is the more promising theranostic agent.

Electrostatic self-assembled Iridium(III) nano-photosensitizer for selectively disintegrated and mitochondria targeted photodynamic therapy

Photodynamic therapy (PDT) is one of effective cancer therapy methods. It is important to develop a PDT reagent with tumor-targeted ability, high phototoxicity and low dark toxicity. In this study, an iridium(III) complex (Irpy) can electrostatically self-assemble with hyaluronic acid (HA) to form nanostructured Irpy-HA, which exhibited stable spheroid structure and outstanding ability of singlet oxygen (1O2) generation. The photophysical property of Irpy has been well studied, which qualified green light absorption ability and could emit red phosphorescence. The nanostructure and stability of self-assembled Irpy-HA have been well investigated, which can keep its nanostructure at least 30 days. More importantly, Irpy-HA can target to a CD44 receptor in cancer cell membrane for enhancing internalization and selective disintegration. Then, Irpy can accumulate in mitochondria and generate 1O2 to realize PDT-induced cell apoptosis by green light irradiation. The Irpy-HA could be used as a nanophotosensitizer for effective photodynamic therapy.

Non-aggregated axially disubstituted silicon phthalocyanines: Synthesis, DNA cleavage and in vitro cytotoxic/phototoxic anticancer activities against SH-SY5Y cell line

In this paper, axially {6-[3-(dimethylamino)phenoxy]hexyl}oxy and {6-[3-(diethylamino)phenoxy]hexyl}oxy groups substituted silicon phthalocyanines were synthesized by reaction of SiPcCl2 with 6-[3-(dimethylamino)phenoxy]hexan-1-ol and 6-[3-(diethylamino)phenoxy]hexan-1-ol in the presence of NaH in toluene. The identity of silicon phthalocyanines was confirmed by 1H NMR, 13C NMR, FT-IR, UV–Vis and mass spectrometry. The aggregation behaviors of the compounds were examined in different solvents and concentrations in DMSO. In all studied solvents and concentrations, the compounds were non-aggregated. These compounds have been screened for DNA cleavage using agarose gel electrophoresis and cytotoxic/phototoxic effects against human neuroblastoma cell line (SH-SY5Y) using MTT assay. The results showed that the compounds (1a and 2a) cleaved significantly supercoiled plasmid DNA in a concentration-dependent fashion with irradiation. The compounds (1a and 2a) exhibited low dark toxicity but excellent phototoxicity with IC50 values 0.56 and 4.46 μM, respectively toward SH-SY5Y cell line. The finding highlights that these compounds presented great potential for photodynamic therapy.

Diketopyrrolopyrrole-Au(I) as singlet oxygen generator for enhanced tumor photodynamic and photothermal therapy

Diketopyrrolopyrrole (DPP) derivatived photosensitizers (PSs) with near infrared (NIR) absorption and good photophysical properties have drawn tremendous attention in cancer phototherapy. However, current DPP derivatives present unsatisfactory quantum yield of singlet oxygen (1O2) due to the large energy gap between the excited singlet and triplet states. To tackle this challenge, herein the DPP core is functionalized with triphenylphosphine-Au(I) group (ThDPP-Au), leading to a high 1O2 quantum yield of 0.65. Theoretical calculation attributes the enhancement to spin-orbit coupling and population of the triplet excition upon photoexcitation. The hydrophilic ThDPP-Au nanoparticals (NPs) are prepared via nano-reprecipitation, which displays homogeneous size and excellent light absorption ability ( e =4.382×104 M−1 cm−1). And the ThDPP-Au NPs exhibit low dark toxicity and high phototoxicity, which can effectively kill tumor cells via 1O2 induced mitochondrial apoptotic pathway upon irradiation. Furthermore, in vivo experiments demonstrate that ThDPP-Au NPs can selective accumulation in tumor and present excellent synergistic photodynamic/photothermal therapy guided by fluorescence and photothermal dual imaging.

Fabrication of a Dual-Stimuli-Responsive Supramolecular Micelle from a Pillar[5]arene-Based Supramolecular Diblock Copolymer for Photodynamic Therapy.

A pH and thermo dual-responsive supramolecular diblock copolymer is constructed by host-guest recognition of pillar[5]arene and viologen salt. The host polymer, poly(N,N-dimethylaminoethyl methacrylate) bearing pillar[5]arene as the terminal group (P[5]A-PDMAEMA) is synthesized by atom transfer radical polymerization (ATRP). Guest polymer, ethyl viologen-ended poly(N-isopropylacrylamide) (EV-PNIPAM) is prepared by reversible addition-fragmentation chain transfer polymerization. The supramolecular diblock copolymer can be self-assembled into stable supramolecular nanoparticles in aqueous solution at 40 °C, which show excellent pH and thermo responsiveness. The nanoparticles are further applied in the encapsulation of photosensitizers (pyropheophorbide-a, PhA) for photodynamic therapy (PDT). The dual-responsive nanoparticles can efficiently release PhA in acidic environment at 25 °C. Based on the result of cell experiments, PhA-loaded nanomicelles exhibit excellent PDT efficacy and low dark toxicity toward A549 cells. Thus, this supramolecular diblock copolymer enriches the methodology of constructing stimuli-responsive drug carriers and presents a great potential in PDT.

Drug delivery micelles with efficient near-infrared photosensitizer for combined image-guided photodynamic therapy and chemotherapy of drug-resistant cancer

The combination of photodynamic therapy (PDT) and chemotherapy (CT) offers a promising approach for the tumor eradication for overcoming multidrug resistance (MDR), which is a major obstacle to effective cancer treatment. However, for PDT, simultaneously achieving near-infrared (NIR) emission and efficient reactive oxygen species (ROS) generation with low dark toxicity is urgently needed but remains challenging. Herein, a series of novel fluorophores with strong NIR emission, hybridized local and charge transfer characteristics, good two-photon absorption, high photostability, low dark cytotoxicity and excellent ROS generation ability are developed. By encapsulating the NIR fluorophore (DEB-BDTO) as a photosensitizer along with a drug resistance inhibitor tariquidar (TQR) within a polymeric prodrug (PMP), a reduction-sensitive drug co-delivery system (DEB/TQR@PMP micelles) is constructed. The DEB/TQR@PMP micelles exhibit a prominent synergistic lethal effect of PDT and CT on SKOV-3 cells and SKOV-3/MDR cells, and can apparently enhance the inhibition of tumor growth compared with sole PDT or CT in the tumor-bearing mouse model. Both in vitro and in vivo experiments prove that the new NIR fluorophores are excellent photosensitizers and can furnish an efficient combination therapy of image-guided PDT and CT within drug delivery micelles, which is particularly useful for eradicating multidrug resistance cancer.

A Redox Stimulation-Activated Amphiphile for Enhanced Photodynamic Therapy.

The development of more efficient photosensitizers with minimal damage to surrounding normal tissues has been a valuable and challenging subject during photodynamic therapy (PDT). Herein, a stimuli-activated porphyrinic photosensitizer (PEG-TPP-DNB; PEG = poly(ethylene glycol); TPP = 5,10,15,20-tetraphenylporphyrin; DNB = 2,4-dinitrobenzene) with capabilities of fluorescence and, remarkably, singlet oxygen quenching was prepared successfully for photodynamic therapy with high efficiency and biosecurity. The amphiphilic PEG-TPP-DNB could be self-assembled into nanomicelles in aqueous media and dissociated in response to reductive thiol such as glutathione. Meanwhile, the fluorescence and singlet oxygen generation of porphyrinic photosensitizer would be activated to regenerate. Moreover, the intracellular uptake and localization effectively confirmed the redox-responsive and activated behavior of PEG-TPP-DNB micelles. The cytotoxicity in vitro revealed that the micelles had low dark toxicity and great phototoxicity, and in vivo bioimaging and antitumor evaluation further indicated that the micelles possessed selective tumor imaging and targeted PDT antitumor effect as well as low systemic toxicity. Overall, this tumor microenvironment-activated photosensitizer system may provide a useful strategy for precise photodynamic therapy.

BODIPY-Decorated Nanoscale Covalent Organic Frameworks for Photodynamic Therapy

SummaryCovalent organic frameworks (COFs), an emerging class of organic porous materials, have attracted intense attention due to their versatile applications. However, the deliberate fabrication of COF-based nanomaterials for nanomedical application remains challenging due to difficulty in their size- and structure-controlled synthesis and poor aqueous dispersibility. Herein, we report two boron-dipyrromethene (BODIPY)-decorated nanoscale COFs (NCOFs), which were prepared by the Schiff-base condensation of the free end –CHO (bonding defects in COFs) on the established imine-based NCOFs with the amino-substituted organic photosensitizer BODIPY via “bonding defects functionalization” approach. Thus BODIPY has been successfully nanocrystallized via the NCOF platform, and can be used for photodynamic therapy (PDT) to treat tumors. These NCOF-based PDT agents featured nanometer size (∼110 nm), low dark toxicity, and high phototoxicity as evidenced by in vitro and in vivo experiments. Moreover, the “bonding defects functionalization” approach might open up new avenues for the fabrication of additional COF-based platforms for biomedical treatment.

Photochemical property of two Ru(II) compounds based on 5-(2-pyrazinyl)tetrazole for cancer phototherapy by changing auxiliary ligand

Ru(II) compounds are potential candidates for photodynamic therapy (PDT) and auxiliary ligands may have an impact on the property of the resulting coordination compounds. In the present study, two Ru(II) compounds based on 5-(2-pyrazinyl)tetrazole (Hpztz) and two classic auxiliary ligands, 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) have been prepared and characterized, namely [Ru(pztz)(bipy)2][PF6] (1) and [Ru(pztz)(phen)2][PF6] (2). The nanoparticles (NPs) of the two compounds have been prepared by self-assembly in aqueous solution. In vitro MTT assay on HeLa cells show that [Ru(pztz)(phen)2][PF6] with a lower IC50 (half-maximal inhibitory concentration) of only 7.4 μg/mL is superior to that of [Ru(pztz)(bipy)2][PF6] (17.8 μg/mL) under irradiation. Meanwhile, negligible dark toxicity have been also observed for the two compounds. In addition, in vivo fluorescence imaging suggests that [Ru(pztz)(phen)2][PF6] NPs are able to target to the tumor by enhanced permeability and retention effect (EPR). Furthermore, in vivo phototherapy on nude mice demonstrate that such NPs can effectively inhibit the growth of the tumor. After treatment for 10 cycles, an obvious decrease in the tumor volume can be observed while the normal tissues, including heart, liver, spleen, lung and kidney, suffer from no damage, indicating the high phototoxicity, low dark toxicity and excellent biocompatibility of [Ru(pztz)(phen)2][PF6] NPs.

Photosensitiser functionalised luminescent upconverting nanoparticles for efficient photodynamic therapy of breast cancer cells.

Photodynamic therapy (PDT) is a well-established treatment of cancer in which cell toxic reactive oxygen species, including singlet oxygen (1O2), are produced by a photosensitiser drug following irradiation of a specific wavelength. Visible light is commonly used as the excitation source in PDT, although these wavelengths do have limited tissue penetration. In this research, upconverting nanoparticles (UCNPs) functionalised with the photosensitiser Rose Bengal (RB) have been designed and synthesised for PDT of breast cancer cells. The use of UCNPs shifts the required excitation wavelength for the production of 1O2 to near infrared light (NIR) thus allowing deeper tissue penetration. The system was designed to maximise the production of 1O2via efficient Förster resonance energy transfer (FRET) from the UCNPs to the photosensitiser. Highly luminescent NaYF4:Yb,Er,Gd@NaYF4 core-shell UCNPs were synthesised that exhibited two main anti-Stokes emission bands at 541 and 652 nm following 980 nm irradiation. RB was chosen as the photosensitiser since its absorption band overlaps with the green emission of the UCNPs. To achieve efficient energy transfer from the nanoparticles to the photosensitiser, the functionalised UCNPs included a short l-lysine linker to attach the RB to the nanocore yielding RB-lysine functionalised UCNPs. The efficient FRET from the UCNPs to the RB was confirmed by luminescence lifetime measurements. The light emitted by the UCNPs at 541 nm, following excitation at 980 nm, generates the 1O2via the RB. Multi-photon and confocal laser scanning microscopies confirmed the internalisation of the RB-lysine-UCNPs by SK-BR-3 breast cancer cells. Cell viability studies revealed that the RB-lysine-UCNPs induced low dark toxicity in cells prior to PDT treatment. Importantly, following irradiation at 980 nm, high levels of cell death were observed in cells loaded with the RB-lysine-UCNPs. Cell death following PDT treatment was also confirmed using propidium iodide and confocal microscopy. The high drug loading capacity (160 RB/nanoparticle) of the UCNPs, the efficient FRET from the UCNPs to the photosensitiser, the high level of accumulation inside the cells and their PDT cell kill suggest that the RB-lysine-UCNPs are promising for NIR PDT and hence suitable for the treatment of deep-lying cancer tumours.

Ultrasensitive redox-responsive porphyrin-based polymeric nanoparticles for enhanced photodynamic therapy

Stimulus-sensitive nanoparticles (NPs) have been established to widely adapt to remarkable abnormalities under the tumor microenvironment, which can observably enhance the therapeutic efficiency, improve the specific targeting ability and reduce the side effects. Photodynamic therapy (PDT) as a promising non-invasive and selective treatment for cancers through photodynamic reaction can profit from stimulus-sensitive NPs. Herein, a harmonious amphiphilic polymer (PEG-b-PTPPDS-b-PEG) with an extremely sensitive redox response is constructed via click chemistry between N3-TPPC6-N3, PEG-N3 and alkynyl-containing disulfide ester for PDT. This polymer can be self-assembled into micelles with excellent stability, ultra-fast sensitivity of redox-triggered porphyrin release, and significant photodynamic anticancer performance. The redox-triggered dissociation of micelles and the release of porphyrin are much faster than common porphyrin-containing polymer. The bio-distribution and phototoxicity of micelles against A549 cells are measured and evaluated in vitro by flow cytometry, confocal scanning laser microscopy (CLSM) and MTT assay, respectively. The results reveal that PEG-b-PTPPDS-b-PEG micelles can effectively enhance the cellular uptake and cellular internalization of porphyrin and have an extremely low dark toxicity with efficient PDT towards A549 cells. This intracellular responsive nanoparticle provides a potential strategy for anticancer therapeutic application.

The investigation of in vitro dark cytotoxicity and photodynamic therapy effect of a 2,6-dibromo-3,5-distyryl BODIPY dye encapsulated in Pluronic® F-127 micelles

A 2,6-dibrominated 3,5-distyryl boron-dipyrromethene (BODIPY) dye with a moderately high singlet oxygen quantum yield was encapsulated in Pluronic® F-127 micelles, and its dark cytotoxicity and photodynamic activity were investigated on the human breast adenocarcinoma MCF-7 cell line. The BODIPY dye exhibited very low dark toxicity and a significant PDT effect when added in drug formulations consisting of 5.0% (v/v) DMSO in supplemented Dulbecco’s modified Eagle’s medium (DMEM) and as Pluronic® F-127 micelle encapsulation complexes in supplemented DMEM alone. An IC50 value of 4 ± 2 μM was obtained when the BODIPY dye was encapsulated in Pluronic® F-127 micelles during in vitro photodynamic activity studies in MCF-7 cancer cells with a 660 nm light emitting diode.

Photophysical and Cellular Imaging Studies of Brightly Luminescent Osmium(II) Pyridyltriazole Complexes.

The series of complexes [Os(bpy)3- n(pytz) n][PF6]2 (bpy = 2,2'-bipyridyl, pytz = 1-benzyl-4-(pyrid-2-yl)-1,2,3-triazole, 1 n = 0, 2 n = 1, 3 n = 2, 4 n = 3) were prepared and characterized and are rare examples of luminescent 1,2,3-triazole-based osmium(II) complexes. For 3 we present an attractive and particularly mild preparative route via an osmium(II) η6-arene precursor circumventing the harsh conditions that are usually required. Because of the high spin-orbit coupling constant associated with the Os(II) center the absorption spectra of the complexes all display absorption bands of appreciable intensity in the range of 500-700 nm corresponding to spin-forbidden ground-state-to-3MLCT transitions (MLCT = metal-to-ligand charge transfer), which occur at significantly lower energies than the corresponding spin-allowed 1MLCT transitions. The homoleptic complex 4 is a bright emitter (λmaxem = 614 nm) with a relatively high quantum yield of emission of ∼40% in deoxygenated acetonitrile solutions at room temperature. Water-soluble chloride salts of 1-4 were also prepared, all of which remain emissive in aerated aqueous solutions at room temperature. The complexes were investigated for their potential as phosphorescent cellular imaging agents, whereby efficient excitation into the 3MLCT absorption bands at the red side of the visible range circumvents autofluorescence from biological specimens, which do not absorb in this region of the spectrum. Confocal microscopy reveals 4 to be readily taken up by cancer cell lines (HeLa and EJ) with apparent lysosomal and endosomal localization, while toxicity assays reveal that the compounds have low dark and light toxicity. These complexes therefore provide an excellent platform for the development of efficient luminescent cellular imaging agents with advantageous photophysical properties that enable excitation and emission in the biologically transparent region of the optical spectrum.

Halogenated Aza-BODIPY for Imaging-Guided Synergistic Photodynamic and Photothermal Tumor Therapy.

It is always a huge challenge to develop novel near-infrared (NIR) phototherapeutic agents suitable for imaging-guided cancer therapy. In order to clarify the positive heavy atom effects on the photodynamic and photothermal efficiencies of phototherapeutic agents, a series of chlorine-, bromide-, or iodine-substituted aza-BODIPYs (B2, B3, and B4, respectively) are designed and synthesized. Among them, B4 exhibits both excellent photodynamic and photothermal effects (singlet oxygen yield of B4 is 1.57 times more than that of B3) and excellent photothermal effects (1.3 °C higher than that of B3). Then, nanoparticles of B4 (IABNs) with excellent biocompatibility are prepared by coating hydrophobic B4 with hydrophilic polymer DSPE-mPEG5000 . IABN exhibits high photostability, excellent biocompatibility, and low dark toxicity both in vivo and in vitro. Furthermore, IABN shows the enhanced photodynamic effect and high photothermal conversion efficiency (34.8%). In addition, the strong fluorescence emission of IABN makes it suitable for fluorescence imaging-guided tumor therapy in vivo. Finally, IABN has successfully healed the Hela tumor-bearing mice under NIR fluorescence imaging- and photothermal imaging-guided synergistic photothermal and photodynamic therapy with low side effects, demonstrating that it is promising for future clinical applications.

Synthesis, Characterization, and Biological Evaluation of a Porphyrin-Based Photosensitizer and Its Isomer for Effective Photodynamic Therapy against Breast Cancer.

A photosensitizer with high phototoxicity, low dark toxicity, and good water solubility is crucial for effective photodynamic therapy (PDT). In this study, a novel class of porphyrin-based water-soluble derivative and its isomers, named photohexer-1 (P-1) and photohexer-2 (P-2), were synthesized and investigated for anticancer activity. Both of the isomers, P-1 and P-2, could be utilized as potential sensitizers for PDT not only owing to their definite constituents but predominantly due to their good absorption in the phototherapeutic window and high generation of intracellular ROS. Therein, P-2 exhibited stronger phototoxicity against breast cancer cells with weaker dark toxicity than P-1; however, both P-1 and P-2 were highly phototoxic as compared to their homologous compound, hematoporphyrin monomethyl ether (HMME). These findings were consistent with the antitumor efficacy in vivo. Moreover, P-1 and P-2 could both effectively localize in multiple subcellular organelles, triggering increased cellular apoptosis or necrosis under laser irradiation as compared to HMME. In conclusion, the findings of the study suggest that the two highly water-soluble porphyrin derivatives may serve as promising putative photosensitizers for improving the therapeutic efficiency of PDT.

Abstract 3213: Evaluation of porphyrin biodistribution for use in photodynamic therapy of retinoblastoma in transgenic mice

Abstract Background: Porphyrins are a group of heterocyclic macrocycle organic compounds. They have shown good efficiency in the photodynamic treatment of tumors in the last twenty years. The photodynamic therapy could be an alternative treatment for retinoblastoma using a photosensitizer with low dark toxicity and low mutagenic properties unlike the conventional chemotherapies. The objectives of this study were to develop a photosensitizer in our lab which is a diethylene glycol mannoconjugated tetraphenyl porphyrin (TPP, MW: 1413.6) and to determine the optimal interval time for photodynamic therapy using the concentration of TPP in eye and blood samples of mice. Materials and method: Transgenic mice developed bilateral retinoblastoma from the retina since 4 weeks of age to 16 weeks of age (tumors fill the ocular globe and the mice will be sacrificed for ethic purpose). The evaluation of the biodistribution of our TPP was realized to know the best drug-light interval to perform the photodynamic therapy. For this purpose, an intraperitoneal injection of 200 µl at 5.25 mg/ml in PEG 400/physiological serum (1:1, v/v) was performed on the LHbetaTag transgenic mice. At different time intervals (8h, 24h, 40h, 48h, and 72h) following injection, the mice were sacrificed and the eyes and blood were collected. TPP in eye samples were extracted in methanol and the level of TPP was measured by ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) analysis (0.5-100 ng/mL). The level of TTP in blood samples was quantified after protein precipitation by UPLC-MS/MS method (5.00-1000 ng/mL). Results: We observed a time dependency accumulation of TPP in eyes with observed Tmax=48 hours. TPP serum concentrations decreased by the same manner up to 48 h. The determination of drug-light interval allowed us to perform the light delivery when the TPP level is highest (48 h) in the ocular tumor tissue (retinoblastoma). Conclusions: Our TPP had a good in vitro photocytotoxicity at very low doses and showed a good efficacy in vivo with subcutaneous patient derived retinoblastoma xenografts in immunodeficient mice. The knowledge of Tmax and this interval is essential to realize the photodynamic therapy with the better efficiency, the final goal being to eradicate the retinoblastoma from the retina. Citation Format: Florent Poyer, Samuel Hugeut, Stéphanie Lemaitre, Olivier Madar, Carole D Thomas, Philippe Maillard, Marie-Paule Teulade-Fichou, Nathalie Cassoux, François Doz, Keyvan Rezai. Evaluation of porphyrin biodistribution for use in photodynamic therapy of retinoblastoma in transgenic mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3213.

Abstract 3201: A theranostic approach using photodynamic therapy to efficiently kill neuroblastoma cancer cells through induction of apoptosis

Abstract Neuroblastoma is an extra-cranial tumour of childhood and arises from the sympatho-adrenal lineage of the neural crest tissue. Despite advances in treatment strategies, significant complications in curing this cancer remain. Furthermore, severe consequential effects on patient health have been associated with chemotherapy and/or radiation. Photodynamic therapy (PDT) with the photosensitiser hypericin (HYP) presents an attractive and efficient adjunctive therapy alternative for this aggressive cancer. HYP, an extract from Hypericum perforatum (St John's Wort) species, has a high quantum yield following photo-activation and a low dark toxicity and genotoxiciy. This study tests the anti-cancer efficacy of HYP-PDT in SK-N-SH neuroblastoma cells using an in vitro tissue culture model. Results show through detailed uptake kinetics that HYP is absorbed effectively by SK-N-SH cells after 6 hours of incubation and live fluorescent confocal microscopy revealed primary localisation of HYP to lysosomes and mitochondria. Through cell viability assays it was determined that 2, 3 and 4μM HYP-PDT resulted in 45.6±5.1% cell death within 24 hours of treatment. Additionally, 24 hours post 0.25μM and 2μM HYP-PDT, we observed distinct morphological changes in SK-N-SH cells using phase contrast microscopy, and determined a high apoptotic mode of cell death using Fluorescent Activated Cell Sorting (FACS). These results demonstrate that HYP-PDT is effective in killing neuroblastoma cells and that the mode of cell death is apoptotic in nature. This study is ongoing with further investigation into the signalling underlying this photo-toxicity with particular emphasis on cell death resistance mechanisms in neuroblastoma cells. Citation Format: Lester M. Davids, Anja Schwar, Dirk Lang. A theranostic approach using photodynamic therapy to efficiently kill neuroblastoma cancer cells through induction of apoptosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3201.