SMALL MOLECULE PHOTOSENSITIZERS FOR PHOTODYNAMIC THERAPY

Abstract

The invention relates to small photosensitizers, their process of preparation and uses of the compounds in optical imaging and photodynamic therapy. The invention provides a compound of formula (I), a derivative or a salt thereof Wherein R1 is selected from the group consisting of amines, anilines, phenols, thiophenols, selenols and aryl groups; R2 and R3 independently are H or halogen; R4 is selected from the group consisting of H, nitre and cyano: and R5 and R6 independently are either absent or oxygen or methyl.

##STR00001##

Claims

1. A compound of formula (I), a derivative or a salt thereof ##STR00011## wherein R1 is selected from the group consisting of amines, anilines, phenols, thiophenols, selenols and aryl groups; R2 and R3 independently are H or halogen; R4 is selected from the group consisting of H, nitro and cyano: and R5 and R6 independently are either absent or oxygen or methyl.

2. The compound, a derivative or a salt thereof according to claim 1 wherein R1 is an amine or an aniline.

3. The compound, a derivative or a salt thereof according to claim 1 wherein R4 is nitro.

4. The compound, a derivative or a salt thereof according to claim 1 wherein R2 and/or R3 are/is H.

5. The compound, a derivative or a salt thereof according to claim 1 wherein R5 and/or R6 are/is absent.

6. The compound according to claim 1 which is selected from the group consisting of the following compounds: ##STR00012## ##STR00013## ##STR00014## ##STR00015## and a derivative or a salt thereof.

7. The compound according to claim 6 which is selected from the group consisting of the following compounds: ##STR00016## ##STR00017## and a derivative or a salt thereof.

8. A process for the preparation of the compound, a derivative or a salt thereof according to claim 1, said process comprising the step of: a) providing an intermediate of formula II ##STR00018## wherein, R is a halogen, preferably Br, Cl or F; R2 and R3 independently are H or halogen, preferably they are both H; and R4 is selected from the group consisting of H, nitro and cyano, preferably is nitro; b) linking the two amino groups by reaction with SeO.sub.2 or other selenium derivatives; and c) performing a substitution reaction to replace the halogen with a nucleophile group, preferably an amine or aniline.

9. The compound, a derivative or a salt thereof according to claim 1 for use in a therapeutic, diagnostic, surgery or analytical method.

10. The compound, a derivative or a salt thereof for use according to claim 9 wherein the method is selected from the group consisting of fluorescence spectroscopy, fluorimetry, fluorescence microscopy, fluorescence tomography, whole-body fluorescence imaging, flow cytometry, fluorescence-assisted cell sorting, fluorescence-guided surgery, fluorescence endomicroscopy and photodynamic therapy.

11. The compound, a derivative or a salt thereof for use according to claim 9 wherein the method comprises labelling, tracking, imaging biomolecules as well as generating singlet oxygen in cells, organs, tissues in vivo, in vitro or ex vivo.

12. The compound, a derivative or a salt thereof for use according to claim 9, wherein the method is photodynamic therapy.

13. The compound, a derivative or a salt thereof for use according to claim 9, wherein the method is fluorescent probes for diagnosis of protein aggregates in neurodegenerative diseases.

14. A method for making a photosensitiser comprising the step of reacting a scaffold of formula II with a compound selected from the group consisting of metabolites, saccharides, lipids, proteins, antibodies, peptides, nucleic acids, aptamers and nanoparticles wherein the method further comprises linking the two amino groups in the scaffold by reaction with SeO.sub.2 or other selenium derivatives.

15. The method of claim 14 wherein the compound is a derivative of an amino acid, peptide, protein, glucose, lactic acid or biolipid.

Description

FIGURES

[0041] FIG. 1 shows phototoxicity assays of PS-SCOTfluor-5 and NBD analogues with different bridging groups in U87 glioblastoma cells. Compounds were administered at 100 μM and cells were illuminated or not under 520 nm light for 10 min. Cell viability was determined by means of an MTT assay.

[0042] FIG. 2 shows phototoxicity assays of PS-SCOTfluor-1,2,3 and 6 in U87 glioblastoma cells. Compounds were administered at 100 μM and cells were illuminated or not under 520 nm light for 10 min. Cell viability was determined by means of an MTT assay.

[0043] FIG. 3 shows fluorescence microscopy phototoxicity assays of PS-SCOTfluor-13 in U87 glioblastoma cells. Compound was administered at 100 μM and illuminated under 520 nm light. Annexin V-Pacific Blue was used as a stain for dead cells. Red fluorescence was used to confirm uptake of PS-SCOTfluor-13 into cells. PS-SCOTfluor-13 showed to kills U87 glioblastoma cells only after irradiation with light. Light alone does not induce any cell death as detected by Annexin V staining.

[0044] FIG. 4 shows flow cytometry phototoxicity assays of PS-SCOTfluor-13 in U87 glioblastoma cells. Compound was administered at 100 μM and illuminated under 520 nm light. Annexin V-Pacific Blue was used as a stain for dead cells. Red fluorescence was used to confirm uptake of PS-SCOTfluor-13 into cells. PS-SCOTfluor-13 showed to kills U87 glioblastoma cells only after irradiation with light but not without light. Light alone does not induce any cell death as detected by Annexin V staining.

[0045] FIG. 5 shows fluorescence microscopy phototoxicity assays of PS-SCOTfluor-13 in U87 glioblastoma cells. Excess unlabelled glucose directly competes with PS-SCOTfluor-13 for transporter recognition in U87 glioblastoma cells and reduces the uptake of PS-SCOTfluor-13 and subsequently cell death as indicated by Annexin V staining.

[0046] FIG. 6 shows fluorescence microscopy images of the phototoxic effect of PS-SCOTfluor-13 in U87 glioblastoma cells but not with 2-NBDG (glucose derivative without Se atom) under the same illumination protocol. 2-NBDG is also uptaken by U87 glioblastoma cells but does not kill the cells after illumination as indicated by Annexin V staining.

[0047] FIG. 7 shows that PS-SCOTfluor-13 kills U87-mCrimson glioblastoma cells in vivo in zebrafish. Briefly, U87-mCrimson glioblastoma cells were injected into the yolk sac of zebrafish embryos. Cells were effectively transplanted as shown by fluorescence microscopy images. Zebrafish were then irradiated with 520 nm light alone or injected with PS-SCOTfluor-13 and then irradiated with 520 nm light. Only those zebrafish that were treated with PS-SCOTfluor-13 and light show a reduction of the glioblastoma transplant as indicated by the loss of fluorescence from the mCrimson reporter.

DEFINITIONS

[0048] As used herein, the term “derivative” is used to refer to the residue of a chemical compound, such as an amino acid, after it has undergone chemical modification. For instance, these could include derivatives incorporating linkers with reactive groups for bioconjugation (e.g. amines, carboxylic acids, succinimidyl esters, maleimides, azides, alkynes, tetrazines), as well as derivatives of antibodies, proteins, peptides and small molecules.

[0049] As used herein, the term “salt” is used to refer to an assembly of cations and anions. These could include sodium, ammonium, quaternary ammonium, calcium, magnesium and potassium as cations or iodine, chloride, bromide, formate, perchlorate, hydrochlorate, sulfate, hydroxide, phosphate and trifluoroacetate as anions. The salt may only include the compound or the derivative of the invention and an anion. The salt may also include additional cations and anions. Preferred cations are of sodium and ammonium. Preferred anions are of iodine, bromide, formate and trifluoroacetate.

[0050] The compounds of the invention and listed above include stereoisomeric mixtures as well as single enantiomers or diastereoisomers. Preferably the compounds are (S)-enantiomers for amino acids, (D)-glucose and (L)-lactic acid.

EXAMPLES

[0051] The preparation of PS-SCOTfluors was achieved in two synthetic steps from a common intermediate of formula II. The detailed preparation of the PS-SCOTfluors is described below as well as the analytical methods used in the examples.

Materials and Synthesis

[0052] Commercially available reagents were used without further purification. Thin-layer chromatography was conducted on Merck silica gel 60F254 sheets and visualized by UV (254 and 365 nm). Silica gel (particle size 35-70 μm) was used for column chromatography. .sup.1H and .sup.13C spectra were recorded in a Bruker Avance 500 spectrometer (at 500 and 126 MHz, respectively). Data for .sup.1H NMR spectra are reported as chemical shift δ (ppm), multiplicity, coupling constant (Hz), and integration. Data for .sup.13C NMR spectra are reported as chemical shifts relative to the solvent peak. HPLC-MS analysis was performed on a Waters Alliance 2695 separation module connected to a Waters PDA2996 photo-diode array detector and a ZQ Micromass mass spectrometer (ESI-MS) with a Phenomenex column (C.sub.18, 5 μm, 4.6×150 mm). Semipreparative scale HPLC purifications were carried out using a Waters semipreparative HPLC system fitted with a Phenomenex column (C.sub.18 Axial, 10 μm, 21.2×150 mm) and employing UV detection.

Synthesis and Characterization of PS-SCOTfluor-1,2,3

4-(4-methoxyphenoxy)-7-nitrobenzo[c][1,2,5]selenadiazole (PS-SCOTfluor-1)

[0053] 4-Fluoro-7-nitrobenzo[c][1,2,5]selenadiazole (20 mg, 0.08 mmol) was dissolved in MeCN (2 mL). 4-Methoxyphenol (12 mg, 0.08 mmol) was then added, followed by triethylamine (14 μL, 0.08 mmol) and reaction was stirred at r.t. for 1.5 h. Volatiles were removed under reduced pressure and the crude product was purified by column chromatography (HEX:EtOAc 8:2.fwdarw.7:3).

[0054] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 8.56 (d, J=8.5 Hz, 1H), 7.29 (d, J=9.1 Hz, 2H), 7.10 (d, J=9.1 Hz, 2H), 6.59 (d, J=8.5 Hz, 1H), 3.82 (s, 3H).

[0055] .sup.13C NMR (126 MHz, DMSO-d.sub.6) δ 157.6, 156.8, 153.4, 152.3, 147.3, 135.5, 131.4, 122.5, 116.0, 106.8, 56.0.

[0056] m/z (ESI): calcd for C.sub.13H.sub.10N.sub.3O.sub.4Se.sup.+ [M+H].sup.+: 352.0, found: 352.0.

4-((4-methoxyphenyl)thio)-7-nitrobenzo[c][1,2,5]selenadiazole (PS-SCOTfluor-2)

[0057] 4-Fluoro-7-nitrobenzo[c][1,2,5]selenadiazole (20 mg, 0.08 mmol) was dissolved in MeCN (2 mL). 4-Methoxythiophenol (10 μL, 0.08 mmol) was then added, followed by triethylamine (14 μL, 0.08 mmol). A red precipitate was immediately formed, and after 5 min stirring at r.t. it was collected by filtration and washed with MeCN.

[0058] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 8.39 (d, J=8.1 Hz, 1H), 7.65 (d, J=8.1 Hz, 2H), 7.20 (d, J=8.1 Hz, 2H), 6.64 (d, J=8.1 Hz, 1H), 3.87 (s, 3H).

[0059] .sup.13C NMR (126 MHz, DMSO-d.sub.6) δ 161.6, 156.8, 150.4, 146.7, 137.9, 137.6, 128.8, 119.5, 118.1, 116.7, 56.0.

[0060] m/z (ESI): calcd for C.sub.13H.sub.10N.sub.3O.sub.3SSe.sup.+ [M+H].sup.+: 368.0, found: 367.9.

4-(4-methoxyphenyl)-7-nitrobenzo[c][1,2,5]selenadiazole (PS-SCOTfluor-3)

[0061] 4-Chloro-7-nitrobenzo[c][1,2,5]selenadiazole (20 mg, 0.08 mmol) and 4-methoxyphenylboronic acid (12 mg, 0.08 mmoll) were placed in a round bottom flask fitted with a reflux condenser under a N.sub.2 atmosphere. Dioxane (2 mL) was then added via a syringe and the mixture was stirred, followed by addition of CsCO.sub.3 (74 mg, 0.24 mmoll) and Pd(PPh.sub.3).sub.4 (20% wt.). Reaction was then heated at 100° C. for 2 h. It was then cooled down to room temperature, diluted with brine (25 mL) and extracted with EtOAc (3×25 mL). The organic layer was dried over anhydrous MgSO.sub.4, the solvent was removed under reduced pressure and the crude product was purified by column chromatography (DCM:Hex 1:1.fwdarw.DCM).

[0062] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 8.57 (d, J=7.8 Hz, 1H), 7.97 (d, J=8.9 Hz, 2H), 7.80 (d, J=7.8 Hz, 1H), 7.14 (d, J=8.9 Hz, 2H), 3.87 (s, 3H).

[0063] .sup.13C NMR (126 MHz, DMSO-d.sub.6) δ 160.8, 159.2, 151.6, 141.5, 139.6, 135.0, 131.9, 129.4, 128.8, 128.3, 124.9, 114.5, 55.8.

[0064] m/z (ESI): calcd for C.sub.13H.sub.10N.sub.3O.sub.3Se.sup.+[M+H].sup.+: 335.0, found: 335.0.

General Method for the Preparation of PS-SCOTfluor-4-20

[0065] 4-Fluoro-7-nitrobenzo[c][1,2,5]selenadiazole (0.08 mmol) was dissolved in MeCN (1 mL). The corresponding amine (0.12 mmol) was then added as well N,N-diethylamine (22 μL, 0.12 mmol) and reaction was stirred at r.t. for 5 mins. Upon completion, volatiles were removed under reduced pressure and the products were purified by column chromatography (DCM:MeOH 98:2)

N,N-diethyl-7-nitrobenzo[c][1,2,5]selenadiazol-4-amine (PS-SCOTfluor-5)

[0066] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 8.50 (d, J=9.4 Hz, 1H), 6.48 (d, J=9.4 Hz, 1H), 4.01 (q, J=7.0 Hz, 4H), 1.32 (t, J=7.0 Hz, 6H).

[0067] .sup.13C NMR (126 MHz, DMSO-d.sub.6) δ 153.9, 152.4, 148.7, 134.1, 128.2, 101.9, 47.8, 13.2. m/z (ESI): calcd for C.sub.10H.sub.12N.sub.4O.sub.2SeNa.sup.+[M+Na].sup.+: 323.0, found: 323.1.

N,N-diethyl-6-iodo-7-nitrobenzo[c][1,2,5]selenadiazol-4-amine (PS-SCOTfluor-6)

[0068] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 6.65 (s, 1H), 3.89 (q, J=7.0 Hz, 4H), 1.26 (t, J=7.0 Hz, 6H).

[0069] .sup.13C NMR (126 MHz, DMSO-d.sub.6) δ 153.2, 151.8, 144.0, 137.1, 112.1, 98.9, 47.00, 13.1.

[0070] m/z (ESI): calcd for C.sub.10H.sub.12IN.sub.4O.sub.2Se.sup.+ [M+H].sup.+: 426.9, found: 426.8.

N-cyclohexyl-7-nitrobenzo[c][1,2,5]selenadiazol-4-amine (PS-SCOTfluor-7)

[0071] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 8.50 (d, J=9.1 Hz, 1H), 6.67 (d, J=9.2 Hz, 1H), 4.06-4.01 (m, 4H), 1.73 (s, 6H).

[0072] .sup.13C NMR (126 MHz, DMSO-d.sub.6) δ 153.6, 153.3, 150.4, 133.4, 130.1, 104.8, 51.3, 26.3, 24.4.

[0073] m/z (ESI): calcd for C.sub.11H.sub.13N.sub.4O.sub.2Se.sup.+[M+H].sup.+: 312.2, found: 312.4.

(R)-2-hydroxy-3-((7-nitrobenzo[c][1,2,5]selenadiazol-4-yl)amino)propanoic acid (PS-SCOTfluor-12)

[0074] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 8.60 (d, J=8.9, 1H), 7.99 (t, J=6.0, 1H), 6.48 (d, J=9.0, 1H), 4.38 (dd, J=7.2, 4.5, 1H), 3.82-3.59 (m, 2H). .sup.13C NMR (126 MHz, DMSO-d.sub.6) δ 174.2, 152.3, 148.7, 135.5, 129.0, 98.4, 69.1, 46.8, 40.9.

[0075] m/z (HRMS ESI): calcd. for C.sub.9H.sub.9N.sub.4O.sub.5Se.sup.+[M+H].sup.+: 332.9727, found: 332.9769.

(2R,3R,4R,5S,6R)-6-(hydroxymethyl)-3-((7-nitrobenzo[c][1,2,5]thiadiazol-4-yl)amino)tetrahydro-2H-pyran-2,4,5-triol (PS-SCOTfluor-13)

[0076] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 8.55 (d, J=7.4 Hz, 1H), 7.03 (s, 1H), 6.57 (d, J=7.4 Hz, 1H), 5.17 (s, 2H), 5.10-5.03 (m, 1H), 4.52-4.45 (m, 1H), 3.85-3.65 (m, 4H), 3.50-3.47 (m, 1H).

[0077] .sup.13C NMR (126 MHz, DMSO-d.sub.6) 152.1, 148.5, 135.6, 128.7, 99.0, 90.5, 73.3, 73.0, 70.8, 61.5, 58.2.

[0078] m/z (HRMS ESI): calcd for C.sub.12H.sub.15N.sub.4O.sub.7S.sup.+[M+H].sup.+: 359.0656, found: 359.0687.

(2R,3R,4R,5S,6R)-3-(ethyl(7-nitrobenzo[c][1,2,5]selenadiazol-4-yl)amino)-6-(hydroxymethyl)tetrahydro-2H-pyran-2,4,5-triol (PS-SCOTfluor-14)

[0079] .sup.1H NMR (500 MHz, Methanol-d.sub.4) δ 8.63 (d, J=9.2 Hz, 1H), 8.62 (d, J=9.2 Hz, 1H), 6.77 (d, J=9.2 Hz, 1H), 6.66 (d, J=9.4 Hz, 1H), 5.73 (d, J=3.2 Hz, 1H), 5.59-5.52 (m, 1H), 5.42 (dd, J=10.7, 3.3 Hz, 1H), 5.07 (d, J=8.1 Hz, 1H), 4.19 (dd, J=10.7, 8.4 Hz, 1H), 4.10 (dd, J=14.6, 7.2 Hz, 1H), 4.01-3.85 (m, 6H), 3.79-3.72 (m, 2H), 3.49-3.42 (m, 2H), 3.38-3.35 (m, 2H), 1.37 (t, J=7.0 Hz, 3H), 1.33 (t, J=6.9 Hz, 3H).

[0080] .sup.13C NMR (126 MHz, Methanol-d.sub.4) δ 154.0, 153.9, 153.8, 153.6, 150.9, 150.6, 133.2, 133.0, 129.9, 129.7, 105.4, 104.7, 94.5, 93.5, 76.5, 72.9, 72.3, 71.7, 70.6, 67.2, 65.4, 61.4, 40.5, 11.8, 11.1.

[0081] m/z (ESI): calcd for C.sub.14H.sub.19N.sub.4O.sub.7Se.sup.+ [M+H].sup.+: 435.0, found 435.1.

2-amino-3-((7-nitrobenzo[c][1,2,5]selenadiazol-4-yl)amino)propanoic acid (PS-SCOTfluor-19)

[0082] .sup.1H NMR (500 MHz, DMSO-d.sub.6) δ 8.66 (br, s, 1H), 8.61 (d, J=8.9 Hz, 1H), 8.25 (br, t, J=5.9 Hz, 1H), 6.60 (d, J=8.9 Hz, 1H), 4.26 (t, J=5.7 Hz, 1H), 4.13-3.87 (m, 2H).

[0083] .sup.13C NMR (126 MHz, DMSO-d.sub.6) δ 169.6, 152.5, 152.1, 148.2, 135.1, 129.7, 98.5, 51.6, 43.1. m/z (HRMS ESI): calcd for C.sub.9H.sub.10N.sub.5O.sub.4Se.sup.+ [M+H].sup.+: 331.9892, found 331.9895.

Photosensitizer Characterization

[0084] Phototoxicity assays of nitrobenzodiazoles (NBD) with different bridging groups (X) listed below was evaluated in U87 glioblastoma cells. All compounds were administered at 100 μM and illuminated for 10 min under 520 nm light.

##STR00008##

[0085] U87 cells were plated at 20,000 cells per well in a 96 well plate in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% FBS, 100 U mL.sup.−1 penicillin and 0.1 mg mL.sup.−1 streptomycin. Once the cells had reached 90% confluency, the media was replaced by Krebs-Ringer bicarbonate buffer (KRB) (129 mM NaCl, 4.7 mM KCl, 1.2 mM KH.sub.2PO.sub.4, 5 mM NaHCO.sub.3, 10 mM HEPES; 2.5 mM CaCl.sub.2, 1.2 mM MgCl.sub.2 and 0.2% BSA, pH 7.4). Appropriate compounds were added to the wells at the indicated concentrations. After 1 h, wells were illuminated using a ThorLabs M530L3 LED torch for 10 mins at 10 mW. After illumination, media was removed and replaced with supplemented DMEM. Cell viability was measured 24 h later by a conventional MTT assay.

[0086] As shown in FIG. 1, Se-bridging atom is essential for effective PDT.

[0087] Phototoxicity assays evaluation of the compounds listed below in U87 glioblastoma cells has demonstrated that amines are the most effective PDT among SeNBD dyes (FIG. 2).

##STR00009##

Spectral Characterization of SeNBD-Amines Conjugated to Bioactive Molecules

[0088] Singlet oxygen generation was determined as a measurement of PS efficacy. Individual wells in a 96 well plate containing DPBF (40 μM) and compounds in EtOH were illuminated using a 520 nm laser with an incident power of 0.3 mW for 4, 2, 1 and 0.5 mins. The absorption of DPBF at 410 nm was measured using a Biotek Synergy H1 Hybrid Reader before (Abs.sub.0) and after (Abs.sub.t) illumination. The absorption of compounds (Abs.sub.PS) was measured at 520 nm.

[0089] These values were introduced to equation 1 to give the rate of singlet oxygen production (k.sub.PS).

[00001]$\begin{array}{cc}\ln \left(\frac{{\mathrm{Abs}}_t}{{\mathrm{Abs}}_0}\right)\times \ln {\mathrm{Abs}}_{\mathrm{PS}}=k_{\mathrm{PS}}t& \left(1\right)\end{array}$

k.sub.PS was then introduced to equation 2 alongside the k value of a reference photosensitiser (k.sub.ref) and its φ.sub.Δ (φ.sub.Δref) to give the singlet oxygen quantum yield of the PS (φ.sub.ΔPS).

[00002]$\begin{array}{cc}{\Phi }_{\Delta \mathrm{PS}}={\Phi }_{\Delta \mathrm{ref}}\frac{k_{\mathrm{PS}}}{k_{\mathrm{ref}}}& \left(2\right)\end{array}$

[0090] The compounds listed below were analysed and compared to 2-NBDG, which is a commercial glucose derivative with no photosensitive properties (shown below).

##STR00010##

TABLE-US-00001 TABLE 1 Singlet oxygen Compound quantum yield (%) PS-SCOTfluor-5  3% PS-SCOTfluor-6  5% PS-SCOTfluor-13 24% PS-SCOTfluor-19 10% 2-NBDG <1%

[0091] Table 1 shows that PS-SCOTfluor-13 is a glucose derivative with high activity as photosensitizer.

Cell-Based Assays

[0092] Phototoxicity assays of PS-SCOTfluor-13 and 2-NBDG in U87 glioblastoma cells were determined. Compounds administered at 100 μM and illuminated under 520 nm light. Annexin V-Pacific Blue was used as a stain for dead cells. Red fluorescence (for PS-SCOTfluor-13) and green fluorescence (for 2-NBDG) was used to confirm uptake of the compounds into cells. PS-SCOTfluor-13 showed to kills U87 glioblastoma cells only after irradiation with light. Light alone does not induce any cell death as detected by Annexin V staining (FIG. 3 for fluorescence microscopy and FIG. 4 for flow cytometry data).

[0093] Excess unlabelled glucose directly competes with PS-SCOTfluor-13 for transporter recognition in U87 glioblastoma cells and reduces the uptake of PS-SCOTfluor-13 and subsequently cell death (FIG. 5). 2-NBDG (glucose derivative without Se atom) is also uptaken by U87 glioblastoma cells but does not kill the cells after illumination (FIG. 6).

[0094] PS-SCOTfluor-13 showed to kills U87 glioblastoma cells in vivo in zebrafish. Briefly, U87-mCrimson glioblastoma cells were injected into the yolk sac of zebrafish embryos. Cells were effectively transplanted as shown by fluorescence microscopy images. Zebrafish were then irradiated with 520 nm light alone or injected with PS-SCOTfluor-13 and then irradiated with 520 nm light. Only those zebrafish that were treated with PS-SCOTfluor-13 and light show a reduction of the glioblastoma transplant as indicated by the loss of fluorescence from the mCrimson reporter (FIG. 7).