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Syntheses and Photodynamic Activity of Pegylated Cationic Zn(II)-Phthalocyanines in HEp2 Cells.

Ongarora BG, Hu X, Verberne-Sutton SD, Garno JC, Vicente MG - Theranostics (2012)

Bottom Line: The most phototoxic compounds were found to be the α-substituted Pcs.The β-substituted ZcPcs 6b and 4b accumulated the most within HEp2 cells but had low photocytoxicity (IC(50) > 100 μM at 1.5 J/cm(2)), possibly as a result of their lower electron density of the ring and more extended conformations compared with the α-substituted Pcs.The results show that the charge distribution about the Pc macrocycle and the intracellular localization of the cationic ZnPcs mainly determine their photodynamic activity.

View Article: PubMed Central - PubMed

Affiliation: Louisiana State University, Department of Chemistry, Baton Rouge LA, 70803, USA.

ABSTRACT
Di-cationic Zn(II)-phthalocyanines (ZnPcs) are promising photosensitizers for the photodynamic therapy (PDT) of cancers and for photoinactivation of viruses and bacteria. Pegylation of photosensitizers in general enhances their water-solubility and tumor cell accumulation. A series of pegylated di-cationic ZnPcs were synthesized from conjugation of a low molecular weight PEG group to a pre-formed Pc macrocycle, or by mixed condensation involving a pegylated phthalonitrile. All pegylated ZnPcs were highly soluble in polar organic solvents but were insoluble in water; they have intense Q absorptions centered at 680 nm and fluorescence quantum yields of ca. 0.2 in DMF. The non-pegylated di-cationic ZnPc 6a formed large aggregates, which were visualized by atomic force microscopy. The cytotoxicity, cellular uptake and subcellular distribution of all cationic ZnPcs were investigated in human carcinoma HEp2 cells. The most phototoxic compounds were found to be the α-substituted Pcs. Among these, Pcs 4a and 16a were the most effective (IC(50) ca. 10 μM at 1.5 J/cm(2)), in part due to the presence of a PEG group and the two positive charges in close proximity (separated by an ethylene group) in these macrocycles. The β-substituted ZcPcs 6b and 4b accumulated the most within HEp2 cells but had low photocytoxicity (IC(50) > 100 μM at 1.5 J/cm(2)), possibly as a result of their lower electron density of the ring and more extended conformations compared with the α-substituted Pcs. The results show that the charge distribution about the Pc macrocycle and the intracellular localization of the cationic ZnPcs mainly determine their photodynamic activity.

No MeSH data available.


Related in: MedlinePlus

(Scheme 2) Synthesis of pegylated ZnPc 16. Reaction conditions: (a) tert-butyl-20-hydroxy-3,6,9,12,15,18-hexaoxaicosan-1-oate, K2CO3, THF, 65 oC, 6 h (78%); (b) 4-tert-butylphthalonitrile, Zn(OAc)2, DMAE, 145 oC, 5 h (16-17%); (c) TFA, CH2Cl2, 0 oC, 3 h (91-94 %); (d) 1,4-bis(N-Boc)-triazaheptane, TEA, HOBt, EDCI, DMF (58-61%); (e) CH3I, DIPA, DMF, r.t., 2 d (59-67%).
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FB: (Scheme 2) Synthesis of pegylated ZnPc 16. Reaction conditions: (a) tert-butyl-20-hydroxy-3,6,9,12,15,18-hexaoxaicosan-1-oate, K2CO3, THF, 65 oC, 6 h (78%); (b) 4-tert-butylphthalonitrile, Zn(OAc)2, DMAE, 145 oC, 5 h (16-17%); (c) TFA, CH2Cl2, 0 oC, 3 h (91-94 %); (d) 1,4-bis(N-Boc)-triazaheptane, TEA, HOBt, EDCI, DMF (58-61%); (e) CH3I, DIPA, DMF, r.t., 2 d (59-67%).

Mentions: The di-cationic ZnPcs 4a,b, 6a,b, 9a,b, 11a,b, and 16a,b were synthesized as shown in Schemes 1 and 2 (Figure A and Figure B), from 3- or 4-nitrophthalonitrile (12a,b). The ZnPcs 1a,b and 2a,b were prepared according to procedures previously reported 35,36. In brief, the nitrophthalonitrile reacted with p-N-Boc-aminophenol in DMF at 80 ºC under basic conditions to give the corresponding p-N-Boc-aminophenoxy)phthalonitriles, which were heated at 140 ºC in dimethylaminoethanol (DMAE) and in the presence of zinc(II) acetate, 3 equiv. 4-tert-butylphthalonitrile and a catalytic amount of 1,5-diazabicyclo(4.3.0)non-5-ene (DBN), giving the Boc-protected α- or β-substituted A3B-type ZnPcs in 15-20% yields 35. Deprotection of the Boc groups using TFA followed by reaction with diglycolic anhydride gave ZnPcs 1a,b, which were conjugated with commercially available tert-butyl-12-amino-4,7,10-trioxadodecanoate, using 1-hydroxybenzotriazole (HOBt), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDCI) and triethylamine (TEA) in DMF to produce pegylated ZnPcs 2a,b after deprotection with TFA 36,38. Reaction of ZnPcs 1a,b and 2a,b with 1,4-bis(N-Boc)-triazaheptane under similar coupling conditions, followed by TFA-mediated Boc-deprotection gave ZnPcs 5a,b and 3a,b, respectively, in 72-79% yields. Quaternization of the amino groups using excess methyl iodide and diisopropylamine (DIPA) in DMF 35 gave the corresponding di-cationic ZnPcs 6a,b and 4a,b in 53-68% yields. The branched ZnPcs 7a,b were prepared via reaction of 1a,b with di-tert-butyl ester protected L-aspartic acid in DMF, using TEA and 2-(1H-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HATU) and HOBt, followed by deprotection with TFA 39. The dicarboxylate terminated ZnPcs 7a,b were coupled to N-Boc-2,2′-(ethylenedioxy)diethylamine or N-Boc-ethylenediamine using TEA, HOBt and EDCI, giving ZnPcs 8a,b and 10a,b respectively, which were quaternized as described above, affording the di-cationic ZnPcs 9a,b and 11a,b in 59-68% yields (Scheme 1/Figure A).


Syntheses and Photodynamic Activity of Pegylated Cationic Zn(II)-Phthalocyanines in HEp2 Cells.

Ongarora BG, Hu X, Verberne-Sutton SD, Garno JC, Vicente MG - Theranostics (2012)

(Scheme 2) Synthesis of pegylated ZnPc 16. Reaction conditions: (a) tert-butyl-20-hydroxy-3,6,9,12,15,18-hexaoxaicosan-1-oate, K2CO3, THF, 65 oC, 6 h (78%); (b) 4-tert-butylphthalonitrile, Zn(OAc)2, DMAE, 145 oC, 5 h (16-17%); (c) TFA, CH2Cl2, 0 oC, 3 h (91-94 %); (d) 1,4-bis(N-Boc)-triazaheptane, TEA, HOBt, EDCI, DMF (58-61%); (e) CH3I, DIPA, DMF, r.t., 2 d (59-67%).
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getmorefigures.php?uid=PMC3475216&req=5

FB: (Scheme 2) Synthesis of pegylated ZnPc 16. Reaction conditions: (a) tert-butyl-20-hydroxy-3,6,9,12,15,18-hexaoxaicosan-1-oate, K2CO3, THF, 65 oC, 6 h (78%); (b) 4-tert-butylphthalonitrile, Zn(OAc)2, DMAE, 145 oC, 5 h (16-17%); (c) TFA, CH2Cl2, 0 oC, 3 h (91-94 %); (d) 1,4-bis(N-Boc)-triazaheptane, TEA, HOBt, EDCI, DMF (58-61%); (e) CH3I, DIPA, DMF, r.t., 2 d (59-67%).
Mentions: The di-cationic ZnPcs 4a,b, 6a,b, 9a,b, 11a,b, and 16a,b were synthesized as shown in Schemes 1 and 2 (Figure A and Figure B), from 3- or 4-nitrophthalonitrile (12a,b). The ZnPcs 1a,b and 2a,b were prepared according to procedures previously reported 35,36. In brief, the nitrophthalonitrile reacted with p-N-Boc-aminophenol in DMF at 80 ºC under basic conditions to give the corresponding p-N-Boc-aminophenoxy)phthalonitriles, which were heated at 140 ºC in dimethylaminoethanol (DMAE) and in the presence of zinc(II) acetate, 3 equiv. 4-tert-butylphthalonitrile and a catalytic amount of 1,5-diazabicyclo(4.3.0)non-5-ene (DBN), giving the Boc-protected α- or β-substituted A3B-type ZnPcs in 15-20% yields 35. Deprotection of the Boc groups using TFA followed by reaction with diglycolic anhydride gave ZnPcs 1a,b, which were conjugated with commercially available tert-butyl-12-amino-4,7,10-trioxadodecanoate, using 1-hydroxybenzotriazole (HOBt), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDCI) and triethylamine (TEA) in DMF to produce pegylated ZnPcs 2a,b after deprotection with TFA 36,38. Reaction of ZnPcs 1a,b and 2a,b with 1,4-bis(N-Boc)-triazaheptane under similar coupling conditions, followed by TFA-mediated Boc-deprotection gave ZnPcs 5a,b and 3a,b, respectively, in 72-79% yields. Quaternization of the amino groups using excess methyl iodide and diisopropylamine (DIPA) in DMF 35 gave the corresponding di-cationic ZnPcs 6a,b and 4a,b in 53-68% yields. The branched ZnPcs 7a,b were prepared via reaction of 1a,b with di-tert-butyl ester protected L-aspartic acid in DMF, using TEA and 2-(1H-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HATU) and HOBt, followed by deprotection with TFA 39. The dicarboxylate terminated ZnPcs 7a,b were coupled to N-Boc-2,2′-(ethylenedioxy)diethylamine or N-Boc-ethylenediamine using TEA, HOBt and EDCI, giving ZnPcs 8a,b and 10a,b respectively, which were quaternized as described above, affording the di-cationic ZnPcs 9a,b and 11a,b in 59-68% yields (Scheme 1/Figure A).

Bottom Line: The most phototoxic compounds were found to be the α-substituted Pcs.The β-substituted ZcPcs 6b and 4b accumulated the most within HEp2 cells but had low photocytoxicity (IC(50) > 100 μM at 1.5 J/cm(2)), possibly as a result of their lower electron density of the ring and more extended conformations compared with the α-substituted Pcs.The results show that the charge distribution about the Pc macrocycle and the intracellular localization of the cationic ZnPcs mainly determine their photodynamic activity.

View Article: PubMed Central - PubMed

Affiliation: Louisiana State University, Department of Chemistry, Baton Rouge LA, 70803, USA.

ABSTRACT
Di-cationic Zn(II)-phthalocyanines (ZnPcs) are promising photosensitizers for the photodynamic therapy (PDT) of cancers and for photoinactivation of viruses and bacteria. Pegylation of photosensitizers in general enhances their water-solubility and tumor cell accumulation. A series of pegylated di-cationic ZnPcs were synthesized from conjugation of a low molecular weight PEG group to a pre-formed Pc macrocycle, or by mixed condensation involving a pegylated phthalonitrile. All pegylated ZnPcs were highly soluble in polar organic solvents but were insoluble in water; they have intense Q absorptions centered at 680 nm and fluorescence quantum yields of ca. 0.2 in DMF. The non-pegylated di-cationic ZnPc 6a formed large aggregates, which were visualized by atomic force microscopy. The cytotoxicity, cellular uptake and subcellular distribution of all cationic ZnPcs were investigated in human carcinoma HEp2 cells. The most phototoxic compounds were found to be the α-substituted Pcs. Among these, Pcs 4a and 16a were the most effective (IC(50) ca. 10 μM at 1.5 J/cm(2)), in part due to the presence of a PEG group and the two positive charges in close proximity (separated by an ethylene group) in these macrocycles. The β-substituted ZcPcs 6b and 4b accumulated the most within HEp2 cells but had low photocytoxicity (IC(50) > 100 μM at 1.5 J/cm(2)), possibly as a result of their lower electron density of the ring and more extended conformations compared with the α-substituted Pcs. The results show that the charge distribution about the Pc macrocycle and the intracellular localization of the cationic ZnPcs mainly determine their photodynamic activity.

No MeSH data available.


Related in: MedlinePlus