Solution properties and photonuclease activity of cationic bis-porphyrins linked with a series of aliphatic diamines

Preparation of porphyrin and phthalocyanine conjugates for biomedical applications

The aim of this review is to offer a succinct overview of the main synthetic techniques used in the preparation of conjugates containing porphyrins, including chlorins and bacteriochlorins and phthalocyanines for biomedical applications and photodynamic therapy (PDT). To illustrate the conjugation techniques representative examples from the literature will be presented.

Interactions of porphyrins with DNA: A review focusing recent advances in chemical modifications on porphyrins as artificial nucleases

The advance of porphyrins as artificial nucleases along the years have developed a class of compounds having potential therapeutic applications. Being an extrovert of chemistry, a variety of chemical modifications have been done on porphyrin macrocycle in order to improve the spectroscopic properties and to adapt as artificial receptors that can recognize molecules. The last twenty years has witnessed broad research in the arena of porphyrin- DNA interactions and their evolution from simple to more complex entities. In this review, we summarize the recent advances in the porphyrin-based structural modifications, with a specific emphasis on various effects of porphyrin on DNA cleavage potency. We particularly detailed the nuclease activity of cationic and anionic porphyrins, porphyrin dimers and conjugates as well as heme proteins till the third generation porphyrins as artificial nucleases.

Synthesis, DNA-binding, and photocleavage properties of a serious of porphyrin-daunomycin hybrids

It is widely accepted that the pharmacological activities of anthracyclines antitumor agents express when the quinone-containing chromophore intercalates into base pairs of the duplex DNA. We have successfully synthesized and investigated the DNA-interactions of hybrids composed with quinone chromophore and cationic porphyrin. Herein, a clinic anticancer drug, daunomycin, is introduced to the porphyrin hybrids through different lengths of amide alkyl linkages, and their interactions and cleavage to DNA were studied compared with the previous porphyrin-quinone hybrids. Spectral results and the determined binding affinity constants (Kb) show that the attachment of daunomycin to porphyrin could improve the DNA-binding and photocleaving abilities. The porphyrin-daunomycin hybrids may find useful employment in investigating the ligand-DNA interaction.

Antitumor activity of G-quadruplex-interactive agent TMPyP4 with photodynamic therapy in ovarian carcinoma cells

The aim of the present study was to investigate the potential effects of photodynamic therapy (PDT) mediated by the cationic porphyrin, 5,10,15,20-tetra-(N-methyl-4-pyridyl)porphine (TMPyP₄), on an ovarian carcinoma cell line and the underlying mechanisms by which TMPyP₄-PDT exerts its actions. The analysis of cell viability, hematoxylin and eosin staining and flow cytometric apoptosis assays revealed that TMPyP₄-PDT potently suppressed the growth of the A2780 cells in a laser energy- and dose-dependent manner. Mechanically, it was observed that TMPyP₄-PDT suppressed the proliferation and motility of the A2780 cells. In addition, the expression levels of minichromosome maintenance protein-2 (MCM2) and carbonic anhydrase IX (CA-IX) were detected by western blot analysis. The results indicated that the TMPyP₄-PDT-induced apoptosis and antimetastatic activity in the A2780 cells was accompanied by the inhibition of the expression of MCM2 and CA-IX. Therefore, TMPyP₄-PDT may represent a potential therapeutic method for the treatment of ovarian carcinoma.

Consecutive intercalation of a cationic porphyrin dimer between the GC base-pairs: a kinetic study

One of the porphyrin moieties of the porphyrin dimer intercalates rapidly between the DNA base-pairs, followed by the slow intercalation of the other. The slow intercalation of the second porphyrin moiety of porphyrin dimer to poly[d(G-C)2] was investigated by normal absorption and circular dichroism spectroscopy. The change in absorbance in the Soret band of porphyrin upon association with poly[d(G-C)2] can be best elucidated by the combination of the two single exponential curves, suggesting the intercalation occurred via two independent first order reactions. Activation energies of these two first order reactions were calculated to be 0.37 kcal/mol and 3.19 kcal/mol, respectively. The intercalation associated with lower activation energy can be assigned to the intercalation of second porphyrin moiety to 5′CG3′ site while that with higher activation energy to 5′GC3′ intercalation site. Increasing the flexibility of poly[d(G-C)2] by adding Na+ ion resulted in an enhancement of the reaction rate for both steps in an exponential manner.

Bis-intercalation of a cationic porphyrin dimer linked with trietylene glycol derivative to DNA from the major groove

The binding mode of a porphyrin dimer to double stranded native DNA was investigated in this study using normal electric absorption, circular dichroism (CD) and linear dichroism (LD) spectroscopies. At the time of mixing, the spectral properties of the porphyrin dimer upon its association with DNA were characterized by hypochromism and a red shift in the absorption spectrum and by complicated CD and negative LD in the Soret region. As time elapsed, the CD spectrum became a negative single band and the negative LD signal increased. These spectral changes suggested that the majority of both porphyrin moieties of the dimer intercalated between the DNA base-pairs. The changes in the spectral characteristics of the DNA bound porphyrin-dimer were similar when the minor groove of DNA was saturated by 4′,6-diamidino-2-phenylindole (DAPI), which is well-known minor groove binding molecule. The spectral properties of DAPI, which can be summarized by a large positive induced CD in the DAPI absorption region (300~400 nm) and wavelength-independent positive reduced LD, remained intact when the porphyrin dimer was present. These observations indicated that both DAPI and porphyrin bind to DNA simultaneously, and furthermore, the bis-intercalation of the porphyrin dimer occurs in the major groove.

DNA binding and photocleavage specificities of a group of tricationic metalloporphyrins

The interactions of 5,10,15-tris(1-methylpyridinium-4-yl)-20-(4-hydroxyphenyl)porphyrinatozinc(II) Zn[TMPyHP](3+) (2) along with Cu[TMPyHP](3+) (3), Co[TMPyHP](4+) (4), Mn[TMPyHP](4+) (5) and the free base porphyrin H(2)[TMPyHP](3+) (1) with duplex DNA have been studied by using a combination of absorption, fluorescence titration, surface-enhanced Raman spectroscopy (SERS), induced circular dichroism (ICD) spectroscopy, thermal DNA denaturation, viscosity measurements as well as gel electrophoresis experiment. Their binding modes and intrinsic binding constants (K(b)) to calf DNA (CT DNA) were comparatively studied and were found significantly influenced by different metals coordinated with the porphyrin plane. Except 3, which has four-coordination structure at the metal, all the metal derivatives showed non-intercalative DNA-binding mode and lower K(b) than the free base porphyrin 1, most probably due to the steric hindrance results from the axial ligands of the inserted metals which are five or six-coordination structures. Meanwhile, the insertion of metals into cationic porphyrin greatly removed the self-aggregation of the metal-free porphyrins, and thus fully enhanced the singlet oxygen ((1)O(2)) productivities in the DNA photocleavage experiments. Therefore, these metalloporphyrins have comparable DNA cleavage ability with the free base porphyrin.

Binding of cationic bis-porphyrins linked with p- or m-xylylenediamine and their zinc(II) complexes to duplex DNA

Spectroscopic, viscometric, and molecular docking analysis of binding of cationic bis-porphyrins linked with p- or m-xylylenediamine (H₂pXy and H₂mXy) and their zinc(II) complexes (ZnpXy and ZnmXy) to duplex DNA are described. H₂pXy and H₂mXy bound to calf thymus DNA (CTDNA) stronger than unichromophoric H₂TMPyP, and showed exciton-type induced circular dichroism spectra of their Soret bands. The H₂TMPyP-like units of the metal-free bis-porphyrins did not intercalate into CTDNA, and thus the binding mode is outside binding with intramolecular stacking. ZnpXy showed favorable binding to A·T over G·C region, and should lie in the major groove of A·T region.

Synthetic control of interchromophoric interaction in cationic bis-porphyrins toward efficient DNA photocleavage and singlet oxygen production in aqueous solution

We have synthesized cationic bis-porphyrins and their zinc(II) complexes with two TMPyP-like chromophores bridged by p- or m-xylylenediamine to develop effective DNA photocleaving agents. The xylylene linkers and zinc ion were introduced to control interchromophoric interaction that should be involved in photosensitization of the cationic bis-porphyrins. The molar absorptivities of all the bis-porphyrins in aqueous solution remained unchanged over a wide range of concentrations, indicating the absence of self-aggregation property. In particular, the molar absorptivity of the zinc(II) complex of the p-xylylenediamine-linked bis-porphyrin in aqueous solution was 2.0 times as large as that of unichromophoric ZnTMPyP, suggesting the absence of both intermolecular and intramolecular interchromophoric interaction. The metal-free p-xylylenediamine-linked bis-porphyrin showed the more efficient conversion ability of supercoiled to nicked circular pUC18 plasmid DNA by photosensitization than the metal-free m-xylylenediamine-linked one. Furthermore, the zinc complexes of the bis-porphyrins exhibited the more potent DNA photocleavage than did the metal-free bis-porphyrins. Singlet oxygen productivity of the four cationic bis-porphyrins was determined by measuring the decomposition rate of 1,3-diphenylisobenzofuran. The amount of singlet oxygen generated by photosensitization of the zinc(II) complex of the p-xylylenediamine-linked bis-porphyrin in aqueous solution was 2.1 times as large as ZnTMPyP, indicating the full singlet oxygen productivity. A significant relationship between the DNA photocleaving abilities and the singlet oxygen productivities of the cationic porphyrins in aqueous solution was found. Hence, the degree of the intramolecular interchromophoric interaction, the DNA photocleaving ability, and the singlet oxygen productivity of the cationic bis-porphyrins in aqueous solution were successfully controlled by means of the introduction of the appropriate linker and metal ion.

Glycosyl bis-porphyrin conjugates: Synthesis and potential application in PDT

Syntheses of new glycosylated neutral and cationic porphyrin dimers linked at the meso-position via a flexible hydrocarbon chain are described. A detailed 1H and 13C NMR study allows their complete structural elucidation. The UV-visible, fluorescence and MALDI mass spectra are also presented. Photocytotoxicities of these compounds against K562 leukaemia cell line are compared to those of Photofrin II.

Self-aggregation inhibits the photonuclease activity of porphyrins

A series of tentacle porphyrins having four aminoalkyl groups at the periphery was synthesized, and the DNA binding properties were investigated by absorption and circular dichroism (CD) spectroscopic methods. The aminopropyl chain was found to facilitate binding, and bisignate induced CD spectra revealed that the porphyrins are self-stacked on the DNA surface. The photonuclease activity of the tentacle porphyrins was also studied, and the aminopropylporphyrin showed the highest activity. The activity increased in proportion to the porphyrin load, but higher loads resulted in the decrease of activity. This inhibitory step corresponded to aggregation of the porphyrin. Thus, the aggregation was suggested to shield the inner porphyrin from the solvent, the production of active oxygen species being suppressed.