Studies On The Bioactivities Of Several Cationic Porphyrins

Porphyrin derivatives have been used as photosensitizers in photodynamic therapy, a new approach developed for the treatment of cancer and bacterial infections. Cationic porphyrins are of considerable interest owing to their possible biomedical applications and the capability of nucleic acid binding and cleavage. In this paper, we studied the interaction between biomacromolecules with some water-soluble porphyrins and their metal complex. These porphyrin derivatives have been widely used in synthesis and application. We concluded their properties of transport, tumor selectivity and DNA damage. Depend on thesis, hydrophobic and bioactive substituents were introduced to enhance the antimicrocial activity and antitumor abilities. The novel cationic porphyrins were tested for their capability of DNA binding and cleavage. The lipid peroxidation induced by these porphyrins was compared with that induced by adriamycin. The mechanism of porphyrin bioactivities was further discussed.The studies in this paper are concluded as below:The binding of three water-soluble cationic porphyrins to human serum albumin (HSA) was investigated by absorption spectrum and fluorescence spectroscopy. Meanwhile, an optical biosensor with a stirred cuvette has been used to monitor theinteraction between immobilized HSA and these porphyrins. The binding constants at 25 ℃ obtained from biosensor analysis were compared with those from fluorescence spectroscopy. The interactions were further investigated at temperatures between 15 and 30 ℃. The thermodynamics parameters, changes of free energy (AG), enthalpy (AH) and entropy (AS), were evaluated from equilibrium data. Although the interaction was governed primarily by electrostatic forces, the differences in porphyrin structure changed their binding modes to some extent. The metal core and the hydrophobicity of side chains affected the affinity to HSA. Porphyrins studied here could bind outside hydrophobic loop with definite distance. In addition, the optical biosensor was proved well suited for investigating the interaction between such porphyrins and HSA.An optical biosensor with a stirred cuvette has also been used to monitor the interaction of immobilized wheat germ agglutinin (WGA) with two water-soluble cationic porphyrins. The association constants (Ka) of the free base porphyrin and its Zn( II) form were 2.66 and 27.31 X 105 M~-1 at 20 ℃ respectively. The interactions of the free base porphyrin were further investigated at temperatures between 15 and 37 ℃. The thermodynamics parameters, changes in free energy, enthalpy, entropy and heat capacity, were evaluated from equilibrium data. The binding was driven by entropic contribution, and showed strong enthalpy-entropy compensation. It was governed primarily by hydrophobic forces. Besides, the free base porphyrin could bind to the same or vicinal sites for iV-acetyl-D-glucosamine on WGA, but the metal porphyrin might not.The binding modes of several cationic porphyrin derivatives to calf thymus DNA and polynucleotide were analysed by absorption spectrum. Free porphyrins intercalated into base pairs of DNA and metal porphyrins tended to external bind to DNA groove. An optical biosensor was used to study the interaction of immobilized synthesized DNA segment and Zn(II) porphyrin. The kinetic and thermodynamic data showed that the binding process was mainly drived by coulombic force anddesolvation. Agarose gel electrophoresis was used to check the cleavage of plasmid DNA mediated by porphyrin derivatives. The results indicated that the cleavage ability to DNA was irrelative to the binding mode, and mostly attributed to the hydroxyl free radical induced by porphyrins.The novel /weso-substituted cationic porphyrins were covalent bonded with methoxycarbonylphenyl and 1-phenylpiperazine. The antimicrobial and antitumor activities of these porphyrins were largely enhanced. The bindings of these porphyrins to calf thymus DNA were studied by combining absorption spectrum, fluorescence and circular dichroism methods. Introduction of phenylpiperazines at /weso-position has apparently affected the mode of the binding. The capabilities of lipid peroxidation and DNA cleavage showed the same tendence as their antimicrobial and antitumor activities, which suggested that porphyrin derivatives could cause damage to the membrane structures and DNA and interfere with the cell growth.The lipid peroxidation induced by ADM, Fe3+ and ferritin was investigated by absorption spectrum. The results indicated that the lipid peroxidation mediated by ADM'Fe(III) was more effective than ADM. Iron played a key role in the process. Meanwhile, ADM could stimulate Fe-dependent lipid peroxidation. The inhibition of superoxide dismutase and some -OH scavenges indicated the participation of -OH. Deferoxamine could chelate iron and largely inhibit the lipid peroxidation, which further proved the importance of iron. Moreover, ADM could promote horse spleen ferritin to release iron and lead to a stronger peroxidation effect, which implied a possible way for ADM cardiotoxicity in vivo.