Browsing by Author "Matos, Cristina P."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Evaluation of the binding of four anti-tumor Casiopeinas to human serum albuminPublication . Correia, Isabel; Borovic, Sladjana; Cavaco, Isabel; Matos, Cristina P.; Roy, Somnath; Santos, Hugo M.; Fernandes, Luz; Capelo, Jose L.; Ruiz-Azuara, Lena; Pessoa, Joao CostaThe metal complexes designated by Casiopeinas (R) are mixed-ligand Cu-II-compounds some of them having promising antineoplastic properties. We report studies of binding of Cu(glycinato)(4,7-dimethyl-1,10-phenanthroline) (Cas-II-Gly (1)), Cu(acetylacetonato)(4,7-dimethy1-1,10-phenanthroline) (Cas-III-Ea (2)), Cu(glycinato) (4,4'-dimethyl-2,2'-bipyridine) (Cas-W-Gly (3)) and Cu(acetylacetonato)(4,4'-dimethyl-2,2'-bipyridine) (Cas-IIIia (4)) to human serum albumin (HSA) by circular dichroism (CD), Electron paramagnetic resonance (EPR) and fluorescence spectroscopy. The results indicate that HSA may bind up to three molecules of the tested Casiopeinas. This is confirmed by inductively coupled plasma atomic absorption spectroscopy measurements of samples of HSA-Casiopeinas after passing by adequate size-exclusion columns. The binding of Cas-II-Gly to HSA was also confirmed by MALDI-TOF mass spectrometric experiments. In the physiological range of concentrations the Casiopeinas form 1:1 adducts with HSA, with conditional binding constants of ca. 1 x 10(9) (1), 4 x 10(7) (2), 1 x 10(6) (3) and 2 x 10(5) (4), values determined from the CD spectra measured, and the fluorescence emission spectra indicates that the binding takes place close to the Trp214 residue. Overall, the data confirm that these Casiopeinas may bind to HSA and may be transported in blood serum by this protein; this might allow some selective tumor targeting, particularly in the case of Cas-Il-Gly. In this work we also discuss aspects associated to the reliability of the frequently used methodologies to determine binding constants based on the measurement of fluorescence emission spectra of solutions containing low concentrations of proteins such as HSA and BSA, by titration with solutions of metal complexes.
- Exploring the cytotoxic activity of new phenanthroline salicylaldimine Zn(II) complexesPublication . Matos, Cristina P.; Addis, Yemataw; Nunes, Patrique; Barroso, Sonia; Alho, Irina; Martins, Marta; Matos, Antonio P. A.; Marques, Fernanda; Cavaco, Isabel; Pessoa, Joao Costa; Correia, IsabelZinc(II) complexes bearing N-salicylideneglycinate (Sal-Gly) and 1,10-phenanthroline (phen) or phenanthroline derivatives [NN= 5-chloro-1,10-phenanthroline, 5-amine-1,10-phenanthroline (amphen), 4,7-diphenyl-1,10-phenanthroline (Bphen) and 5,6-epoxy-5,6-dihydro-1,10-phenanthroline] are synthesized. Complexes formulated as [Zn(NN)(2)(H2O)(2)](2+) (NN = phen and amphen), are also prepared. The cytotoxicity of the compounds is evaluated towards a panel of human cancer cells: ovarian (A2780), breast (MCF7) and cervical (HeLa), as well as non-tumoral V79 fibroblasts. All compounds display higher cytotoxicity than cisplatin (IC50 = 22.5 +/- 5.0 mu M) towards ovarian cells, showing IC50 values in the low micromolar range. Overall, all compounds show higher selectivity for the A2780 cells than for the non tumoral cells and higher selectivity indexes (IC50(V79)/IC50(A2780) than cisplatin. [Zn(Sal-Gly)(NNI(H2O)] complexes induce caspase-dependent apoptosis in A2780 cells, except [Zn(Sal-Gly)(Bphen)(H2O)], one of the most cytotoxic of the series. The cellular uptake in the ovarian cells analyzed by Inductively Coupled Plasma mass spectrometry indicates different Zn distribution profiles. Transmission electronic microscopy shows mitochondria alterations and apoptotic features consistent with caspase activationells incubated with EZn(Sal-Gly)(amphen)(H2O)] present additional nuclear membrane alterations in agreement with significant association with the nucleus. The increase of reactive oxygen species and lipid peroxidation forms could be related to apoptosis induction. [Zn(NN)(2)(H2O)(2)](2+) complexes have high ability to bind DNA through intercalation/groove binding, and circular dichroism data suggests that the main type of species that interact with DNA is [Zn(NN)](2+). Studies varying the % of fetal bovine serum (1-15%) in cell media show that albumin binding decreases the complex activity, indicating that distinct speciation of Zn- and phen-containing species in cell media may affect the cytotoxicity.