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Summary
The Marie Curie project “Cu metallonucleases” aimed to investigate on the effect of estrogens ligands
in the biological anticancer properties of Cu(II) complexes. It is well known that many cancer cells
show overexpression of estrogen receptors in the cell membrane. Exploiting these particular features,
the idea was to bioconjugate estrogens (testosterone and estradiol) to Cu(II) complexes to increase the
selectivity for tumoral cells.
Six complexes have been synthesised (see chart below), which differ for the presence of testosterone
or estradiol, phenanthroline or necuproine, halogens or phenanthroline in the coordination sphere of
the metal. The complexes have been fully characterised through ESI Mass Spectroscopy, Elemental
Analyses, Cyclic Voltammetry and IR Spectroscopy.
DNA binding properties have been investigated using different techniques and different types of
DNA. Competition studies with ethidium bromide (major groove binder), Hoechst dye (minor groove
binder), viscosity, DNA melting point analyses show that all the complexes can bind quite strongly
with the nuclear DNA. From melting point analyses with the pure oligonucleotides Poly [d(A-T)2]
and poly[d(G-C)2] is clearly demonstrated that the complexes bind stronger to the major
groove of the DNA (poly[d(G-C)2]) than to the minor groove of the DNA (Poly [d(A-T)2]).
DNA cleavage studies investigated via gel-electrophoresis, show that the complexes can
cleave the DNA at low micromolar concentration with a oxidative mechanism.
For the DNA binding and cleavage analyses a similar trend is observed for the complexes, 5
 6  1  2  3  4. The necuproine scaffold in complexes 3 and 4 decreases the binding and
the cleavage (as stated by previous work in literature). The presence of a phenanthroline in the
coordination sphere of the complexes (5 and 6) definitively increases the binding properties to DNA
(major intercalation due to the planar phen ring) and the cleavage activity.
Cytotoxicity analyses versus different tumoral cell lines are currently undergoing.
In conclusion, the effect of estrogen ligands improve the binding and the cleavage activity of Cu(II)
complexes with very high binding constant for complexes 5 and 6.