Photocytotoxicity and DNA photocleavage activity of La(III) and Gd(III) complexes of phenanthroline bases

Hussain, Akhtar ; Saha, Sounik ; Majumdar, Ritankar ; Dighe, Rajan R. ; Chakravarty, Akhil R. (2011) Photocytotoxicity and DNA photocleavage activity of La(III) and Gd(III) complexes of phenanthroline bases Indian Journal of Chemistry - Section A: Inorganic, Physical, Theoretical and Analytical Chemistry, 50A (3-4). pp. 519-530. ISSN 0376-4710

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Lanthanide(III) complexes [La(B)(acac)3] (1-3) and [Gd(B)(acac)3] (4-6), where B is a N,N-donor phenanthroline base, viz., 1,10-phenanthroline (phen in 1, 4), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 2, 5) and dipyrido[3,2-a:2',3'-c]phena-zine (dppz in 3, 6), have been prepared and characterized. The Gd(III) complexes 4-6 are structurally characterized by single crystal X-ray crystallography. The complexes display GdO6N2 coordination with the ligands showing bidentate chelating mode of bonding. The complexes are non-electrolytic in aqueous DMF and exhibit ligand-centered absorption bands in the UV region. The dppz complexes show a band at 380 nm in DMF. The La(III) complexes are diamagnetic. The Gd(III) complexes are paramagnetic with magnetic moment that corresponds to seven unpaired electrons. The complexes are avid binders to calf thymus DNA giving Kb values in the range of 4.7×104-6.1×105 M−1 with a relative binding order: 3, 6 (dppz) > 2, 5 (dpq) > 1, 4 (phen). The binding data suggest DNA surface and/or groove binding nature of the complexes. The dpq and dppz complexes efficiently cleave SC DNA to its nicked circular form in UV-A light of 365 nm via formation of both singlet oxygen (1O2) and hydroxyl radical (HO·) species. The dppz complexes 3 and 6 exhibit significant PDT effect in HeLa cervical cancer cells giving respective IC50 value of 460(±50) and 530(±30) nM in UV-A light of 365 nm, and are essentially non-toxic in dark with an IC50 value of >100 μM. The dppz ligand alone is cytotoxic in dark and UV-A light. A significant decrease in the dark toxicity of the dppz base is observed on binding to the Ln(III) ion while retaining its photocytotoxicity.

Item Type:Article
Source:Copyright of this article belongs to National Institute of Science Communication and Information Resources.
Keywords:Bioinorganic Chemistry; Lanthanides; Phenanthroline Bases; Crystal Structures; DNA Binding; DNA Photocleavage; Photocleavage; Photocytotoxicity; Cytotoxicity
ID Code:78280
Deposited On:19 Jan 2012 06:46
Last Modified:18 May 2016 21:09

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