Photocytotoxic luminescent lanthanide complexes of DTPA–bisamide using quinoline as photosensitizer. Issue 130 (17th December 2015)

• Record Type: Journal Article
• Authors: Singh, Khushbu; Banerjee, Samya; Patra, Ashis K.
• Is Part Of: RSC advances. Volume 5:Issue 130(2015)
• Page Start: 107503
• Page End: 107513
• Publication Date: 2015-12-17
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c5ra24329g
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Luminescent lanthanide(iii ) complexes of DTPA–bisamide quinoline as photosensitizer were studied for their structures, luminescent properties, binding with DNA and protein, photo-induced DNA cleavage, photocytotoxicity and cellular uptake studies. Abstract : Lanthanide complexes [Ln(DTPAAQ)(DMF)] (1–3 ) (Ln = Pr (1 ), Eu (2 ), Tb (3 ), H3 DTPAAQ = N, N ′′-bis(3-amidoquinolyl) diethylenetriamine- N, N ′, N ′′-triacetic acid, DMF = N, N -dimethylformamide) were studied for their structures, photophysical properties, DNA and protein binding, DNA photocleavage, photocytotoxicity and cellular internalization. The crystal structures of complexes [Ln(DTPAAQ)(DMF)] (1–3 ) display a discrete mononuclear nine-coordinate {LnN3 O6 } tricapped-trigonal prism (TTP) coordination geometry. The europium and terbium complexes show strong luminescence properties in the visible region having a long luminescence lifetime ( τ = 0.51–0.64 ms). The conjugated 3-aminoquinoline moieties act as efficient light harvesting antennae, which upon photoexcitation transfer their energy to Eu(iii ) or Tb(iii ) for their characteristic 5 D0 → 7 F J or 5 D4 → 7 F J f–f transitions respectively. The complexes display efficient binding affinity to DNA ( K b = 3.4 × 10 4 − 9.8 × 10 4 M −1 ) and BSA ( K BSA = 3.03 × 10 4 − 6.57 × 10 4 M −1 ). Europium and terbium complexes give enhanced luminescence upon interacting with CT-DNA suggesting possible luminescence-based sensing applications for these complexes. Complexes1–3 show moderate cleavage of supercoiled (SC) DNA to its nicked circular (NC) form on exposure to UV-A light of 312 nm involving formation of singlet oxygen ( 1 O2 ) and hydroxyl radicals (˙OH) in type-II and photoredox pathways. Eu(iii ) and Tb(iii ) complexes exhibit remarkable photocytotoxicity with human cervical cancer cell line (HeLa) (IC50 = 20.7–28.5 μM) while remaining essentially noncytotoxic up to 150 μM in the dark. Complexes are nontoxic in nature thus suitable for designing cellular imaging agents. Fluorescence microscopy data reveal primarily cytosolic localization of the Eu(iii ) and Tb(iii ) complexes in HeLa cells.