Cobalt(III) Complexes for Light-Activated Delivery of Acetylacetonate-BODIPY, Cellular Imaging, and Photodynamic Therapy

Jana, Avishek and Kundu, Paramita and Paul, Subhadeep and Kondaiah, Paturu and Chakravarty, Akhil R (2022) Cobalt(III) Complexes for Light-Activated Delivery of Acetylacetonate-BODIPY, Cellular Imaging, and Photodynamic Therapy. In: Inorganic Chemistry, 61 (18). pp. 6837-6851. ISSN 0020-1669

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Abstract

Cobalt(III) complexes [Co(TPA)(L1)](ClO4) 2 (1),[Co(4-COOH-TPA)(L 1)](ClO4) 2(2),[Co(TPA)(L2)]Cl 2 (3), and [Co(4-COOH-TPA)(L2 )]Cl 2 (4) having acetylacetonate- linked boron-dipyrromethene ligands (L 1, acac-BODIPY; L 2,acac-diiodo-BODIPY) were prepared and characterized, and their utility as bioimaging and phototherapeutic agents was evaluated (TPA, tris-(2-pyridylmethyl)amine; 4-COOH-TPA, 2-((bis-(2-pyridylmethyl)amino)methyl)isonicotinic acid). HL1, HL 2, and complex 1 were structurally characterized by X-ray crystallography. Complexes 1 and 2 on photoactivation or in a reducing environment (excess GSH, ascorbic acid, and 3-mercaptopropionic acid) released the acac-BODIPY ligand. They exhibited strong absorbance near 501 nm (ε ∼ (5.2−5.8) × 10 4 M−1 cm−1 ) and emission bands near 513 nm (ΦF ∼ 0.13, λex = 490 nm) in dimethyl sulfoxide (DMSO). Complexes 3 and 4 with absorption maxima at ∼536 and ∼538 nm (ε ∼ (1.2−1.8) × 10 4 M−1 cm−1 ), respectively, afforded high singlet oxygen quantum yield (Φ Δ ∼ 0.79) in DMSO. Complexes 1−4 showed Co(III)−Co(II) redox responses near −0.2 V versus saturated calomel electrode (SCE) in dimethylformamide (DMF)−0.1 M tetrabutylammonium perchlorate (TBAP). The photocleavage of pUC19 DNA by complex 4 revealed the formation of both singlet oxygen and superoxide anion radicals as the reactive oxygen species (ROS). Confocal fluorescence microscopy showed the selective accumulation of complex 1 in the endoplasmic reticulum (ER) in A-549 cells. Complex 4 exhibited a high phototherapeutic index value (PI > 7000) in HeLa cancer cells (IC50 ∼ 0.007 μM in visible light of 400−700 nm, total dose ∼5 J cm−2 ). The ancillary ligands in the complexes demonstrated a structure−activity relationship and modulated the Co(III)−Co(II) redox potential, the complex solubility, acac-BODIPY ligand release kinetics, and phototherapeutic efficacy.

Item Type:	Journal Article
Publication:	Inorganic Chemistry
Publisher:	American Chemical Society
Additional Information:	The copyright of this article belongs to the American Chemical Society.
Department/Centre:	Division of Biological Sciences > Molecular Reproduction, Development & Genetics Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	25 May 2022 04:56
Last Modified:	25 May 2022 04:56
URI:	https://eprints.iisc.ac.in/id/eprint/72391

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