Targeted photoresponsive carbazole-coumarin and drug conjugates for efficient combination therapy in leukemia cancer cells

Abstract

Phototriggered drug delivery systems (PTDDSs) facilitate controlled delivery of drugs loaded on photoactive platform to the target region under light stimulation. The present study investigated the synthesis and efficacy of carbazole-coumarin (CC)-fused heterocycles as a PTDDS platform for the photocontrolled release of a chemotherapeutic agent, chlorambucil, in an in vitro model of human breast and leukemia cancer cells. CC-fused heterocycles were constructed using 4-hydroxycarbazole as the starting material, and further modification of these heterocycles yielded two CC derivatives. CC-7 with an additional - COOH group and CC-8 with the triphenylphosphonium (TPP) group, a mitochondria-targeting ligand introduced in the carbazole ring, dissolved in polar solvents and exhibited emission bands at 360 and 450 nm, respectively. The results indicate that visible light of 405 nm triggers the photolysis of the CC-drug conjugate and efficiently delivers the drug in both in vitro cancer cell models. Cytotoxicity evaluation indicates the suppression of proliferation of both types of cells treated with CC-8 under synergy effect combining drug potency and photosensitization. Further, the lower IC₅₀ of CC-8 toward leukemia cells suggests the efficacy of the TPP ligand in increasing the bioavailability of CC-drug conjugates in leukemia treatment. Studies on mitochondria-targeting drug delivery systems are required for improving the performance of anticancer drugs.

Keywords: Carbazole; Chlorambucil; Coumarin; Mitochondrial targeting; Photodynamic therapy; Phototriggered drug delivery systems; Synergy effect; Triphenylphosphonium ligands.