Organelle-specific Phototheranostic Metal-based Curcumin Derivatives as CSC Targeting and Antiangiogenic Agents Selective to Cancer

Roy, Souryadip (2025) Organelle-specific Phototheranostic Metal-based Curcumin Derivatives as CSC Targeting and Antiangiogenic Agents Selective to Cancer. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Souryadip Roy (18RS063)) 18RS063.pdf - Submitted Version Restricted to Repository staff only Download (28MB)

Abstract

Research into the therapeutic potential of curcumin, an antioxidant from turmeric (Curcuma longa), has been expanding rapidly, despite ongoing debates. While researchers have identified several limitations of native curcumin, such as physiological instability, low bioavailability, rapid excretion, and photo bleaching, they have also proposed various solutions to address these issues. To overcome the limitations solutions have been proposed which includes functional group modifications, polymeric or liposomal encapsulation and metal complexation. The metal conjugation has emerged as a promising approach to enhance stability while exploring new mechanisms of action in chemotherapy. Recent interest in photodynamic therapy has further highlighted the potential of curcumin-based metal complexes, leveraging curcumin’s phototherapeutic properties. Researchers have experimented with numerous metals to create curcumin derivatives and explore their photo-induced therapeutic capabilities. My introduction chapter I focuses on curcumin-metal complexes, their phototherapeutic effects, their role in generating different reactive oxygen species (ROS) types, and their various organelle-targetabilities. It also discusses future research directions, positioning this area as a promising avenue for alternative cancer treatments using phototherapy. Half-sandwich RuII –arene complexes with curcuminoids exhibit excellent chemotherapeutic effects, but their photoactivity remains unexplored. In my chapter II, we present a 1,3-diketone coordinated RuII –arene complex as a type-I photosensitizer (PS) displaying excellent efficacy against cancer stem cell (CSC) enriched oral squamous cell carcinoma (OSCC). The phenolic −OH of curcumin functionalized with ethylmorpholine provides stability and adequate lipophilicity to direct Morphocumin (ligand) and its metal complex towards lysosomes. Both ligand and complex show excellent phototherapeutic index against triple-negative-breast cancer and OSCC cell lines along with the inhibition of the formation of 3D-spheroids of the CSC enriched OSCC cell line SCC070. The CSC enrichment was confirmed by fluorescence-activated single cell sorting (FACS) studies using CD44 as the marker. Complex showed excellent performance against preformed 3D-spheroids (ca. 60–100 μm) of GFP tagged Notch1 overexpressing SCC070–hICN–GFP and downregulated certain stemness-related genes (cMYC, SOX2, OCT4, ALDH1A1, and ABCG2). cMYC activation in multiple cancers is crucial to sustaining the Warburg effect, so the downregulation of cMYC by the RuII –arene complex should significantly affect both the CSCs and bulk cancer cells. In vivo, both Morphocumin, and its RuII –arene complex showed no systemic toxicity to zebrafish embryos in the dark. The Warburg effect, which generates increased demand of glucose in cancer cells is an exploitable phenomenon to enhance uptake of anticancer drugs. In my chapter III, we introduce an aqueous-stable cytotoxic ternary Ru(II) bis-bipyridyl morphocumin complex that selectively releases the standalone cytotoxic and lysosome-targeting morphocumin in the presence of excess hydrogen peroxide (H₂O₂), a stable reactive oxygen species (ROS) commonly found in tumor microenvironments. In addition, the complex promotes accumulation of ROS in cellular environment which would enhance the morphocumin release thus creating a domino effect in the higher ROS population. The selectivity of the complex was further enhanced by encapsulating it in a reversible-addition fragmentation chain transfer (RAFT) generated self-assembled glycopolymer. Comparative analysis of the stability and activity of Ru(II) bis-bipyridyl morphocumin complex with the reported Ru(II) bis-bipyridyl curcumin complex reveals the superiority of Ru(II) bis-bipyridyl morphocumin complex in solution stability, organelle specificity, and cellular mechanism of action. Both complexes exhibit phototherapeutic properties under low-intensity visible light exposure against triple-negative breast carcinoma (MDA-MB-231) and pancreatic adenocarcinomas (MIA PaCa-2 and PANC-1). However, increasing drug incubation time diminishes the phototoxicity versus dark toxicity difference, revealing the limited phototherapeutic index of O,O-coordinating Ru(II) ternary polypyridyl complexes. Ru(II) bis-bipyridyl morphocumin complex induces apoptosis through the intrinsic pathway. The complex encapsulated in the self-assembling nanoparticle of a glucose-conjugated polymer, provides 9-fold increase in selectivity when compared with pancreatic cancer cell (MIA PaCa-2) vs. non-carcinogenic fast growing HEK293 cell line. Deprivation of glucose in the culture medium further improves the drug doses by another 5-fold. Photodynamic therapy (PDT) combined with Photoactivated Chemotherapy (PACT) has been emerged as one of the crucial strategies to tackle the drawbacks of PDT and PACT individually. Benzimidazole-based ligand design and structural modulation has shown excellent results previously in metal-based chemotherapy to phototherapy. In my chapter IV, we represent four pyrazolyl-benzimidazole based Ruthenium bis-bipyridyl di-cationic complexes with extensive investigation on their stability profile and structure-activity. The ligands were previously shown as VEGFR2 phosphorylation inhibitors. Replacement of arene motif with bipyridyl core manifests a shift in anticancer activity from chemotherapy to phototherapy. The Iodine conjugation in ligands is found to be impactful for not only photo-release of these anti-angiogenic ligands, but also plays crucial role to generate singlet oxygen (¹O₂). Both Iodine-conjugated complex exhibits superiority in terms of activity against triple negative breast cancer MDA-MB-231, Human pancreatic adenocarcinoma MIA-PaCa-2 over non-cancerous human foreskin fibroblast HFF-1. They manifest G2/M phase arrest in cell cycle and ablate cancer cells via photo-mediated ROS generation to disrupt mitochondrial membrane potential by apoptosis. In my chapter V, we decided to shift from therapeutic to diagnostic area of research. Lysosomes, key to cellular and organismal stability, are promising targets for disease treatment. Dysfunctional lysosomes are linked to diseases such as cancer, neurodegenerative disorders, atherosclerosis, and rheumatoid arthritis. Therefore, visualizing lysosomes is vital for understanding intracellular metabolism, cell membrane recycling, and assessing drug and gene delivery systems. Fluorescent probes, with high sensitivity, specificity, quick response times, and ease of use, are valuable tools for analytical sensing and optical imaging. Solid-state organic fluorophores (SSOFs) could help address the aggregation-caused quenching (ACQ) effect in bioimaging. Despite their significant impact on medicinal chemistry, the use of curcumin derivatives as fluorescent probes is limited due to their inherent toxicity, instability, ACQ effect in buffers, and photostability issues. Here, A novel Boron-curcumin analogue has been tried to be developed to overcome these limitations, marking the introduction of the first curcumin-based agent for long-term lysosome tracking. A simplest modification on the core of previously known lysosome targeting stable curcumin derivative, Morphocumin followed by a Boron conjugation leads to a non-toxic derivative as a representative of orange lysosome tracking probe.

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