Development of innovative drug delivery strategies for organelle- targeted and bioorthogonally activated cancer therapeutics = 세포소기관을 표적으로 삼고 생물직교적으로 활성화된 암 치료제를 위한 혁신적인 약물 전달 전략 개발

다국어 초록 (Multilingual Abstract)

Recent progress in targeted drug delivery and intracellular chemical modulation is crucial for enhancing the therapeutic index of contemporary chemotherapeutics, catalysts, and antioxidant agents. Nonetheless, the clinical efficacy of numerous small molecules is often hindered by their inadequate cellular uptake, poor tissue specificity, and instability in physiological environments. To address these issues, a variety of molecular engineering techniques, such as cell-penetrating peptides, organelle-targeting motifs, and guanidine- rich transporters, have been developed as effective methods to improve intracellular delivery, biocompatibility, and functional precision. For instance, oxaliplatin, a primary chemotherapeutic for advanced colorectal cancer, faces challenges such as insufficient cellular uptake and nonspecific accumulation, which contribute to drug resistance and systemic toxicity. To mitigate these problems, a cancer-selective cell-penetrating peptide (BR2) was covalently linked to oxaliplatin using a heterobifunctional linker to create the peptide–drug conjugate BR2-Oxal. This conjugate showed enhanced and selective uptake in colon cancer cells, a significantly higher apoptotic response, and minimal internalization in normal cells. BR2-Oxal preferentially accumulated tumors in vivo and demonstrated stronger tumor suppression than oxaliplatin, underscoring the effectiveness of peptide- mediated targeted delivery and its potential to enhance oxaliplatin-based treatment. In addition to peptide-guided delivery, bioorthogonal catalysis is a fundamentally different approach for achieving spatially controlled chemical activation within living cells. Our group has developed a new bioorthogonal catalyst, Cat 34, which combines a ruthenium- based transition metal catalyst for abiotic reactions, a triphenylphosphonium (TPP) moiety for targeting mitochondria, and a guanidine-rich molecular transporter for rapid cellular entry. Cat 34 remained stable in biological media and efficiently catalyzed the intracellular decaging of a fluorescent prodye (Rho-alloc) and a mitochondrial prodrug (NIC-alloc), resulting in localized mitochondrial dysfunction and apoptosis. These results illustrate that the engineered catalytic platforms can be used for selective organelle-level chemistry for therapeutic and diagnostic purposes. Another strategy focuses on enhancing the stability and skin permeation of L-ascorbic acid (AA), a vital water-soluble antioxidant with limited transdermal penetration and significant instability in aqueous environments. A stable AA derivative, vitagen, is complexed with a guanidine-rich scyllo-inositol transporter to form vitagen/scyllo-G6. This ionic complex exhibited significantly improved aqueous stability, superior free- radical scavenging capacity, enhanced skin permeability, and higher cellular uptake in keratinocytes, while maintaining low cytotoxicity. The complex also reduced intracellular reactive oxygen species (ROS) levels more effectively than AA did. In vivo studies have confirmed improved dermal permeation. Finally, we synthesized a D-mannitol–based molecular transporter containing four guanidine groups, a fluorescent probe, and a TPP moiety to enhance cancer cell uptake and mitochondrial targeting of oxaliplatin. When ionically complexed with a negatively charged modified oxaliplatin derivative, this system exhibited potent cytotoxicity against both sensitive and oxaliplatin-resistant colorectal cancer (CRC) cells, further validating guanidinium-rich carriers as effective platforms for overcoming drug resistance. Collectively, these studies highlight the transformative potential of molecular transporters, organelle-targeting motifs, and bioorthogonal activation strategies for overcoming longstanding barriers in drug delivery and intracellular chemistry. Whether by enhancing chemotherapeutic specificity, enabling targeted catalytic prodrug activation, or stabilizing antioxidant agents for improved transdermal delivery, these approaches emphasize a converging paradigm: precise molecular engineering can significantly elevate the efficacy, safety, and functional versatility of therapeutic and diagnostic agents across biomedical applications.

목차 (Table of Contents)

• Abstract i
• Table of contents iv
• List of figures viii
• List of tables xv
• Abbreviations xvi
• Part 1. General introduction 1
• 1.1. Targeted drug delivery in cancer therapy 3
• 1.1.1. Cell-penetrating peptides in TDDS 5
• 1.1.2. Molecular transporters in TDDS 14
• 1.2. Bioorthogonal reactions 21
• 1.2.1. Targeted bioorthogonal catalysis 23
• 1.2.2. Ruthenium complexes in bioorthogonal catalysis 26
• 1.3. References 29
• Part 2. Targeted delivery of oxaliplatin into cancer cells using a cancer-specific cell-penetrating peptide, BR2 46
• 2.1. Introduction 47
• 2.2. Objectives 51
• 2.3. Results and Discussion 52
• 2.3.1. Synthesis of oxaliplatin conjugate and its linker 52
• 2.3.2. Conjugation of BR2 to oxaliplatin derivative 55
• 2.3.3. Cellular uptake study of the F-BR2-Oxal conjugate 56
• 2.3.4. Cytotoxicity studies of the BR2-Oxal conjugate 60
• 2.3.5. Detecting apoptosis using the TUNEL assay 64
• 2.3.6. In vivo antitumor activity of the conjugate 66
• 2.3.7. Immunohistochemistry studies 68
• 2.4. Conclusion 71
• 2.5. Experimental section 72
• 2.6. References 83
• Part 3. In situ bioorthogonal generation of therapeutics in mitochondria using a guanidine-rich molecular transporter 92
• 3.1. Introduction 93
• 3.2. Objectives 97
• 3.3. Results and Discussion 98
• 3.3.1. Synthesis and characterization of bioorthogonal catalyst Cat 34 98
• 3.3.2. Catalytic deprotection of Rho-alloc under biologically relevant media 106
• 3.3.3. Intracellular bioorthogonal reactions in mitochondria 113
• 3.3.4. Prodrug activation at mitochondria 120
• 3.4. Conclusion 131
• 3.5. Experimental section 133
• 3.6. References 158
• Part 4. Intracellular and transdermal delivery of vitagen for improved antioxidant effect using a guanidine-rich molecular transporter based on scyllo-inositol 167
• 4.1. Introduction 167
• 4.2. Objectives 172
• 4.3. Results and Discussion 173
• 4.3.1. Synthesis and characterization 173
• 4.3.2. In vitro skin permeability 177
• 4.3.3. In vitro antioxidant activity 183
• 4.3.4. Cytotoxicity studies 185
• 4.3.5. Cellular uptake study 187
• 4.3.6. Intracellular ROS scavenging 190
• 4.3.7. Transdermal delivery of FITC-vitagen by molecular transporter 194
• 4.4. Conclusion 198
• 4.5. Experimental section 199
• 4.6. References 211
• Part 5. Targeted delivery of oxaliplatin by a mitochondria-targeting guanidine-rich molecular transporter suppresses tumor growth of colorectal cancer 218
• 5.1. Introduction 219
• 5.2. Objectives 223
• 5.3. Results and Discussion 224
• 5.3.1. Synthesis and characterization 224
• 5.3.2. Cellular uptake and subcellular colocalization 229
• 5.3.3. In vitro drug delivery via molecular transporter 234
• 5.3.4. Detecting apoptosis using TUNEL assay 241
• 5.4. Conclusion 244
• 5.5. Experimental section 246
• 5.6. References 269
• Part 6. Novel synthesis of water-soluble poly(p-phenyleneethynylene) (PPE) polymers and their potential use 279
• 6.1. Introduction 280
• 6.2. Objectives 284
• 6.3. Results and Discussion 285
• 6.3.1. Synthesis and characterization of monomers 285
• 6.3.2. Polymerization via Sonogashira coupling reactions 289
• 6.4. Conclusion 293
• 6.5. Experimental section 294
• 6.6. References 330
• Korean abstract 338
• Curriculum Vitae 341
• Acknowledgments 348