The mitochondrion is a dynamic eukaryotic organelle that controls lethal and vital functions of the cell. Being a critical center of metabolic activities and involved in many diseases, mitochondria have been attracting attention as a potential target for therapeutics, especially for cancer treatment. Structural and functional differences between healthy and cancerous mitochondria, such as membrane potential, respiratory rate, energy production pathway, and gene mutations, could be employed for the design of selective targeting systems for cancer mitochondria. A number of mitochondria-targeting compounds, including mitochondria-directed conventional drugs, mitochondrial proteins/metabolism-inhibiting agents, and mitochondria-targeted photosensitizers, have been discussed. Recently, certain drug-free approaches have been introduced as an alternative to induce selective cancer mitochondria dysfunction, such as intramitochondrial aggregation, self-assembly, and biomineralization. In this review, we discuss the recent progress in mitochondria-targeted cancer therapy from the conventional approach of drug/cytotoxic agent conjugates to advanced drug-free approaches.In healthy cells, mitochondria execute a controlled regulation of multiple functions to maintain the cellular growth-death cycle. However, in the case of tumor cells, to meet the higher metabolic demand of rapidly proliferating cells, dysregulation of mitochondrial metabolism occurs [14,15]. The difference between cancer cell mitochondria and normal cells includes several functional alterations, such as mutation of mtDNA that lead to OXPHOS (oxidative phosphorylation) inhibition and thus deficient respiration and ATP generation, mutation of mtDNA-encoded mitochondrial enzymes, such as SDH (succinate dehydrogenase), IDH1 (isocitrate dehydrogenase 1), IDH2 (isocitrate dehydrogenase 2) [16], and structural differences, such as higher membrane potential of cancer cell mitochondria and higher basicity inside the mitochondrial lumen. The evasion of cell death or inhibition of mitochondria-mediated apoptosis is a hallmark for cancer. Mitochondria generate ROS, which is necessary for signaling under normal conditions. However, when apoptosis is inhibited in the case of cancer, ROS contributes to the neoplastic transformation. Furthermore, for supporting tumor cell survival under harsh tumorigenic conditions, such as nutrient depletion and hypoxia, mitochondria provide flexibility in several pathways either by up-or downregulation [17]. This altered mitochondrial metabolism of cancer cells compared with that of their normal counterparts is advantageous for the selective targeting of cancer mitochondria in therapeutics, which focuses on the cancer mitochondria specific features [18]. Directing the therapeutic agent to the mitochondria is an efficient way of eliminating cancer cells because the designed drug molecules could act at the central point of the cell, and therefore, engineering mitochondrial-targeted therapeutic agents have gained much interest in cancer thera...

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Self-assembly of peptides containing both l- and d-isomers often results in nanostructures with enhanced properties compared to their enantiomeric analogues, such as faster kinetics of formation, higher mechanical strength, and enzymatic stability. However, occurrence and consequences of the heterochiral assembly in the cellular microenvironment are unknown. In this study, we monitored heterochiral assembly of amphiphilic peptides inside the cell, specifically mitochondria of cancer cells, resulting in nanostructures with refined morphological and biological properties owing to the superior interaction between the backbones of opposite chirality. We have designed a mitochondria penetrating tripeptide containing a diphenyl alanine building unit, named as Mito-FF due to their mitochondria targeting ability. The short peptide amphiphile, Mito-FF co-assembled with its mirror pair, Mito-ff, induced superfibrils of around 100 nm in diameter and 0.5–1 μm in length, while enantiomers formed only narrow fibers of 10 nm in diameter. The co-administration of Mito-FF and Mito-ff in the cell induced drastic mitochondrial disruption both in vitro and in vivo. The experimental and theoretical analyses revealed that pyrene capping played a major role in inducing superfibril morphology upon the co-assembly of racemic peptides. This work shows the impact of chirality control over the peptide self-assembly inside the biological system, thus showing a potent strategy for fabricating promising peptide biomaterials by considering chirality as a design modality.

Recent advances in supramolecular chemistry research have led to the development of artificial chemical systems that can form self-assembled structures that imitate proteins involved in the regulation of cellular function. However, intracellular polymerization systems that operate inside living cells have been seldom reported. In this study, we developed an intramitochondrial polymerization-induced selfassembly system for regulating the cellular fate of cancer cells. It showed that polymeric disulfide formation inside cells occurred due to the high reactive oxygen species (ROS) concentration of cancer mitochondria. This polymerization barely occurs elsewhere in the cell owing to the reductive intracellular environment. The polymerization of the thiolcontaining monomers further increases the ROS level inside the mitochondria, thereby autocatalyzing the polymerization process and creating fibrous polymeric structures. This process induces dysfunction of the mitochondria, which in turn activates cell necroptosis. Thus, this in situ polymerization system shows great potential for cancer treatment, including that of drug-resistant cancers.

Metal‐organic framework (MOF) nanoparticles have recently emerged as a promising vehicle for drug delivery with high porosity and feasibility. However, employing a MOF‐based drug delivery system remains a challenge due to the difficulty in controlling interfaces of particles in a biological environment. In this paper, protein corona‐blocked Zr6‐based MOF (PCN‐224) nanoparticles are presented for targeted cancer therapy with high efficiency. The unmodified PCN‐224 surface is precoated with glutathione transferase (GST)‐fused targetable affibody (GST‐Afb) proteins via simple mixing conjugations instead of chemical modifications that can induce the impairment of proteins. GST‐Afb proteins are shown to stably protect the surface of PCN‐224 particles in a specific orientation with GST adsorbed onto the porous surface and the GST‐linked Afb posed outward, minimizing the unwanted interfacial interactions of particles with external biological proteins. The Afb‐directed cell‐specific targeting ability of particles and consequent induction of cell death is demonstrated both in vitro and in vivo by using two kinds of Afb, which targets the surface membrane receptor, human epidermal growth factor receptor 2 (HER2) or epidermal growth factor receptor (EGFR). This study provides insight into the way of regulating the protein‐adhesive surface of MOF nanoparticles and designing a more effective MOF‐hosted targeted delivery system.