Design, synthesis and biological evaluation of mitochondria targeting theranostic agents

Molecular engineering and bioimaging applications of C2-alkenyl indole dyes with tunable emission wavelengths covering visible to NIR light

As an important member of dyes, small-molecule fluorescent dyes show indispensable value in biomedical fields. Although various molecular dyes have been developed, full-color dyes covering blue to red region derived from a single chromophore are still in urgent demand. In this work, a series of dyes based on C2-alkenyl indole skeleton were synthesized, namely AI dyes, and their photophysical properties, cytotoxicity, and imaging capacity were verified to be satisfactory. Particularly, the maximal emission wavelengths of these dyes could cover a wide range from visible to NIR light with large Stokes shifts. Besides, the optical and structural discrepancies between the C2- and C3- alkenyl AI dyes were discussed in detail, and the theoretical calculations were conducted to provide insights on such structure-activity relationship. Finally, as a proof-of-concept, a fluorescent probe AI-Py-B capable of imaging endogenous ONOO- was presented, demonstrating the bioimaging potentials of these alkenyl indole dyes. This work is anticipated to open up new possibilities for developing dye engineering and bio-applications of natural indole framework.

Mitochondria-Targeted COUPY Photocages: Synthesis and Visible-Light Photoactivation in Living Cells

Releasing bioactive molecules in specific subcellular locations from the corresponding caged precursors offers great potential in photopharmacology, especially when using biologically compatible visible light. By taking advantage of the intrinsic preference of COUPY coumarins for mitochondria and their long wavelength absorption in the visible region, we have synthesized and fully characterized a series of COUPY-caged model compounds to investigate how the structure of the coumarin caging group affects the rate and efficiency of the photolysis process. Uncaging studies using yellow (560 nm) and red light (620 nm) in phosphate-buffered saline medium have demonstrated that the incorporation of a methyl group in a position adjacent to the photocleavable bond is particularly important to fine-tune the photochemical properties of the caging group. Additionally, the use of a COUPY-caged version of the protonophore 2,4-dinitrophenol allowed us to confirm by confocal microscopy that photoactivation can occur within mitochondria of living HeLa cells upon irradiation with low doses of yellow light. The new photolabile protecting groups presented here complement the photochemical toolbox in therapeutic applications since they will facilitate the delivery of photocages of biologically active compounds into mitochondria.

Design, Synthesis, Biological Evaluation, and Preliminary Mechanistic Study of a Novel Mitochondrial-Targeted Xanthone

α-Mangostin, a natural xanthone, was found to have anticancer effects, but these effects are not sufficient to be effective. To increase anticancer potential and selectivity, a triphenylphosphonium cation moiety (TPP) was introduced to α-mangostin to specifically target cancer cell mitochondria. Compared to the parent compound, the cytotoxicity of the synthesized compound 1b increased by one order of magnitude. Mechanistic analysis revealed that the anti-tumor effects were involved in the mitochondrial apoptotic pathway by prompting apoptosis and arresting the cell cycle at the G0/G1 phase, increasing the production of reactive oxygen species (ROS), and reducing mitochondrial membrane potential (Δψ_m). More notably, the antitumor activity of compound 1b was further confirmed by zebrafish models, which remarkably inhibited cancer cell proliferation and migration, as well as zebrafish angiogenesis. Taken together, our results for the first time indicated that TPP-linked 1b could lead to the development of new mitochondrion-targeting antitumor agents.

Design and application of DNA nanostructures for organelle-targeted delivery of anticancer drugs

INTRODUCTION

DNA nanostructures targeting organelles are of great significance for the early diagnosis and precise therapy of human cancers. This review is expected to promote the development of DNA nanostructure-based cancer treatment with organelle-level precision in the future.

AREAS COVERED

In this review, we introduce the different principles for targeting organelles, summarize the progresses in the development of organelle-targeting DNA nanostructures, highlight their advantages and applications in disease treatment, and discuss current challenges and future prospects.

EXPERT OPINION

Accurate targeting is a basic problem for effective cancer treatment. However, current DNA nanostructures cannot meet the actual needs. Targeting specific organelles is expected to further improve the therapeutic effect and overcome tumor cell resistance, thereby holding great practical significance for tumor treatment in the clinic. With the deepening of the research on the molecular mechanism of disease development, especially on tumorigenesis and tumor progression, and increasing understanding of the behavior of biological materials in living cells, more versatile DNA nanostructures will be constructed to target subcellular organelles for drug delivery, essentially promoting the early diagnosis of cancers, classification, precise therapy and the estimation of prognosis in the future.

Recent Developments of Coumarin-based Hybrids in Drug Discovery

Coumarin scaffold is a highly significant O-heterocycle, namely benzopyran-2-ones, form an elite class of naturally occurring compounds that possess promising therapeutic perspectives. Based on its broad spectrum of biological activities, the privileged coumarin scaffold is applied to medicinal and pharmacological treatments by several rational design strategies and approaches. Structure-activity relationships of the coumarin-based hybrids with various bioactivity fragments revealed significant information toward the further development of highly potent and selective disorder therapeutic agents. The molecular docking studies between coumarins and critical therapeutic enzymes demonstrated mode of action by forming noncovalent interactions with more than one receptor, further rationally confirm information about structure-activity relationships. This review summarizes recent developments relating to coumarin-based hybrids with other pharmacophores aiming to numerous feasible therapeutic enzymatic targets to combat various therapeutic fields, including anticancer, antimicrobic, anti-Alzheimer, anti-inflammatory activities.

A tailored and red-emissive type I photosensitizer to potentiate photodynamic immunotherapy

Photodynamic immunotherapy (PDIT) emerges and shows great potentials in eradicating malignant tumors for the advantages on simultaneously damaging primary tumors, inhibiting tumors metastasis and recurrence. However, hypoxic microenvironment of tumor...

Development of Mitochondria-Targeted Small-Molecule Dyes for Myocardial PET and Fluorescence Bimodal Imaging

Mitochondria-targeting positron emission tomography (PET) and fluorescent dual-modal probes are rarely reported. As one of the most promising lipophilic cations, F16 and its derivatives (F16s) have never been used for myocardial imaging. In this work, 14 F16s are synthesized and evaluated for cardiac imaging. In vitro cell fluorescence imaging revealed that the lead probe 5MEF is precisely localized in the mitochondria of cardiomyocytes. In addition, it shows excellent ex vivo fluorescence imaging quality with the heart-to-muscle and heart-to-liver ratios up to ∼2. Furthermore, the radiofluorinated probe ¹⁸F-5MEF is successfully prepared and shows a high initial heart uptake of 8.66 ± 0.34 % ID/g at 5 min post injection. It displays a high heart imaging performance, a long retention time in the heart, and a low background in the most normal tissues as revealed by PET. To our knowledge, this is the first time novel F16 analogues are designed and developed for myocardial dual-modal imaging.

Engineered Cell-Penetrating Peptides for Mitochondrion-Targeted Drug Delivery in Cancer Therapy

Mitochondrion is a promising target in cancer therapy. However, gaining access to this organelle is difficult due to the obstacles to cross the complicated mitochondrial membrane. Cell-penetrating peptides (CPPs) with mitochondrion-targeting ability, named mitochondrion-targeting peptides (MTPs), are efficient tools to deliver exogenous therapeutics into mitochondria. Herein, we report several new MTPs, which can be readily synthesized via resin-based solid-phase peptide synthesis. In particular, MTP3 (compound 5), consisting of three positively charged arginines and two D- and L- alternating naphthylalanines, demonstrated excellent mitochondrion-targeting ability with high Pearson's correlation coefficient, suggesting that MTP3 has good potential for mitochondrion-targeted drug delivery. As proof-of-concept, the feasibility of MTP3 was validated by the preparation of a mitochondrion-targeting prodrug (compound 17, doxorubicin-based prodrug). This prodrug was subsequently confirmed to be specifically transported to the mitochondria of tumor cells, where it was able to release the native doxorubicin upon intracellular GSH activation, leading to mitochondrial depolarization and eventually cell death. Importantly, compound 17 showed good cytotoxicity against human tumor cells while negligible toxicity towards normal cells, indicating its potential as a potent mitochondrial medicine for targeted cancer therapy. Our study thus opens a way for engineered CPPs to be used to deliver bioactive cargos in mitochondrion-targeted cancer therapy.

Bridging the Gap Between Nature and Antioxidant Setbacks: Delivering Gallic Acid to Mitochondria

Research on mitochondria-targeted active molecules became a hot topic in the past decade. Development of mitochondria permeability transition pore (mPTP )-targeting agents with clinical applications is needed not only because of the importance of the target in several diseases but also due to the fact that the current developed molecules have shown poor clinical success. In fact, only a reduced percentage reach mitochondria , effectively preventing pathological mPTP opening. The mitochondrial-targeting strategies should be a promising solution to increase the selectivity of compounds to the mPTP , reducing also their potential side effects. Chemical conjugation of bioactive molecules with a lipophilic cation such as the triphenylphosphonium (TPP ⁺) has been established as a robust strategy to specifically target mitochondria . Phytochemicals such as hydroxybenzoic acids are normal constituents of the human diet. These molecules display beneficial healthy effects, ranging from antioxidant action through diverse mechanisms to modulation of mitochondrial-related apoptotic system, although their therapeutic application is limited due to pharmacokinetic drawbacks. Accordingly, the development of a new antioxidant based on the dietary benzoic acid-gallic acid -is described as well as the demonstration of its mitochondriotropic characteristics.

Novel Strategies for Disrupting Cancer-Cell Functions with Mitochondria-Targeted Antitumor Drug-Loaded Nanoformulations

Any variation in normal cellular function results in mitochondrial dysregulation that occurs in several diseases, including cancer. Such processes as oxidative stress, metabolism, signaling, and biogenesis play significant roles in cancer initiation and progression. Due to their central role in cellular metabolism, mitochondria are favorable therapeutic targets for the prevention and treatment of conditions like neurodegenerative diseases, diabetes, and cancer. Subcellular mitochondria-specific theranostic nanoformulations for simultaneous targeting, drug delivery, and imaging of these organelles are of immense interest in cancer therapy. It is a challenging task to cross multiple barriers to target mitochondria in diseased cells. To overcome these multiple barriers, several mitochondriotropic nanoformulations have been engineered for the transportation of mitochondria-specific drugs. These nanoformulations include liposomes, dendrimers, carbon nanotubes, polymeric nanoparticles (NPs), and inorganic NPs. These nanoformulations are made mitochondriotropic by conjugating them with moieties like dequalinium, Mito-Porter, triphenylphosphonium, and Mitochondria-penetrating peptides. Most of these nanoformulations are meticulously tailored to control their size, charge, shape, mitochondriotropic drug loading, and specific cell-membrane interactions. Recently, some novel mitochondria-selective antitumor compounds known as mitocans have shown high toxicity against cancer cells. These selective compounds form vicious oxidative stress and reactive oxygen species cycles within cancer cells and ultimately push them to cell death. Nanoformulations approved by the FDA and EMA for clinical applications in cancer patients include Doxil, NK105, and Abraxane. The novel use of these NPs still faces tremendous challenges and an immense amount of research is needed to understand the proper mechanisms of cancer progression and control by these NPs. Here in this review, we summarize current advancements and novel strategies of delivering different anticancer therapeutic agents to mitochondria with the help of various nanoformulations.

Medicinal Chemistry Targeting Mitochondria: From New Vehicles and Pharmacophore Groups to Old Drugs with Mitochondrial Activity

Interest in tumor cell mitochondria as a pharmacological target has been rekindled in recent years. This attention is due in part to new publications documenting heterogenous characteristics of solid tumors, including anoxic and hypoxic zones that foster cellular populations with differentiating metabolic characteristics. These populations include tumor-initiating or cancer stem cells, which have a strong capacity to adapt to reduced oxygen availability, switching rapidly between glycolysis and oxidative phosphorylation as sources of energy and metabolites. Additionally, this cell subpopulation shows high chemo- and radioresistance and a high capacity for tumor repopulation. Interestingly, it has been shown that inhibiting mitochondrial function in tumor cells affects glycolysis pathways, cell bioenergy, and cell viability. Therefore, mitochondrial inhibition may be a viable strategy for eradicating cancer stem cells. In this context, medicinal chemistry research over the last decade has synthesized and characterized "vehicles" capable of transporting novel or existing pharmacophores to mitochondrial tumor cells, based on mechanisms that exploit the physicochemical properties of the vehicles and the inherent properties of the mitochondria. The pharmacophores, some of which have been isolated from plants and others, which were synthesized in the lab, are diverse in chemical nature. Some of these molecules are active, while others are prodrugs that have been evaluated alone or linked to mitochondria-targeted agents. Finally, researchers have recently described drugs with well-proven safety and efficacy that may exert a mitochondria-specific inhibitory effect in tumor cells through noncanonical mechanisms. The effectiveness of these molecules may be improved by linking them to mitochondrial carrier molecules. These promising pharmacological agents should be evaluated alone and in combination with classic chemotherapeutic drugs in clinical studies.

Mitocans Revisited: Mitochondrial Targeting as Efficient Anti-Cancer Therapy

Mitochondria are essential cellular organelles, controlling multiple signalling pathways critical for cell survival and cell death. Increasing evidence suggests that mitochondrial metabolism and functions are indispensable in tumorigenesis and cancer progression, rendering mitochondria and mitochondrial functions as plausible targets for anti-cancer therapeutics. In this review, we summarised the major strategies of selective targeting of mitochondria and their functions to combat cancer, including targeting mitochondrial metabolism, the electron transport chain and tricarboxylic acid cycle, mitochondrial redox signalling pathways, and ROS homeostasis. We highlight that delivering anti-cancer drugs into mitochondria exhibits enormous potential for future cancer therapeutic strategies, with a great advantage of potentially overcoming drug resistance. Mitocans, exemplified by mitochondrially targeted vitamin E succinate and tamoxifen (MitoTam), selectively target cancer cell mitochondria and efficiently kill multiple types of cancer cells by disrupting mitochondrial function, with MitoTam currently undergoing a clinical trial.

Design, synthesis and bioactivity evaluation of coumarin-chalcone hybrids as potential anticancer agents

The selenoprotein thioredoxin reductases (TrxRs) have been extensively studied as a potential target for the development of anticancer drugs. Herein, we designed, synthesized, and evaluated a series of coumarin-chalcone hybrids as TrxR inhibitors. Most of them exhibited enhancing anticancer activity than Xanthohumol (Xn). The representative Xn-2 (IC₅₀ = 3.6 μM) was a fluorescence agent, wherein drug uptake can be readily monitored in living cells by red fluorescence imaging. Xn-2 down-regulated the expression of TrxR, remarkedly induced ROS accumulation to activate mitochondrial apoptosis pathway. Furthermore, Xn-2 inhibited cancer cell metastasis and abolished the colony formation ability of cancer cells. Taken together, these results highlight that compound Xn-2 may be a promising theranostic TrxR inhibitor for human cancer therapy.

Tuning the near infrared II emitting wavelength of small molecule dyes by single atom alteration

A series of small molecule dyes demonstrate the feasibility of manipulating Near Infrared II emission by simply altering the donors' heteroatoms, which involved both electronegativity and intramolecular steric effects. Furthermore, these dyes show high resolution and stability for in vivo imaging after being complexed with human serum albumin.

Mitochondria-targeting fluorescent molecules for high efficiency cancer growth inhibition and imaging

Fluorescent mitochondria-accumulating delocalized lipophilic cations (DLCs) for cancer therapy have drawn significant attention in the field of cancer theranostics. One of the most promising fluorescent DLCs, F16, can selectively trigger the apoptosis and necrosis of cancer cells, making it an attractive targeted theranostic drug candidate. However, it suffers from low clinical translation potential, largely due to its inefficient anti-cancer activity (IC50 in the μM range) and poorly understood structure-activity relationship (SAR). In this report, eleven indole-ring substituted F16 derivatives (F16s) were synthesized. Among these derivatives, 5BMF was identified as a highly effective theranostic agent, with in vitro studies showing a low IC50 of ∼50 nM (to H2228 cells) and high cancer to normal cell selectivity index of 225. In vivo studies revealed that tumors treated with 5BMF were significantly suppressed (almost no growth over the treatment period) compared to the PBS treated control group, and also no obvious toxicity to mice was found. In addition, the tumor imaging capability of 5BMF was demonstrated by in vivo fluorescence imaging. Finally, we report for the first time a proposed SAR for F16 DLCs. Our work lays down a solid foundation for translating 5BMF into a novel and highly promising DLC for cancer theranostics.

Synthesis of Ergosterol Peroxide Conjugates as Mitochondria Targeting Probes for Enhanced Anticancer Activity

Inspired by the significant bioactivity of ergosterol peroxide, we designed and synthesized four fluorescent coumarin and ergosterol peroxide conjugates 8a–d through the combination of ergosterol peroxide with 7-N,N-diethylamino coumarins fluorophore. The cytotoxicity of synthesized conjugates against three human cancer cells (HepG2, SK-Hep1, and MCF-7) was evaluated. The results of fluorescent imaging showed that the synthesized conjugates 8a–d localized and enriched mainly in mitochondria, leading to significantly enhanced cytotoxicity over ergosterol peroxide. Furthermore, the results of biological functions of 8d showed that it could suppress cell colony formation, invasion, and migration; induce G2/M phase arrest of HepG2 cells, and increase the intracellular ROS level.

Mitochondria-targeting theranostics

BACKGROUND

Interest in subcellular organelle-targeting theranostics is substantially increasing due to the significance of subcellular organelle-targeting drug delivery for maximizing therapeutic effects and minimizing side effects, as well as the significance of theranostics for delivering therapeutics at the correct locations and doses for diseases throughout diagnosis. Among organelles, mitochondria have received substantial attention due to their significant controlling functions in cells.

MAIN BODY

With the necessity of subcellular organelle-targeting drug delivery and theranostics, examples of mitochondria-targeting moieties and types of mitochondria-targeting theranostics were introduced. In addition, the current studies of mitochondria-targeting theranostic chemicals, chemical conjugates, and nanosystems were summarized.

CONCLUSION

With the current issues of mitochondria-targeting theranostic chemicals, chemical conjugates, and nanosystems, their potentials and alternatives are discussed.

Mitochondria-targeting drug conjugates for cytotoxic, anti-oxidizing and sensing purposes: current strategies and future perspectives

Mitochondrial targeting is a promising approach for solving current issues in clinical application of chemotherapy and diagnosis of several disorders. Here, we discuss direct conjugation of mitochondrial-targeting moieties to anticancer drugs, antioxidants and sensor molecules. Among them, the most widely applied mitochondrial targeting moiety is triphenylphosphonium (TPP), which is a delocalized cationic lipid that readily accumulates and penetrates through the mitochondrial membrane due to the highly negative mitochondrial membrane potential. Other moieties, including short peptides, dequalinium, guanidine, rhodamine, and F16, are also known to be promising mitochondrial targeting agents. Direct conjugation of mitochondrial targeting moieties to anticancer drugs, antioxidants and sensors results in increased cytotoxicity, anti-oxidizing activity and sensing activity, respectively, compared with their non-targeting counterparts, especially in drug-resistant cells. Although many mitochondria-targeted anticancer drug conjugates have been investigated in vitro and in vivo, further clinical studies are still needed. On the other hand, several mitochondria-targeting antioxidants have been analyzed in clinical phases I, II and III trials, and one conjugate has been approved for treating eye disease in Russia. There are numerous ongoing studies of mitochondria-targeted sensors.

Mitochondrial-Targeting Anticancer Agent Conjugates and Nanocarrier Systems for Cancer Treatment

The mitochondrion is an important intracellular organelle for drug targeting due to its key roles and functions in cellular proliferation and death. In the last few decades, several studies have revealed mitochondrial functions, attracting the focus of many researchers to work in this field over nuclear targeting. Mitochondrial targeting was initiated in 1995 with a triphenylphosphonium-thiobutyl conjugate as an antioxidant agent. The major driving force for mitochondrial targeting in cancer cells is the higher mitochondrial membrane potential compared with that of the cytosol, which allows some molecules to selectively target mitochondria. In this review, we discuss mitochondria-targeting ligand-conjugated anticancer agents and their in vitro and in vivo behaviors. In addition, we describe a mitochondria-targeting nanocarrier system for anticancer drug delivery. As previously reported, several agents have been known to have mitochondrial targeting potential; however, they are not sufficient for direct application for cancer therapy. Thus, many studies have focused on direct conjugation of targeting ligands to therapeutic agents to improve their efficacy. There are many variables for optimal mitochondria-targeted agent development, such as choosing a correct targeting ligand and linker. However, using the nanocarrier system could solve some issues related to solubility and selectivity. Thus, this review focuses on mitochondria-targeting drug conjugates and mitochondria-targeted nanocarrier systems for anticancer agent delivery.

Self-assembly of Fluorescent Dehydroberberine Enhances Mitochondria-Dependent Antitumor Efficacy

Selective imaging and inducing mitochondrial dysfunction in tumor cells using mitochondria-targeting probes has become as a promising approach for cancer diagnosis and therapy. Here, we report the design of a fluorescent berberine analog, dehydroberberine (DH-BBR), as a new mitochondria-targeting probe capable of self-assembling into monodisperse organic nanoparticles (DTNPs) upon integration with a lipophilic counter anion, allowing for enhanced fluorescence imaging and treatment of tumors in living mice. X-ray crystallography revealed that the self-assembly process was attributed to a synergy of different molecular interactions, including π-π stacking, O⋅⋅⋅π interaction and electrostatic interaction between DH-BBR and counter anions. We demonstrated that DTNPs could efficiently enter tumor tissue following intravenous injection and enhance mitochondrial delivery of DH-BBR via an electrostatic interaction driven anion exchange process. Selective accumulation in the mitochondria capable of emitting strong fluorescence and causing mitochondrial dysfunction was achieved, enabling efficient inhibition of tumor growth in living mice. This study demonstrates promise for applying lipophilic anions to control molecular self-assembly and tune antitumor activity of mitochondria-targeting probes, which can facilitate to improve cancer treatment in vivo.

Discovery of a new mitochondria permeability transition pore (mPTP) inhibitor based on gallic acid

Pharmacological interventions targeting mitochondria present several barriers for a complete efficacy. Therefore, a new mitochondriotropic antioxidant (AntiOxBEN₃) based on the dietary antioxidant gallic acid was developed. AntiOxBEN₃ accumulated several thousand-fold inside isolated rat liver mitochondria, without causing disruption of the oxidative phosphorylation apparatus, as seen by the unchanged respiratory control ratio, phosphorylation efficiency, and transmembrane electric potential. AntiOxBEN₃ showed also limited toxicity on human hepatocarcinoma cells. Moreover, AntiOxBEN₃ presented robust iron-chelation and antioxidant properties in both isolated liver mitochondria and cultured rat and human cell lines. Along with its low toxicity profile and high antioxidant activity, AntiOxBEN₃ strongly inhibited the calcium-dependent mitochondrial permeability transition pore (mPTP) opening. From our data, AntiOxBEN₃ can be considered as a lead compound for the development of a new class of mPTP inhibitors and be used as mPTP de-sensitiser for basic research or clinical applications or emerge as a therapeutic application in mitochondria dysfunction-related disorders.

A novel delocalized lipophilic cation-chlorambucil conjugate inhibits P-glycoprotein in HepG2/ADM cells

Multidrug resistance (MDR) limits the application of a large number of cancer-fighting agents in clinical therapy. One reason is that P-glycoprotein (Pgp) efflux pumps are usually overexpressed and lead to drug efflux in the cancer cells, which limits the viability of many chemotherapeutics. Current available inhibitors which block the Pgp pump efflux are usually not widely used in clinical practice, because they change other drug pharmacokinetic profiles or increase side effects. Here, through covalent linkage of cancer-targeting delocalized lipophilic cation FF and DNA-damaging drug nitrogen mustard chlorambucil (CLB), we rationally designed and synthesized a tumor-targeting anticancer agent FFCLB. And we found and proved that the FFCLB was capable of reducing the outflow of Pgp substrates efficiently. This conjugate selectively improves adriamycin uptake and toxicity through reducing MDR1 mRNA and Pgp protein expression. Based on molecular targeted strategy, this study can facilitate the discovery of superior MDR reducing agents to provide a more effective and safer way of resensitizing MDR.

Synthesis and biological evaluation of novel steroidal 5α,8α-epidioxyandrost-6-ene-3β-ol-17-(O-phenylacetamide)oxime derivatives as potential anticancer agents

Inspired by the significant anti-cancer activity of our previously screened natural ergosterol peroxide (EP, 1), we synthesized and characterized a series of novel 5α,8α-epidioxyandrost-3β-ol-17-(O-phenylacetamide)oxime derivatives (9a-o). The anti-proliferative activity of the synthesized compounds against human hepatocellular carcinoma cells (HepG2, Sk-Hep1) and human breast cancer cells (MCF-7, MDA-MB231) were investigated. Compounds 9d, 9f, 9h, 9j and 9m displayed good anti-proliferative activity (most IC₅₀<20μM) in vitro. Furthermore, fluorescence imaging showed that the designed coumarin-9d conjugate (12) localized mainly in mitochondria, leading to enhanced anticancer activities over the parent structure.

Synthesis of 5α,8α-Ergosterol Peroxide 3-Carbamate Derivatives and a Fluorescent Mitochondria-Targeting Conjugate for Enhanced Anticancer Activities

Inspired by the significant anticancer activity of our previously screened natural ergosterol peroxide (1), we synthesized and characterized a series of novel ergosterol peroxide 3-carbamate derivatives. The antiproliferative activities of the synthesized compounds against human hepatocellular carcinoma cells (HepG2, SK-Hep1) and human breast cancer cells (MCF-7, MDA-MB231) were investigated. 5α,8α-Epidioxyergosta-3-yl-(piperazine-1)carbamate (3 d) and 5α,8α-epidioxyergosta-3-yl-(piperidin-4-methylamine)carbamate (3 f) and their hydrochloride salts exhibited significant in vitro antiproliferative activities against the tested tumor cell lines, with IC₅₀ values ranging from 0.85 to 4.62 μm. Furthermore, fluorescent imaging showed that the designed coumarin-3 d conjugate (5) localized mainly in mitochondria, leading to enhanced anticancer activities over the parent structure 1. As a whole, it appeared that substituent changes at the C3 position could serve as a promising launch point for further design of this type of steroidal anticancer agent.

Development and sensing applications of fluorescent motifs within the mitochondrial environment

The potential use of fluorescent molecular probes to measure ions and biomolecules has contributed incessantly to the understanding of chemical and biological systems. The approach has many advantages such as high sensitivity, simplicity and non-destructive cellular imaging that offer visible information about the targeted species. In this article, our objective is to discuss fluorescent probes that have sensing applications within the mitochondrial environment. Mitochondria are cellular organelles which are well known for their unique physiological functions and have been found to be associated with various diseases and disorders. It is therefore, important to develop new tools and tactics that can provide useful information concerning the mitochondrial environment which in turn is essential to understand its biophysical functioning and related diseases.

A phosphorescent rhenium(i) histone deacetylase inhibitor: mitochondrial targeting and paraptosis induction

A phosphorescent rhenium(i) tricarbonyl polypyridine complex with mitochondria-specific localization, HDAC inhibitory activity and paraptosis-inducing capability has been explored as a multifunctional agent.

Small conjugate-based theranostic agents: an encouraging approach for cancer therapy

We review the latest developments on small conjugate based theranostic agents for tumor treatment and diagnosis using fluorescence and magnetic resonance imaging (MRI).