Mitochondrial-targeted prodrug cancer therapy using a rhodamine B labeled fluorinated docetaxel

Liver-targeted delivery based on prodrug: passive and active approaches

BACKGROUND

The liver, a central organ in human metabolism, is often the primary target for drugs. However, conditions such as viral hepatitis, cirrhosis, non-alcoholic fatty liver disease (NAFLD), and hepatocellular carcinoma (HCC) present substantial health challenges worldwide. Existing treatments, which suffer from the non-specific distribution of drugs, frequently fail to achieve desired efficacy and safety, risking unnecessary liver harm and systemic side effects.

PURPOSE

The aim of this review is to synthesise the latest progress in the design of liver-targeted prodrugs, with a focus on passive and active targeting strategies, providing new insights into the development of liver-targeted therapeutic approaches.

METHODS

This study conducted an extensive literature search through databases like Google Scholar, PubMed, Web of Science, and China National Knowledge Infrastructure (CNKI), systematically collecting and selecting recent research on liver-targeted prodrugs. The focus was on targeting mechanisms, including the Enhanced Permeability and Retention (EPR) effect, the unique microenvironment of liver cancer, and active targeting through specific transporters and receptors.

RESULTS

Active targeting strategies achieve precise drug delivery by binding specific ligands to liver surface receptors. Passive targeting takes advantage of the EPR effect and tumour characteristics to enrich drugs in liver tumours. The review details successful cases of using small molecule ligands, peptides, antibodies and nanoparticles as drug carriers.

CONCLUSION

Liver-targeted prodrug strategies show great potential in enhancing the efficacy of drug treatment and reducing side effects for liver diseases. Future research should balance the advantages and limitations of both targeting strategies, focusing on optimising drug design and targeting efficiency, especially for clinical application. In-depth research on liver-specific receptors and the development of innovative targeting molecules are crucial for advancing the field of liver-targeted prodrugs.

Advancements in nano drug delivery system for liver cancer therapy based on mitochondria-targeting

Based on poor efficacy and non-specific toxic side effects of conventional drug therapy for liver cancer, nano-based drug delivery system (NDDS) offers the advantage of drug targeting delivery. Subcellular targeting of nanomedicines on this basis enables more precise and effective termination of tumor cells. Mitochondria, as the crucial cell powerhouse, possesses distinctive physical and chemical properties in hepatoma cells different from that in hepatic cells, and controls apoptosis, tumor metastasis, and cellular drug resistance in hepatoma cells through metabolism and dynamics, which serves as a good choice for drug targeting delivery. Thus, mitochondria-targeting NDDS have become a recent research focus, showcasing the design of cationic nanoparticles, metal nanoparticles, mitochondrial peptide modification and so on. Although many studies have shown good results regarding anti-tumor efficacy, it is a long way to go before the successful translation of clinical application. Based on these, we summarized the specificity and importance of mitochondria in hepatoma cells, and reviewed the current mitochondria-targeting NDDS for liver cancer therapy, aiming to provide a better understanding for current development process, strengths and weaknesses of mitochondria-targeting NDDS as well as informing subsequent improvements and developments.

Development and Application of Cationic Nile Blue Probes in Live-Cell Super-Resolution Imaging and Specific Targeting to Mitochondria

Mitochondria are essential organelles involved in various metabolic processes in eukaryotes. The imaging, targeting, and investigation of cell death mechanisms related to mitochondria have garnered significant interest. Small-molecule fluorescent probes have proven to be robust tools for utilizing light to advance the study of mitochondrial biology. In this study, we present the rational design of cationic Nile blue probes carrying a permanent positive charge for these purposes. The cationic Nile blue probes exhibit excellent mitochondrial permeability, unique solvatochromism, and resistance to oxidation. We observed weaker fluorescence in aqueous solutions compared to lipophilic solvents, thereby minimizing background fluorescence in the cytoplasm. Additionally, we achieved photoredox switching of the cationic Nile blue probes under mild conditions. This enabled us to demonstrate their application for the first time in single-molecule localization microscopy of mitochondria, allowing us to observe mitochondrial fission and fusion behaviors. Compared to conventional cyanine fluorophores, this class of dyes demonstrated prolonged resistance to photobleaching, likely due to their antioxidation properties. Furthermore, we extended the application of cationic Nile blue probes to the mitochondria-specific delivery of taxanes, facilitating the study of direct interactions between the drug and organelles. Our approach to triggering cell death without reliance on microtubule binding provides valuable insights into anticancer drug research and drug-resistance mechanisms.

Converting bile acids into mitocans

Cholic acid (1, CD), deoxycholic (3, DCA), chenodeoxycholic acid (5, CDCA), ursodeoxycholic acid (7, UDCA), and lithocholic acid (9, LCA) were acetylated and converted into their piperazinyl spacered rhodamine B conjugates 16-20. While the parent bile acids showed almost no cytotoxic effects for several human tumor cell lines, the piperazinyl amides were cytostatic but an even superior effect was observed for the rhodamine B conjugates. Extra staining experiments showed these compounds as mitocans; they led to a cell arrest in the G1 phase.

Mechanistic investigations of antitumor activity of a Rhodamine B‑oleanolic acid derivative bioconjugate

Cancer remains a major health problem worldwide due to its high mortality rate. New therapeutic options highlight the importance of discovering new compounds that target the tumor microenvironment, interrupt angiogenesis and act selectively. The present study assessed the antitumor effect and investigated the mechanism of action of a rhodamine B-conjugated oleanolic acid derivative (RhodOA). Consequently, the compound was tested on different human tumor cell lines (A375 melanoma, A549 lung adenocarcinoma and MDA-MB-231 breast adenocarcinoma) and on a non-tumor cell line HaCaT human keratinocyte. RhodOA produced a dose-dependent decrease in tumor cell viability especially in the melanoma cells while affecting the keratinocytes less. In melanoma cells, RhodOA reduced cell migration and produced condensation of cell nuclei and of actin fibers. Furthermore, an impairment in melanoma cell mitochondrial function was observed, while the mitochondrial function of keratinocytes was left intact. In the in ovo chorioallantoic membrane model, RhodOA elicited antiangiogenic effect, without showing irritation effect on the membrane. The study provides information on the selective antitumor effect of the derivative and its ability to inhibit cellular respiration, therefore RhodOA can be classified as ‘MITOCAN’.

Ester and amide derivatives of rhodamine B exert cytotoxic effects on different human tumor cell lines

Three esters of rhodamine B (1–3) differing in their alkyl chain lengths as well as several rhodamine B amides (4–9) were synthesized in good yields and tested for their cytotoxicity in SRB assays employing several human tumor cell lines. The rhodamine B esters were unselective but showed cytotoxicity of as low as EC50 = 0.15 ± 0.02 µM. The rhodamine B amides were slightly less cytotoxic but showed good selectivity against MCF-7 and A2780 tumor cell lines. Especially a morpholinyl derivative 4 was ~20 time more cytotoxic for MCF-7 than for nonmalignant NIH 3T3 cells.

Natural products and phytochemical nanoformulations targeting mitochondria in oncotherapy: an updated review on resveratrol

Mitochondria are intracellular organelles with two distinct membranes, known as an outer mitochondrial membrane and inner cell membrane. Originally, mitochondria have been derived from bacteria. The main function of mitochondria is the production of ATP. However, this important organelle indirectly protects cells by consuming oxygen in the route of energy generation. It has been found that mitochondria are actively involved in the induction of the intrinsic pathways of apoptosis. So, there have been efforts to sustain mitochondrial homeostasis and inhibit its dysfunction. Notably, due to the potential role of mitochondria in the stimulation of apoptosis, this organelle is a promising target in cancer therapy. Resveratrol is a non-flavonoid polyphenol that exhibits significant pharmacological effects such as antioxidant, anti-diabetic, anti-inflammatory and anti-tumor. The anti-tumor activity of resveratrol may be a consequence of its effect on mitochondria. Multiple studies have investigated the relationship between resveratrol and mitochondria, and it has been demonstrated that resveratrol is able to significantly enhance the concentration of reactive oxygen species, leading to the mitochondrial dysfunction and consequently, apoptosis induction. A number of signaling pathways such as sirtuin and NF-κB may contribute to the mitochondrial-mediated apoptosis by resveratrol. Besides, resveratrol shifts cellular metabolism from glycolysis into mitochondrial respiration to induce cellular death in cancer cells. In the present review, we discuss the possible interactions between resveratrol and mitochondria, and its potential application in cancer therapy.

Enhanced Subcellular Trafficking of Resveratrol Using Mitochondriotropic Liposomes in Cancer Cells

Mitochondria are membrane-enclosed organelles present in most eukaryotic cells, described as “power houses of the cell”. The mitochondria can be a target for inducing cancer cell death and for developing strategies to bypass multi drug resistance (MDR) mechanisms. 4-Carboxybutyl triphenylphosphonium bromide-polyethylene glycol-distearoylphosphatidylethanolamine (TPP-DSPE-PEG) and dequalinium-polyethylene glycol-distearoylphosphatidylethanolamine (DQA-DSPE-PEG) were synthesized as mitochondriotropic molecules. Mitochondria-targeting liposomes carrying resveratrol were constructed by modifying the liposome’s surface with TPP-PEG or DQA-PEG, resulting in TLS (Res) and DLS (Res), respectively, with the aim to obtain longer blood circulation and enhanced permeability and retention (EPR). Both TLS (Res) and DLS (Res) showed dimensions of approximately 120 nm and a slightly positive zeta potential. The enhanced cellular uptake and selective accumulation of TLS (Res) and DLS (Res) into the mitochondria were demonstrated by behavioral observation of rhodamine-labeled TLS or DLS, using confocal microscopy, and by resveratrol quantification in the intracellular organelle, using LC–MS/MS. Furthermore, TLS (Res) and DLS (Res) induced cytotoxicity of cancer cells by generating reactive oxygen species (ROS) and by dissipating the mitochondrial membrane potential. Our results demonstrated that TLS (Res) and DLS (Res) could provide a potential strategy to treat cancers by mitochondrial targeting delivery of therapeutics and stimulation of the mitochondrial signaling pathway.

Docetaxel-Loaded Hyaluronic Acid-Cathepsin B-Cleavable-Peptide-Gold Nanoparticles for the Treatment of Cancer

Gold nanoparticles are commonly used for medical applications such as drug delivery and as therapeutic and diagnostic materials because of their unique properties. In this study, we prepared docetaxel (DTX)-loaded hyaluronic acid-cleavable-peptide-gold nanoparticles for the treatment of cancer by selectively delivering DTX into the tumor and, thus, enhancing the therapeutic effect of DTX; further, we determined synergistic effects of the nanoparticles using laser treatment. The DTX-loaded hyaluronic acid-cleavable-peptide-gold nanoparticles prepared in this study had an average size of 75 nm and negative surface charge. The nanoparticles revealed greater cytotoxicity and higher tumor suppression efficacy in tumor models than free DTX under near-infrared laser irradiation. Therefore, the nanoparticle formulation prepared in this study could be utilized for targeted drug delivery and in combination with other cancer therapies.

Triphenylphosphine-docetaxel conjugate-incorporated albumin nanoparticles for cancer treatment

Aim: The objective of this study was to develop a mitochondria-targeted anticancer drug, docetaxel (DTX), for chemotherapy. Materials & methods: The DTX was conjugated to 4-carboxybutyl triphenylphosphonium (TPP) to enhance mitochondrial targeting, and the TPP–DTX conjugate was further loaded into folate-cholesteryl albumin (FA-chol-BSA) nanoparticles (NPs) to improve its biocompatibility. Results & conclusion: In vitro studies showed that TPP–DTX and its NP primarily accumulated in the mitochondria; generated high reactive oxygen species, leading to mitochondrial disruption and cell apoptosis; and had a higher cytotoxicity against cancer cells. In vivo antitumor studies indicated that the NP significantly suppressed tumor growth compared with free drugs in xenograft tumor-bearing mice. Our results demonstrated that TPP–DTX@FA-chol-BSA NPs could be a promising mitochondria-targeted anticancer prodrug for chemotherapy.

Lipid-based DNA/siRNA transfection agents disrupt neuronal bioenergetics and mitophagy

A multitude of natural and artificial compounds have been recognized to modulate autophagy, providing direct or, through associated pathways, indirect entry points to activation and inhibition. While these pharmacological tools are extremely useful in the study of autophagy, their abundance also suggests the potential presence of unidentified autophagic modulators that may interfere with experimental designs if applied unknowingly. Here, we report unanticipated effects on autophagy and bioenergetics in neuronal progenitor cells (NPCs) incubated with the widely used lipid-based transfection reagent lipofectamine (LF), which induced mitochondria depolarization followed by disruption of electron transport. When NPCs were exposed to LF for 5 h followed by 24, 48, and 72 h in LF-free media, an immediate increase in mitochondrial ROS production and nitrotyrosine formation was observed. These events were accompanied by disrupted mitophagy (accumulation of dysfunctional and damaged mitochondria, and of LC3II and p62), in an mTOR- and AMPK-independent manner, and despite the increased mitochondrial PINK1 (PTEN-inducible kinase 1) localization. Evidence supported a role for a p53-mediated abrogation of parkin translocation and/or abrogation of membrane fusion between autophagosome and lysosomes. While most of the outcomes were LF-specific, only two were shared by OptiMEM exposure (with no serum and reduced glucose levels) albeit at lower extents. Taken together, our findings show that the use of transfection reagents requires critical evaluation with respect to consequences for overall cellular health, particularly in experiments designed to address autophagy-inducing effects and/or energy stress.

Mitochondria-Targeted Triphenylphosphonium-Based Compounds: Syntheses, Mechanisms of Action, and Therapeutic and Diagnostic Applications

Mitochondria are recognized as one of the most important targets for new drug design in cancer, cardiovascular, and neurological diseases. Currently, the most effective way to deliver drugs specifically to mitochondria is by covalent linking a lipophilic cation such as an alkyltriphenylphosphonium moiety to a pharmacophore of interest. Other delocalized lipophilic cations, such as rhodamine, natural and synthetic mitochondria-targeting peptides, and nanoparticle vehicles, have also been used for mitochondrial delivery of small molecules. Depending on the approach used, and the cell and mitochondrial membrane potentials, more than 1000-fold higher mitochondrial concentration can be achieved. Mitochondrial targeting has been developed to study mitochondrial physiology and dysfunction and the interaction between mitochondria and other subcellular organelles and for treatment of a variety of diseases such as neurodegeneration and cancer. In this Review, we discuss efforts to target small-molecule compounds to mitochondria for probing mitochondria function, as diagnostic tools and potential therapeutics. We describe the physicochemical basis for mitochondrial accumulation of lipophilic cations, synthetic chemistry strategies to target compounds to mitochondria, mitochondrial probes, and sensors, and examples of mitochondrial targeting of bioactive compounds. Finally, we review published attempts to apply mitochondria-targeted agents for the treatment of cancer and neurodegenerative diseases.

Rhodamine B conjugates of triterpenoic acids are cytotoxic mitocans even at nanomolar concentrations

Triterpenoic acids 1-6 exhibited very low or no cytotoxicity at all, but their corresponding 2,3-di-O-acetyl-piperazinyl amides 13-18 showed low EC₅₀ values for several human tumor cell lines. Their cytotoxicity, however, was also high for the non-malignant mouse fibroblasts NIH 3T3. A significant improvement was achieved by preparing the rhodamine B derivatives 19-24. While rhodamine B is not cytotoxic (up to a concentration of 30μM - cut-off of the assay), the triterpenoid piperazine-spacered rhodamine B derivatives were cytotoxic in nano-molar concentration. Compound 24 (a diacetylated maslinic acid derivative) was most toxic for several human tumor cell lines but less toxic for mouse fibroblasts NIH 3T3. Staining and double-staining experiments revealed 24 to act as a mitocan.

Novel fluorinated docetaxel analog for anti-hepatoma: Molecular docking and biological evaluation

N-De-tert-butoxycarbonyl-N-[2-(1,1,1-trifluoro-2-methyl)propyloxycarbonyl]-2-debenzoyl-2-(m-fluorobenzoyl)-docetaxel (4FDT), a novel fluorinated docetaxel analog, was evaluated for its anti-hepatoma effect and possible druggability. In molecular docking studies, 4FDT coincided with paclitaxel in a part of the nucleus. In in vitro studies, 4FDT demonstrated higher anti-hepatoma activity approximately 1.5 times greater than that of docetaxel. More interestingly, 4FDT had been determined to have better anticancer effects, even 90 times greater in patient-derived xenografts (PDX) liver cancer cell lines than sorafenib. In the in vivo studies, 4FDT could effectively reduce the growth rate of liver cancer H22 and HepG2 cells. Furthermore, in a preliminary study on the ex vivo distribution of 4FDT, 4FDT-IR783 was primarily concentrated in the liver 1h after injection, and most of it was metabolized from the liver in 24h. Finally, the acute toxicity test revealed fewer side effects for 4FDT (approximately 16% than docetaxel). The water solubility, which was 11 times greater than that of docetaxel, confirmed the good druggability of 4FDT. All of these results demonstrated 4FDT's great potential to be a candidate drug for liver cancer treatment.

Magnetic solid phase extraction using ionic liquid-coated core-shell magnetic nanoparticles followed by high-performance liquid chromatography for determination of Rhodamine B in food samples

Three hydrophobic ionic liquids (ILs) (1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6), 1-hexyl-3-methyl-imidazole hexafluoro-phosphate ([HMIM]PF6), and 1-octyl-3-methylimidazole hexafluorophosphate ([OMIM]PF6)) were used to coat Fe3O4@SiO2 nanoparticles (NPs) with core-shell structures to prepare magnetic solid phase extraction (MSPE) agents (Fe3O4@SiO2@IL). A novel method of MSPE coupled with high-performance liquid chromatography for the separation/analysis of Rhodamine B was then established. The results showed that Rhodamine B was adsorbed rapidly on Fe3O4@SiO2@[OMIM]PF6 and was released using ethanol. Under optimal conditions, the pre-concentration factor for the proposed method was 25. The linear range, limit of detection (LOD), correlation coefficient (R), and relative standard deviation (RSD) were found to be 0.50-150.00 μgL(-1), 0.08 μgL(-1), 0.9999, and 0.51% (n=3, c=10.00 μgL(-1)), respectively. The Fe3O4@SiO2 NPs could be re-used up to 10 times. The method was successfully applied to the determination of Rhodamine B in food samples.

Novel delivery approaches for cancer therapeutics

Currently, a majority of cancer treatment strategies are based on the removal of tumor mass mainly by surgery. Chemical and physical treatments such as chemo- and radiotherapies have also made a major contribution in inhibiting rapid growth of malignant cells. Furthermore, these approaches are often combined to enhance therapeutic indices. It is widely known that surgery, chemo- and radiotherapy also inhibit normal cells growth. In addition, these treatment modalities are associated with severe side effects and high toxicity which in turn lead to low quality of life. This review encompasses novel strategies for more effective chemotherapeutic delivery aiming to generate better prognosis. Currently, cancer treatment is a highly dynamic field and significant advances are being made in the development of novel cancer treatment strategies. In contrast to conventional cancer therapeutics, novel approaches such as ligand or receptor based targeting, triggered release, intracellular drug targeting, gene delivery, cancer stem cell therapy, magnetic drug targeting and ultrasound-mediated drug delivery, have added new modalities for cancer treatment. These approaches have led to selective detection of malignant cells leading to their eradication with minimal side effects. Lowering multi-drug resistance and involving influx transportation in targeted drug delivery to cancer cells can also contribute significantly in the therapeutic interventions in cancer.

Mitochondrial dysfunction in gliomas

Mitochondrial (mt) dysfunction in gliomas has been linked to abnormalities of mt energy metabolism, marked by a metabolic shift from oxidative phosphorylation to glycolysis ("Warburg effect"), disturbances in mt membrane potential regulation and apoptotic signaling, as well as to somatic mutations involving the Krebs cycle enzyme isocitrate dehydrogenase. Evolving biological concepts with potential therapeutic implications include interaction between microtubule proteins and mitochondria (mt) in the control of closure of voltage-dependent anion channels and in the regulation of mt dynamics and the mt-endoplasmic reticulum network. The cytoskeletal protein βIII-tubulin, which is overexpressed in malignant gliomas, has emerged as a prosurvival factor associated in part with mt and also as a marker of chemoresistance. Mt-targeted therapeutic strategies that are discussed include the following: (1) metabolic modulation with emphasis on dichloroacetate, a pyruvate dehydrogenase kinase inhibitor; (2) tumor cell death via apoptosis induced by tricyclic antidepressants, microtubule-modulating drugs, and small molecules or compounds capable of inflicting reactive oxygen species-dependent tumor cell death; and (3) pretreatment mt priming and mt-targeted prodrug cancer therapy.