Mitochondrial Targeting Capabilities Research Articles

Nanozyme-catalyzed oxygen self-supplying mitochondria-targeting nanoplatform for precise photodynamic therapy

Local hypoxia in tumors poses significant challenges to the effectiveness of oxygen-dependent photodynamic therapy (PDT). Herein, a versatile mitochondrial targeting and pH-responsive nanozyme platform (noted as Mito CPs-p) is developed for solving local hypoxia in tumors and enhancing the PDT efficiency. Mito CPs-p, which consists of carbon-dot-supported atomically dispersed platinum (CPs) with further surface modifications of triphenylphosphine (PPh3) and pH-responsive porphyrin polymers. The PDT of Mito CPs-p was activated in acidic tumor microenvironment and exposed platinum for catalyzing endogenous H2O2 decomposition to produce O2 at tumor sites, due to the hydrophobic-hydrophilic transition of pH-responsive porphyrin-containing polymers in Mito CPs-p from hydrophobic to hydrophilic, which can markedly enhance PDT efficiency. Besides, the rational integration of mitochondria-targeting will improve the bioavailability of reactive oxygen species and further strengthen the PDT efficiency. In vitro results indicated that Mito CPs-p has exhibited excellent mitochondrial targeting capability and the ROS yield of Mito CPs-p was dramatically amplified. In vivo data further revealed that the Mito CPs-p displayed superb therapeutic efficacy. Hence, the Mito CPs-p provides new insights for efficient PDT in hypoxia solid tumors.

A novel mitochondria-targeting DHODH inhibitor induces robust ferroptosis and alleviates immune suppression

Dihydroorotate dehydrogenase (DHODH)-mediated ferroptosis defense is a targetable vulnerability in cancer. Currently, only a few DHODH inhibitors have been utilized in clinical practice. To further enhance DHODH targeting, we introduced the mitochondrial targeting group triphenylphosphine (TPP) to brequinar (BRQ), a robust DHODH inhibitor, resulting in the creation of active molecule B2. This compound exhibits heightened anticancer activity, effectively inhibiting proliferation in various cancer cells, and restraining tumor growth in melanoma xenografts in mice. B2 achieves these effects by targeting DHODH, triggering the formation of reactive oxygen species (ROS), promoting mitochondrial lipid peroxidation, and inducing ferroptosis in B16F10 and A375 cells. Surprisingly, B2 significantly downregulates PD-L1 and alleviates immune suppression. Importantly, B2 exhibits no apparent adverse effects in mice. Collectively, these findings highlight that enhancing the mitochondrial targeting capability of the DHODH inhibitor is a promising therapeutic approach for melanoma treatment.

Study of transient absorption spectroscopy of a D-π-A structure aggregation-induced emission luminogen and its photodynamic therapy application.

Photodynamic therapy (PDT) represents an emerging and noninvasive modality that has gained clinical approval for the treatment of cancers, leveraging photosensitizers for optimal therapeutic efficacy. In this study, we synthesized a photosensitizer (denoted as DTCSPP) exhibiting a donor-π-acceptor (D-π-A) structural motif. The DTCSPP manifests aggregation-induced emission (AIE) characteristics, along with good biocompatibility and mitochondrial targeting capabilities attributed to its intrinsic charge and D-π-A architecture. The excited-state intramolecular charge transfer of DTCSPP was systematically investigated in both solution and aggregate states using femtosecond transient absorption spectroscopy (fs-TA). The fs-TA results revealed that DTCSPP exhibited a more rapid and facile excited-state molecular motion in the solution state compared to the aggregate state, implying the predominance of nonradiative decay in its photophysical processes within the solution. Given its ability to simultaneously generate type I and type II reactive oxygen species and induce ferroptosis and autophagy in cancer cells, DTCSPP demonstrates effectiveness in PDT at both cellular and in vivo levels. This study contributes a comprehensive understanding of the excited-state intramolecular charge transfer dynamics of charged D-π-A type AIE photosensitizers, shedding light on their potential application in PDT. The multifaceted capabilities of DTCSPP underscore its promise in advancing the field of anticancer therapeutics, providing valuable insights for the identification of anticancer targets and the development of novel drugs.

Fluorescent probes based on quinoline and naphthidine derivatives with NIR and AIE properties for real-time monitoring mitochondrial viscosity during mitophagy

As a special form of autophagy, mitophagy is a pivotal mechanism governing cellular metabolism and physiology. Viscosity monitoring is an important aspect for real-time visualization of the mitophagy process. Hence, the development of high-performance viscosity probes is crucial for investigating dynamic pathological processes related to mitophagy. This study presents the discovery of mitochondria near-infrared and aggregation-induced emission probes with neutral structure. Probes 1a-1b were connected quinoline/naphthidine malononitrile and coumarin units with a double bond, the absorption maxima were at 433–471 nm; emission maxima were at 605–720 nm with large Stokes shifts of 170–279 nm in solvents of different polarity. As the environmental viscosity increases from 0.89 cP to 856 cP, the fluorescence intensity of probe 1a and probe 1b is enhanced by 418-fold and 769-fold, respectively, which due to the restricted rotation and inhibited twisted intramolecular charge transfer in high viscosity systems. In addition to excellent NIR, hypotoxicity, and mitochondrial targeting capabilities, probes 1a-1b were successfully applied to detect changes in mitochondrial viscosity during starvation or rapamycin-induced mitophagy. These remarkable features make probes 1a-1b as promising candidates for investigating dynamic pathological processes related to mitophagy with significant potential for biological applications.

A cyanine derivative-based NIR fluorescent probe for hydrogen sulfide bioimaging and food spoilage monitoring

Hydrogen sulfide (H2S) is a vital gas signaling molecule that performs crucial physiological functions in biological systems, and it can also cause food safety problems. In this study, we developed a cyanine derivative-based mitochondrial-targeted near-infrared fluorescent probe PC-H2S for detecting H2S. When PC-H2S reacted with H2S, it reached maximum fluorescence intensity at 656 nm and detection limit as low as 34 nM, and exhibited strong chromogenic response from green to red for H2S. Moreover, PC-H2S could be utilized to identify H2S generated during food spoilage and thus monitored the process of food spoilage. More significantly, PC-H2S showed excellent mitochondrial targeting capabilities and endogenous/exogenous H2S imaging of living cells and zebrafish could be performed. As a result, this research provides an attractive method for detecting H2S in food and biological systems and has potential value in physiopathological research.

Therapy of mitochondria-targeted hybrid nanozymes for reactive oxygen species-induced diseases

The development of enzyme mimetics that clear excess mitochondrial reactive oxidative stress (ROS) could provide effective treatment for a wide variety of diseases. Herein, nanomaterials were used to create artificial hybrid nanozymes. These nanozymes are composed of metal nanoparticle cores that act as centers of enzymatic activity and modifications for mitochondrial targeting capabilities. The artificial nanozyme possesses both catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx)-like properties. In spite of low doses, it exhibits cytoprotective properties against ROS-mediated damage and significantly enhances therapeutic effects after acute spinal cord injury (SCI), acute colitis, collagen induced arthritis (CIA), and obesity. Moreover, this artificial nanozyme ensures biocompatibility. This study demonstrates good biocompatibility and protective properties of this artificial nanozyme, which will facilitate recovery from ROS-related diseases and lay the groundwork for future development of nanozyme.

Self-reported and self-facilitated theranostic oxygen nano-economizer for precise and hypoxia alleviation-potentiated photodynamic therapy.

Photodynamic therapy (PDT) has been extensively investigated for cancer treatment by virtue of singlet oxygen-induced oxidative damage to tumors. Nevertheless, the therapeutic efficiency of PDT is still limited by the low singlet oxygen yield attributed to the improper irradiation duration and the tumor hypoxic microenvironment. To tackle these challenges, we elaborately design a theranostic oxygen nano-economizer to self-report the optimal irradiation duration and alleviate tumor hypoxia simultaneously, which is engineered by fluorescent 9,10-anthracenyl bis (benzoic acid) (DPA)-MOF, tetrakis (4-carboxyphenyl) porphyrin (TCPP), triphenyl phosphine (TPP) and redox-responsive lipid-PEG (DSPE-SS-PEG2k). Upon laser irradiation, the fluorescence of DPA-MOF could be quenched, thereby self-reporting the optimal irradiation duration for sufficient PDT. The decoration of DSPE-SS-PEG2k and TPP endows the theranostic oxygen nano-economizer with a tumor-specific response and mitochondrial targeting capability, respectively. Notably, singlet oxygen generated from TCPP reduces oxygen consumption by disrupting the entire oxidative phosphorylation (OXPHOS) pathway in the mitochondria of tumor cells, further improving the level of singlet oxygen in a self-facilitated manner for hypoxia alleviation-potentiated PDT. As expected, such a self-reported and self-facilitated theranostic oxygen nano-economizer exhibits potent antitumor activity in the 4T1 tumor-bearing mouse model. This study offers a theranostic paradigm for precise and hypoxia alleviation-potentiated cancer therapy.

Tuning long-term mitochondrial imaging and photodynamic therapy capabilities through rational design of aggregation-induced emission luminogens

Many aggregation-induced emission luminogens (AIEgens) not only act as photosensitizers to generate cytotoxic reactive oxygen species under the irradiation of appropriate light, but also emit bright fluorescence for positioning and tracking, realizing image-guided photodynamic therapy. However, few AIEgens can achieve long-term near-infrared bioimaging, and the design of AIEgens rarely involves multi-faceted functional optimization and the combined use of different AIE groups. In this study, a series of low-toxic salicylaldehyde-based Schiff base AIEgens (NPy-AIE, NNPy-AIE, TPy-AIE and TTPy-AIE) are rational designed from multiple aspects to study structure-function relationships, which all exhibit excellent long-term bioimaging capability. Starting from NPy-AIE, its water solubility is enhanced by increasing the number of cations and constructing hydrophilic groups to obtain NNPy-AIE. Dimethylaniline groups of NPy-AIE are replaced with triphenylamine groups to acquire TPy-AIE with enhanced AIE activity. Thiophene groups are introduced in TPy-AIE to obtain TTPy-AIE with larger conjugation structure and electron donor-acceptor strength. The first two red-emitting AIEgens have better long-term mitochondrial targeting capability. NNPy-AIE has better water solubility and mitochondrial membrane potential detection capabilities. In particular, the latter two near-infrared emitting AIEgens can not only achieve long-term in vivo and in vitro near-infrared imaging, but also generate singlet oxygen under white light irradiation, which increases the level of intracellular reactive oxygen species and the proportion of apoptotic cells, showing potential as photosensitizers for image-guided photodynamic therapy. In vivo photodynamic therapy experiment of TTPy-AIE in 4T1 tumor-bearing mice has confirmed its excellent biocompatibility and photodynamic therapy ability.

Multipotent Poly(Tertiary Amine-Oxide) Micelles for Efficient Cancer Drug Delivery.

The cancer drug delivery process involves a series of biological barriers, which require the nanomedicine to exhibit different, even opposite properties for high therapeutic efficacy. The prevailing design philosophy, i.e., integrating these properties within one nanomedicine via on‐demand property transitions such as PEGylation/dePEGylation, complicates nanomedicines’ composition and thus impedes clinical translation. Here, polyzwitterionic micelles of poly(tertiary amine‐oxide)‐block‐poly(ε‐caprolactone) (PTAO‐PCL) amphiphiles that enable all the required functions are presented. The zwitterionic nature and unique cell membrane affinity confer the PTAO micelles long blood circulation, efficient tumor accumulation and penetration, and fast cellular internalization. The mitochondrial targeting capability allows drug delivery into the mitochondria to induce mitochondrial dysfunction and overcome tumor multidrug resistance. As a result, the PTAO/drug micelles exhibit potent anticancer efficacy. This simple yet multipotent carrier system holds great promise as a generic platform for potential clinical translation.

Cationization to boost both type I and type II ROS generation for photodynamic therapy

The pursuing of photosensitizers (PSs) with efficient reactive oxygen species (ROS) especially type I ROS generation in aggregate is always in high demand for photodynamic therapy (PDT) and photoimmunotherapy but remains to be a big challenge. Herein, we report a cationization molecular engineering strategy to boost both singlet oxygen and radical generation for PDT. Cationization could convert the neutral donor-acceptor (D-A) typed molecules with the dicyanoisophorone-triphenylamine core (DTPAN, DTPAPy) to their A-D-A′ typed cationic counterparts (DTPANPF6 and DTPAPyPF6). Our experiment and simulation results reveal that such cationization could enhance the aggregation-induced emission (AIE) feature, promote the intersystem crossing (ISC) processes, and increase the charge transfer and separation ability, all of which work collaboratively to promote the efficient generation of ROS especially hydroxyl and superoxide radicals in aggregates. Moreover, these cationic AIE PSs also possess specific cancer cell mitochondrial targeting capability, which could further promote the PDT efficacy both in vitro and in vivo. Therefore, we expect this delicate molecular design represents an attractive paradigm to guide the design of type I AIE PSs for the further development of PDT.

DNA topoisomerases as additional targets for anticancer monofunctional platinum(ii) complexes.

Topoisomerases are ubiquitous enzymes and important targets for DNA-oriented anticancer drugs. Two mitochondrion-targeted monofunctional platinum(ii) complexes, [Pt(ortho-PPh3CH2Py)(NH3)2Cl](NO3)2 (OPT) and [Pt(para-PPh3CH2Py)(NH3)2Cl](NO3)2 (PPT; PPh3 = triphenylphosphonium, Py = pyridine), show significant inhibition towards the activity of DNA topoisomerases in addition to their DNA binding and mitochondrial targeting capabilities. OPT exhibits strong cytotoxicity toward the human renal clear cell carcinoma 786-O and the murine prostate cancer RM-1 cell lines. The complex could bind to the minor groove of DNA, as well as DNA topoisomerases I and IIα, thereby acting as an inhibitor of topoisomerase I/IIα and causing DNA damage. The damage was evidenced by the enhanced expression of γ-H2AX, Chk1/2 phosphorylation, p53 and cell cycle arrest in the G2/M phase. In contrast, the inhibitory effect of PPT on DNA topoisomerases was largely limited to the isolated enzymes. The results demonstrate that the cellular inhibition of the complex towards the DNA topoisomerases positively correlated with its mitochondrial accumulation. Molecular docking provided more detailed structural insights into the interactions of OPT or PPT with DNA and topoisomerase I/IIα. The binding sites of OPT and PPT in topoisomerase-DNA complexes are different from each other. Aside from previously revealed DNA and mitochondrial targets, this study discovered new evidence that DNA topoisomerases may also serve as targets of monofunctional platinum(ii) complexes. For a multispecific platinum complex, strong DNA binding ability does not necessarily lead to potent cytotoxicity as other factors including the cell types, mitochondrial accumulation, and activity of DNA topoisomerases also affect the outcome of DNA damage.

Mitochondria-targeted ratiometric fluorescent imaging of cysteine.

As an indispensable biothiol, cysteine (Cys) plays a critical part in cellular redox homeostasis, and pathological and physiological processes. One of the main sources of reactive oxygen species (ROS) in human cells is the substrate end of the respiratory chain in the mitochondrial inner membrane. Therefore, it is valuable to develop probes targeting mitochondria to detect Cys. In this work, we designed a novel fluorescent probe, 2-(2-(6-(acryloyloxy) naphthalen-2-yl) vinyl)-3-ethylbenzothiazol-3-ium (ANET). The naphthyl benzothiazole is the fluorophore group and the acrylate moiety is the Cys response site to avoid the interference of homocysteine (Hcy) and glutathione (GSH). ANET combines multiple strengths for detecting Cys: targeting mitochondria, ratiometric fluorescence, high selectivity, and a large Stokes shift. After ANET reacted with Cys, the fluorescence signals changed from green (λem = 525 nm) to orange red (λem = 595 nm), and the detection limit was calculated to be 74 nM through a linear relationship between ratiometric fluorescence F595/F525 and Cys concentration. The imaging of Cys was confirmed in HepG2 cells.

Tuning the hydrophobicity of pyridinium-based probes to realize the mitochondria-targeted photodynamic therapy and mitophagy tracking

Targeting mitochondria and dynamically tracking mitophagy are profoundly important in the field of photodynamic therapy (PDT) which relies on the photosensitizers (PSs) under light irradiation. While simultaneously realizing the effective reactive oxygen species (ROS) generation, accurately mitochondrial targeting, and dynamic tracking in a single PS still is a challenging issue. In this context, a series of pyridinium-based cationic fluorogens with aggregation induced emission (AIE) has been developed for this issue. The hydrophobicity of these fluorogens can be finely tuned by modulating the length of the alkyl chains on pyridinium unit. The well-tuned hydrophobicity of TL8C with C8-alkyl chain gives rise to the specifically mitochondrial targeting capability of TL8C based on the appropriate synergistic effect of hydrophobic and electrostatic interaction. Meanwhile, TL8C can produce ROS in high efficiency. The excellent mitochondrial targeting and the effective ROS generation allow TL8C for the specifically mitochondria-targeted PDT as well as the real time monitoring of mitophagy.

Anionic Polymers Promote Mitochondrial Targeting of Delocalized Lipophilic Cations.

Mitochondria are therapeutic targets in many diseases including cancer, metabolic disorders, and neurodegenerative diseases. Therefore, strategies to deliver therapeutics of interest to mitochondria are important for therapeutic development. As delocalized lipophilic cations (DLCs) preferentially accumulate in mitochondria, DLC-conjugation has been utilized to facilitate therapeutic delivery systems with mitochondrial targeting capability. Here we report that upon DLC-conjugation, anionic polymers exhibit significantly improved mitochondrial targeting when compared to cationic polymers and charge-neutral polymers. Considering that the cell membrane generally bears a net negative charge, the observed phenomenon is unexpected. Notably, the DLC-conjugated anionic polymers circumvent endosomal entrapment. The rapid mitochondrial accumulation of DLC-conjugated anionic polymers is likely a membrane-potential-driven process, along with the involvement of the mitochondrial pyruvate carrier. Moreover, the structural variations on the side chain of DLC-conjugated anionic polymers do not compromise the overall mitochondrial targeting capability, widely extending the applicability of anionic macromolecules in therapeutic delivery systems.

A sequential targeting nanoplatform for anaplastic thyroid carcinoma theranostics

Effective accumulation of nanoparticles (NPs) in tumor regions is one of the major motivations in nanotechnology research and that the establishment of an efficient targeting nanoplatform for the treatment of malignant tumors is urgently needed for theranostic applications. In this study, we engineered multifunctional sequential targeting NPs for achieving synergistic antiangiogenic photothermal therapy (PTT) and multimodal imaging-guided diagnosis for anaplastic thyroid carcinoma (ATC) theranostics. Antibody bevacizumab with an affinity towards vascular endothelial growth factor (VEGF) on the tumor cell surface was conjugated onto the surface of polymer NPs for VEGF targeting and antiangiogenic therapy. Encapsulated IR825 was employed as a photothermal agent (PTA) with a mitochondrial targeting capability, which further cascades NPs into mitochondria to enhance hyperthermic efficiency in the ablation of tumor cells. Importantly, the combination of bevacizumab and IR825 in a single nanosystem achieved desirable accumulations of NPs and that sequential targeted PTT combined with antiangiogenesis significantly promoted the therapeutic efficiency in eradicating tumors by near-infrared (NIR) laser irradiation. Furthermore, these NPs are extraordinary contrast agents for photoacoustic, ultrasound and fluorescence imaging applications, providing multimodal imaging capabilities for therapeutic monitoring and a precise diagnosis. Therefore, this multifunctional nanoplatform provides a promising theranostic strategy for extremely malignant ATC. Statement of significanceAnaplastic thyroid carcinoma (ATC), with extremely aggressive behavior, lacks a satisfactory therapeutic method and a comprehensive early diagnostic strategy. Herein, we successfully synthesized a sequential targeting nanoplatform (IR825@Bev-PLGA-PFP NPs) with theranostic function, which specifically binds to VEGF on the tumor cell surface and further cascades into mitochondria to achieve effective accumulation of NPs in the tumor regions. As a result, it solves the urgent demand for ATC detection and therapy. By breaking the limitation of traditional target, such as low efficacy and frequent recurrence as the results of low accumulation, sequential targeting combined with synergistic antiangiogenic PTT completely eradicates tumors without any residual tissue and side effect. Therefore, this strategy paves a solid way for further investigation in the theranostic progressing of ATC.

Mitochondria-Targeted and Ultrasound-Activated Nanodroplets for Enhanced Deep-Penetration Sonodynamic Cancer Therapy.

Sonodynamic therapy (SDT), a promising alternative for cancer therapy, utilizes a sonosensitizer combined with ultrasound (US) irradiation to damage tumor cells/tissues for therapeutic purposes. The ability of sonosensitizers to specifically accumulate in tumor cells/tissues could greatly influence their therapeutic efficiency. In this work, we report the use of US-activated sonosensitizer (IR780)-based nanodroplets (IR780-NDs) for SDT, which provide numerous benefits for killing cancer cells compared with traditional methods. For instance, IR780-NDs showed effective surface-to-core diffusion both in vitro and in vivo. In the presence of US, the acoustic droplet vaporization (ADV) effect significantly assisted the conveyance of IR780-NDs from the circulatory system to tumor regions, and the acoustic wave force also increased the penetration depth within tumor tissues. Furthermore, IR780-NDs possesses mitochondrial targeting capabilities, which improves the precision and accuracy of SDT delivery. During the in vitro assessment, the overproduction of reactive oxygen species (ROS) was observed following mitochondrial targeting, which rendered cancer cells more susceptible to ROS-induced apoptosis. Additionally, IR780-ND is a suitable candidate for photoacoustic and fluorescence imaging and can also enhance US imaging because of the ADV-generated bubbles, which provides the potential for SDT guidance and monitoring. Therefore, with combined modalities, IR780-NDs can be a promising theranostics nanoplatform for cancer therapy.