Enhanced Photodynamic Cancer Treatment by Mitochondria-Targeting and Brominated Near-Infrared Fluorophores

Cyanine dyes in the mitochondria-targeting photodynamic and photothermal therapy

Mitochondrial dysregulation plays a significant role in the carcinogenesis. On the other hand, its destabilization strongly represses the viability and metastatic potential of cancer cells. Photodynamic and photothermal therapies (PDT and PTT) target mitochondria effectively, providing innovative and non-invasive anticancer therapeutic modalities. Cyanine dyes, with strong mitochondrial selectivity, show significant potential in enhancing PDT and PTT. The potential and limitations of cyanine dyes for mitochondrial PDT and PTT are discussed, along with their applications in combination therapies, theranostic techniques, and optimal delivery systems. Additionally, novel approaches for sonodynamic therapy using photoactive cyanine dyes are presented, highlighting advances in cancer treatment.

Totally Caged Type I Pro-Photosensitizer for Oxygen-Independent Synergistic Phototherapy of Hypoxic Tumors

Activatable type I photosensitizers are an effective way to overcome the insufficiency and imprecision of photodynamic therapy in the treatment of hypoxic tumors, however, the incompletely inhibited photoactivity of pro-photosensitizer and the limited oxidative phototoxicity of post-photosensitizer are major limitations. It is still a great challenge to address these issues using a single and facile design. Herein, a series of totally caged type I pro-photosensitizers (Pro-I-PSs) are rationally developed that are only activated in tumor hypoxic environment and combine two oxygen-independent therapeutic mechanisms under single-pulse laser irradiation to enhance the phototherapeutic efficacy. Specifically, five benzophenothiazine-based dyes modified with different nitroaromatic groups, BPN 1-5, are designed and explored as latent hypoxia-activatable Pro-I-PSs. By comparing their optical responses to nitroreductase (NTR), it is identified that the 2-methoxy-4-nitrophenyl decorated dye (BPN 2) is the optimal Pro-I-PSs, which can achieve NTR-activated background-free fluorescence/photoacoustic dual-modality tumor imaging. Furthermore, upon activation, BPN 2 can simultaneously produce an oxygen-independent photoacoustic cavitation effect and a photodynamic type I process at single-pulse laser irradiation. Detailed studies in vitro and in vivo indicated that BPN 2 can effectively induce cancer cell apoptosis through synergistic effects. This study provides promising potential for overcoming the pitfalls of hypoxic-tumor photodynamic therapy.

Activatable NIR Fluorescence Probe for Epinephrine Detection and Bioimaging Based on Anionic Heptamethine Cyanine

Epinephrine (EP) is an essential catecholamine in the human body. Currently, most EP detection methods are not suitable for in vivo detection due to material limitations. An organic small molecule fluorescent probe based on a chemical cascade reaction for the detection of EP was designed. Anionic heptamethine cyanine dye was selected as a fluorescent dye because of its NIR fluorescence emission with excellent biocompatibility. The secondary amine of EP nucleophilically attacks the carbonate of the probe with its stronger nucleophilicity and further undergoes intramolecular nucleophilic cyclization to release the fluorophore. Other substances containing only primary amines or no β-OH lack reaction competitiveness due to their weaker nucleophilicity or inability to undergo further cyclization. The fluorescence recovery of the probe was linearly related to the EP concentration of 2-75 μmol/L. The detection limit was 0.4 μmol/L. The recovery rate was 94.78-111.32%. Finally, we successfully achieved bioimaging of EP in living cells and EP analogue in nematodes.

A Light-Triggered J-Aggregation-Regulated Therapy Conversion: from Photodynamic/Photothermal Therapy to Long-Lasting Chemodynamic Therapy for Effective Tumor Ablation

Reactive oxygen species (ROS) have become an effective tool for tumor treatment. The combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT) takes advantage of various ROS and enhances therapeutic effects. However, the activation of CDT usually occurs before PDT, which hinders the sustained maintenance of hydroxyl radicals (⋅OH) and reduces the treatment efficiency. Herein, we present a light-triggered nano-system based on molecular aggregation regulation for converting cancer therapy from PDT/photothermal therapy (PTT) to a long-lasting CDT. The ordered J-aggregation enhances the photodynamic properties of the cyanine moiety while simultaneously suppressing the chemodynamic capabilities of the copper-porphyrin moiety. Upon light irradiation, Cu-PCy JNPs demonstrate strong photodynamic and photothermal effects. Meanwhile, light triggers a rapid degradation of the cyanine backbone, leading to the destruction of the J-aggregation. As a result, a long-lasting CDT is sequentially activated, and the sustained generation of ⋅OH is observed for up to 48 hours, causing potent cellular oxidative stress and apoptosis. Due to their excellent tumor accumulation, Cu-PCy JNPs exhibit effective in vivo tumor ablation through the converting therapy. This work provides a new approach for effectively prolonging the chemodynamic activity in ROS-based cancer therapy.

The Role of HSP90 and TRAP1 Targets on Treatment in Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is the predominant form of liver cancer and arises due to dysregulation of the cell cycle control machinery. Heat Shock Protein 90 (HSP90) and mitochondrial HSP90, also referred to as TRAP1 are important critical chaperone target receptors for early diagnosis and targeting HCC. Both HSP90 and TRAP1 expression was found to be higher in HCC patients. Hence, the importance of HSP90 and TRAP1 inhibitors mechanism and mitochondrial targeted delivery of those inhibitors function is widely studied. This review also focuses on importance of protein-protein interactions of HSP90 and TRAP1 targets and association of its interacting proteins in various pathways of HCC. To further elucidate the mechanism, systems biology approaches and computational biology approach studies are well explored in the association of inhibition of herbal plant molecules with HSP90 and its mitochondrial type in HCC.

Self-assembled nanodrug delivery systems for anti-cancer drugs from traditional Chinese medicine

Traditional Chinese medicine (TCM) is a combination of raw herbs and herbal extracts with a plethora of documented beneficial bioactivities, which has unique advantages in anti-tumor therapy, and many of its major bioactive molecules have been identified in recent years due to advances in chemical separation and structural analysis. However, the major chemical classes of plant-derived bioactive compounds frequently possess chemical properties, including poor water solubility, stability, and bioavailability, that limit their therapeutic application. Alternatively, natural small molecules (NSMs) containing these components possess modifiable groups, multiple action sites, hydrophobic side chains, and a rigid skeleton with self-assembly properties that can be exploited to construct self-assembled nanoparticles with therapeutic effects superior to their individual constituents. For instance, the construction of a self-assembled nanodrug delivery system can effectively overcome the strong hydrophobicity and poor in vivo stability of NSMs, thereby greatly improving their bioavailability and enhancing their anti-tumor efficacy. This review summarizes the self-assembly methods, mechanisms, and applications of a variety of NSMs, including terpenoids, flavonoids, alkaloids, polyphenols, and saponins, providing a theoretical basis for the subsequent research on NSMs and the development of SANDDS.

Elsinochrome A induces cell apoptosis and autophagy in photodynamic therapy

Elsinochrome A (EA) is a perylene quinone natural photosensitizer, photosensitizer under light excitation generates reactive oxygen species (ROS) to induce apoptosis, so can be used for treating tumors, that is so-called photodynamic therapy (PDT). However, the molecular mechanism, especially related to apoptosis and autophagy, is still unclear. In this study, we aimed to explore the mechanism of EA-PDT-induced B16 cells apoptosis and autophagy. The action of EA-PDT on mitochondrial permeability transition pore (MPTP), mitochondrial membrane potential (MMP) and the mitochondrial function were researched by fluorescence technique and Extracellular Flux Analyzer. Illumina sequencing, tandem mass tags Quantitative Proteomics and Western Blot studied the mechanism at the gene and protein levels. The results indicated that EA-PDT had excellent phototoxicity in vitro. EA could bind to the mitochondria. EA-PDT for 5 min caused MPTP opening, MMP decreasing and abnormal mitochondrial function with a concentration-dependent characteristic. EA-PDT resulted in an increase intracellular ROS and the number of autophagosomes. Caspase2, caspase9 and tnf were upregulated, and bcl2, prkn, atg2, atg9 and atg10 were downregulated. Our results indicated that EA-PDT induced cell apoptosis and autophagy through the mediation of ROS/Atg/Parkin. This study can provide enlightenment for exploring potential targets of drug development for the PDT of melanoma.

From Chemotherapy to Phototherapy - Changing the Therapeutic Action of a Metallo-Intercalating RuII -ReI Luminescent System by Switching its Sub-Cellular Location

The synthesis of a new heterodinuclear ReI RuII metallointercalator containing RuII (dppz) and ReI (dppn) moieties is reported. Cell-free studies reveal that the complex has similar photophysical properties to its homoleptic M(dppz) analogue and it also binds to DNA with a similar affinity. However, the newly reported complex has very different in-cell properties to its parent. In complete contrast to the homoleptic system, the RuII (dppz)/ReI (dppn) complex is not intrinsically cytotoxic but displays appreciable phototoxic, despite both complexes displaying very similar quantum yields for singlet oxygen sensitization. Optical microscopy suggests that the reason for these contrasting biological effects is that whereas the homoleptic complex localises in the nuclei of cells, the RuII (dppz)/ReI (dppn) complex preferentially accumulates in mitochondria. These observations illustrate how even small structural changes in metal based therapeutic leads can modulate their mechanism of action.

An X-ray activatable gold nanorod encapsulated liposome delivery system for mitochondria-targeted photodynamic therapy (PDT)

In this work, we developed a mitochondria-targeted nanomaterial for neoadjuvant X-ray-triggered photodynamic therapy of rectal cancer. Herein, we designed a biodegradable liposome incorporating a photosensitizer, verteporfin, to generate X-ray-induced reactive oxygen species, gold nanorods as radiation enhancers, and triphenylphosphonium as the mitochondrial targeting moiety. The average size of the nanocarrier was about 150 nm. Due to the synergetic effect between X-ray and a combination of verteporfin and gold nanorods, as well as precise site-targeted TPP-modified liposomal nanocarriers, our nanoconjugates generated sufficient cytotoxic singlet oxygen within the mitochondria under X-ray irradiation, triggering the loss of membrane potential and mitochondria-related apoptosis of cancer cells.

Biomimetic Nanovesicle with Mitochondria-Synthesized Sonosensitizer and Mitophagy Inhibition for Cancer Sono-Immunotherapy

Mitochondria are crucial for both sonodynamic therapy and antitumor immunity. However, how to accurately damage mitochondria and meanwhile prevent the mitophagy and immune checkpoint inhibition is still a great challenge. Herein, hexyl 5-aminolevulinate hydrochloride (HAL) and 3-methyladenine (3MA) are loaded into the tumor cell-derived microparticle (X-MP), which can direct the target delivery of the prepared HAL/3MA@X-MP to the tumor cells. HAL induces the confined biosynthesis and accumulation of sonosensitizer PpIX in mitochondria, leading to the localized generation of reactive oxygen species (ROS) upon ultrasound irradiation and, thus, the efficient mitochondrial damage. Meanwhile, 3MA not only inhibits mitophagy but also down-regulates the PD-L1 expression, promoting the immunogenic cell death (ICD) while blocking the immune checkpoint recognition. The smart synergism of precise mitochondrial damage, mitophagy inhibition and antitumor immunity results in potent therapeutic efficacy without obvious side effects.

Photodynamic Priming Overcomes Per- and Polyfluoroalkyl Substance (PFAS)-Induced Platinum Resistance in Ovarian Cancer†

Per- and polyfluoroalkyl substances (PFAS) are widespread environmental contaminants linked to adverse outcomes, including for female reproductive biology and related cancers. We recently reported, for the first time, that PFAS induce platinum resistance in ovarian cancer, potentially through altered mitochondrial function. Platinum resistance is a major barrier in the management of ovarian cancer, necessitating complementary therapeutic approaches. Photodynamic therapy (PDT) is a light-based treatment modality that reverses platinum resistance and synergizes with platinum-based chemotherapy. The present study is the first to demonstrate the ability of photodynamic priming (PDP), a low-dose, sub-cytotoxic variant of PDT, to overcome PFAS-induced platinum resistance. Comparative studies of PDP efficacy using either benzoporphyrin derivative (BPD) or 5-aminolevulinic acid-induced protoporphyrin IX (PpIX) were conducted in two human ovarian cancer cell lines (NIH:OVCAR-3 and Caov-3). BPD and PpIX are clinically approved photosensitizers that preferentially localize to, or are partly synthesized in, mitochondria. PDP overcomes carboplatin resistance in PFAS-exposed ovarian cancer cells, demonstrating the feasibility of this approach to target the deleterious effects of environmental contaminants. Decreased survival fraction in PDP + carboplatin treated cells was accompanied by decreased mitochondrial membrane potential, suggesting that PDP modulates the mitochondrial membrane, reducing membrane potential and re-sensitizing ovarian cancer cells to carboplatin.

Mitochondria-Targeting and Multiresponsive Nanoplatform Based on AIEgens for Synergistic Chemo-Photodynamic Therapy and Enhanced Immunotherapy

Although photodynamic therapy (PDT) has become an attractive strategy for cancer treatment, its clinical application still suffers from some limitations, including insufficient delivery of photosensitizers, hypoxic tumor environment, and the development of PDT resistance. To address these limitations, a new class of mitochondria-targeting and fluorinated polymer with aggregation-induced emission characteristics was fabricated to sensitize PDT and co-deliver chemotherapeutic drugs. The amphiphilic fluoropolymer was able to efficiently carry oxygen and SN-38 (the active metabolite of irinotecan) and self-assemble into multifunctional micellar nanoparticles (SN-38-TTCF@O₂ NPs). Upon internalization into tumor cells, these NPs could successfully escape lysosomes, selectively target mitochondria, efficiently produce reactive oxygen species (ROS) under light irradiation, and release drugs in response to ROS. In the HCT116 tumor xenograft model, they preferentially accumulated in tumor tissue and significantly alleviated tumor hypoxia, resulting in synergistic chemo-PDT efficacy without distinct toxicity. Furthermore, the nanoscale chemo-PDT induced immunogenic cell death, promoted the recruitment and activation of cytotoxic T lymphocytes, and ultimately augmented the anti-tumor efficacy of anti-PD-1 antibody in the murine CT26 tumor model. These results may provide novel insights into the development of efficient chemo-PDT nanomedicine to improve the outcome of immunotherapy.

Rapid photonic curing effects of xenon flash lamp on ITO-Ag-ITO multilayer electrodes for high throughput transparent electronics

High-throughput transparent and flexible electronics are essential technologies for next-generation displays, semiconductors, and wearable bio-medical applications. However, to manufacture a high-quality transparent and flexible electrode, conventional annealing processes generally require 5 min or more at a high temperature condition of 300 °C or higher. This high thermal budget condition is not only difficult to apply to general polymer-based flexible substrates, but also results in low-throughput. Here, we report a high-quality transparent electrode produced with an extremely low thermal budget using Xe-flash lamp rapid photonic curing. Photonic curing is an extremely short time (~ μs) process, making it possible to induce an annealing effect of over 800 °C. The photonic curing effect was optimized by selecting the appropriate power density, the irradiation energy of the Xe-flash lamp, and Ag layer thickness. Rapid photonic curing produced an ITO-Ag-ITO electrode with a low sheet resistance of 6.5 ohm/sq, with a high luminous transmittance of 92.34%. The low thermal budget characteristics of the rapid photonic curing technology make it suitable for high-quality transparent electronics and high-throughput processes such as roll-to-roll.

Enlarging the Stokes Shift by Weakening the π-Conjugation of Cyanines for High Signal-to-Noise Ratiometric Imaging

The signal-to-noise ratio (SNR) is one of the key features of a fluorescent probe and one that often defines its potential utility for in vivo labeling and analyte detection applications. Here, it is reported that introducing a pyridine group into traditional cyanine-7 dyes in an asymmetric manner provides a series of tunable NIR fluorescent dyes (Cy-Mu-7) characterized by enhanced Stokes shifts (≈230 nm) compared to the parent cyanine 7 dye (<25 nm). The observed Stokes shift increase is ascribed to symmetry breaking of the Cy-Mu-7 core and a reduction in the extent of conjugation. The fluorescence signals of the Cy-Mu-7 dyes are enhanced upon confinement within the hydrophobic cavity of albumin or via spontaneous encapsulation within micelles in aqueous media. Utilizing the Cy-Mu-7, ultra-fast in vivo kidney labeling in mice is realized, and it is found that the liver injury will aggravate the burden of kidney by monitoring the fluorescence intensity ratio of kidney to liver. In addition, Cy-Mu-7 could be used as efficient chemiluminescence resonance energy transfer acceptor for the reaction between H₂ O₂ and bisoxalate. The potential utility of Cy-Mu-7 is illustrated via direct monitoring fluctuations in endogenous H₂ O₂ levels in a mouse model to mimic emergency room trauma.

A mitochondria-anchored supramolecular photosensitizer as a pyroptosis inducer for potent photodynamic therapy and enhanced antitumor immunity

BACKGROUND

The discovery of a potent photosensitizer with desirable immunogenic cell death (ICD) ability can prominently enhance antitumor immunity in photodynamic therapy (PDT). However, majority of commercially-available photosensitizers suffer from serious aggregation and fail to elicit sufficient ICD. Pyroptosis as a newly identified pattern for potent ICD generation is rarely disclosed in reported photosensitizers. In addition, the photosensitizer with excellent mitochondria-anchored ability evokes prominent mitochondria oxidative stress, and consequently induces ICD.

RESULTS

Herein, a novel supramolecular photosensitizer LDH@ZnPc is reported, without complicated preparation, but reveals desirable pyroptosis-triggered ability with mitochondria anchoring feature. LDH@ZnPc is obtained through isolation of ZnPc using positive charged layered double hydroxides (LDH), and excellent mitochondria-anchored ability is achieved. More importantly, LDH@ZnPc-mediated PDT can effectively initiate gasdermin D (GSDMD)-dependent pyroptosis of tumor cells. In vitro and in vivo results verify robust ICD ability and potent tumor inhibition efficacy, and antitumor immunity towards distant tumor inhibition.

CONCLUSIONS

This study reveals that LDH@ZnPc can act as an excellent pyroptosis inducer with simultaneous mitochondria anchoring ability for enhancing photodynamic therapy and boosting antitumor immunity.

Site-selected thionated benzothioxanthene chromophores as heavy-atom-free small-molecule photosensitizers for photodynamic therapy

Photodynamic therapy is a clinically approved anticancer modality that employs a light-activated agent (photosensitizer) to generate cytotoxic reactive oxygen species (ROS). There is therefore a growing interest for developing innovative photosensitizing agents with enhanced phototherapeutic performances. Herein, we report on a rational design synthetic procedure that converts the ultrabright benzothioxanthene imide (BTI) dye into three heavy-atom-free thionated compounds featuring close-to-unit singlet oxygen quantum yields. In contrast to the BTI, these thionated analogs display an almost fully quenched fluorescence emission, in agreement with the formation of highly populated triplet states. Indeed, the sequential thionation on the BTI scaffold induces torsion of its skeleton reducing the singlet-triplet energy gaps and enhancing the spin-orbit coupling. These potential PSs show potent cancer-cell ablation under light irradiation while remaining non-toxic under dark condition owing to a photo-cytotoxic mechanism that we believe simultaneously involves singlet oxygen and superoxide species, which could be both characterized in vitro. Our study demonstrates that this simple site-selected thionated platform is an effective strategy to convert conventional carbonyl-containing fluorophores into phototherapeutic agents for anticancer PDT.

NIR-II Emissive Ru(II) Metallacycle Assisting Fluorescence Imaging and Cancer Therapy

Despite the success of emissive Ruthenium (Ru) agents in biomedicine, problems such as the visible-light excitation/emission and single chemo- or phototherapy modality still hamper their applications in deep-tissue imaging and efficient cancer therapy. Herein, an second nearinfrared window (NIR-II) emissive Ru(II) metallacycle (Ru1000, λ_em  = 1000 nm) via coordination-driven self-assembly is reported, which holds remarkable deep-tissue imaging capability (≈6 mm) and satisfactory chemo-phototherapeutic performance. In vitro results indicate Ru1000 displays promising cellular uptake, good cancer-cell selectivity, attractive anti-metastasis properties, and remarkable anticancer activity against various cancer cells, including cisplatin-resistant A549 cells (IC₅₀  = 3.4 × 10^-6  m vs 92.8 × 10^-6  m for cisplatin). The antitumor mechanism could be attributed to Ru1000-induced lysosomal membrane damage and mitochondrial-mediated apoptotic cell death. Furthermore, Ru1000 also allows the high-performance in vivo NIR-II fluorescence imaging-guided chemo-phototherapy against A549 tumors. This work may provide a paradigm for the development of long-wavelength emissive metallacycle-based agents for future biomedicine.

A mitochondria-targeting lipid-small molecule hybrid nanoparticle for imaging and therapy in an orthotopic glioma model

Hybrid lipid‒nanoparticle complexes have shown attractive characteristics as drug carriers due to their integrated advantages from liposomes and nanoparticles. Here we developed a kind of lipid-small molecule hybrid nanoparticles (LPHNPs) for imaging and treatment in an orthotopic glioma model. LPHNPs were prepared by engineering the co-assembly of lipids and an amphiphilic pheophorbide a‒quinolinium conjugate (PQC), a mitochondria-targeting small molecule. Compared with the pure nanofiber self-assembled by PQC, LPHNPs not only preserve the comparable antiproliferative potency, but also possess a spherical nanostructure that allows the PQC molecules to be administrated through intravenous injection. Also, this co-assembly remarkably improved the drug-loading capacity and formulation stability against the physical encapsulation using conventional liposomes. By integrating the advantages from liposome and PQC molecule, LPHNPs have minimal system toxicity, enhanced potency of photodynamic therapy (PDT) and visualization capacities of drug biodistribution and tumor imaging. The hybrid nanoparticle demonstrates excellent curative effects to significantly prolong the survival of mice with the orthotopic glioma. The unique co-assembly of lipid and small molecule provides new potential for constructing new liposome-derived nanoformulations and improving cancer treatment.

Triarylboron-Based High Photosensitive Probes for Apoptosis Detection, Tumor-Targeted Imaging, and Selectively Inducing Apoptosis of Tumor Cells by Photodynamics

Herein, a series of triarylboron-based fluorescent probes were developed for distinguishing apoptosis from living cells and even necrosis. They also demonstrate high photosensitivity because they can produce detectable reactive oxygen species (ROS) under an ultra-low light power density (1.5 mW/cm²). By changing the peripheral groups to regulate the performance, we identified a multifunctional probe, TAB-6-amyl, which can be used not only for selectively imaging apoptosis but also for the targeted imaging of SKOV-3 cells in vitro and in vivo. It could further specifically induce the apoptosis of SKOV-3 cells under light irradiation. During the study, we also found that TAB-6-amyl can cross the blood-brain barrier (BBB). Therefore, another probe based on this kind of structure, TAB-5-M-1-cRGD, was constructed for the targeted imaging of brain glioma cells and inducing their apoptosis. This study offers some promising tools for apoptosis detection and tumor photodynamic therapy (PDT).

Мitochondrial therapy of melanoma B16/F10, pathophysiological parameters of tumor regression

The aim is to evaluate the pathophysiological parameters of the efficacy of liver mitochondrial transplantation in animals with B16/F10 melanoma. Materials and methods. In our experiment we used female and male mice of BALB/c Nude strain (n=28). Experimental groups were as follows: the reference group (n=14) with B16/ F10 melanoma; the main group (n=14) with B16/F10 melanoma + mitochondrial therapy (MC therapy). Statistical analysis of results was carried out with the Statistica 10.0 software. Results. The subcutaneous tumor in the mice of both sexes became detectable on day 5 from the time of the tumor inoculation, and the regressive effect produced by MC therapy was recorded in the males beginning with day 8 of the tumor growth. At the end of the experiment, on day 22, the difference in the average volumes of the tumor node was reported to be 3.2 times, i.e. a significant inhibition of the tumor growth in the group of the males with MC therapy was revealed. In the females on day 5 of the tumor growth, differences in the volume of the tumor focus between the reference group and the group with MC therapy were not recorded, however, a statistically significant difference was found in the sex-related comparison of the groups of the animals with MC therapy. It was determined that in the females with MC therapy, the area of the tumor spot during that period (5 days) was 1.4 times (p<0.05) less than that in the corresponding group of the males. On day 8, in the females completed MC therapy, the tumor has not yet concentrated into a solid structure, but remained as a flat tumor entity, and only by day 12 the tumor has formed from a flat structure into a volumetric tumor type. As a result, by the end of the experiment, on day 22, smaller volumes of the tumor nodes remained in the group of females treated with MC therapy, and the difference with the reference group was 2.7 times (p<0.05). Conclusion. Thus, within the framework of the experiment, it has been found that the application of mitochondrial therapy using allogeneic liver mitochondria in the BALB/c Nude mice with B16/F10 melanoma retards the tumor growth in the mice of both sexes.

Polymethine dyes for PDT: recent advances and perspectives to drive future applications

It has been proved that the effectiveness of photodynamic therapy (PDT) is closely related to the intrinsic features of the photosensitizer (PS). Over the recent years, several efforts have been devoted to the discovery of novel and more efficient photosensitizers showing higher efficacy and lower side effects. In this context, squaraine and cyanine dyes have been reported to potentially overcome the drawbacks related to the traditional PSs. In fact, squaraines and cyanines are characterized by sharp and intense absorption bands and narrow emission bands with high extinction coefficients typically in the red and near-infrared region, good photo and thermal stability and a strong fluorescent emission in organic solvents. In addition, biocompatibility and low toxicity make them suitable for biological applications. Despite these interesting intrinsic features, their chemical instability and self-aggregation properties in biological media still limit their use in PDT. To overcome these drawbacks, the self-assembly and incorporation into smart nanoparticle systems are forwarded promising approaches that can control their physicochemical properties, providing rational solutions for the limitation of free dye administration in the PDT application. The present review summarizes the latest advances in squaraine and cyanine dyes for PDT application, analyzing the different strategies, i.e.the self-assembly and the incorporation into nanoparticles, to further enhance their photochemical properties and therapeutic potential. The in vivo assessments are still limited, thus further delaying their effective application in PDT.

Heptamethine Cyanine–Based Application for Cancer Theranostics

Cancer is the most common life-threatening malignant disease. The future of personalized cancer treatments relies on the development of functional agents that have tumor-targeted anticancer activities and can be detected in tumors through imaging. Cyanines, especially heptamethine cyanine (Cy7), have prospective application because of their excellent tumor-targeting capacity, high quantum yield, low tissue autofluorescence, long absorption wavelength, and low background interference. In this review, the application of Cy7 and its derivatives in tumors is comprehensively explored. Cy7 is enormously acknowledged in the field of non-invasive therapy that can “detect” and “kill” tumor cells via near-infrared fluorescence (NIRF) imaging, photothermal therapy (PTT), and photodynamic therapy (PDT). Furthermore, Cy7 is more available and has excellent properties in cancer theranostics by the presence of multifunctional nanoparticles via fulfilling multimodal imaging and combination therapy simultaneously. This review provides a comprehensive scope of Cy7’s application for cancer NIRF imaging, phototherapy, nanoprobe-based combination therapy in recent years. A deeper understanding of the application of imaging and treatment underlying Cy7 in cancer may provide new strategies for drug development based on cyanine. Thus, the review will lead the way to new types with optical properties and practical transformation to clinical practice.

Conditionally Activatable Photoredox Catalysis in Living Systems

The transformational effect of photoredox catalytic chemistries has inspired new opportunities, enabling us to interrogate nature in ways that are not possible otherwise and to unveil new biotechnologies in therapy and diagnosis. However, the deployment of artificial photoredox catalysis in living systems remains challenging, mired by the off-target risk and safety concerns of photocatalyst toxicity. Here, we present an appealing approach, namely conditionally activatable photoredox catalysis (ConAPC), and as a proof of concept design the first ConAPC architecture (Se-NO2) based upon classic self-immolative chemistry, in which the inherent photocatalytic properties can be temporarily caged while the species becomes active only at the tumor sites via sensing to specific biomarkers. Such a masking strategy allows a spatial-temporal control of photoresponsivity in vitro and in vivo. In particular, for ConAPC design, a new biologically benign metal-free photocatalyst (Se-NH2), which is able to initiate NIR photoredox catalysis to manipulate the cellular electron pool in an O2-independent mechanism of action, is identified. With this unique strategy, potent tumor-specific targeting photocatalytic eradication (TGI: 95%) is obtained in a mouse model. Impressively, favorable features such as high-resolution tumor recognition (SBR: 33.6) and excellent biocompatibility and safety are also achieved. This work therefore offers a new possibility for chemists to leverage artificial photocatalytic reactions toward the development of facile and intelligent photocatalytic theranostics.

Mitochondria-Targeted Nanocarriers Promote Highly Efficient Cancer Therapy: A Review

Mitochondria are the primary organelles which can produce adenosine triphosphate (ATP). They play vital roles in maintaining normal functions. They also regulated apoptotic pathways of cancer cells. Given that, designing therapeutic agents that precisely target mitochondria is of great importance for cancer treatment. Nanocarriers can combine the mitochondria with other therapeutic modalities in cancer treatment, thus showing great potential to cancer therapy in the past few years. Herein, we summarized lipophilic cation- and peptide-based nanosystems for mitochondria targeting. This review described how mitochondria-targeted nanocarriers promoted highly efficient cancer treatment in photodynamic therapy (PDT), chemotherapy, combined immunotherapy, and sonodynamic therapy (SDT). We further discussed mitochondria-targeted nanocarriers’ major challenges and future prospects in clinical cancer treatment.

Photosensitizer-based metal-organic frameworks for highly effective photodynamic therapy

Photodynamic therapy (PDT) uses a photosensitizer, molecular oxygen, and visible light as an alternative clinical protocol against located malignant tumors and other diseases. More recently, PDT has been combined to immunotherapy as a promising option to treat metastatic cancer. However, previous generations of photosensitizers (PSs) revealed clinical difficulties such as long-term skin photosensitivity (first generation), the need for drug delivery vehicles (second generation), and intracellular self-aggregation (third generation), which have generated a somewhat confusing scenario in PDT approaches and evolution. Recently, metal-organic frameworks (MOFs) with exceptionally high PS loading as a building unit of MOF framework have emerged as fourth-generation PS and presented outstanding outcomes under pre-clinical studies. For PS-based MOFs, the inorganic building unit (metal ions/clusters) plays an important role as a coadjuvant in PDT to alleviate hypoxia, to decrease antioxidant species, to yield ROS, or to act as a contrast agent for imaging-guided therapy. In this review, we intend to carry out a broad update on the recent history and the characteristics of PS-based MOFs from basic chemistry to the structure relationship with biological application in PDT. The details and variables that result in different photophysics, size, and morphology, are discussed. Also, we present an overview of the achievements on the pre-clinical assays in combination with other strategies, including alleviating hypoxia in solid tumors, chemotherapy, and the most recent immunotherapy for cancer.

Photodynamic Therapy-Mediated Immune Responses in Three-Dimensional Tumor Models

Photodynamic therapy (PDT) is a promising non-invasive phototherapeutic approach for cancer therapy that can eliminate local tumor cells and produce systemic antitumor immune responses. In recent years, significant efforts have been made in developing strategies to further investigate the immune mechanisms triggered by PDT. The majority of in vitro experimental models still rely on the two-dimensional (2D) cell cultures that do not mimic a three-dimensional (3D) cellular environment in the human body, such as cellular heterogeneity, nutrient gradient, growth mechanisms, and the interaction between cells as well as the extracellular matrix (ECM) and therapeutic resistance to anticancer treatments. In addition, in vivo animal studies are highly expensive and time consuming, which may also show physiological discrepancies between animals and humans. In this sense, there is growing interest in the utilization of 3D tumor models, since they precisely mimic different features of solid tumors. This review summarizes the characteristics and techniques for 3D tumor model generation. Furthermore, we provide an overview of innate and adaptive immune responses induced by PDT in several in vitro and in vivo tumor models. Future perspectives are highlighted for further enhancing PDT immune responses as well as ideal experimental models for antitumor immune response studies.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Hierarchical nanoclusters with programmed disassembly for mitochondria-targeted tumor therapy with MR imaging

Mitochondria are crucial metabolic organelles involved in tumorigenesis and tumor progression, and the induction of abnormal mitochondria metabolism is recognized as a strategy with strong potential for the exploration of advanced tumor therapeutics. Herein, hierarchical manganese silicate nanoclusters modified with triphenylphosphonium (MSNAs-TPP) were designed and synthesized for mitochondria-targeted tumor theranostics. The as-prepared MSNAs-TPP retains considerable dimensional and structural stability in the neutral physiological environment, favoring its accumulation at the tumor site. More interestingly, MSNAs-TPP may disassemble in a responsive manner to an acidic tumor microenvironment into ultrasmall manganese silicate nanocapsules (∼6 nm), enabling deep tumor penetration and mitochondria targeting. When reaching the mitochondria, the nanocapsules effectively deplete mitochondrial glutathione (GSH), and simultaneously release catalytic Mn²⁺ ions to induce amplified oxidative stress in the structure with the enriched CO₂ and H₂O₂ from mitochondria metabolism. As a result, MSNAs-TPP presents considerable antitumor effect without a clear side effect, both in vitro and in vivo. The study may provide an alternative concept in the development of intelligent nanotherapeutics for tumor treatment with high efficacy.

Mito-Bomb: Targeting Mitochondria for Cancer Therapy

Cancer has been one of the most common life-threatening diseases for a long time. Traditional cancer therapies such as surgery, chemotherapy (CT), and radiotherapy (RT) have limited effects due to drug resistance, unsatisfactory treatment efficiency, and side effects. In recent years, photodynamic therapy (PDT), photothermal therapy (PTT), and chemodynamic therapy (CDT) have been utilized for cancer treatment owing to their high selectivity, minor resistance, and minimal toxicity. Accumulating evidence has demonstrated that selective delivery of drugs to specific subcellular organelles can significantly enhance the efficiency of cancer therapy. Mitochondria-targeting therapeutic strategies are promising for cancer therapy, which is attributed to the essential role of mitochondria in the regulation of cancer cell apoptosis, metabolism, and more vulnerable to hyperthermia and oxidative damage. Herein, the rational design, functionalization, and applications of diverse mitochondria-targeting units, involving organic phosphine/sulfur salts, quaternary ammonium (QA) salts, peptides, transition-metal complexes, guanidinium or bisguanidinium, as well as mitochondria-targeting cancer therapies including PDT, PTT, CDT, and others are summarized. This review aims to furnish researchers with deep insights and hints in the design and applications of novel mitochondria-targeting agents for cancer therapy.

A Simple Route toward Next-Generation Thiobase-Based Photosensitizers for Cancer Theranostics

Sulfur-substituted biocompatible carbonyl fluorophores have been recognized as effective heavy-atom-free photosensitizers (PSs) for cancer therapy due to their remarkable phototherapeutic properties. However, guidelines on their molecular design are still a substantial challenge. Most of the existing thiocarbonyl-based PSs are nonemissive in both the solution and restricted states, which hinders their further biomedical applications. Herein, we report the interesting finding that sulfur-substituted coumarins exhibit an uncommon phenomenon, aggregation-induced emission. More intriguingly, we also found that the introduction of a strong electron-accepting trifluoromethyl group is crucial to facilitate the mitochondrial-targeting ability of neutral coumarin fluorophores. The resulting CMS-2 PS displayed selective imaging of mitochondria and exhibited much higher photodynamic therapy efficiency toward cancer cells than that of the commercial PS erythrosine B. This work provides deep insight into the molecular design of heavy-atom-free thiobase-based PSs and simultaneously offers a great opportunity to develop novel mitochondrial-targeting fluorescent indicators with neutral bioinspired platforms.

Ultrasound (US)-activated redox dyshomeostasis therapy reinforced by immunogenic cell death (ICD) through a mitochondrial targeting liposomal nanosystem

Introduction: An imbalance in redox homeostasis consistently inhibits tumor cell proliferation and further causes tumor regression. Thus, synchronous glutaminolysis inhibition and intracellular reactive oxygen (ROS) accumulation cause severe redox dyshomeostasis, which may potentially become a new therapeutic strategy to effectively combat cancer. Methods: Mitochondrial-targeting liposomal nanoparticles (abbreviated MLipRIR NPs) are synthesized by the encapsulation of R162 (inhibitor of glutamate dehydrogenase 1 [GDH1]) and IR780 (a hydrophobic sonosensitizer) within the lipid bilayer, which are exploited for ultrasound (US)-activated tumor dyshomeostasis therapy reinforced by immunogenic cell death (ICD). Results: R162 released from MLipRIR NPs disrupts the glutaminolysis pathway in mitochondria, resulting in downregulated enzymatic activity of glutathione peroxidase (GPx). In addition, loaded IR780 can generate high levels of ROS under US irradiation, which not only interrupts mitochondrial respiration to induce apoptosis but also consumes local glutathione (GSH). GSH depletion accompanied by GPx deactivation causes severe ferroptosis of tumor cells through the accumulation of lipid peroxides. Such intracellular redox dyshomeostasis effectively triggers immunogenic cell death (ICD), which can activate antitumor immunity for the suppression of both primary and distant tumors with the aid of immune checkpoint blockade. Conclusions: Taking advantage of multimodal imaging for therapy guidance, this nanoplatform may potentiate systemic tumor eradication with high certainty. Taken together, this state-of-the-art paradigm may provide useful insights for cancer management by disrupting redox homeostasis.

An Approach to Developing Cyanines with Simultaneous Intersystem Crossing Enhancement and Excited-State Lifetime Elongation for Photodynamic Antitumor Metastasis

Heavy-atom-based photosensitizers usually exhibit shortened triplet-state lifetimes, which is not ideal for hypoxic tumor photodynamic therapy. Although several heavy-atom-free photosensitizers possess long triplet-state lifetimes, the clinical applicability is limited by their short excitation wavelengths, poor photon capture abilities, and intrinsically hydrophobic structures. Herein we developed a novel NIR heavy-atom-free photosensitizer design strategy by introducing sterically bulky and electron-rich moieties at the meso position of the pentamethine cyanine (Cy5) skeleton, which simultaneously enhanced intersystem crossing (ISC) and prolonged excited-state lifetime. We found that the ¹O₂ generation ability is directly correlated to the electron-donating ability of the meso substituent in cyanine, and the excited-state lifetime was simultaneously much elongated when the substituents were anthracene derivatives substituted at the 9-position. Our star compound, ANOMe-Cy5, exhibits intense NIR absorption, the highest ¹O₂ quantum yield (4.48-fold higher than Cy5), the longest triplet-state lifetime (9.80-fold longer than Cy5), and lossless emission intensity (nearly no change compared with Cy5). Such excellent photophysical properties coupled with its inherently cationic and hydrophilic nature enable the photosensitizer to realize photoablation of solid tumor and antitumor lung metastasis. This study highlights the design of a new generation of NIR photosensitizers for imaging-guided photodynamic cancer treatment.

Hyaluronic Acid Coated Liposomes Co-Delivery of Natural Cyclic Peptide RA-XII and Mitochondrial Targeted Photosensitizer for Highly Selective Precise Combined Treatment of Colon Cancer

Background

Natural cyclopeptide RA-XII, isolated from Rubia yunnanensis, is a promising chemotherapeutic agent for colon cancer. The photosensitizer protoporphyrin-IX attached with triphenylphosphonium (TPP) could possess mitochondria targeting capacity and exert photodynamic therapy (PDT) by inducing oxidizing damage to the mitochondria and cell apoptosis eventually. In this work, pH-sensitive liposomes were constructed to simultaneously deliver RA-XII as a chemotherapeutic drug and modified porphyrin as a mitochondria-targeting photosensitizer to treat colon cancer, and verified its mechanism of action and antitumor therapeutic efficacy.

Methods

The colon cancer targeting liposome nanoparticle RA/TPPP-Lip was synthesized using thin film hydration. The therapeutic effect and targeting ability of RA/TPPP-Lip was investigated in vitro. And use HCT116 cell allogeneic subcutaneous transplantation tumor model to investigate the anti-tumor and targeting effects of RA/TPPP-Lip in vivo.

Results

RA/TPPP-Lip gained the targeting ability through surface-modified HA to increase the accumulation of RA-XII and TPPP in colon cancer cells. A series of in vitro experimental results showed that TPPP produced cytotoxic ROS under laser irradiation to directly damage cell mitochondria and played a combined role with RA-XII, making RA/TPPP-Lip the best colon cancer cell growth inhibitory effect. Furthermore, in vivo antitumor experiments showed that the RA/TPPP-Lip substantially accumulated at the tumor site and efficiently repressed tumor growth in nude mice.

Conclusion

We have successfully designed a new cancer-targeted nanomedicine platform (RA/TPPP-Lip) for the collaborative treatment of colon cancer, which can achieve the targeted continuous release of multiple therapeutic drugs. This work provides a new strategy for precise combination therapy, which may promote the further development of collaborative cancer treatment platforms.

Targeting the tumor microenvironment with amphiphilic near-infrared cyanine nanoparticles for potentiated photothermal immunotherapy

Despite the potential of photothermal therapy (PTT) for cancer treatments, PTT alone has limitations in treating metastatic tumors and preventing tumor recurrence, highlighting the need to combine PTT with immunotherapy. This study reports tumor microenvironment (TME)-targeting, near-infrared (NIR) dye derivative-based nanomedicine for effective combined PTT-immunotherapy. Amphiphilic NIR dye cyanine derivatives are used not only for constructing the nanoparticle mass, but also for creating a stable complex with CpG adjuvant; a peptide specific to fibronectin extra domain B (APT_EDB) is also introduced as a TME-targeting ligand, yielding the TME-targeting nanomedicine, APT_EDB-cyNP@CpG. APT_EDB-cyNP@CpG shows cancer-targeting ability in EDB-overexpressing CT26 colon tumor-bearing mice. When combined with laser irradiation, it induces immunogenic cell death (ICD) and subsequently leads to significant increase in CD8⁺ T cell population in the tumor, resulting in greater antitumor therapeutic efficacy than does cyNP@CpG lacking the TME-targeting ligand. Moreover, the combination of APT_EDB-cyNP@CpG-based PTT and an immune checkpoint blockade (ICB) antibody leads to remarkable antitumor efficacy against the laser-irradiated primary tumor as well as distant tumor through potentiation of systemic cancer cell-specific T cell immunity. Furthermore, the PTT-immunotherapy combination regimen is highly effective in inhibiting tumor recurrence and metastasis.

Mitochondria Targeted O2 Economizer to Alleviate Tumor Hypoxia for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) often suffers from the exacerbated tumor hypoxia and the heterogeneous distribution of photosensitizers, leading to an inefficient ROS productivity and availability. In this work, a mitochondria targeted O₂ economizer (designated as Mito-OxE) is developed to improve PDT efficiency by alleviating tumor hypoxia and enhancing the subcellular localization of photosensitizers. Specifically, the photosensitizer of protoporphyrin IX (PpIX) is modified with the hydrophilic polyethylene glycol and the lipophilic cation of triphenylphosphine (TPP) to fabricate the biocompatible mitochondria targeted photosensitizers (designated as Mito-PSs). And Mito-OxE is prepared by using Mito-PSs to load the mitochondrial oxidative phosphorylation inhibitors of atovaquone (ATO). Benefiting from the targeting capability of TPP, Mito-OxE can selectively accumulate in mitochondria after cellular uptake. Subsequently, the mitochondrial respiration would be suppressed to with the participation of ATO, resulting in a local hypoxia mitigation for enhanced PDT. Compared with Mito-PSs, Mito-OxE maximizes the therapeutic effect against hypoxic tumors under light irradiation. This design of mitochondria targeted O₂ economizer would advance the development of targeted drug delivery system for effective PDT regardless of hypoxic microenvironment.

Beyond Photo: Xdynamic Therapies in Fighting Cancer

Reactive oxygen species (ROS)-related therapeutic approaches are developed as a promising modality for cancer treatment because the aberrant increase of intracellular ROS level can cause cell death due to nonspecific oxidation damage to key cellular biomolecules. However, the most widely considered strategy, photodynamic therapy (PDT), suffers from critical limitations such as limited tissue-penetration depth, high oxygen dependence, and phototoxicity. Non-photo-induced ROS generation strategies, which are defined as Xdynamic therapies (X = sono, radio, microwave, chemo, thermo, and electro), show good potential to overcome the drawbacks of PDT. Herein, recent advances in the development of Xdynamic therapies, including the design of systems, the working mechanisms, and examples of cancer therapy application, are introduced. Furthermore, the approaches to enhance treatment efficiency of Xdynamic therapy are highlighted. Finally, the perspectives and challenges of these strategies are also discussed.

Potential of Cyanine Derived Dyes in Photodynamic Therapy

Photodynamic therapy (PDT) is a method of cancer treatment that leads to the disintegration of cancer cells and has developed significantly in recent years. The clinically used photosensitizers are primarily porphyrin, which absorbs light in the red spectrum and their absorbance maxima are relatively short. This review presents group of compounds and their derivatives that are considered to be potential photosensitizers in PDT. Cyanine dyes are compounds that typically absorb light in the visible to near-infrared-I (NIR-I) spectrum range (750-900 nm). This meta-analysis comprises the current studies on cyanine dye derivatives, such as indocyanine green (so far used solely as a diagnostic agent), heptamethine and pentamethine dyes, squaraine dyes, merocyanines and phthalocyanines. The wide array of the cyanine derivatives arises from their structural modifications (e.g., halogenation, incorporation of metal atoms or organic structures, or synthesis of lactosomes, emulsions or conjugation). All the following modifications aim to increase solubility in aqueous media, enhance phototoxicity, and decrease photobleaching. In addition, the changes introduce new features like pH-sensitivity. The cyanine dyes involved in photodynamic reactions could be incorporated into sets of PDT agents.

Organelle-Targeted Photosensitizers for Precision Photodynamic Therapy

Subcellular organelles are the cornerstones of cells, and destroying them will cause cell dysfunction and even death. Therefore, realizing precise organelle targeting of photosensitizers (PSs) can help reduce PS dosage, minimize side effects, avoid drug resistance, and enhance therapeutic efficacy in photodynamic therapy (PDT). Organelle-targeted PSs provide a new paradigm for the construction of the next generation of PSs and may provide implementable strategies for future precision medicine. In this Review, the recent targeting strategies of different organelles and the corresponding design principles of molecular and nanostructured PSs are summarized and discussed. The current challenges and opportunities in organelle-targeted PDT are also presented.

Supramolecular Dipeptide-Based Near-Infrared Fluorescent Nanotubes for Cellular Mitochondria Targeted Imaging and Early Apoptosis

Herein, we have designed and synthesized unsymmetrical visible Cy-3 and near-infrared (NIR) Cy-5 chromophores anchoring mitochondria targeting functional group conjugated with a Phe-Phe dipeptide by a microwave-assisted Fmoc solid phase peptide synthesis method on Wang resin. These dipeptide-based Cy-3-TPP/FF as well as Cy-5-TPP/FF molecules self-assemble to form fluorescent nanotubes in solution, and it has been confirmed by TEM, SEM, and AFM. The Cy-3-TPP/FF and Cy-5-TPP/FF molecules in solution exhibit narrow excitation as well as emission bands in the visible and NIR region, respectively. These lipophilic cationic fluorescent peptide molecules spontaneously and selectively accumulate inside the mitochondria of human carcinoma cells that have been experimentally validated by live cell confocal laser scanning microscopy and display a high Pearson's correlation coefficient in a colocalization assay. Live cell multicolor confocal imaging using the NIR Cy-5-TPP/FF in combination with other organelle specific dye is also accomplished. Moreover, these lipophilic dipeptide-based cationic molecules reach the critical aggregation concentration inside the mitochondria because of the extremely negative inner mitochondrial membrane potential [(ΔΨ_m)_cancer ≈ -220 mV] and form supramolecular nanotubes which are accountable for malignant mitochondria targeted early apoptosis. The early apoptosis is arrested using Cy-5-TPP/FF and confirmed by annexin V-FITC/PI apoptosis detection assay.

Which is Better for Nanomedicines: Nanocatalysts or Single-Atom Catalysts?

With the rapid advancements in nanotechnology and materials science, numerous nanomaterials have been used as catalysts for nanomedical applications. Their design and modification according to the microenvironment of diseases have been shown to achieve effective treatment. Chemists are in pursuit of nanocatalysts that are more efficient, controllable, and less toxic by developing innovative synthetic technologies and improving existing ones. Recently, single-atom catalysts (SACs) with excellent catalytic activity and high selectivity have attracted increasing attention because of their accurate design as nanomaterials at the atomic level, thereby highlighting their potential for nanomedical applications. In this review, the recent advances in nanocatalysts and SACs are briefly summarized according to their synthesis, characterizations, catalytic mechanisms, and nanomedical applications. The opportunities and future scope for their development and the issues and challenges for their application as nanomedicine are also discussed. As far as it is known, the review is the systematic comparison of nanocatalysts and SACs, especially in the field of nanomedicine, which has promoted the development of nanocatalytic medicine.

Light-Driven Cascade Mitochondria-to-Nucleus Photosensitization in Cancer Cell Ablation

Nuclei and mitochondria are the only cellular organelles containing genes, which are specific targets for efficient cancer therapy. So far, several photosensitizers have been reported for mitochondria targeting, and another few have been reported for nuclei targeting. However, none have been reported for photosensitization in both mitochondria and nucleus, especially in cascade mode, which can significantly reduce the photosensitizers needed for maximal treatment effect. Herein, a light-driven, mitochondria-to-nucleus cascade dual organelle cancer cell ablation strategy is reported. A functionalized iridium complex, named BT-Ir, is designed as a photosensitizer, which targets mitochondria first for photosensitization and subsequently is translocated to a cell nucleus for continuous photodynamic cancer cell ablation. This strategy opens new opportunities for efficient photodynamic therapy.

Single Small Molecule-Assembled Mitochondria Targeting Nanofibers for Enhanced Photodynamic Cancer Therapy in Vivo

Photodynamic therapy (PDT) has emerged as an attractive alternative in cancer therapy, but its therapeutic effects are limited by the nonselective subcellular localization and poor intratumoral retention of small-molecule photosensitizes. Here a fiber-forming nanophotosensitizer (PQC NF) that is composed of mitochondria targeting small molecules of amphiphilicity is reported. Harnessing the specific mitochondria targeting, the light-activated PQC NFs produce approximately 110-fold higher amount of reactive oxygen species (ROS) in cells than free photosensitizers and can dramatically induce mitochondrial disruption to trigger intense apoptosis, showing 20-50 times better in vitro anticancer potency than traditional photosensitizers. As fiber-shaped nanomaterials, PQC NFs also demonstrated a long-term retention in tumor sites, solving the challenge of rapid clearance of small-molecule photosensitizers from tumors. With these advantages, PQC NFs achieve a 100% complete cure rate in both subcutaneous and orthotopic oral cancer models with the administration of only a single dose. This type of single small molecule-assembled mitochondria targeting nanofibers offer an advantageous strategy to improve the in vivo therapeutic effects of conventional PDT.

Chemodynamic/photothermal synergistic therapy based on Ce-doped Cu–Al layered double hydroxides

Ultrathin CuAlCe layered double hydroxide nanosheets loaded with indocyanine green (ICG) were designed, and showed excellent synergetic chemodynamic/photothermal therapy.