Nucleus-localized platinum(ii)–triphenylamine complexes as potent photodynamic anticancer agents

The para-position coordinated platinum–triphenylamine conjugates exhibited much better PDT anticancer activity than their meta-position coordinated isomers.

Traceable in-cell synthesis and cytoplasm-to-nucleus translocation of a zinc Schiff base complex as a simple and economical anticancer strategy

A facile and cheap strategy based on visualized in-cell synthesis of theranostic Zn Schiff base complexes realizes cancer-specific therapy.

Folate receptor-targeted theranostic IrSx nanoparticles for multimodal imaging-guided combined chemo-photothermal therapy

Nano-drug delivery systems with multi-modality imaging capacities are worth pursuing because they integrate diagnostic and therapeutic functions. Herein, we report the design, synthesis and evaluation of modified iridium sulfide (IrS_x) nanoparticles (NPs) for cancer therapy in vitro and in vivo. This nanosystem was prepared by modifying IrS_x with polyethylene glycol (PEG) conjugated to the targeting ligand folate (FA) for multimodal imaging-guided combined chemo-photothermal therapy. Upon PEG modification, the small IrS_x NPs (about 4 nm) self-assembled into much larger (about 120 nm) IrS_x-PEG-FA NPs, which exhibited high photostability, ideal photothermal effect, high drug loading and pH-/photothermal-responsive drug release properties. By using the model anticancer drug camptothecin (CPT), we demonstrated that CPT@IrS_x-PEG-FA can effectively target FA-receptor-positive cancer cells in vitro and show efficient tumor accumulation in vivo. The combination of CPT@IrS_x-PEG-FA treatment and irradiation with an 808 nm laser resulted in complete tumor elimination. Moreover, photothermal/photoacoustic (PA)/computed tomography (CT) imaging provided an effective means to monitor the therapeutic effects. Interestingly, the nanoparticles can be cleared, resulting in low systematic toxicity of CPT@IrS_x-PEG-FA. Our work demonstrates that the as-prepared IrS_x-PEG-FA NPs present a promising platform for the construction of multifunctional theranostic agents for cancer therapy.

Monitoring mitochondrial viscosity with anticancer phosphorescent Ir(iii) complexes via two-photon lifetime imaging

Precise quantitative measurement of viscosity at the subcellular level presents great challenges. Two-photon phosphorescence lifetime imaging microscopy (TPPLIM) can reflect micro-environmental changes of a chromophore in a quantitative manner. Phosphorescent iridium complexes are potential TPPLIM probes due to their rich photophysical properties including environment-sensitive long-lifetime emission and high two-photon absorption (TPA) properties. In this work, a series of iridium(iii) complexes containing rotatable groups are developed as mitochondria-targeting anticancer agents and quantitative viscosity probes. Among them, Ir6 ([Ir(ppy-CHO)₂(dppe)]PF₆; ppy-CHO: 4-(2-pyridyl)benzaldehyde; dppe: cis-1,2-bis(diphenylphosphino)ethene) shows satisfactory TPA properties and long lifetimes (up to 1 μs). The emission intensities and lifetimes of Ir6 are viscosity-dependent, which is mainly attributed to the configurational changes in the diphosphine ligand as proved by ¹H NMR spectra. Ir6 displays potent cytotoxicity, and mechanism investigations show that it can accumulate in mitochondria and induce apoptotic cell death. Moreover, Ir6 can induce mitochondrial dysfunction and monitor the changes in mitochondrial viscosity simultaneously in a real-time and quantitative manner via TPPLIM. Upon Ir6 treatment, a time-dependent increase in viscosity and heterogeneity is observed along with the loss of membrane potential in mitochondria. In summary, our work shows that multifunctional phosphorescent metal complexes can induce and precisely detect microenvironmental changes simultaneously at the subcellular level using TPPLIM, which may deepen the understanding of the cell death mechanisms induced by these metallocompounds.

Cancer-specific chemotherapeutic strategy based on the vitamin K3 mediated ROS regenerative feedback and visualized drug release in vivo

A promising theranostic nanosystem VK3-CPT@Ru-CD is designed and fabricated by the host-guest driven self-assembly between the fluorescent adamantine-functionalized Ru(II) complexes and the ROS-labile-cyclodextrin modified thioketal linkers, in which anticancer drug camptothecin (CPT) and vitamin K3 (VK3) are effectively co-encapsulated. On account of the generative feedback between the intracellular redox cycling of VK3 and the high degree of ROS-triggered collapse of nanoparticles, VK3-CPT@Ru-CD can facilitate cancer-specific ROS amplification and drug release selectively in cancer cells, thus realizing the selective killing of tumor with minimal side-effects both in vitro and in vivo, the therapeutic effect of which is more prominent than the free anti-cancer drugs. More interestingly, the menadione structure of encapsulated VK3 can effectively quench the inherent fluorescence of Ru-CD, and a fluorescence lightening up phenomenon is observed accompanied with the ROS-triggered drug release, which can be utilized for real-time tracking of drug release in vitro and in vivo.

Three-in-One Self-Assembled Nanocarrier for Dual-Drug Delivery, Two-Photon Imaging, and Chemo-Photodynamic Synergistic Therapy

We herein present a three-in-one nanoplatform (named Fu/LD@RuCD) for dual-drug delivery, two-photon imaging, and chemo-photodynamic synergistic therapy, enabled by simple self-assembly between adamantine-functionalized ruthenium complexes ([Ru(phen-ad)₃](PF₆)₂, Ru) and natural cyclodextrin (β-CD) monomers. By host-guest chemistry, nanocarrier RuCD 70-90 nm in diameter is fabricated through a very simple mixing step in water at room temperature, in which the octahedral configuration of Ru complex provides a rigid skeleton and the hydrogen bonding of secondary hydroxyl groups formed between two adjacent β-CD monomers displays a bridging role allowing for three-dimensional architectures. The dual-drug-loaded nanoparticle Fu/LD@RuCD (Fu: 5-fluorouracil; LD: lonidamine) effectively penetrates into cancer cells in 8 h and selectively accumulates in lysosomes, in which dual-drug release is promoted by the mildly acidic environment. Under visible light irradiation, nanocarrier RuCD exhibits excellent photodynamic therapy capability by producing sufficient reactive oxygen species and damaging lysosomes, accordingly 5-fluorouracil and lonidamine can escape from lysosomes and reach their sites of action, resulting in mitochondria dysfunction and cancer cell apoptosis. Simultaneously, the excellent photophysical properties of the nanocarrier enable the facile track of drug delivery under one-photon and two-photon excitation. Moreover, in vivo anticancer investigations show that Fu/LD@RuCD can effectively inhibit the tumor growth without systemic side effects by chemo-photodynamic synergistic therapy, and the therapeutic effect is better than the free anticancer drugs and the sole therapeutic modality.

DNA-binding, photocleavage and anti-cancer activity of tin(IV) corrole

A new tin(IV) corrole, 5,10,15-tris(4-methoxycarbonylphenyl) corrole tin(IV) (1-Sn) was synthesized and characterized. The DNA binding, photocleavage and anti-cancer activity were studied and compared with its free-base. The interaction of 1-Sn and its free-base 1 with calf thymus DNA had been investigated by spectroscopic methods, viscosity measurements and molecular docking analysis. The results revealed that 1-Sn and 1 could interact with calf thymus DNA via an outside groove binding mode. Furthermore, although 1 displayed no photonuclease activity, 1-Sn exhibited good photonuclease activity as indicated by agarose gel electrophoresis, and superoxide anion might be the active intermediate for the DNA scission. Finally, 1 was nontoxic but 1-Sn displayed cytotoxicity towards A549 tumor cell lines.

Photophysical properties of free-base and manganese(iii) N-confused porphyrins

The photophysical properties of N-confused 5,10,15,20-tetraphenyl porphyrin derivatives have been studied using steady-state and time-resolved spectroscopic techniques. The peripherally substituted N-confused 5,10,15,20-tetraphenyl free-base porphyrins (NCTPPs) show stronger B-band absorptions in DCM than in DMAc, while much stronger emissions have been observed in DMAc, which may be due to the shorter times (τIC) of internal conversion from the B-band to the Q-band. The Q-band spectral structures of NCTPPs in DCM are significantly different from those in DMAc. The introduction of ortho-OCH3 results in the strongest emission in both DCM and DMAc and significant fluorescence after N-methylation even though the emissions of other N-methyl complexes are quenched. The N-methylation of NCTPPs leads to a larger τIC and shorter emission lifetime. The excited-state dynamics of manganese(iii) N-confused porphyrins (Mn(Cl)NCH3NCTPPs) are influenced by both peripheral substituents and manganese(iii) metal ion, and exhibit ultrafast intersystem crossing processes.

Targeted reversal and phosphorescence lifetime imaging of cancer cell metabolism via a theranostic rhenium(I)-DCA conjugate

Cancer cell metabolism is quite different from normal cells. Targeting cancer metabolism and untuning the tumor metabolic machine has emerged as a promising strategy for cancer therapy. We have developed a multi-functional Re-dca conjugate (Re-dca 2) by conjugating the metabolic modulator dichloroacetate (DCA) to mitochondria-targeted rhenium(I) complex, allowing its efficient penetration into cancer cells and selective accumulation in mitochondria, thus achieving the cancer cell metabolism reversal from glycolysis to glucose oxidation at pharmacologically relevant DCA doses. Mechanism studies confirm the inhibition effect of Re-dca 2 on the activity of pyruvate dehydrogenase kinase (PDK) and capture the metabolic reversal window in Re-dca 2 treated NCI-1229 cells at the early stage of drug treatment, resulting in selective killing of malignant cells cocultured with normal cells, significant inhibition of cancer cell metastasis and invasion, as well as excellent anti-angiogenesis activities in zebrafish embryos. By comparison, DCA-free Re(I) analogue is also investigated under the same conditions. Although this analogue also exhibits cytotoxicity due to the Re(I) core, metabolic reversal is not induced by this analogue and its anti-metastasis activity is much lower than Re-dca 2, indicating the synergistic effect of Re(I) core and DCA moiety on cancer therapy. In vivo anti-cancer investigations also indicate that the mitochondria-targeted Re-dca 2 can effectively inhibit the tumor growth without affecting the body weight of nude mice, and the therapeutic effect is much better than the DCA-free Re(I) analogue 2a. Simultaneously, the O₂-sensitive phosphorescent lifetimes of Re-dca 2 can be utilized for PLIM imaging of intracellular oxygen consumption, thus reflecting the Re-dca 2 induced glycolysis-to-glucose oxidation reversal at the early drug treatment stage. The excellent phosphorescence of Re-dca 2 can also be utilized for real-time tracking of mitochondrial morphological changes during treatment. In a word, rational design of phosphorescent metallodrug and metabolic modulator conjugates for synergistic treatment is a promising strategy for simultaneous untuning and tracking tumor metabolic machine, thus providing new clues for cancer therapy and mechanisms.

Correction: A self-assessed photosensitizer: inducing and dual-modal phosphorescence imaging of mitochondria oxidative stress

Correction for ‘A self-assessed photosensitizer: inducing and dual-modal phosphorescence imaging of mitochondria oxidative stress’ by Jing Yang et al., Chem. Commun., 2018, DOI: 10.1039/c7cc07797a.

A self-assessed photosensitizer: inducing and dual-modal phosphorescence imaging of mitochondria oxidative stress

Mitochondria-targeted Ir(iii)–nitroxide conjugates act as self-assessed PDT agents by simultaneously inducing and dual-modal phosphorescence imaging of mitochondrial oxidative stress.

Cyclometalated iridium(iii) complexes induce mitochondria-derived paraptotic cell death and inhibit tumor growthin vivo

A potent anticancer Ir(iii) complex induces paraptotic cell death by causing mitochondrial dysfunction rapidly and inhibits tumor growth significantlyin vivo.

Dual Functions of Cyclometalated Iridium(III) Complexes: Anti-Metastasis and Lysosome-Damaged Photodynamic Therapy

Four phosphorescent cyclometalated iridium(III) complexes containing benzimidazole moiety have been designed and synthesized. These Ir(III) complexes can effectively inhibit several cancerous processes, including cell migration, invasion, colony formation, and angiogenesis. Interestingly, they show a much higher singlet oxygen quantum yield in an acidic solution than in a neutral solution. Upon irradiation at 425 nm with low energy (1.2 J cm^-2), they can induce apoptosis through lysosomal damage, evaluation of reactive oxygen species level, and activation of caspase-3/7. The highest phototoxicity index is >476, with almost no dark cytotoxicity observed for Ir4. Ir4 can also inhibit tumor growth effectively in nude mice in vivo after photodynamic therapy. An in vitro assay against 70 kinases indicates that maternal embryonic leucine zipper kinase (MELK), PIK3CA, and AMPK are the possible molecular targets. The half maximal inhibitory concentration of Ir4 toward MELK is 1.27 μM. Our study demonstrates that these Ir(III) complexes are promising anticancer agents with dual functions, including metastasis inhibition and lysosome-damaged photodynamic therapy.

Ruthenium complex-modified carbon nanodots for lysosome-targeted one- and two-photon imaging and photodynamic therapy

Nanohybrids can in most cases kill cancer cells more efficiently as compared with free photosensitizers. In this work, we constructed nanohybrid Ru1@CDs composed of carbon nanodots (CDs) and a phosphorescent Ru(ii) complex (Ru1) for one- and two-photon photodynamic therapy of cancer. The photosensitizer and imaging agent Ru1 is decorated onto the nanocarrier CDs covalently. Ru1 and Ru1@CDs can penetrate into cancer cells through an energy-dependent mechanism and endocytosis, respectively. Both Ru1 and Ru1@CDs are capable of lysosome-targeted phosphorescence imaging and photodamage under either 450 nm (one-photon) or 810 nm (two-photon) excitation. Conjugation with CDs can increase the cellular uptake efficacy of Ru1. Mechanism investigations show that both Ru1 and Ru1@CDs can induce apoptosis through generation of reactive oxygen species and cathepsin-initiated apoptotic signaling pathways. Upon two-photon excitation, Ru1@CDs show better penetrability, as well as higher inhibitory effects on cancer cell growth in both 2D cell and 3D multicellular tumor spheroid models. Our work provides an effective strategy for the construction of multifunctional imaging and phototherapeutic nanohybrids for the treatment of cancer.

A Platinum(II)-based Photosensitive Tripod as an Effective Photodynamic Anticancer Agent through DNA Damage

Herein, two photosensitive platinum(II)-based tripods were designed and synthesized. Notably, complex 1 ({[Pt(dien)]₃ L}(NO₃ )₆ , L=tri(4-pyridylphenyl)amine and dien=diethylenetriamine), which mainly accumulated in the cell nucleus, exhibited very low cytotoxicity in the absence of light irradiation, but displayed a remarkable increase in cytotoxicity upon visible light irradiation. Mechanistic investigations revealed that the tripod interacted with DNA in the nucleus, induced ROS generation upon light irradiation, and consequently elicited rapid DNA damage response; thereby triggering cancer cell apoptosis.

Simultaneously Inducing and Tracking Cancer Cell Metabolism Repression by Mitochondria-Immobilized Rhenium(I) Complex

Mitochondrial metabolism is essential for tumorigenesis, and the development of cancer is usually accompanied by alternations of mitochondrial function. Emerging studies have demonstrated that targeting mitochondria and mitochondrial metabolism is an effective strategy for cancer therapy. In this work, eight phosphorescent organometallic rhenium(I) complexes have been synthesized and explored as mitochondria-targeted theranostic agents, capable of inducing and tracking the therapeutic effect simultaneously. Complexes 1b-4b can quickly and efficiently penetrate into A549 cells, specifically localizing within mitochondria, and their cytotoxicity is superior to cisplatin against the cancer cells screened. Notably, complex 3b [Re(CO)₃(DIP) (py-3-CH₂Cl)]⁺ containing thiol-reactive chloromethylpyridyl moiety for mitochondria immobilization shows higher cytotoxicity and selectivity against cancer cells than other Re(I) complexes without mitochondria-immobilization properties. Mechanistic studies show that complexes 1b-4b induce a cascade of mitochondria-dependent events including mitochondrial damage, mitochondrial respiration inhibition, cellular ATP depletion, reactive oxygen species (ROS) elevation, and caspase-dependent apoptosis. By comparison, mitochondria-immobilized 3b causes more effective repression of mitochondrial metabolism than mitochondrial-nonimmobilized complexes. The excellent phosphorescence and O₂-sensitive lifetimes of mitochondria-immobilized 3b can be utilized for real-time tracking of the morphological changes of mitochondria and mitochondrial respiration repression during therapy process, accordingly providing reliable information for understanding anticancer mechanisms.

Multi-step encapsulation of chemotherapy and gene silencing agents in functionalized mesoporous silica nanoparticles

Drug to carrier ratio is an important consideration in designing drug platforms, since a low loading capacity necessitates the use of high doses of carriers, which can result in side effects. Here, we have engineered a platform to co-deliver small molecule drugs and small interfering RNA (siRNA). This platform consists of cyclodextrin-grafted polyethylenimine (CP) functionalized mesoporous silica nanoparticles (MSNP). A unique multi-step encapsulation procedure was used to obtain a high loading capacity for doxorubicin (DOX) and siRNA oligos specific for the PKM2 gene that encodes pyruvate kinase M2, an enzyme catalyzing the final rate-limiting step in glycolysis. We systematically characterized this platform (CP-MSNP@DOX/PKM2) in vitro and evaluated its therapeutic efficacy in vivo with a mouse model of triple negative breast cancer (TNBC). Exposure of TNBC cells to CP-MSNP@DOX/PKM2 resulted in suppressed target gene expression, reduced cell proliferation, and enhanced apoptosis. Intravenous administration of the drug substantially decreased the tumor burden in comparison to DOX or siRNA monotherapy. In conclusion, we have developed a platform for efficient co-delivery of small molecule drugs and therapeutic siRNA.

Light-Up Mitophagy in Live Cells with Dual-Functional Theranostic Phosphorescent Iridium(III) Complexes

Phosphorescent Ir(III) complexes are expected to be new multifunctional theranostic platforms that enable the integration of imaging capabilities and anticancer properties. Mitophagy is an important selective autophagic process that degrades dysfunctional mitochondria. Until now, the regulation of mitophagy is still poorly understood. Herein, we present two phosphorescent cyclometalated iridium(III) complexes (Ir1 and Ir2) that can accumulate in mitochondria and induce mitophagy. Because of their intrinsic phosphorescence, they can specially image mitochondria and track mitochondrial morphological alterations. Mechanism studies show that Ir1 and Ir2 induce mitophagy by depolarization of mitochondrial membrane potential, depletion of cellular ATP, perturbation in mitochondrial metabolic status, and induction of oxidative stress. Moreover, no sign of apoptosis is observed in Ir1- and Ir2-treated cells under the same conditions that an obvious mitophagic response is initiated. We demonstrate that Ir1 is a promising theranostic agent that can induce mitophagy and visualize changes in mitochondrial morphology simultaneously.

Graphene Oxide Decorated with Ru(II)-Polyethylene Glycol Complex for Lysosome-Targeted Imaging and Photodynamic/Photothermal Therapy

The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) can kill cancer cells more efficiently as compared with PTT or PDT treatment alone. In this work, we use nanohybrid rGO-Ru-PEG composed of reduced nanographene oxide (rGO) sheet and a phosphorescent polyethylene glycol modified Ru(II) complex (Ru-PEG) for combined PTT and PDT of cancer. Photosensitizer and imaging agent Ru-PEG is decorated onto delivery and PTT agent rGO via π-π stacking and hydrophobic interactions. The chemical structure and morphology have been characterized by various methods. The release of Ru-PEG from rGO surface is pH-dependent, and irradiation can increase the release rate considerably. The combined effects of PDT and PTT have been evaluated by cytotoxicity assay under serial irradiation at 808 nm (PTT) and 450 nm (PDT). Mechanism investigation shows that the nanohybrid can induce apoptosis through generation of reactive oxygen species (ROS) and cathepsin-initiated apoptotic signaling pathways under light excitation. rGO-Ru-PEG can be applied to in vivo photothermal imaging, and high treatment efficacy was achieved for in vivo antitumor experiments when irradiated with an 808 nm laser and a 450 nm laser. Our work provides an effective strategy for the construction of multifunctional imaging and phototherapeutic nanohybrids for the treatment of cancer.

Photoinduced δ electron transfer in phenylene bridged Mo2 dimers

Photoinduced electron transfer (ET) in Mo₂ dimers, [Mo₂(DAniF)₃]₂(μ-E₂C(ph)CE₂) (DAniF = N,N'-di(p-anisyl)formamidinate, E = O or S), has been studied by femtosecond transient spectral techniques. Using a 355 nm laser pulse, the δ electrons on the Mo-Mo quadruple bonds are selectively excited and subsequent charge separation yields diradicals [Mo₂]˙^--ph-[Mo₂]˙⁺ and [Mo₂]-ph˙^--[Mo₂]˙⁺. The charge separation (CS) and recombination (CR) rates are derived by fitting the decay kinetic data of the excited states. Surprisingly, it is found that the CR rate constants (k_CR-1, ∼10¹² s^-1) for [Mo₂]˙^--ph-[Mo₂]˙⁺ are larger than the data (k_CR-2) for [Mo₂]-ph˙^--[Mo₂]˙⁺ by about one order of magnitude, although in the first case, the ET distance is doubled and the electronic coupling between the donor and acceptor is weaker. Optical analyses reveal that the free energy changes (ΔG°) for the two CR processes correspond to the δ → δ* and the metal (δ) to bridging ligand (π*) transition energies, respectively, and thus, the ET kinetics is dominated likely by the driving force (-ΔG°).

Mixed-ligand iridium(iii) complexes as photodynamic anticancer agents

Phosphorescent iridium(iii) complexes are rationally designed as photodynamic anticancer agents.

Iridium(iii) complexes with five-membered heterocyclic ligands for combined photodynamic therapy and photoactivated chemotherapy

In this work, three iridium(iii) complexes were investigated as combined photodynamic and photoactivated chemotherapeutic agents.