Water-Soluble Fluorescent Sensors for Quantification of Trace Cisplatin in Body Fluids from Clinical Cancer Patients

Accurate quantification of cisplatin (cDDP) in body fluids (blood, urine, and ascites) is crucial in monitoring therapeutic processes, assessing drug metabolism, and optimizing treatment schedules for cancer patients. Nonetheless, due to the inherent fluorescence and complexity of the body fluid matrix, along with the low cDDP concentrations in these fluids during treatment, using fluorescent sensors for fluid detection remains a subject of ongoing research. Herein, a series of water-soluble cDDP-activatable fluorescent sensors was rationally constructed by introducing thioether groups to the xanthene skeleton based on the chalcogenophilicity of platinum. These sensors exhibit excellent sensitivity and certain anti-interference capabilities for sensing cDDP in living cells, rat tissues, and zebrafish. Especially, with a simplified sample pretreatment procedure, for the first time, Rh3 and Rh4 have enabled quantitative detection of cDDP levels in diversiform body fluids from clinical ovarian and bladder cancer patients. These results are highly consistent with those obtained by ICP-MS detection. This work paves the way for utilizing fluorescent sensors in clinical body fluid analysis, thus potentially revolutionizing the monitoring methods of cDDP in clinic settings.

Real time precisely tracing the fluctuations of mitochondrial SO2 in cells during ferroptosis and tissues using a mitochondrial-immobilized ratiometric fluorescent probe

Mitochondrial sulfur dioxide (SO2) plays important roles in physiological and pathological activities. Unfortunately, it is lack of a reliable tool to precisely visualize the mitochondrial SO2 and elaborate its complicated functions in various cytoactivities. Here we report a mitochondrial-immobilized fluorescent probe PM-Cl consisting of coumarin and benzyl chloride modified benzothiazole, which enables selective visualization of mitochondrial SO2via chemical immobilization. The spectral results demonstrated that probe PM-Cl could respond to SO2 with high selectivity and sensitivity. Co-localization and the fluorescence of cytolysis extraction verified the excellent mitochondrial targeting and anchoring abilities. Due to the chemical immobilization, probe PM-Cl could firmly retain into mitochondria after stimulation of carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and H2O2. Significantly, a series of fluorescence images are indicative of capability for detecting the fluctuations of SO2 in mitochondria during ferroptosis. Furthermore, PM-Cl also could visualize SO2 in myocardium and muscle tissues after the stimulation of CCCP. Taken together, probe PM-Cl is a very potential molecular tool for precisely detecting mitochondrial SO2 to explore its complex functions in physiological and pathological activities.

Direct targeting of mitochondria by cisplatin leads to cytotoxicity in zebrafish lateral-line hair cells

Cisplatin is a chemotherapy drug that causes permanent hearing loss by injuring cochlear hair cells. Hair cell mitochondria have emerged as potential mediators of hair cell cytotoxicity. Using in vivo live imaging of hair cells in the zebrafish lateral-line organ expressing a genetically encoded indicator of cumulative mitochondrial activity, we first demonstrate that greater redox history increases susceptibility to cisplatin. Next, we conducted time-lapse imaging to understand dynamic changes in mitochondrial homeostasis and observe elevated mitochondrial and cytosolic calcium that surge prior to hair cell death. Furthermore, using a localized probe that fluoresces in the presence of cisplatin, we show that cisplatin directly accumulates in hair cell mitochondria, and this accumulation occurs before mitochondrial dysregulation and apoptosis. Our findings provide evidence that cisplatin directly targets hair cell mitochondria and support that the mitochondria are integral to cisplatin cytotoxicity in hair cells.

RAPTA-coordinated polydiacetylene self-assembly: A chameleon-like prodrug with a dual-lock strategy for real-time release monitoring of metallodrug

Herein, we report the first-ever design strategy of modifying RAPTA-C into a self-reporting prodrug candidate based on Ru-coordinated polydiacetylene self-assembly. This nanosystem exhibits a dual lock strategy that responds to visible light and pH-stimuli sequentially one by one with a concomitant color change for controlled RAPTA-C release and real-time release monitoring in human gastric cancer cells.

Fluorescence-Guided Spatial Drug Screening in 3D Colorectal Cancer Spheroids

The limited recapitulation of critical cancer features in 2D cultures causes poor translatability of preclinical results from in vitro assays to in vivo tumor models. This contributes to slow drug development with a low success rate. 3D cultures better recapitulate the tumor microenvironment, enabling more accurate predictions when screening drug candidates and improving the development of chemotherapeutics. Platinum (Pt) (IV) compounds are promising prodrugs designed to reduce the severe systemic toxicity of widely used Food and Drug Administration (FDA)-approved Pt(II) drugs such as cisplatin. Here, this work presents spatiotemporal evaluations in 3D colorectal cancer (CRC) spheroids of mitochondria-targeting Pt(IV) complexes. CRC spheroids provide a greater pathophysiological recapitulation of in vivo tumors than 2D cultures by a marked upregulation of the ABCG2 chemoresistance marker expression. Furthermore, new 3D-staining protocols are introduced to evaluate the real-time decrease in mitochondria membrane potential (ΔΨ) in CRC spheroids, and a Pt-sensing dye to quantify the Pt mitochondrial accumulation. Finally, this work demonstrates a correlation between in vitro results and the efficacy of the compounds in vivo. Overall, the CRC spheroids represent a fast and cost-effective model to assess the behavior of Pt compounds in vitro and predict their translational potential in CRC treatment.

Cisplatin drives mitochondrial dysregulation in sensory hair cells

Cisplatin is a chemotherapy drug that causes permanent hearing loss by injuring cochlear hair cells. The mechanisms that initiate injury are not fully understood, but mitochondria have emerged as potential mediators of hair cell cytotoxicity. Using in vivo live imaging of hair cells in the zebrafish lateral-line organ expressing a genetically encoded indicator of cumulative mitochondrial activity, we first demonstrate that greater redox history increases susceptibility to cisplatin. Next, we conducted time-lapse imaging to understand dynamic changes in mitochondrial homeostasis and observe elevated mitochondrial and cytosolic calcium that surge prior to hair cell death. Furthermore, using a localized probe that fluoresces in the presence of cisplatin, we show that cisplatin directly accumulates in hair cell mitochondria, and this accumulation occurs before mitochondrial dysregulation and apoptosis. Our findings provide evidence that cisplatin directly targets hair cell mitochondria and support that the mitochondria are integral to cisplatin cytotoxicity in hair cells.

Sequential dual-locking strategy using photoactivated Pt(IV)-based metallo-nano prodrug for enhanced chemotherapy and photodynamic efficacy by triggering ferroptosis and macrophage polarization

Selective activation of Pt(IV) prodrugs within tumors has emerged as a promising strategy in tumor treatment. Although progress has been made with photo- and ultrasound-activated Pt(IV) prodrugs, concerns remain over the non-specific activation of photosensitizers (PS) and the potential for phototoxicity and chemical toxicity. In this study, a sequential dual-locked Pt(IV) nano-prodrug that can be activated by both the acidic tumor microenvironment and light was developed. The Pt(IV) prodrug was prepared by conjugating PS-locked Pt(IV) to a polymeric core, which was then chelated with metallo iron to lock its photoactivity and form a metallo-nano prodrug. Under acidic tumor microenvironment conditions, the metallo-nano prodrug undergoes dissociation of iron, triggering a reduction process in oxaliplatin under light irradiation, resulting in the activation of both chemotherapy and photodynamic therapy (PDT). Additionally, the prodrug could induce metallo-triggered ferroptosis and polarization of tumor-associated macrophages (TAM), thereby enhancing tumor inhibition. The dual-lock strategy employed in a nanoparticle delivery system represents an expansion in the application of platinum-based anticancer drugs, making it a promising new direction in cancer treatment.

Investigating the Therapeutic Effects of Ferroptosis on Myocardial Ischemia-Reperfusion Injury Using a Dual-Locking Mitochondrial Targeting Strategy

Research on ferroptosis in myocardial ischemia/reperfusion injury (MIRI) using mitochondrial viscosity as a nexus holds great promise for MIRI therapy. However, high-precision visualisation of mitochondrial viscosity remains a formidable task owing to the debilitating electrostatic interactions caused by damaged mitochondrial membrane potential. Herein, we propose a dual-locking mitochondria-targeting strategy that incorporates electrostatic forces and probe-protein molecular docking. Even in damaged mitochondria, stable and precise visualisation of mitochondrial viscosity in triggered and medicated MIRI was achieved owing to the sustained driving forces (e.g., pi-cation, pi-alkyl interactions, etc.) between the developed probe, CBS, and the mitochondrial membrane protein. Moreover, complemented by a western blot, we confirmed that ferrostatin-1 exerts its therapeutic effect on MIRI by improving the system xc-/GSH/GPX4 antioxidant system, confirming the therapeutic value of ferroptosis in MIRI. This study presents a novel strategy for developing robust mitochondrial probes, thereby advancing MIRI treatment.

An iridium(iii)-based photosensitizer disrupting the mitochondrial respiratory chain induces ferritinophagy-mediated immunogenic cell death

Cancer cells have a strategically optimized metabolism and tumor microenvironment for rapid proliferation and growth. Increasing research efforts have been focused on developing therapeutic agents that specifically target the metabolism of cancer cells. In this work, we prepared 1-methyl-4-phenylpyridinium-functionalized Ir(iii) complexes that selectively localize in the mitochondria and generate singlet oxygen and superoxide anion radicals upon two-photon irradiation. The generation of this oxidative stress leads to the disruption of the mitochondrial respiratory chain and therefore the disturbance of mitochondrial oxidative phosphorylation and glycolysis metabolisms, triggering cell death by combining immunogenic cell death and ferritinophagy. To the best of our knowledge, this latter is reported for the first time in the context of photodynamic therapy (PDT). To provide cancer selectivity, the best compound of this work was encapsulated within exosomes to form tumor-targeted nanoparticles. Treatment of the primary tumor of mice with two-photon irradiation (720 nm) 24 h after injection of the nanoparticles in the tail vein stops the primary tumor progression and almost completely inhibits the growth of distant tumors that were not irradiated. Our compound is a promising photosensitizer that efficiently disrupts the mitochondrial respiratory chain and induces ferritinophagy-mediated long-term immunotherapy.

Synthesis and anticancer mechanisms of four novel platinum(II) 4'-substituted-2,2':6',2''-terpyridine complexes

Mitophagy, a selective autophagic process, has emerged as a pathway involved in degrading dysfunctional mitochondria. Herein, new platinum(II)-based chemotherapeutics with mitophagy-targeting properties are proposed. Four novel binuclear anticancer Pt(II) complexes with 4'-substituted-2,2':6',2''-terpyridine derivatives (tpy1-tpy4), i.e., [Pt2(tpy1)(DMSO)2Cl4]·CH3OH (tpy1Pt), [Pt(tpy2)Cl][Pt(DMSO)Cl3]·CH3COCH3 (tpy2Pt), [Pt(tpy3)Cl][Pt(DMSO)Cl3] (tpy3Pt), and [Pt(tpy4)Cl]Cl·CH3OH (tpy4Pt), were designed and prepared. Moreover, their potential antitumor mechanism was studied. Tpy1Pt-tpy4Pt exhibited more selective cytotoxicity against cisplatin-resistant SK-OV-3/DDP (SKO3cisR) cancer cells compared with those against ovarian SK-OV-3 (SKO3) cancer cells and normal HL-7702 liver (H702) cells. This selective cytotoxicity of Tpy1Pt-tpy4Pt was better than that of its ligands (i.e., tpy1-tpy4), the clinical drug cisplatin, and cis-Pt(DMSO)2Cl2. The results of various experiments indicated that tpy1Pt and tpy2Pt kill SKO3cisR cancer cells via a mitophagy pathway, which involves the disruption of the mitophagy-related protein expression, dissipation of the mitochondrial membrane potential, elevation of the [Ca2+] and reactive oxygen species levels, promotion of mitochondrial DNA damage, and reduction in the adenosine triphosphate and mitochondrial respiratory chain levels. Furthermore, in vivo experiments indicated that the dinuclear anticancer Pt(II) coordination compound (tpy1Pt) has remarkable therapeutic efficiency (ca. 52.4%) and almost no toxicity. Therefore, the new 4'-substituted-2,2':6',2''-terpyridine Pt(II) coordination compound (tpy1Pt) is a potential candidate for next-generation mitophagy-targeting dinuclear Pt(II)-based anticancer drugs.

Selective fluorescence turn-on detection of combination cisplatin-etoposide chemotherapy based on N-CDs/GSH-CuNCs nanoprobe

Cisplatin (CIS) and etoposide (ETP) combination therapy is highly effective for treating various cancers. However, the potential for pharmacokinetic interactions between these drugs necessitates selective sensing methods to quantitate both CIS and ETP levels in patient's plasma. This work develops a dual fluorescence probe strategy using glutathione-capped copper nanoclusters (GSH-CuNCs) and nitrogen-doped carbon dots (N-CDs) for the simultaneous analysis of CIS and ETP. The fluorescence signal of GSH-CuNCs at 615 nm increased linearly with CIS concentration while the N-CD emission at 480 nm remained unaffected. Conversely, the N-CD fluorescence was selectively enhanced by ETP with no interference with the CuNC fluorescence. Extensive materials characterization including UV-vis, fluorescence spectroscopy, XRD, and TEM confirmed the synthesis of the nanoprobes. The sensor showed high sensitivity with limits of detection of 6.95 ng mL-1 for CIS and 7.63 ng mL-1 for ETP along with excellent selectivity against potential interferences in rabbit plasma. Method feasibility was demonstrated with application to real rabbit plasma samples. The method was further applied to estimate the pharmacokinetic parameters of CIS before and after ETP coadministration. The dual nanoprobe sensing strategy enables rapid and selective quantitation of CIS and ETP levels to facilitate therapeutic drug monitoring and optimization of combination chemotherapy regimens.

High Biocompatible Poly(lactic-co-glycolic acid)-Based Nanosensitizer With Magnetic Resonance Imaging Capacity for Tumor Targeted Microwave Hyperthermia and Chemotherapy

Microwave (MW) hyperthermia has been widely studied in tumor therapy, while the lack of specificity, and the potential toxicity induced by instability or difficulty in degradation of existed MW thermal sensitizers still limits the application. Herein, a new biocompatible Poly(lactic-co-glycolic acid) (PLGA)-based nanosensitizer of Dtxl-Gd@PLGA-PEG-TPP (DGPPT) with capacities of magnetic resonance (MR) imaging and mitochondrial targeting for MW hyperthermia combined with chemotherapy was constructed via a double emulsion solvent evaporation method. The modified TPP significantly enhanced the specificity of sensitizer for targeting mitochondria, a heat-sensitive energy supply plant in cells. Thus the MW thermal damage induced by the loaded Gd in PLGA nanospheres was also strengthened. Together, the system could also achieve MR imaging due to the existence of Gd. In addition, the encapsulated Dtxl performed the chemotherapy of inhibiting mitochondrial function for assisting with MW hyperthermia. In vivo experiments demonstrated that PLGA had high biocompatibility that no obvious damage occurred even the dose was up to 200 mg/kg. Meanwhile, DGPPT+MW representing the combination of mitochondrial targeting and MW hyperthermia-chemotherapy has also been proved to shrink tumor size effectively. This study provides a new direction for building biosafe and multifunctional MW sensitizer with active targeting ability to impede tumor growth.

Ultrafast Ratiometric Detection of Aflatoxin B1 Based on Fluorescent β-CD@Cu Nanoparticles and Pt2+ Ions

Rapid detection of aflatoxin B1 (AFB1) is a very important task in food safety monitoring. However, it is still challenging to achieve highly sensitive detection without antibody or aptamer biomolecules. In this work, a rapid detection of aflatoxin B1 was achieved using a ratiometric fluorescence probe without antibody or aptamer for the first time. In the ratiometric fluorescence system, the fluorescence emission of AFB1 at 433 nm was significantly enhanced due to the β-cyclodextrin-AFB1 host-guest interaction and the complexation of AFB1 and Pt²⁺. Meanwhile, the inclusion of aflatoxin B1 also quenched the fluorescence emission of β-CD@Cu nanoparticles (NPs) at 650 nm based on inner filter effect mechanism. On the basis of the above effects, the ratiometric detection of aflatoxin B1 was achieved in the range of 0.03-10 ng/mL with a low detection limit of 0.012 ng/mL (3σ/s). In addition, the β-CD@Cu NPs based nanoprobe could achieve stable response within 1 min to AFB1. The above ratiometric detection also demonstrated excellent application potential in the rapid on-site detection of AFB1 in food due to the advantages of convenience, rapidness, and high accuracy.

Albumin-targeting of an oxaliplatin-releasing platinum(iv) prodrug results in pronounced anticancer activity due to endocytotic drug uptake in vivo

Oxaliplatin is a very potent platinum(ii) drug which is frequently used in poly-chemotherapy schemes against advanced colorectal cancer. However, its benefit is limited by severe adverse effects as well as resistance development. Based on their higher tolerability, platinum(iv) prodrugs came into focus of interest. However, comparable to their platinum(ii) counterparts they lack tumor specificity and are frequently prematurely activated in the blood circulation. With the aim to exploit the enhanced albumin consumption and accumulation in the malignant tissue, we have recently developed a new albumin-targeted prodrug, which supposed to release oxaliplatin in a highly tumor-specific manner. In more detail, we designed a platinum(iv) complex containing two maleimide moieties in the axial position (KP2156), which allows selective binding to the cysteine 34. In the present study, diverse cell biological and analytical tools such as laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS), isotope labeling, and nano-scale secondary ion mass spectrometry (NanoSIMS) were employed to better understand the in vivo distribution and activation process of KP2156 (in comparison to free oxaliplatin and a non-albumin-binding succinimide analogue). KP2156 forms very stable albumin adducts in the bloodstream resulting in a superior pharmacological profile, such as distinctly prolonged terminal excretion half-life and enhanced effective platinum dose (measured by ICP-MS). The albumin-bound drug is accumulating in the malignant tissue, where it enters the cancer cells via clathrin- and caveolin-dependent endocytosis, and is activated by reduction to release oxaliplatin. This results in profound, long-lasting anticancer activity of KP2156 against CT26 colon cancer tumors in vivo based on cell cycle arrest and apoptotic cell death. Summarizing, albumin-binding of platinum(iv) complexes potently enhances the efficacy of oxaliplatin therapy and should be further developed towards clinical phase I trials.

In Vitro Anticancer Activity of Nanoformulated Mono- and Di-nuclear Pt Compounds

Nanoformulations of mononuclear Pt complexes cis-PtCl₂ (PPh₃ )₂ (1), [Pt(PPh₃ )₂ (L-Cys)] ⋅ H₂ O (3, L-Cys=L-cysteinate), trans-PtCl₂ (PPh₂ PhNMe₂ )₂ (4; PPh₂ PhNMe₂ =4-(dimethylamine)triphenylphosphine), trans-PtI₂ (PPh₂ PhNMe₂ )₂ (5) and dinuclear Pt cluster Pt₂ (μ-S)₂ (PPh₃ )₄ (2) have comparable cytotoxicity to cisplatin against murine melanoma cell line B16F10. Masking of these discrete molecular entities within the hydrophobic core of Pluronic® F-127 significantly boosted their solubility and stability, ensuring efficient cellular uptake, giving in vitro IC₅₀ values in the range of 0.87-11.23 μM. These results highlight the potential therapeutic value of Pt complexes featuring stable Pt-P bonds in nanocomposite formulations with biocompatible amphiphilic polymers.