A tumor microenvironment-activated metal-organic framework-based nanoplatform for amplified oxidative stress-induced enhanced chemotherapy.

Engineering a highly tumor microenvironment-responsive nanoplatform toward effective chemotherapy has always been a challenge in targeted cancer treatment. Metal-organic frameworks are a promising delivery system to reformulate previously approved drugs for enhanced chemotherapy, such as disulfiram (DSF). Herein, a tumor microenvironment-activated metal-organic framework-based nanoplatform DSF@MOF-199@FA has been fabricated to realize amplified oxidative stress-induced enhanced chemotherapy. Our results unveil that the copper ions and DSF released by DSF@MOF-199@FA in an acidic environment can be converted into toxic bis(N, N-diethyl dithiocarbamate) copper and then induce cell apoptosis. Simultaneously, we determined that the apoptosis outcome is further promoted by amplified oxidative stress through effective generation of reactive oxygen species and GSH elimination. In conclusion, this work provides a promising platform for effective anticancer treatment.

Visualizing intracellular membrane interactions and cell type-specific differentiation in ferroptosis and apoptosis with Boranil-Carbazole derivative.

Intracellular lipid systems play essential roles in various physiological functions and cell growth processes. However, our understanding of the intricate interactions within this system, especially between mitochondria and lipid droplets, is limited, particularly in the context of cancer cells' altered lipid metabolism. To address this, our study introduces an N-B-O BODIPY-hexylcarbazole derivative, named Cz-Boranil, that sets a new benchmark in visualizing these critical interactions. Cz-Boranil's unique capability lies in its ability to display distinct intracellular distribution patterns in both normal and cancer cells, offering nuanced cell type-specific differentiation. More impressively, this probe tracks the coordinated interactions of lipid droplets and mitochondria during the critical processes of ferroptosis and apoptosis. We believe that the innovative capabilities of Cz-Boranil will revolutionize our understanding of intracellular lipid interactions and prove pivotal in identifying and studying cancerous cells.

Nanoscale myelinogenesis image in developing brain via super-resolution nanoscopy by near-infrared emissive curcumin-BODIPY derivatives.

Understanding the intricate nanoscale architecture of neuronal myelin during central nervous system development is of utmost importance. However, current visualization methods heavily rely on electron microscopy or indirect fluorescent method, lacking direct and real-time imaging capabilities. Here, we introduce a breakthrough near-infrared emissive curcumin-BODIPY derivative (MyL-1) that enables direct visualization of myelin structure in brain tissues. The remarkable compatibility of MyL-1 with stimulated emission depletion nanoscopy allows for unprecedented super-resolution imaging of myelin ultrastructure. Through this innovative approach, we comprehensively characterize the nanoscale myelinogenesis in three dimensions over the course of brain development, spanning from infancy to adulthood in mouse models. Moreover, we investigate the correlation between myelin substances and Myelin Basic Protein (MBP), shedding light on the essential role of MBP in facilitating myelinogenesis during vertebral development. This novel material, MyL-1, opens up new avenues for studying and understanding the intricate process of myelinogenesis in a direct and non-invasive manner, paving the way for further advancements in the field of nanoscale neuroimaging.

Modeling Instantaneous Firing Rate of Deep Brain Stimulation Target Neuronal Ensembles in the Basal Ganglia and Thalamus.

OBJECTIVE: Deep brain stimulation (DBS) is an effective treatment for movement disorders, including Parkinson disease and essential tremor. However, the underlying mechanisms of DBS remain elusive. Despite the capability of existing models in interpreting experimental data qualitatively, there are very few unified computational models that quantitatively capture the dynamics of the neuronal activity of varying stimulated nuclei-including subthalamic nucleus (STN), substantia nigra pars reticulata (SNr), and ventral intermediate nucleus (Vim)-across different DBS frequencies. MATERIALS AND METHODS: Both synthetic and experimental data were used in the model fitting; the synthetic data were generated by an established spiking neuron model that was reported in our previous work, and the experimental data were provided using single-unit microelectrode recordings (MERs) during DBS (microelectrode stimulation). Based on these data, we developed a novel mathematical model to represent the firing rate of neurons receiving DBS, including neurons in STN, SNr, and Vim-across different DBS frequencies. In our model, the DBS pulses were filtered through a synapse model and a nonlinear transfer function to formulate the firing rate variability. For each DBS-targeted nucleus, we fitted a single set of optimal model parameters consistent across varying DBS frequencies. RESULTS: Our model accurately reproduced the firing rates observed and calculated from both synthetic and experimental data. The optimal model parameters were consistent across different DBS frequencies. CONCLUSIONS: The result of our model fitting was in agreement with experimental single-unit MER data during DBS. Reproducing neuronal firing rates of different nuclei of the basal ganglia and thalamus during DBS can be helpful to further understand the mechanisms of DBS and to potentially optimize stimulation parameters based on their actual effects on neuronal activity.

Four-Photon Absorption Iron Complex for Magnetic Resonance/Photoacoustic Dual-Model Imaging and an Enhanced Ferroptosis Process.

Four-photon absorption (4PA) multimodal therapeutic agent applied to tumor ferroptosis process tracking is rarely reported. In this paper, two functionalized terpyridine iron complexes (TD-FeCl3, TD-Fe-TD) with four-photon absorption properties were designed and synthesized. The four-photon absorption cross sections of TD-FeCl3 reached 6.87 × 10-74cm8·s3·photon-3. Due to its strong near-infrared absorption, TD-FeCl3 has excellent photoacoustic imaging (PAI) capability for accurate PA imaging. TD-FeCl3 has an efficient longitudinal electron relaxation rate (r1 = 2.26 mM-1 s-1) and high spatial resolution, which can be applied as T1-weighted magnetic resonance imaging (MRI) contrast agent for tumor imaging in vivo. In addition, Fe3+ as a natural ferroptosis tracer, TD-FeCl3, is able to deplete glutathione (GSH) effectively, which can further enhance the ferroptosis process. We found that the series of cheap transition metal complexes has four-photon absorption activity and can be used as multimodal (MRI/PAI) diagnostic agents for tumor tracing processes.

Three-Photon AIE Pt(II) Complexes as Cysteine-Targeting Theranostic Agents for Tumor Imaging and Chemotherapy.

Herein, we have synthesized a series of three-photon fluorescent Pt(II) complexes targeting a tumor-associated biothiol, cysteine (Cys), which allows it to be detected without any interference from other intracellular proteins. We focused on how to significantly improve the fluorescence response of Cys via regulating the recognition units in probes. The reaction of K2PtCl4 with L-CH3 or L-COOEt in DMSO solution gave Lyso-Pt-CH3 and Lyso-Pt-COOEt, respectively, which present four-coordinated square-planar geometries in mononuclear structures. Lyso-Pt-CH3 consists of a Cys aptamer labeled with typical aggregation-induced emission (AIE) characteristics, which shows strong three-photon absorption cross section (3PA) only in the presence of Cys. It was found that Lyso-Pt-CH3 displayed a perfect signal-to-noise ratio for imaging lysosomes and for rapid detection of Cys. Using Lyso-Pt-CH3, Cys-related cellular mechanisms were proposed. We confirm that cystine (Cyss) could be absorbed in cells through cystine/glutamate antiporters (system xc-) and is then converted to Cys under the effect of enzymes. All of these suggest that Lyso-Pt-CH3 might be a potential candidate as a simple and straightforward biomarker of lysosome-related Cys in vitro. Lyso-Pt-CH3 can effectively identify tumor tissues with excessive levels of Cys. Lyso-Pt-CH3 also showed excellent antitumor activity than cisplatin. This work provides a novel strategy for the rational design of controllably activated and Cys-targeted Pt(II) anticancer prodrugs for clinical diagnosis and treatment.

Cancer Cell Membrane Labeling Fluorescent Doppelganger Enables In Situ Photoactivated Membrane Dynamics Tracking via Two-Photon Fluorescence Imaging Microscopy.

Various suborganelles are delimited by lipid bilayers, in which high spatial and temporal morphological changes are essential to many physiological and pathological processes of cells. However, almost all the amphiphilic fluorescent molecules reported until now are not available for in situ precise tracking of membrane dynamics in cell apoptosis. Here, the MO (coumarin pyridine derivatives) was devised by engineering lipophilic coumarin and cationic pyridine salt, which not only lastingly anchored onto the plasma membrane in dark due to appropriate amphipathicity and electrostatic interactions but also in situ reflected the membrane damage and heterogeneity with secretion of extracellular vesicles (EVs) under reactive oxygen species regulation and was investigated by two-photon fluorescence lifetime imaging microscopy. This work opens up a new avenue for the development of plasma membrane staining and EV-based medicines for the early diagnosis and treatment of disease.

Fine Tuning of Multiphoton AIE Emission Behavior, Organelle Targeting, and Fluorescence Lifetime Imaging of Terpyridine Derivatives by Alkyl Chain Engineering.

In this work, a series of multiphoton terpyridine agents (ZA, ZA-Mex, and ZA-Hex) for fluorescence lifetime imaging microscopy (FLIM) are designed and synthesized. The results from photophysical property research reveal that ZA-Hex, as an N-hexylated terpyridine salt, has stronger three-photon aggregation-induced emission (AIE) properties compared to ZA-Mex due to enhanced intramolecular charge transfer (ICT) performance. All three terpyridine derivatives possess suitable fluorescence intensities and stable fluorescence lifetimes under different pH conditions (pH = 4.0-8.0), thereby performing multiphoton fluorescence lifetime imaging. For biological imaging applications, it is found that ZA shows good lipid droplet (LD) turn-on fluorescence performance, and ZA-Hex could easily accumulate in mitochondria with high specificity. This is the first report of terpyridine salts as three-photon AIE probes used for multiphoton FLIM imaging.

Novel two-photon absorption compounds with different organic cations: facile synthesis, photophysical properties, detection of viscosity, and selective imaging of the endoplasmic reticulum in living cells.

Three novel imidazole-based two-photon absorption compounds bearing different organic cations (1PIPy, 2PIQu, and 3PIIm) were facilely synthesized and fully characterized by 1H NMR, 13C NMR, FT-IR, and HRMS. The linear and nonlinear photophysical properties of the target compounds were systematically investigated in various solvents, supplemented with the density functional theory calculations to shed light on their structure-property relationships. The maximum two-photon action cross-sections (Φ × Î´max) were determined to be 22.4-98.2 (CH2Cl2), 9.6-41.3 (DMF), and 3.9-11.8 (H2O) GM. It is found that 3PIIm shows significant viscosity sensitivity with a sharp 27-fold increase in fluorescence intensity. Its fluorescence intensity also exhibits a linear relationship with the viscosity of the media in a logarithmic plot. The Φ × Î´max value of 3PIIm in highly viscous glycerol was found to be 107.5 GM. Cytotoxicity tests indicate that these compounds have relatively low cytotoxicity. All the target compounds were successfully characterized by one- and two-photon fluorescence imaging in living cells. The colocalization experiments reveal that 1PIPy and 3PIIm are specially located in the endoplasmic reticulum (ER) with the Pearson's coefficients above 0.90. 3PIIm can also monitor the fluctuation of ER viscosity during etoposide-induced apoptosis.

In Situ Coordination and Confinement of Two-Photon Active Unit Within Metal-Organic Frameworks for High-Order Multiphoton-Excited Fluorescent Performance.

Exploration of high-order multiphoton-excited fluorescent (H-MPEF) material for bioimaging with deeper tissue penetration and higher spatial resolution has attracted great interest but remains a challenge. Herein, a H-MPEF-responsive metal-organic framework-based material, ZLPH, was rationally fabricated by the pore confinement of a two-photon active unit (ZL) using the "ship-in-bottle" strategy. It demonstrated that the judicious selection effectively avoided the annoying weakened/quenched H-MPEF behavior due to the instability of ZL in the molecular state. Moreover, the obtained material, ZLPH, exhibited bright four-photon-excited fluorescence (4PEF) under the excitation of a 1550 nm femtosecond laser. In view of deep-tissue biological applications, it is envisioned that this work provides a promising platform for bright H-MPEF imaging.

Coordination-Regulated Terpyridine-Mn(II) Complexes for Photodynamic Therapy Guided by Multiphoton Fluorescence/Magnetic Resonance Imaging.

The synergy of multiphoton fluorescence imaging (MP-FI) and magnetic resonance imaging (MRI) provides an imaging platform with high resolution and unlimited penetration depth for early disease detection. Herein, two kinds of terpyridine-Mn(II) complexes (FD-Mn-O2NO and FD-Mn-FD) possessing seven and six coordination modes, respectively, were designed rationally for photodynamic therapy (PDT) guided by MP-FI/MRI. The complexes obtain different multiphoton fluorescence/magnetic resonance properties by adjusting the number of terpyridine ligands. Among them, FD-Mn-FD exhibits the following superiorities: (1) The optimal three-photon excitation wavelength of FD-Mn-FD falls at 1450 nm (NIR-II), which brings high sensitivity and deep tissue penetration in MP-FI. (2) FD-Mn-FD has effective longitudinal relaxation efficiency (r1 = 2.6 m M-1 s-1), which can be used for T1-weighted MRI, overcoming the problems of limited tissue penetration depth and low spatial resolution. (3) FD-Mn-FD generates endogenous 1O2 under irradiation by 808 nm light, thereby enhancing the PDT effect in vitro and in vivo. To the best of our knowledge, the complex FD-Mn-FD is the first complex to guide PDT through MP-FI/MRI, providing a blueprint for accurate and effective early detection and timely treatment of the complex in the early stages of cancer.

Two-photon responsive porphyrinic metal-organic framework involving Fenton-like reaction for enhanced photodynamic and sonodynamic therapy.

Designing new oxygenation nanomaterials by oxygen-generating or oxygen-carrying strategies in hypoxia-associated anti-tumor therapy is a high priority target yet challenge. In this work, we fabricated a nanoplatform involving Fenton-like reaction, Pd@MOF-525@HA, to relieve tumor hypoxia via oxygen-generating strategy for enhanced oxygen-dependent anti-tumor therapy. Thereinto, the porphyrinic MOF-525 can produce singlet oxygen (1O2) via light or ultrasonic irradiation for photodynamic and sonodynamic therapy. Notably, the well-dispersed Pd nanocubes within MOF-525 can convert H2O2 into O2 to mitigate the hypoxic environment for enhanced therapy outcome. Moreover, the two-photon activity and cancer cell specific targeting capability of Pd@MOF-525@HA gave rise to deeper tissue penetration and near-infrared light-induced fluorescence imaging to achieve precise guidance for cancer therapy. This work provides a feasible way in designing new oxygenation nanomaterials to relieve tumor hypoxia for enhanced cancer treatment.

Embedding Multiphoton Active Units within Metal-Organic Frameworks for Turning on High-Order Multiphoton Excited Fluorescence for Bioimaging.

The fabrication of high-order multiphoton excited fluorescent materials for second near-infrared (NIR-II, 1000-1700 nm) light-induced fluorescence imaging has always been an intractable challenge. In this study, a reasonable strategy guided by theoretical calculations was employed to fabricate a novel high-order multiphoton excited fluorescence (H-MPEF)-responsive UiO-type metal-organic framework (MOF, ZrTc). Strategically, the functionalization of the photonic-responsive thiazolothiazole-based organic ligand gave rise to amplified H-MPEF (four-photon activity) performance and prolonged excitation wavelength (1550 nm) of ZrTcI. The results reveal that the extended π-electron system, enhanced charge transfer, improved dipole moment, and weakened π-π stacking interactions within the MOFs endow them with excellent H-MPEF performance for NIR-II light-induced fluorescence imaging. It is an extremely rare report on H-MPEF bioimaging using MOFs and provide a universal strategy for the fabrication of H-MPEF-responsive materials.

Control the Single-, Two-, and Three-Photon Excited Fluorescence of Atomically Precise Metal Nanoclusters.

It remains challenging to control the single-, two-, and three-photon excited fluorescence of metal nanoclusters. In this work, the control over the non-linear optics of metal nanoclusters as single-, two-, and three-photon excited fluorescence has been accomplished via exploiting the solvent effect. An emissive nanocluster, Au9 Ag6 (SPht OMe)4 (DPPOE)3 Cl3 , was synthesized and structurally determined. The solvent effect can not only control the fluorescence of this nanocluster, but more significantly, it can also regulate the photoluminescence nature of the cluster as single-, two-, and three-photon excited fluorescence. We concluded that the increased solution polarity, improved dipole moment, enlarged HOMO-LUMO energy gap, and reduced solution viscosity of the cluster in solutions endow them with excellent high-order multiphoton excited fluorescence. The results provide an intriguing cluster template that enables us to manipulate the linear and nonlinear optics at the atomic level.

Self-Monitoring the Endo-Lysosomal Escape and Near-Infrared-Activated Mitophagy To Guide Synergistic Type-I Photodynamic and Photothermal Therapy.

Considering the multiple biological barriers before the entry of photosensitizers (PSs) into cytoplasm, it is of paramount importance to track PSs to elucidate their behaviors and distributions to guide the photodynamic therapy (PDT). Also, the developed PSs suffer from strong oxygen dependency. However, reports on such ideal theranostic platforms are rare. Herein, we developed a theranostic platform (CMTP-2) based on the coumarin-based D-π-A system, which, for the first time, can reveal the holistic intracellular delivery pathway and near-infrared (NIR)-activated mitophagy to guide synergistic type-I PDT and photothermal therapy. The dynamic endo-lysosomal escape of CMTP-2 was monitored, as well as its changeable distributions in endosomes, lysosomes, and mitochondria, demonstrating the preferential accumulation in mitochondria at the end. Upon NIR-I irradiation, CMTP-2 generated toxic radicals and heat, triggering the execution of mitophagy and apoptosis. In vivo experiments on mice indicated that CMTP-2 under 808 nm irradiation realized complete cancer ablation, showing great potential for advancements in synergistic phototherapy.

Revealing Sulfur Dioxide Regulation to Nucleophagy in Embryo Development by an Adaptive Coloration Probe.

Understanding signaling molecules in regulating organelles dynamics and programmed cell death is critical for embryo development but is also challenging because current imaging probes are incapable of simultaneously imaging the signaling molecules and the intracellular organelles they interact with. Here, we report a chemically and environmentally dual-responsive imaging probe that can react with gasotransmitters and label cell nuclei in distinctive fluorescent colors, similar to the adaptive coloration of chameleons. Using this intracellular chameleon-like probe in three-dimensional (3D) super-resolution dynamic imaging of live cells, we discovered SO2 as a critical upstream signaling molecule that activates nucleophagy in programmed cell death. An elevated level of SO2 prompts kiss fusion between the lysosomal and nuclear membranes and nucleus shrinkage and rupture. Significantly, we revealed that the gasotransmitter SO2 is majorly generated in the yolk, induces autophagy there at the initial stage of embryo development, and is highly related to the development of the auditory nervous system.

A multi-photon fluorescent probe based on quinoline groups for the highly selective and sensitive detection of lipid droplets.

Compared to general fluorescent probes, multi-photon fluorescent probes exhibit deeper tissue penetration, lower auto-fluorescence and lower photo-toxicity in the bio-imaging field. Herein, we synthesized a series multi-photon fluorescent probe (L1-L3) based on quinolone groups. Of notably, the three-photon fluorescence of L3 significantly enhanced when L3 interacted with liposome; moreover, L3 exhibited high selectivity towards lipid droplets in living cells. Due to its large Stokes shift, high selectivity and photon-stability, L3 was successfully used in lipid droplet imaging via multi-photon fluorescence bio-imaging.

Halogen-modified carbazole derivatives for lipid droplet-specific bioimaging and two-photon photodynamic therapy.

Lipid droplets (LDs) are dynamic multifunctional organelles that participate in the regulation of many metabolic processes, visualization of which is necessary for biological research. In this work, a series of two-photon responsive fluorescent probes (C-H, C-Br, and C-I) based on carbazole units were designed and synthesized. Thereinto, an iodine-modified carbazole derivative C-I exhibited an exciting lipid droplet targeting ability due to its excellent lipophilicity. Meanwhile, benefiting from its larger Stokes shift and two-photon absorption cross-section, C-I was employed for two-photon confocal laser scanning microscopy (CLSM) and stimulated emission depletion (STED) microscopy imaging to observe LDs more accurately. In addition, given the heavy atom effect, C-I can effectively generate reactive oxygen species (ROS) leading to cancer cell apoptosis under near-infrared light irradiation. Notably, we explained the process of cell apoptosis through in vitro simulation experiments. This study provides a promising platform for visualization of lipid droplets.

Functional Platinum(II) Complexes with Four-Photon Absorption Activity, Lysosome Specificity, and Precise Cancer Therapy.

Multiphoton materials are in special demand in the field of photodynamic therapy and multiphoton fluorescence imaging. However, rational design methodology for these brands of materials is still nascent. This is despite transition-metal complexes favoring optimized nonlinear-optical (NLO) activity and heavy-atom-effected phosphorescent emission. Here, three four-photon absorption (4PA) platinum(II) complexes (Pt1-Pt3) are achieved by the incorporation of varied functionalized C^N^C ligands with high yields. Pt1-Pt3 exhibit triplet metal-to-ligand charge-transfer transitions at ∼460 nm, which are verified multiple times by transient absorption spectra, time-dependent density functional theory calculations, and low-temperature emission spectra. Further, Pt1-Pt3 undergo 4PA. Notably, one of the complexes, Pt2, has maximum 4PA cross-sectional values of up to 15.2 × 10-82 cm8 s3 photon-3 under excitation of a 1600 nm femtosecond laser (near-IR II window). The 4PA cross sections vary when Pt2 is binding to lecithin and when it displays its lysosome-specific targeting behavior. On the basis of the excellent 4PA property of Pt2, we believe that those 4PA platinum(II) complexes have great potential applications in cancer theranostics.

In Situ Monitoring of Mitochondria Regulating Cell Viability by the RNA-Specific Fluorescent Photosensitizer.

Cell viability is greatly affected by external stimulus eliciting correlated dynamical physiological processes for cells to choose survival or death. A few fluorescent probes have been designed to detect whether the cell is in survival state or apoptotic state, but monitoring the regulation process of the cell undergoing survival to death remains a long-standing challenge. Herein, we highlight the in situ monitor of mitochondria regulating the cell viability by the RNA-specific fluorescent photosensitizer L. At normal conditions, L anchored mitochondria and interacted with mito-RNA to light up the mitochondria with red fluorescence. With external light stimulus, L generated reactive oxide species (ROS) and cause damage to mitochondria, which activated mitochondrial autophagy to prevent death, during which the red fluorescence of L witnessed dynamical distribution in accordance with the evolution of vacuole structures containing damaged mitochondria into autophagosomes. However, with ROS continuously increasing, the mitochondrial apoptosis was eventually commenced and L with red fluorescent was gradually accumulated in the nucleoli, indicating the programmed cell death. This work demonstrated how the delicate balance between survival and death are regulated by mitochondria.