Precisely modulating the chromatin tracker via substituent engineering: reporting pathological oxidative stress during mitosis.

An in-depth understanding of cancer-cell mitosis presents unprecedented advantages for solving metastasis and proliferation of tumors, which has aroused great interest in visualizing the behavior via a luminescence tool. We developed a fluorescent molecule CBTZ-yne based on substituent engineering to acquire befitting lipophilicity and electrophilicity for anchoring lipid droplets and the nucleus, in which the low polarity environment and nucleic acids triggered a "weak-strong" fluorescence and "short-long" fluorescence-lifetime response. Meaningfully, CBTZ-yne visualized chromatin condensation, alignment, pull-push, and separation as well as lipid droplet dynamics, for the first time, precisely unveiling the asynchronous cellular mitosis processes affected by photo-generation reactive oxygen species according to the subtle change of fluorescence-lifetime. Our work suggested a new guideline for tracking the issue of the proliferation of malignant tumors in photodynamic therapy.

Three-Four Photon Transition Mn(II) Complex Monitoring Lysosome-Related ATP in Real Time via Fluorescence Lifetime Imaging.

Currently, in situ monitoring of the adenosine triphosphate (ATP) level in lysosomes is critical to understand their involvement in various biological processes, but it remains difficult due to the interferences of limited targeting and low resolution of fluorescent probes. Herein, we report a classic Mn(II) probe (FX2-MnCl2) with near-infrared (NIR) nonlinear (NLO) properties, accompanied by three-four photon transition and fivefold fluorescence enhancement in the presence of ATP. FX2-MnCl2 combines with ATP through dual recognition sites of diethoxy and manganese ions to reflect slightly fluorescence lifetime change. Through the synergy of multiphoton fluorescence imaging (MP-FI) and multiphoton fluorescence lifetime imaging microscopy (MP-FLIM), it is further demonstrated that FX2-MnCl2 displays lysosome-specific targeting behavior, which can monitor lysosome-related ATP migration under NIR laser light. This work provides a novel multiphoton transformation fluorescence complex, which might be a potential candidate as a simple and straightforward biomarker of lysosome ATP in vitro for clinical diagnosis.

Tumor Stimulus-Activatable Pretheranostic Agent: One Key to Three Locks.

The uncontrollable distribution of antitumor agents remains a large obstacle for specific and efficient cancer theranostics; thus, efficient construction of tumor-specific systems is highly desirable. In this work, a general design of tumor stimulus-activatable pretheranostic agents was put forward via a series of structures-tunable triphenylamine derivatives (TPA-2T-FSQ, TPA-2T-BSZ, and TPA-2T-ML) with phenothiazine, benzothiazine, and thiomorpholine as identifying groups of hypochlorite (HClO), respectively. Notably, the sulfur atom in phenothiazine of TPA-2T-FSQ was more easily oxidized to sulfoxide groups by HClO, transforming into an electron acceptor to form an excellent push-pull electronic system, which was beneficial to a large redshift of absorbance and emission wavelengths. Based on this, TPA-2T-FSQ resorted to a key of overexpressed HClO in the tumor to open "three locks", viz, NIR fluorescence, photothermal, and photoacoustic signals for multimodal diagnostic and treatment of the tumor. This study provided an elegant design to adopt tumor stimulus-triggerable pretheranostic for improving theranostic accuracy and efficiency, which was regarded as a promising candidate for precision medicine.

Enhanced pH-Responsive Chemo/Chemodynamic Synergistic Cancer Therapy Based on In Situ Cu2+ Di-Chelation.

Considering the chemodynamic therapy and chemotherapy independent of external stimulus witnessing great advantage in the clinical translation, developing a smart nanoplatform that can realize enhanced chemo/chemodynamic synergistic therapy in the tumor microenvironment (TME) is of great significance. Herein, we highlight the enhanced pH-responsive chemo/chemodynamic synergistic cancer therapy based on in situ Cu2+ di-chelation. The alcohol-withdrawal drug disulfiram (DSF) and chemotherapeutic drug mitoxantrone (MTO) were embedded into PEGylated mesoporous CuO (denoted as PEG-CuO@DSF@MTO NPs). The acidic TME triggered the collapse of CuO and the concurrent release of Cu2+, DSF, and MTO. Then, the in situ complexation between Cu2+ and DSF, as well as the coordination between Cu2+ and MTO not only prominently enhanced the chemotherapeutic performance but also triggered the chemodynamic therapy. In vivo mouse model experiments demonstrated that the synergistic therapy can remarkably eliminate tumors. This study provides an interesting strategy to design intelligent nanosystems, which could proceed to clinical translations.

A multifunctionally reversible detector: Photoacoustic and dual-channel fluorescence sensing for SO2/H2O2.

In this work, the phenothiazine fragment with powerful electron-donating ability was specifically selected to construct a multifunctional detector (noted as T1) in double-organelle with near-infrared region I (NIR-I) absorption. The changes of SO2/H2O2 content in mitochondria and lipid droplets were observed through red/green channels respectively, which was due to the reaction between benzopyrylium fragment of T1 and SO2/H2O2 to achieve red/green fluorescence conversion. Additionally, T1 was endowed with photoacoustic properties deriving from NIR-I absorption to reversibly monitor SO2/H2O2in vivo. This work was significant for more accurately deciphering the physiological and pathological processes in living organisms.

Pt-N Coordination Rendering the Chemotherapeutic Agent with Photoactivated ROS Generation and Self-Reporting Cell Uptake.

The performance of chemotherapeutic agents has been largely restrained by the dose-dependent toxic side effects. In this work, cisplatin (CDDP) was endowed with the capability of photoactivated reactive oxygen species (ROS) generation and self-reporting cell uptake via coordination with a small organic molecule MSN. In the resultant MSN-Pt, the Pt-N coordination could obviously enhance the intermolecular charge transfer (ICT) process that allows the integration of fluorescence imaging, photogenerated ROS, and chemotherapeutic performance. The resultant MSN-Pt can recognize between normal and cancer cells and quickly penetrate the cancer cell membrane, self-reporting the cell uptake. Upon light illumination, mitochondria and nuclei were severely damaged. An in vivo mouse model demonstrated that MSN-Pt completely inhibited the tumor growth, exhibiting a higher efficacy compared with that of CDDP. This work provides a facile strategy to develop chemotherapy (CT) drugs for drug-resistant cancers.

Unveiling upsurge of photogenerated ROS: control of intersystem crossing through tuning aggregation patterns.

Photo-induced reactive oxygen species (ROS) generation by organic photosensitizers (PSs), which show potential in significant fields such as photodynamic therapy (PDT), are highly dependent on the formation of the excited triplet state through intersystem crossing (ISC). The current research on ISC of organic PSs generally focuses on molecular structure optimization. In this manuscript, the influence of aggregation patterns on ISC was investigated by constructing homologous monomers (S-TPA-PI and L-TPA-PI) and their homologous dimers (S-2TPA-2PI and L-2TPA-2PI). In contrast to J-aggregated S-TPA-PI, S-2TPA-2PI-aggregate forming "end-to-end" stacking through π-π interaction could generate ROS more efficiently, due to a prolonged exciton lifetime and enhanced ISC rate constant (k ISC), which were revealed by femtosecond transient absorption spectroscopy and theoretical calculations. This finding was further validated by the regulation of aggregation patterns induced by host-guest interaction. Moreover, S-2TPA-2PI could target mitochondria and achieve rapid mitophagy to cause more significant cancer cell suppression. Overall, the delicate supramolecular dimerization tactics not only revealed the structure-property relationship of organic PSs but also shed light on the development of a universal strategy in future PDT and photocatalysis fields.

Near-infrared light activated photosensitizer with specific imaging of lipid droplets enables two-photon excited photodynamic therapy.

Two-photon excited phototherapy has attracted considerable attention due to its advantages such as deeper penetration depth and higher spatial resolution. The lack of a high-performance photosensitizer with large two-photon absorption cross-sections and specific targeting ability makes the efficacy of phototherapy in the treatment of cancer unsatisfactory. Here, a new BODIPY-derived photosensitizer 6DBF2 is designed with two-photon photosensitization for two-photon excited photodynamic therapy in vivo. 6DBF2 possesses good two-photon absorption and efficient 1O2 generation upon near-infrared laser excitation. Excellent targeting specificities to lipid droplets of 6DBF2 without any encapsulation or modification at a low working concentration of 0.1 µM is in favor of efficient photodynamic therapy. In vitro cancer cell ablation and in vivo tumor ablation inside mice models upon two-photon irradiation in NIR demonstrate the outstanding therapeutic performance of 6DBF2 in two-photon excited photodynamic therapy. This work thus discusses a rare example of lipid droplets targeting two-photon excited photodynamic therapy for deep cancer tissue imaging and treatment under near-infrared light irradiation.

Photo-Activated Ratiometric Fluorescent Indicator for Real-Time and Visual Detection of Plasma Membrane Homeostasis.

Development of an activated ratiometric indicator that is specific to plasma membrane (PM) viscosity exhibits great application prospects in disease diagnosis and treatment but remains a great challenge. Herein, a photo-activated fluorescent probe (CQ-IC) was designed and prepared tactfully, which could analyze and real-time monitor the microenvironmental homeostasis of the PM based on a two-channel ratiometric imaging model. Interestingly, upon light irradiation, CQ-IC generates reactive oxygen species and thus increases the cellular viscosity, which increases two emission peaks at 480 and 610 nm. This work would propose a new strategy to sensor PM homeostasis and effectively guide the treatment of viscosity-related diseases among various physiological and pathological processes.

Black graphitic carbon nitride nanosheets with mid-gap states realizing highly efficient near-infrared photo-thermal conversion for photoacoustic imaging.

Developing metal-free photo-thermal transduction nanoagents (PTNAs) with high conversion efficiency addresses the balance between superior photothermal performance and good biocompatibility in the field of bio-applications of PTNAs. Herein, we highlight the bandgap-engineered black graphitic carbon nitride nanosheets (denoted as B-g-C3N4) as a novel metal-free PTNA with high conversion efficiency (62% at 808 nm) for photoacoustic imaging. The B-g-C3N4 absorbed infrared light with a narrowed bandgap and electronic states within the band (known as mid-gap states) due to the synergistic effect of sulfur incorporation, nitrogen vacancies and the porous structure. Notably, the mid-gap states mediated the non-irradiative recombination of electrons and holes, bringing about energy dissipated as phonons. Owing to the high conversion efficiency as well as superior biocompatibility, HeLa cells incubated with B-g-C3N4 can be ablated under 808 nm light illumination. Furthermore, the B-g-C3N4 realized cross-sectional multispectral optoacoustic tomography (MSOT) imaging of the U14-tumor-bearing mouse. This work expands the catalogue of highly efficient metal-free PTNAs, showing great promise in biological applications.

Molecular Tailoring Based on Forster Resonance Energy Transfer for Initiating Two-Photon Theranostics with Amplified Reactive Oxygen Species.

The fabrication of multifunctional photosensitizers (PSs) with abundant Type I/II ROS for efficient theranostics in the "therapeutic window" (700-900 nm) is an appealing yet significantly challenging task. We herein report a molecular tailoring strategy based on intramolecular two-photon Forster Resonance Energy Transfer (TP-FRET) to obtain a novel theranostic agent (Lyso-FRET), featuring the amplified advantage of energy donor (NH) and acceptor (COOH), because of the reuse of fluorescence energy with high efficiency of FRET (∼83%). Importantly, under the excitation by the near-infrared (840 nm) window, Lyso-FRET can not only penetrate the deeper tissue with a higher resolution for fluorescence imaging due to the nonlinear optical (NLO) nature, but also generate more Type I (superoxide anion) and Type II (singlet oxygen) reactive oxygen species for hypoxic PDT. Moreover, Lyso-FRET targeting lysosomes further promotes the effect of treatment. The experiments in vitro and in vivo also verify that the developed TP-FRET PS is conducive to treating deep hypoxic tumors. This strategy provides new and significant insights into the design and fabrication of advanced multifunctional PSs.

Solvatochromic Two-Photon Fluorescent Probe Enables In Situ Lipid Droplet Multidynamics Tracking for Nonalcoholic Fatty Liver and Inflammation Diagnoses.

Intracellular lipid storage and regulation occur in lipid droplets, which are of great significance to the physiological activities of cells. Herein, a lipid droplet-specific fluorescence probe (lip-YB) with a high quantum yield (QYlip-YB = 73.28%), excellent photostability, and quickly polarity sensitivity was constructed successfully. Interestingly, lip-YB exhibited remarkable two-photon (TP) characteristics, which first realized real-time monitoring of the lipid droplet multidynamics process, diagnosing nonalcoholic fatty liver disease (NAFLD) and inflammation in living mice via TP fluorescence imaging. It is found that the as-prepared lip-YB provides a new avenue to design lipid droplet-specific imaging probes, clarifies its roles and mechanisms in cell metabolism, and can timely intervene in lipid droplet-related diseases during various physiological and pathological processes.

Interface-Engineered Mesoporous FeB with Programmed Drug Release for Synergistic Cancer Theranostics.

The pursuit of mesoporous Fe-based nanoagents addresses the field of developing alternative Fe-bearing nanoagents for synergistic cancer therapy with the expectation that the use of an essential element may avoid the issues raised by the exogenous administration of other metal element-based nanoagents. Herein, we highlight the interface-engineered mesoporous FeB (mFeB) where the core mFeB is interfacially oxidized into an FeOOH nanosheet loaded with the chemotherapeutic drug doxorubicin (DOX) and further encapsuled within the double-sulfide-bonded SiO2 outer layer, denoted as mFeB@DOX-ss-SiO2, which can realize programmed drug release for synergistic cancer theranostics. When only in a tumor microenvironment, the nanoagent can be activated to release DOX from the mFeB and FeOOH nanosheets as well as expose the easily oxidized mFeB to spontaneously transform to FeOOH nanosheets with Fenton activity to facilitate chemodynamic therapy (CDT). In addition, the high photothermal conversion efficiency of mFeB@DOX-ss-SiO2 would promote CDT. Also, owing to the inherent nature of ferromagnetism and red fluorescence of DOX, mFeB@DOX-ss-SiO2 can realize T2-weighted magnetic resonance imaging and fluorescence imaging. In vivo mouse model experiments demonstrate that mFeB@DOX-ss-SiO2 with good biocompatibility realizing CDT/photothermal therapy/chemotherapy achieved complete tumor suppression. This study opens up a new way to explore theranostic nanoagents.

Polarity-Sensitive Probe: Dual-Channel Visualization of the "Chameleon" Migration with the Assistance of Reactive Oxygen Species.

The real-time and differentiated visualization of the organelles is favorable for exploring the distribution and interaction. However, most visual probes emit monochromatic fluorescence and target a single organelle, which impedes the in-depth study of their interplay. To overcome this obstacle, we tactfully conceived a polarity-sensitive fluorescent DPDO-C that could accurately discriminate polarity changes in the cellular environment, exhibiting distinct fluorescence in lipid droplets (LDs) and mitochondria. Remarkably, the probe DPDO-C could migrate from mitochondria to LDs with the assistance of reactive oxygen species, which was conducive to further monitoring of the number and size of LDs as well as the interactions between LDs and other organelles. Moreover, the nuanced difference between normal and fatty liver tissues was also distinguished by two-color fluorescence imaging, which could act as a promising candidate for the early diagnosis of fatty liver.

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.

Near-Infrared multifunctional theranostic agent with Wave-Like aggregates modulated by substituent position effect.

Precise design of organic photosensitizers (PSs) promoted the technological innovation for multimodal imaging-guided synergistic therapy. Nonetheless, various group substitution could not only optimize the basic photophysical behavior, but possibly change the aggregate, which handicaps the deep understanding of the "Formula-Aggergete-Property" relationship. Bearing this in mind, herein two isomers, named 6-TDE and 7-TDE, were prepared via substituting position modification. Among them, 6-TDE exhibited the grid-like structure, while 7-TDE presented wavy-like structure. Despite the aggregates were different, 6-TDE and 7-TDE shared common features including partly twisted backbone and non-overlapped-orbit, hence resulting in similar optical physical behavior such as decent extinction coefficient, near-IR emission, large stockes shifts, etc. Meanwhile, though two PSs could both generated Type-I and Type-II ROS, 7-TDE possessed smaller singlet-triplet splitting (ΔEST), which exhibited favorable ROS as well as outstanding mitochondrial targeting, achieving efficient photodynamic therapy (PDT) effect. During this process, mitochondrial autophagy could be tracked and observed effectively and in real-time. Moreover, 7-TDE presented outstanding performance in multimodal imaging, including fluorescence imaging (FLI), photoacousticimaging (PAI) and photothermal imaging (PTI). This study enriches the strategy of precise molecular engineering to optimize theranostic agents.

Unveiling Mechanism of Organic Photogenerator for Hydroxyl Radicals Generation by Molecular Modulation.

Photodynamic therapy (PDT) with organic photosensitizers generally goes through the oxygen-dependent process, generating singlet oxygen and/or superoxide anion. However, the generation of reactive oxygen species is often suppressed as a result of hypoxia, one of the common features in tumors, therefore limiting the effectiveness of the tumor treatments. Consequently, it is urgent and significant to develop an oxygen-independent hydroxyl radical photogenerator and unveil the mechanism. In this work, a hydroxyl radical (·OH) photogenerator originating from the electron transfer process is engineered. Detailed mechanism studies reveal that the optimized photosensitizer, WS2D, which contains a bithiophene unit, could both promote charge carrier generation and accelerate reaction efficiency, resulting in the efficient production of ·OH. In addition, WS2D nanoparticles are constructed to improve the polydispersity and stability in aqueous solution, which exhibit excellent biocompatibility and mitochondrial targeting. Bearing the above advantages, WS2D is employed in phototheranostics, which could release ·OH effectively and damage mitochondria precisely, achieving high PDT efficiency in vitro and in vivo. Overall, this work successfully provides valuable insights into the structural design of a hydroxyl radicals (·OH) photogenerator with great practical perspectives.

Real-time imaging mitochondrial viscosity dynamic during mitophagy mediated by photodynamic therapy.

Photodynamic therapy has been generally developed and approved as a promising theranostic technique in recent years, which requires photosensitizers to bear high efficiency of reactive oxygen species production, precisely targeting ability and excellent biocompatibility. The real-time monitoring the microenvironments such as viscosity dynamic involved in mitophagy mediated by photodynamic therapy is significantly important to understand therapeutic process but barely reported. In this work, a pyridinium-functionalized triphenylamine derivative, (E)-4-(2-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)vinyl)-1-methylpyridin-1-ium iodide (Mito-I), was exploited as photosensitizer for mitochondria-targeted photodynamic therapy and as fluorescent probe for imaging the mitochondrial viscosity dynamic during mitophagy simultaneously. The results indicated that the additional phenyl ring in Mito-I was beneficial to promote its efficiency of singlet oxygen production. The excellent capability of targeting mitochondria and singlet oxygen generation allowed Mito-I for the specifically mitochondria-targeted photodynamic therapy. Moreover, Mito-I displayed off-on fluorescence response to viscosity with high selectivity and sensitivity. The observed enhancement in fluorescence intensity of Mito-I revealed the increasingly mitochondrial viscosity during mitophagy mediated by the photodynamic therapy of Mito-I. As a result, this work presents a rare example to realize the mitochondria-targeting photodynamic therapy as well as the real-time monitoring viscosity dynamic during mitophagy, which is of great importance for the basic medical research involved in photodynamic therapy.

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.

Defective transition metal hydroxide-based nanoagents with hypoxia relief for photothermal-enhanced photodynamic therapy.

Recently, phototherapy has attracted much attention due to its negligible invasiveness, insignificant toxicity and excellent applicability. The construction of a newly proposed nanosystem with synergistic photothermal and photodynamic tumor-eliminating properties requires a delicate structure design. In this work, a novel therapeutic nanoplatform (denoted as BCS-Ce6) based on defective cobalt hydroxide nanosheets was developed, which realized hypoxia-relieved photothermal-enhanced photodynamic therapy against cancer. Defective cobalt hydroxide exhibited high photothermal conversion efficacy at the near-infrared region (49.49% at 808 nm) as well as enhanced catalase-like activity to produce oxygen and greatly boost the singlet oxygen generation by a photosensitizer, Ce6, realizing efficacious dual-modal phototherapy. In vivo and in vitro experiments revealed that BCS-Ce6 can almost completely extinguish implanted tumors in a mouse model and present satisfactory biocompatibility during the treatment. This work sets a new angle of preparing photothermal agents and constructing comprehensive therapeutic nanosystems with the ability to modulate the hypoxic tumor microenvironment for efficient cancer therapy.