Theranostic Fluorescent Probes

Mitochondria-targeted and near-infrared phosphorescent Ir(III) complexes for specific detection of Hg2+ and photodynamic therapy

S: Mercury ions (Hg2+) are highly toxic and prone to bioaccumulation, showing a strong attraction to proteins and enzymes that contain sulfur. Even minute quantities of Hg2+ can lead to severe health issues. Given that mitochondria are a primary target organelle of Hg2+, it is essential to create a probe that can accurately detect Hg2+ within intracellular mitochondria. In this study, we developed two innovative Ir(III) complex probes that emit near-infrared light. The crystal structure of Ir2 was determined using X-ray techniques, which reveals that Ir2 contains a pyridine group capable of recognizing Hg2+ and targeting mitochondria, allowing for the precise identification of Hg2+ both in vitro and within the mitochondria of living cells. Additionally, these two novel near-infrared phosphorescent Ir(III) complexes demonstrate significant capabilities in producing ROS including singlet oxygen, ·O2- and ·OH, which renders them effective photosensitizers under visible light exposure for photodynamic therapy (PDT). This research offers a promising approach for detecting Hg2+ in vitro and in the mitochondrial microenvironment of living cells, which have some implications for the future development of pertinent transition metal complexes for mitochondria-targeted photodynamic therapy in cancer cells.

Reprogrammed glycolysis-induced augmentation of NIR-II excited photodynamic/photothermal therapy

Small molecule-based multifunctional optical diagnostic materials have garnered considerable interest due to their highly customizable structures, tunable excited-state properties, and remarkable biocompatibility. We herein report the synthesis of a multifaceted photosensitizer, PPQ-CTPA, which exhibits exceptional efficacy in generating Type I reactive oxygen species (ROS) and thermal energy under near-infrared-II (NIR-II, >1000 nm) laser excitation at 1064 nm, thereby combining photodynamic therapy (PDT) and photothermal therapy (PTT) functionalities. To enhance therapeutic efficacy, we engineered lonidamine (LND) by conjugating it with triphenylphosphonium (TPP) cations, producing LND-TPP. This compound inhibits mitochondrial glycolysis and downregulates heat shock protein 90 (HSP 90) levels in a breast cancer mouse model, potentiating both PDT and PTT. For in vivo applications, PPQ-CTPA and LND-TPP are encapsulated within the amphiphilic polymer DSPE-SS-PEG to obtain PPQ-CTPAL NPs. In breast cancer cell lines, PPQ-CTPAL NPs are decomposed by cellular GSH, simultaneously releasing the dual-functioning photosensitizer PPQ-CTPL and the mitochondria-disrupting agent LND-TPP. Upon 1064 nm laser irradiation, we found that tumor growth in breast cancer mice is effectively restrained by PPQ-CTPAL NPs. This work highlights the synergistic integration of PDT, PTT, and chemotherapy facilitated by NIR-II fluorescence, photoacoustic, and photothermal imaging under 1064 nm irradiation, underscoring the clinical potential of multifunctional phototherapeutic agents.

Advancements in small molecule fluorescent probes for the detection of formaldehyde in environmental and food samples: A comprehensive review

Formaldehyde (FA), a hazardous substance with carcinogenicity and mutagenicity, necessitates sensitive and accurate detection methods for protecting public health and the environment. While numerous reviews have explored FA fluorescent probes, the current literature predominantly emphasizes biological systems, leaving a gap in addressing FA's roles in environmental monitoring and food safety. This review discusses recognition mechanisms for FA detection, including 2-aza-Cope rearrangement, methylenehydrazine reaction, formimine formation, and other mechanisms. Furthermore, this review underscores the practical applications of these probes in real-world contexts, namely their incorporation into test strips, hydrogels, and membranes for environmental monitoring and food safety. Moreover, this review highlights future directions for developing intelligent detection systems that combine fluorescent probes with data processing algorithms and artificial intelligence technologies. By synthesizing the current knowledge in this area, this review aims to stimulate future research and advancements in FA detection technology, ultimately contributing to improved environmental management and public health protection.

Multifunctional carbon dots for pH sensing, intracellular imaging, amino acid classification, and test strip development

Intracellular pH is a key indicator of cellular stability and plays a critical role in understanding biological processes and diagnosing various diseases. In this study, yellow-emitting carbon dots (C-dots) were synthesized via hydrothermal treatment of o-phenylenediamine and p-aminobenzoic acid. These C-dots exhibited pH-sensitive fluorescence, with intensity increasing as the pH ranged from 2.0 to 10.0, displaying a pKa value of 5.14 and a linear response between pH 4.0 and 6.0. The observed pH sensitivity is mainly due to the abundant carboxyl groups on the C-dots' surface, which undergo protonation, deprotonation, and electrostatic transfer in response to pH changes. Additionally, these C-dots effectively detected both acidic and alkaline amino acids in aqueous solutions and on test strips. Notably, they were successfully used for intracellular imaging of amino acids, offering a significant advantage over toxic small-molecule reagents that can alter pH levels in living cells. These pH-sensitive C-dots have the potential to enhance applications in both analytical detection and biological imaging, expanding their use in variety of fields.

A robust H2O2-responsive AIEgen with multiple-task performance: Achieving food analysis, visualization of dual organelles and diagnosis of liver injury

Drug- and alcohol-induced liver injury poses a serious threat to human health with long-lasting clinical, social and economic consequences. As a reactive oxygen species (ROS), hydrogen peroxide (H2O2) is widely-used as a molecular biomarker of liver injury. H2O2 is also utilized as a processing aid in the food industry. Therefore, monitoring the levels of H2O2 in liver and food samples is important for disease diagnosis and food safety demanding the development of efficient sensing and visualization tools. To address this challenge, we report a novel aggregation-induced emission (AIE) fluorescent probe for detecting H2O2 named TVQ-B, featuring near-infrared (NIR) emission (740 nm), large Stokes shift (195 nm), fast response time and high selectivity. Interestingly, H2O2 can activate the dual organelles targeting ability of TVQ-B for mitochondria and lipid droplets, enabling dual-channel imaging of H2O2. Importantly, the TVQ-B probe has been successfully used to monitor H2O2 in food samples, living cells, zebrafish and mice. This fluorescence imaging approach using endogenous H2O2 as a marker provides a robust and convenient diagnostic protocol for drug- and alcohol-induced liver injury. Based on this protocol, TVQ-B-based visualization provided potent evidence for the therapeutic efficacy of natural flavonolignan silybin for the reduction of negative effects of alcohol consumption.

Monitoring the level of hydrogen sulfide in arthritis and its treatment with a novel near-infrared fluorescent probe

Hydrogen sulfide (H2S) is a physiological gaseous transmitter that plays a crucial role in maintaining the cellular redox state. Arthritis is usually accompanied by redness, swelling, pain, dysfunction and deformity of the joints, and in severe cases can lead to joint disability. Disorders of H2S level are associated with the pathological process of arthritis. In this paper, a near-infrared fluorescent probe (TX-H2S) was developed to detect the alterations in H2S levels of arthritis. TX-H2S has excellent response performance to H2S such as near-infrared emission (725 nm), large Stokes shift (125 nm) and high fluorescence enhancement (72-fold). Owing to low cytotoxicity, the probe can be employed to observe the alterations of exogenous and endogenous H2S level in HeLa and HepG2 cells. By making full use of near-infrared emission and good biocompatibility, the probe can be employed for exogenous H2S imaging in mice, and is able to track the fluctuation of H2S level during arthritis and its treatment. These make the probe have the potential to invent an efficient tool for the diagnosis of arthritic disease and its treatment.

Advanced Postsynthetic Modification of COF: Elevating Hydrophilicity for Efficient Doxorubicin Delivery

Covalent organic frameworks (COFs) show great potential as drug delivery systems (DDSs) due to their customizable structures, stability, and capacity for pore surface functionalization. However, their natural hydrophobicity limits their dispersion in water, posing challenges for biological applications. We address this issue by initially reducing a COF (Az-COF) to an amine-linked form (Az-AL-COF) and subsequently sulfonating it to obtain Az-AL-SO3H-COF, a water-dispersible derivative. Water contact angle (WCA) analysis confirmed increased hydrophilicity across the series of 84.5, 61.2, and 54.7° for Az-COF, Az-AL-COF, and Az-AL-SO3H-COF, respectively. Using doxorubicin (Dox) as a model drug, the modified COFs exhibited pH-sensitive drug release, with greater release at acidic pH (5.6) compared to neutral pH (7.4). Cytotoxicity assays revealed that Az-AL-SO3H-COF was biocompatible with normal cells (MCF-10) while effectively suppressing the growth of cancer cells (MDA-MB-231). The Dox-loaded sulfonated COF (Dox@Az-AL-SO3H-COF) showed selective cytotoxicity against cancer cells, highlighting its potential as a pH-responsive, biocompatible DDS for cancer treatment.

Construction of a mitochondrial-targeting near-infrared fluorescent probe for detection of viscosity changes in type 2 diabetes mellitus and nonalcoholic steatohepatitis

The intracellular viscosity plays a pivotal role as a physicochemical factor and an important indicator of organelles performance. Abnormal changes in subcellular viscosity are often associated with cellular malfunction and various diseases. Nonalcoholic steatohepatitis (NASH) is the most common liver disease related with type 2 diabetes mellitus (T2DM), and both are linked to aberrant mitochondrial viscosity. In this study, we styled and screened a novel near-infrared probe termed MT-E, carrying the double bonds as the viscosity response groups, that was employed to image the viscosity changes in HepG2 cells, zebrafish and animal models. MT-E has a superior mitochondrial targeting ability, as well as a large Stokes shift (167 nm). Additionally, utilizing the excellent performance of MT-E, we first monitored the increased viscosity trends in both T2DM mice and NASH mice, suggesting that there is a strong correlation between T2DM and NASH. More groundbreakingly, we have successfully revealed, from fluorescence imaging, the extraordinary potential of Aloin in treating T2DM mice that can effectively reduce viscosity. This is a sign that MT-E may have a steering role in mitochondrial viscosity-associated disorders.

A self-aggregated thermally activated delayed fluorescence nanoprobe for HClO imaging and activatable photodynamic therapy

Hypochlorous acid (HClO/ClO-) is a common ROS that exhibits elevated activity levels in cancer cells. In this study, an ClO--triggered TADF probe, PTZ-MNI, was designed based on a naphthalimide core. PTZ-MNI self-assemble in aqueous environments, exhibiting significantly enhanced fluorescence that demonstrated typical aggregation-induced delayed fluorescence (AIDF) characteristics. The probe not only showed high sensitivity to ClO- but also exhibited remarkable selectivity over other reactive oxygen species and disturbance. PTZ-MNI displayed TADF characteristic, including sensitivity to oxygen in toluene, insensitivity to oxygen in aggregated states that maintain long fluorescence lifetimes, a vertical conformation, and a minimal ΔEST of 0.01 eV. Cell imaging studies showed the probe could trace ClO- by red to green fluorescence in HeLa cell. The colocalization analysis indicated its excellent lysosome-targeting specificity. In addition, PTZ-MNI-O, the compound after oxidation, exhibited effective ROS generation ability and significant PDT effect after irradiation. This work provides guidance for the rational design of responsive TADF luminescent materials used in cell imaging and activatable-PDT.

Recent advances in bioresponsive macrocyclic gadolinium(III) complexes for MR imaging and therapy

Magnetic resonance (MR) imaging is a non-invasive clinical diagnostic modality that provides anatomical and physiological information with sub-millimetre spatial resolution at the organ and tissue levels. It utilizes the relaxation times (T1 and T2) of protons in water to generate MR images. However, the intrinsic MR contrast produced by water relaxation in organs and tissues is limited. To enhance the sensitivity and specificity of MR imaging, about 30%-45% of all clinical MR diagnoses need to use contrast media. Currently, all clinically approved MR contrast agents are linear or macrocyclic gadolinium(III) (Gd(III)) complexes, which are not specific to particular biological events. Due to the relatively high potential for releasing toxic free Gd(III), linear Gd(III) complexes raise safety concerns, making macrocyclic Gd(III) probes the preferred choice for clinical MR imaging without acute safety issues. To enhance the capability of MR imaging for detecting dynamic biological processes and conditions, many bioresponsive macrocyclic Gd(III) complexes capable of targeting diverse biomarkers have been developed. This review provides a concise and timely summary of bioresponsive macrocyclic Gd(III) contrast agents, particularly those developed between 2019 and 2024. We focus on three major types of Gd(III) agent that respond specifically to changes in pH, chemicals, and enzymes, highlighting their molecular design strategies, proton-relaxivity responses, and applications in in vitro and in vivo MR imaging for monitoring specific biomedical conditions and therapies.

Self-Assembled Triple-Targeted Radiosensitizer Enhances Hypoxic Tumor Targeting and Radio-Immunotherapy Efficacy

Targeted delivery of radiosensitizers and real-time monitoring of hypoxia are crucial for overcoming radiotherapy resistance in hypoxic tumors. Here, we report A-Cy-Ni-RGD, a triple-targeted nitroimidazole (Ni)-linked radiosensitizer that self-assembles into nanoparticles (A-Cy-Ni-RGD NPs) for bimodal near-infrared fluorescence (NIR FL) and photoacoustic (PA) imaging-guided radio-immunotherapy. A-Cy-Ni-RGD NPs specifically accumulate in αvβ3-positive tumors, where they are hydrolyzed by carboxylesterase to form Cy-Ni-RGD NPs, with enhanced FL at 710 nm and dual PA signals at 680 and 730 nm. Under hypoxic conditions, nitroreductase (NTR) further reduces these NPs, covalently labeling endogenous proteins and increasing NP size. This process partially alleviates aggregation-caused quenching effect, increasing the FL710 signal and decreasing the PA730 signal, enabling real-time tracking of tumor-specific delivery and hypoxia. Following low-dose X-ray irradiation (2 Gy), elevated NTR expression promotes further Cy-Ni-RGD NPs reduction, enhancing proteins labeling and causing DNA damage. Moreover, radiosensitization with A-Cy-Ni-RGD NPs triggers robust immunogenic cell death, stimulating antitumor immunity that inhibits tumor growth and metastasis, significantly prolonging survival in mice with orthotopic 4T1 tumors. This work underscores the potential of self-assembling, triple-targeted radiotheranostic agents for improving tumor targeting, imaging, and radiotherapy efficacy in hypoxic tumors.

Indacenodithienothiophene-based A-D-A-type phototheranostics for immuno-phototherapy

The development of phototherapeutics with high photothermal conversion efficiency (PCE) and strong ability to generate reactive oxygen species under single near-infrared (NIR) laser irradiation for immuno-phototherapy applications remains a significant challenge. Herein, we optimally selected the molecule IT-4 F with an acceptor-donor-acceptor (A-D-A) strucssture to prepare water-dispersible nanoparticles (NPs) by assembly with DSPE-PEG-NH2. Such NPs have NIR absorption and fluorescence peaks at 728 and 817 nm, respectively. They can generate singlet oxygen (1O2) and superoxide anion (O2-·) under laser irradiation, with a 1O2 generation quantum yield of 31.5%. They can also effectively convert photon-energy into heat with a high PCE of 42.8%. The outstanding properties of IT-4 F NPs enable them to be used in NIR fluorescence imaging guided photothermal therapy (PTT), and photodynamic therapy (PDT). Moreover, PDT and PTT triggered immunogenic cell death and PANoptosis in tumor cells, which not only inhibited tumor growth and metastasis in mice model, but also induced a robust immune response, evidenced by increased infiltration of CD8+ T cells, CD4+ T cells, dendritic cells, and a decreased presence of immunosuppressive cells such as myeloid-derived suppressor cells and regulatory T cells. The efficacy of IT-4 F NPs in organoid of human breast cancer was also verified.

Dual-emission fluorescent probe with sequential two-step ESIPT activation mechanism for selective hydrazine detection and multifunctional applications

Hydrazine is a commonly used chemical in various industries, including pharmaceuticals, agriculture, and aerospace. However, its high toxicity may cause serious harm to the natural environments and human health. The development of new methods for sensitive and selective detection of hydrazine is of great significance. In this study, we present a fluorescent probe that employs a unique two-step excited-state intramolecular proton transfer (ESIPT) activation mechanism for hydrazine detection. This probe integrates a phthalimide group into benzothiazole scaffold with its fluorescence initially quenched due to the inhibition of ESIPT process and photo-induced electron transfer (OFF state). Upon exposure to hydrazine, the nucleophilic cleavage of the phthalimide group activates the first ESIPT process, yielding yellow emission (ON1 state). A subsequent deprotection step triggers the second ESIPT process, producing blue fluorescence (ON2 state). These three states fluorescent change along with dual-emission signal output provide a highly sensitive and reliable method for hydrazine detection and monitoring, with a limit of detection (LOD) of 18 nM. Moreover, this probe showed versatile applications in environmental monitoring, food sample analysis, plant imaging, and bioimaging, including a convenient smartphone-assisted quantitative assay. The dual-activation mechanism offers valuable insights for the design of novel ESIPT probes, paving the way for promoting their applications in chemical, biological, and environmental fields.

Development of a near-infrared fluorescent probe for in situ monitoring of hydrogen peroxide in plants

In plants, hydrogen peroxide (H2O2), one of the significant reactive oxygen species, plays a dual function. Investigating its concentration is essential for understanding its production and scavenging mechanisms in plants. In this study, a near-infrared fluorescent probe (Cy-Bo) was developed, which is based on the hemicyanine compound. By introducing indole salts into the oxygenated anthraquinone structure, the conjugated system is expanded, enabling the probe to emit long-wavelength fluorescence in the near-infrared region, thereby minimizing interference from other biomolecules in plant tissues (λex = 650 nm, λem = 720 nm). As for the specific recognition of H2O2, the pinacol phenylborate ester was selected to be the recognition group. It shows good linearity (R2 = 0.998) in the concentration range of 0.5-100 μM, with a detection limit of 0.07 μM. Furthermore, this probe Cy-Bo has been used for in vivo fluorescence imaging in plants due to its good bio-penetration and in-situ imaging capabilities. The results reveal a significant increase in H2O2 concentration in Arabidopsis thaliana under progressively increasing drought, high-temperature, and salt stress. This tool provides a non-invasive, in situ imaging method for detecting H2O2 in plants, which has a fast response, easy operation, and high sensitivity. It enables visual monitoring of H2O2 fluctuations and aids in advancing physiological and pathological studies related to H2O2.

A zwitterionic chromophore as both a biomarker-activatable optical imaging probe and a therapeutic agent for the detection and treatment of acute lung injury with bacterial infection

Acute lung injury (ALI), often complicated by bacterial infection, poses significant challenges in diagnosis and treatment. Nitric oxide (NO) plays a key role in the pathophysiology of ALI, making it an ideal biomarker for early detection. In this study, we developed a zwitterionic chromophore, ZW-N, designed as both a biomarker-activatable imaging probe and a therapeutic agent for ALI with bacterial infection. The chromophore ZW-N integrates quaternary ammonium groups for antimicrobial activity and zwitterionic sulfonate groups to enhance biocompatibility and water solubility. Built on a flexible propanyl linker that couples two heptamethine cyanine dyes, ZW-N enables biomarker-responsive dual-modal imaging via optoacoustic (OA) imaging and near-infrared second-window (NIR-II) fluorescence imaging. Moreover, the chromophore ZW-N demonstrates therapeutic efficacy when combined with the clinically used antioxidant N-acetylcysteine (NAC) to treat ALI with bacterial infection. This dual-functional chromophore offers a promising platform for non-invasive, real-time monitoring of ALI, providing significant potential for improved detection and a more effective treatment strategy.

Recent Advances in Enzyme-Activated Dual-Locked Probes for Biological Applications

Enzymes catalyze reactions involved in diverse physiological, pathological, and pharmacological processes. By employing the optical probe, fluorescence imaging enables non-invasive, real-time detection and assessment of disease states based on enzymatic activity. However, most enzyme-activated probes are single-locked probes that respond to a single biomarker. In comparison to single-locked probes, enzyme-activated dual-locked probes can effectively minimize the occurrence of false-positive signals, circumvent the problem of low specificity associated with biologically active substances, and facilitate precise imaging. This review systematically summarizes the design and application of dual-locked probes in disease diagnosis, with the aim of providing inspiration for researchers in the field.

Reconfigurable logic operations for fluorescent sensing of drug resistant and/or hypoxic cancer cells

Precision diagnosis is of great importance and can be achievable through information processing sensors. A distyryl pyridinium BODIPY decorated with nitroreductase and esterase enzyme responsive modules is shown to display configurable fluorescence read out upon enzyme-catalysed elimination reaction creating pyridine distyryl BODIPYs. Discrimination of the cellular profile, i.e. drug resistance and hypoxic microenvironment, is achieved with a single molecule through reconfigurable molecular logic gate operations.

Regulated cell death mechanisms in mitochondria-targeted phototherapy

Phototherapy, comprising photodynamic therapy (PDT) and photothermal therapy (PTT), was first introduced over a century ago and has since evolved into a versatile cancer treatment modality. While numerous studies have explored regulated cell death (RCD) mechanisms induced by phototherapy, a comprehensive synthesis centered on mitochondria-targeted phototherapeutic strategies and agents as mediators of RCD is still lacking. This review provides a systematic and in-depth analysis of recent advances in mitochondria-centered mechanisms driving phototherapy-induced death pathways, including apoptosis, autophagy, pyroptosis, immunogenic cell death, ferroptosis, and cuproptosis. We highlight the critical role of mitochondria as central regulators of these death pathways in response to phototherapeutic interventions. Moreover, we discuss fundamental design strategies for developing precision-targeted phototherapeutic materials to enhance efficacy and minimize off-target effects. Finally, we identify prevailing challenges and propose future research directions to address these hurdles, paving the way for next-generation mitochondria-targeted phototherapy as a highly effective strategy for cancer management.

Unlocking the Power of Photothermal Agents: A Universal Platform for Smart Immune NIR-Agonists for Precise Cancer Therapy

Selective ablation of tumor cells allows safe eradication, thereby minimizing off-target damage, while specifically inducing immunogenic cell death (ICD) rather than commonly non-immunogenic apoptosis of tumor cells enables activation of anti-tumor immune response against residual cancer cells, including metastatic lesions. Herein, we present a general strategy leveraging a novel photothermal agent (PTA) that concomitantly enables precise tumor killing and activation of anti-tumor immunity. The unique PTA scaffold exhibits unexpected inherent endoplasmic reticulum (ER)-targeting capability and potent near-infrared (NIR) photothermal activity, inducing NIR-controlled immunogenic pyroptosis in various tumor cell lines via targeting ER stress in an oxygen-independent manner. Moreover, both ER-targeting and NIR-activity of our scaffold can be modulated on demand by chemical caging/uncaging, allowing quick activation with diverse biological and bioorthogonal molecular triggers. The potency of this universal platform is demonstrated via its application to develop a membrane protein-activatable NIR-agonist that selectively activates ICD in tumor sites while priming anti-tumor immunity, minimizing off-target effects and enhancing efficacy against mouse breast tumors. This versatile approach could lead to customization of various personalized and effective immune NIR-agonists for specific photoimmunotherapy applicable to diverse solid tumors.

Cyclometalated Iridium(III) Schiff Base Complexes for Chemiluminogenic Bioprobes

Chemiluminogenic bioimaging has emerged as a promising paradigm due to its independence from light excitation, thereby circumventing challenges related to light penetration depth and background autofluorescence. However, the availability of effective chemiluminophores remains limited, which substantially impedes their bio-applications. Herein, we discovered for the first time that cyclometalated iridium(III) Schiff base complexes can unexpectedly generate chemiluminescence. Notably, the chemiluminescence reaction was rapid, with a half-life of only 0.86 s, significantly faster than previously reported examples. Unlike conventional chemiluminescent scaffolds, the distinguishing feature of the chemiluminogenic iridium(III) complex is its unique intramolecular imine-to-amide conversion upon reaction with reactive oxygen species (ROS). Intriguingly, the chemiluminogenicity of these complexes is not influenced by the cyclometalating ligands but is closely associated with the Schiff base ligand, allowing for tuning of the emission colors via altering the cyclometalating ligands. Additionally, we formulated one of the Schiff base complexes (1) as water-soluble chemiluminogenic nanoparticles (CLNPs) and successfully employed them as activatable chemiluminescence bioprobes for precise and rapid imaging of hypochlorite-related biological events both in vitro and in vivo. We believe that this significant finding of the development of chemiluminogenic Schiff base complexes will greatly facilitate the designing of innovative chemiluminophores for theranostic applications.

Programming a multiplex lanthanide nanoparticle for customized cancer treatment with real-time efficiency feedback

Customized cancer therapy relies on timely therapeutic effect evaluation to provide prescription adjustment for individual cases. However, currently reported therapeutic reagents are rarely integrated with imaging probes for self-evaluation of effects. Contrast imaging agents to measure tumor size changes must be administrated separately after therapy, complicating the therapeutic process and delaying reporting time. Herein, we design a customized therapy platform (LNPs-RB/Pep/cRGD) by conjugating lanthanide nanoparticles (LNPs) with the photosensitizer rose bengal, a caspase-3 substrate peptide (with Cy7.5 labelled at the terminal), and the tumor-targeting molecule cRGD. LNPs exhibit NIR-IIb downconversion luminescence under 980 nm/808 nm excitations for in vivo imaging, and visible upconversion luminescence under high-power 980 nm excitation for photodynamic therapy (PDT). By sequentially programming NIR excitation wavelength and power, NIR-IIb-imaging guided PDT and real-time cancer cell apoptosis imaging are achieved as therapeutic efficiency feedback. PDT induces cell apoptosis, generating caspase-3, which cleaves Cy7.5-containing peptide fragments from LNPs. This process corresponds to a recovery in vivo of NIR-IIb ratiometric imaging at 808 nm versus 980 nm excitation. The cleaved Cy7.5-containing peptide fragment is cleared into urine for NIR imaging. Both cell apoptosis imaging processes are completed 12 h after PDT, which is 7 days earlier than tumor size measurement. Therefore, customized therapy is achieved by timely adjusting PDT dosage, enhancing therapeutic efficacy.

Fluorescent probes in autoimmune disease research: current status and future prospects

Autoimmune diseases (AD) present substantial challenges for early diagnosis and precise treatment due to their intricate pathogenesis and varied clinical manifestations. While existing diagnostic methods and treatment strategies have advanced, their sensitivity, specificity, and real-time applicability in clinical settings continue to exhibit significant limitations. In recent years, fluorescent probes have emerged as highly sensitive and specific biological imaging tools, demonstrating substantial potential in AD research.This review examines the response mechanisms and historical evolution of various types of fluorescent probes, systematically summarizing the latest research advancements in their application to autoimmune diseases. It highlights key applications in biomarker detection, dynamic monitoring of immune cell functions, and assessment of drug treatment efficacy. Furthermore, this article analyzes the technical challenges currently encountered in probe development and proposes potential directions for future research. With ongoing advancements in materials science, nanotechnology, and bioengineering, fluorescent probes are anticipated to achieve higher sensitivity and enhanced functional integration, thereby facilitating early detection, dynamic monitoring, and innovative treatment strategies for autoimmune diseases. Overall, fluorescent probes possess substantial scientific significance and application value in both research and clinical settings related to autoimmune diseases, signaling a new era of personalized and precision medicine.

An information processing triple input fluorescent probe for melanoma cancer

BACKGROUND

Multi-analyte responsive fluorescent sensors are promising tools for selective imaging of malignant tissues. Glutathione tripeptide is a common cancer biomarker. Tyrosinase enzyme is involved in melanogenesis and neuroactive dopamine synthesis. Activity/level of this enzyme is significantly altered in various diseases including melanoma and neurological diseases. Molecular tools capable of sensing different cellular states are yet to be developed. In the research presented here, a novel reconfigurable pyridinium functionalized distyryl-BODIPY P2 is developed as tyrosinase sensor with the synergistic effect of glutathione and carboxylesterase to discriminate different pathological cellular states.

RESULTS

Acetyl-masked tyrosinase responsive 3-hydroxybenzyl substrate analogue is attached to the sensor. Following the ester hydrolysis by carboxylesterase, tyrosinase mediated oxidation to catechol followed by spontaneous 1,6-elimination generates pyridine BODIPY P1, resulting in 81 nm hypsochromic shift in aqueous solution compared to parent probe P2. Glutathione further enhances the response by removing acetyl group and/or reducing the quinone by-product back to cleavable quinol. A molecular AND logic gate can be constructed with enzymes and GSH, enabling multi-analyte melanoma sensing. Setting the fluorescence output threshold, distinct phenotypes can be diagnosed i.e. drug-resistant melanoma. Tyrosinase expressing B16-F10 melanoma cells display a significantly increased fluorescence when incubated with P2 compared to breast cancer cells. When inhibitor of any of the inputs is used, fluorescence intensity is significantly reduced, proving the synergistic effect of all disease parameters.

SIGNIFICANCE

With versatile chemistry and sufficient solubility in aqueous media, this structure provides the first triple input Near-IR fluorescent sensor for melanoma with the potential of discriminating different pathological status. Modular structure can provide a common scaffold for information processing molecular sensors for hydrolytic/oxidoreductive enzymes and/or disease associated analytes.

Activatable Photosensitizers: From Fundamental Principles to Advanced Designs

Photodynamic therapy (PDT) is a promising treatment that uses light to excite photosensitizers in target tissue, producing reactive oxygen species and localized cell death. It is recognized as a minimally invasive, clinically approved cancer therapy with additional preclinical applications in arthritis, atherosclerosis, and infection control. A hallmark of ideal PDT is delivering disease-specific cytotoxicity while sparing healthy tissue. However, conventional photosensitizers often suffer from non-specific photoactivation, causing off-target toxicity. Activatable photosensitizers (aPS) have emerged as more precise alternatives, offering controlled activation. Unlike traditional photosensitizers, they remain inert and photoinactive during circulation and off-target accumulation, minimizing collateral damage. These photosensitizers are designed to "turn on" in response to disease-specific biostimuli, enhancing therapeutic selectivity and reducing off-target effects. This review explores the principles of aPS, including quenching mechanisms stemming from activatable fluorescent probes and applied to activatable photosensitizers (RET, PeT, ICT, ACQ, AIE), as well as pathological biostimuli (pH, enzymes, redox conditions, cellular internalization), and bioresponsive constructs enabling quenching and activation. We also provide a critical assessment of unresolved challenges in aPS development, including limitations in targeting precision, selectivity under real-world conditions, and potential solutions to persistent issues (dual-lock, targeting moieties, biorthogonal chemistry and artificial receptors). Additionally, it provides an in-depth discussion of essential research design considerations needed to develop translationally relevant aPS with improved therapeutic outcomes and specificity.

Development of Donor-Acceptor Architecture-Based Potential Theranostic Fluorescent Probes for Alzheimer's Disease

The cholinergic deficits and deposition of β-amyloid (Aβ) species are regarded as the key events contributing to the progression of Alzheimer's disease (AD). Herein, a series of novel donor-acceptor architecture-type potential theranostic agents were designed, synthesized, and evaluated for their potential against cholinesterase (ChE) enzymes and detection of Aβ species, which are primary targets in the development of therapeutics for AD. The optimal compound/probe 18 containing a benzothiazolium fluorophore with a bifunctional electron-donating N-aryl piperazine scaffold exhibited potent inhibitory activities against acetylcholinesterase (AChE; IC50 = 0.172 ± 0.011 μM) and butyrylcholinesterase (BuChE; IC50 = 1.376 ± 0.141 μM). Measurement of fluorescence properties showed that probe 18 exhibited emission maxima (λem) of >610 nm in dimethyl sulfoxide (DMSO) and >590 nm in PBS, suitable for the fluorescence imaging. In vitro studies demonstrated a change in fluorescence characteristics and high binding affinities (18; Kd = 0.731 μM) upon binding with Aβ aggregates. The affinity of probe 18 toward Aβ aggregates was further observed in elavGAL4 > UAS Aβ, the Drosophila larval brain sections, using a fluorescence imaging technique. The in vivo acute oral toxicity evaluation indicated a safety profile of the lead probe 18. Moreover, in vivo behavioral studies including Y-maze and novel object recognition tests signified that the administration of compound 18 improved cognitive and spatial memory impairment at a dose of 10 and 20 mg/kg in the scopolamine-induced cognitive deficit model.

Small-Molecule Fluorescent Probes for Butyrylcholinesterase

Butyrylcholinesterase plays an indispensable role in organisms, and its abnormal expression poses a significant threat to human health and safety, covering various aspects including liver-related diseases, diabetes, obesity, cardiovascular and cerebrovascular diseases, and neurodegenerative diseases. In addition, toxic substances such as organophosphorus and carbamate pesticides markedly inhibit BChE activity. BChE activity serves as a critical parameter for the clinical diagnosis of acute organophosphorus pesticide poisoning and the evaluation of organophosphorus and carbamate pesticide residues. Therefore, the accurate and reliable detection of butyrylcholinesterase activity is particularly urgent and important for in-depth analysis of its biological function, diagnosis and therapy of related diseases, drug screening and sensitive detection of pesticide residues. Fluorescent probes have become a promising tool for sensing and imaging of butyrylcholinesterase, due to its advantages of high spatio-temporal resolution, high selectivity, non-invasive, high sensitivity, and tailored molecule structures. Here, this paper provides a comprehensive overview of the research progress in the sensing, imaging and therapy of butyrylcholinesterase utilizing fluorescent probes. This paper might be a useful guideline for researchers to design new high-performance fluorescence probes for BChE, and making further contributions to this intriguing field.

Electrostatic Co-Assembly of Cyanine Pair for Augmented Photoacoustic Imaging and Photothermal Therapy

Molecular phototheranostic dyes are of eminent interest for oncological diagnosis and imaging-guided phototherapy. However, it remains challenging to develop photosensitizers (PSs) that simultaneously integrate high-contrast photoacoustic imaging and efficient therapeutic capabilities. In this work, a supramolecular strategy is employed to construct a molecular pair phototheranostic agent via the direct self-assembly of two cyanines, C5TNa (anionic) and Cy-Et (cationic). The Coulombic interactions between C5TNa and Cy-Et facilitate the formation of a complementary cyanine pair (C5T-ET) and the creation of supramolecular CT-J-type aggregates in water. This complementary cyanine pair (C5T-ET) results in completely quenched fluorescence and significantly enhances nonradiative deactivation (≈22 ps), leading to a 3.3-fold increase in photothermal conversion efficiency and a 7.1-fold enhancement in photoacoustic response compared to indocyanine green (ICG). As a result, the J-type aggregate cyanine pair (C5T-ET) demonstrates high photoacoustic imaging capability and remarkable antitumor phototheranostic efficacy in vivo, highlighting its potential for clinical applications. This work provides strong experimental evidence for the superior performance of the complementary cyanine pair (C5T-ET) in enhancing photosensitization and photoacoustic response. It is believed that this strategy will propel the advancement of controllable dye J-aggregates and contribute to the practical implementation of photoacoustic imaging and phototherapy in vivo.

A near infrared light activated phenothiazine based cancer cell specific phototherapeutic system: a synergistic approach to chemo-photothermal therapy

In the pursuit of more effective cancer therapies, phototherapy has emerged as a promising approach due to its non-invasive nature and high precision. This study presents the development of a near-infrared (NIR) light-responsive phenothiazine (PTZ) based phototherapeutic system designed for targeted cancer treatment. This phototherapeutic system integrates four crucial elements for enhanced therapeutic efficacy: cancer cell-specific activity, mitochondrial targeting, photothermal conversion, and controlled drug release. The PTZ system utilizes the acidochromic 1,3-oxazine ring, which opens in the acidic tumor microenvironment, forming a positive iminium ion (CN+). This ionic species targets cancer cell mitochondria, ensuring precise localization. Under NIR light irradiation (640 nm), the phototherapeutic system undergoes a red shift in the absorption and reduction in the fluorescence intensity, demonstrating a significant photothermal effect that converts light to heat, thereby inducing tumor cell apoptosis. Furthermore, NIR light triggers the controlled release of the anticancer drug chlorambucil, enabling precise spatiotemporal drug delivery. The closed form of the phototherapeutic system also facilitates drug release upon visible light irradiation (≥410 nm) with high photochemical efficiency. This dual-mode photothermal and photocontrolled drug delivery offers a synergistic approach to cancer therapy, maximizing therapeutic outcomes while minimizing side effects. Our findings underscore the potential of this innovative phototherapeutic system to advance cancer treatment through targeted, controlled, and effective drug delivery.

Indole-Boron-Difluoride Complexes with Anticancer and Fluorescence Properties

Eight indole-boron-difluoride complexes were synthesized from 2,3-arylpyridylindole derivatives via Sonogashira coupling and Larock heteroannulation. These complexes exhibited distinct photophysical properties. Solvent polarity influenced their spectral behavior showing hypsochromic absorption, bathochromic emission shifts, and aggregation-induced emission (AIE) in mixed solvents. The ¹⁹F NMR shifts and photophysical properties, including excitation, emission maxima, and Stokes shift, correlated with Hammett substituent constants highlighting electronic effects on molecular properties. The synthesized complexes exhibited a range of intramolecular charge transfer (ICT) behaviors, as evidenced by their Lippert-Mataga parameters. TD-DFT calculations aligned with experimental data, offering insight into spectroscopic behavior. Notably, the indole-boron-difluoride complex bearing a methyl ester group exhibited significant anticancer activity against HeLa cells and potential for fluorescence imaging, indicating its promise for biomedical applications in cell imaging and therapy.

Fluorescence enhancement of cyanine/hemicyanine dyes with adamantane as an auxochrome through host-guest inclusion with methylated cyclodextrin in water

Fluorescence of cyanine dyes is often quenched in aqueous solution, limiting their application in water or biological system. In this work, a novel strategy of host-guest interaction based on cyanine derivatives containing auxochromes was proposed to enhance fluorescence in aqueous solution and cell imaging. By using the host (methylated β-cyclodextrin, M-β-CD) to inclusion and suppress the TICT effect of the dye, the fluorescence was significantly enhanced at lower host concentration. Cyanine and hemicyanine dyes (Ad-NH-1a, Ad-NH-1b and Ad-NH-2) with adamantyl group as auxochrome were designed and prepared by using host-guest complexation to inhibit the TICT effect of dyes, thus realizing the purpose of significantly enhancing the fluorescence of dyes at lower concentration. After adding M-β-CD, the fluorescence quantum yields of these dyes increased to 15.9 %, 21.8 %, and 6.08 %, respectively. In comparison, the fluorescence quantum yield of the dyes Ad-CONH-1 and Ad-CONH-2 containing adamantyl groups, increased only modestly from 1.78 to 2.83 times. Encouraged by these satisfactory results, further cell experiments were conducted with Ad-NH-1a, Ad-NH-1b, and Ad-NH-2. The experiment showed that adding a lower concentration of M-β-CD significantly reduced the clear imaging dosage of the probe (0.3 μM) without altering the organelle targeting of the probes.

Enhanced Cytotoxicity of [10]-Gingerol-Coumarin-Triazole Hybrid as a Theranostic Agent for Triple Negative Breast Cancer

A leading cause of death worldwide, breast cancer is the second most prevalent cancer in women. Triple-negative breast cancer is an aggressive subtype that lacks targeted therapies and requires novel therapeutic approaches in clinical practice to improve the overall survival. Theranostic agents that integrate diagnostic and therapeutic capabilities in a single entity are promising strategies for personalized cancer management. Hybrid compounds combining biologically relevant moieties with different modes of action can enhance cytotoxicity and improve pharmacological properties. We focus on a hybrid containing coumarin, triazole, and [10]-gingerol, a compound with known antimetastatic potential in TNBC. The LSPN281 hybrid exhibited superior cytotoxic activity in a TNBC cell line in vitro compared to the individual coumarin and [10]-gingerol controls. Additionally, the hybrid shows enhanced cellular uptake and mitochondrial localization, suggesting its potential as a theranostic agent for TNBC.

A Dual-Channel Fluorescent Probe for Accurate Diagnosis and Precise Photodynamic Killing of Bacterial Infections by Employing Dual-Mechanism Responses

Bacterial infections pose a huge challenge to global public health, exacerbated by the growing threat of antibiotic resistance due to overuse of antibiotics, and there is an urgent need to develop epidemiological control methods that enable accurate detection and precise treatment. In this study, we present an innovative dual-response integrated probe, Nap-CefTTPy, which is capable of dual-channel fluorescence imaging, synergizing with photodynamic therapy for the accurate diagnosis and precise treatment of bacterial infections. The probe has excellent selectivity for bacteria and can produce two independent spectral responses to bacteria through two different response mechanisms under a single laser excitation, achieving accurate diagnosis of dual-channel bacterial infections. At the same time, it can also produce reactive oxygen species for synergistic photodynamic therapy, which ensures the accuracy of diagnosis and treatment. In a mouse bacterial infection model, it largely promoted the wound healing of S. aureus-infected mice. This platform represents a significant advancement in the field, providing a novel approach for the dual-code mutual correction diagnosis and photodynamic therapy of bacterial infections.

Mitochondria-targeting nanostructures from enzymatically degradable fluorescent amphiphilic polyesters

Water-soluble π-conjugated luminescent bioprobes have been broadly used in biomedical research but are limited by the nonbiodegradability associated with their rigid C-C backbones. In the present work, we introduced three naphthalene monoimide (NMI)-functionalized amphiphilic fluorescent polyesters (P1, P2, and P3) prepared by transesterification of functional diols with an activated diester monomer of adipic acid. These polyesters featured a side-chain NMI fluorophore, imparting the required hydrophobicity for self-assembly in water and endowing the polymeric nanoassemblies with green fluorescence. Two polymers (P1 and P2) were intrinsically cationic at physiological pH (7.4), while neutral P3 exhibited pH-triggered (pH ∼6.2) cationic features due to the protonation of the tertiary amine groups present in its backbone. These biocompatible polymers revealed around 85% cellular uptake after 1 hour of incubation. However, the initial uptake for the cationic polymers (P1 and P2) within 15 minutes was significantly greater than that of the neutral P3 because of their stronger electrostatic interactions with the negatively charged cell membranes. Notably, cationic P1 and P2 could specifically target mitochondria in cancerous HeLa cells by escaping the initial endosome/lysosome trap. In contrast, neutral P3 exhibited cell-selective mitochondria targeting in cancerous (HeLa) cells over non-cancerous (NKE) cells. This is attributed to P3's protonation-induced positive charge accumulation in the acidic environment of cancer cells, unlike in the non-acidic environment of non-cancerous cells. This possibly causes P3 nanoassemblies to behave similarly to P1 and P2 in HeLa cells despite P3 being intrinsically neutral. The insights gained from this work may be relevant for future development of cell-specific, mitochondria-targeted drug delivery systems from enzymatically degradable polyester backbones.

Ultra-photostable fluorescent dye molecular engineering-for measuring plant cells' membrane-spacing through a "deposition-embedding" strategy

The plant cell membrane serves as a barrier, isolating the cell's interior from its external environment. Unlike animal cells, where the cytoplasmic membrane can be easily fluorescently labeled through genetic engineering, plant cells often rely more heavily on small molecule fluorescent probes to address the problem of probe internalization. Meanwhile, due to cellular internalization, current plasma fluorescent probes struggle to stain cell membranes for long periods of time. In addition, these probes tend to accumulate in the cell wall, making it impossible to achieve specific, high-noise-to-noise staining of cell membranes. In response to these challenges, we propose a novel "deposition-embedding" strategy for developing a plant cell membrane probe. The compound PTBT-O-NPh2, with its low solubility and high hydrophobicity, is designed to limit membrane penetration. Instead, it rapidly deposits on the membrane surface and embeds itself into the lipid environment via strong hydrogen bonding with phospholipid molecules. Additionally, its exceptional resistance to photobleaching and long-term retention capability allow it to measure membrane-spacing over a period of 120 hours. These findings suggest that the "deposition-embedding" strategy could be instrumental in developing a new generation of fluorescent dyes for studying plant mechanobiology.

Dual functional nanoplatforms potentiate osteosarcoma immunotherapy via microenvironment modulation

Osteosarcoma (OS), a highly aggressive bone tumor, presents significant challenges in terms of effective treatment. We identified that cellular autophagy was impaired within OS by comparing clinical OS samples through bioinformatic analyses and further validated the inhibition of mitochondrial autophagy in OS at the transcriptomic level. Based on this finding, we investigated the therapeutic potential of a dual functional metal nanoplatform (MnSx) to facilitate a transition from the protective effect of low-level autophagy in OS to the killing effect of high-level autophagy in OS. MnSx facilitated intracellular H2S generation via endocytosis, leading to the S-sulfhydration of ubiquitin-specific peptidase 8 (USP8) and subsequent promotion of mitochondrial autophagy in vitro. Additionally, MnSx activated the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway, further enhancing the cellular autophagic response and accelerating tumor cell death. Moreover, it was demonstrated in vivo that MnSx, on the one hand, mediated the activation of tumor autophagy by USP8 via intracellular H2S, while Mn2+ promoted the maturation of dendritic cells, activated cytotoxic T lymphocytes and contributed to tumor eradication. Such tumor killing could be suppressed by the autophagy inhibitor chloroquine. Importantly, synergistic combination therapy with immune checkpoint inhibitors showed promise for achieving complete remission of OS. This study highlights the potential of MnSx as a dual-functional therapeutic platform for OS treatment and offers novel directions for future research in this field.

Hypochlorous Acid-Activatable NIR Fluorescence/Photoacoustic Dual-Modal Probe with High Signal-to-Background Ratios for Imaging of Liver Injury and Plasma Diagnosis of Sepsis

Hypochlorous acid can be employed as a biomarker for blood infection (such as sepsis) and tissue damage (such as drug-induced liver injury, DILI), and the diagnosis of tissue damage or blood infection can be achieved through the detection of hypochlorous acid in relevant biological samples. Considering the complex environment and the diverse interferences in living organisms and blood plasma, developing new detection methods for HClO with high signal-to-background ratios is particularly important, and it can improve the accuracy of detection and quality of imaging based on a higher contrast, which makes the detection of HClO clearer and more accurate. Here, based on the advantages of the NIR fluorescence/photoacoustic dual-modal probe, we reported a hypochlorous acid-activatable NIR fluorescence/photoacoustic dual-modal probe (NIRF-PA-HClO) based on the spirolactam ring-opening strategy in this paper. NIRF-PA-HClO showed excellent NIRF/PA dual-modal responses with high SBRs for HClO in solution, cells, and mice. Moreover, NIRF-PA-HClO was successfully applied for high-contrast imaging of DILI. Finally, NIRF-PA-HClO was employed for the blood plasma diagnosis of sepsis with satisfactory results. In summary, the above results proved that NIRF-PA-HClO would be a potentially useful tool for the study of physiological and pathological roles of HClO, the investigation of the pathology and therapeutic mechanisms of hepatotoxicity, and the diagnosis of blood infection. Also, the development of NIRF-PA-HClO provides new design mentality for constructing other analyte-activatable NIRF/PA dual-modal probes with high SBRs.

An endoplasmic reticulum-targeting hydroxyl radical fluorescent probe for imaging of ferroptosis and screening of natural protectants

The real-time and in situ detection of hydroxyl radicals (˙OH) in the endoplasmic reticulum (ER) is helpful to understand ferroptosis at its very early stage due to the crucial role of ˙OH in the ER in ferroptosis initiation. Herein, an ER-targeting ˙OH fluorescent probe (ER-OH) has been developed, which showed a large fluorescence increase at 645 nm in response to ˙OH. ER-OH was applied to monitor ferroptosis by fluorescence imaging, revealing a significant increase of the ˙OH level in the ER during this process. With the imaging of ER-OH, a high-throughput screening method was developed to evaluate the anti-ferroptosis activity of a series of natural protectants. Through this screening, the natural flavonoid derivative icariside I was found for the first time to be highly effective in inhibiting ferroptosis by direct scavenging of the excess cytotoxic oxides (e.g. ˙OH and lipid peroxides) and restoring the level of GPX4. ER-OH could also be used for in vivo imaging of ˙OH in a mouse tumor model. This work provides not only a new tool for ferroptosis monitoring but also a direct insight into the regulation mechanism of ferroptosis and development of new drugs for ferroptosis-related diseases.

Renal-Clearable Biomass-Derived Carbon Dots with Red Fluorescence for Masked Cryptic Kidney Injury Imaging

Masked cryptic kidney injury (MCKI), an early stage of acute kidney injury (AKI), is challenging to detect and diagnose, especially in the modern context where toxic substances, such as surfactants, are increasingly misused. Consequently, there is an urgent need for methods for the visual diagnosis of MCKI. In this study, we synthesized environmentally friendly spirulina-derived carbon dots (SpiCDs) using spirulina as a biobased raw material through a simple hydrothermal process. These SpiCDs, with their ultrasmall size, enable efficient renal clearance. In cellular experiments, SpiCDs rapidly entered SDS-damaged cells, facilitating dynamic monitoring of the cell membrane damage process. In vivo animal experiments demonstrated that SpiCDs were efficiently excreted through the kidneys and began to accumulate in the bladder within 10 min after tail vein injection. The detection of red fluorescence in excreted urine confirmed the renal metabolic pathway of the SpiCDs. Furthermore, in an MCKI model induced by SDS, SpiCDs showed accelerated excretion and earlier accumulation in the bladder, indicating an increased sensitivity to kidney injury. These results suggest that SpiCDs provide a promising approach for the early diagnosis of MCKI, offering insights into its visual detection and monitoring.

A Triple-Responsive and Dual-NIR Emissive Fluorescence Probe for Precise Cancer Imaging and Therapy by Activating Pyroptosis Pathway

Revealing changes in the tumor microenvironment is crucial for understanding cancer and developing sensitive methods for precise cancer imaging and diagnosis. Intracellular hydrogen peroxide (H2O2) and microenvironmental factors (e.g., viscosity and polarity) are closely linked to various physiological and pathological processes, making them potential biomarkers for cancer. However, a triple-response theranostic probe for precise tumor imaging and therapy has not yet been achieved due to the lack of effective tools. Herein, we present a mitochondria-targeting near-infrared (NIR) fluorescent probe, VPH-5DF, capable of simultaneously monitoring H2O2, viscosity, and polarity through dual NIR channels. The probe specifically detects H2O2 via NIR emission (λem = 650 nm) and shows high sensitivity to microenvironmental viscosity/polarity in the deep NIR channel (λem ≈ 750 nm). Furthermore, the probe not only monitors mitochondrial polarity, viscosity, and fluctuations in endogenous/exogenous H2O2 levels but also distinguishes cancer cells from normal cells through multiple parameters. Additionally, VPH-5DF can be employed to monitor alterations in H2O2 levels, as well as changes in viscosity and polarity, during drug-induced pyroptosis in living cells. After treatment with VPH-5DF, chemotherapy-induced oxidative damage to the mitochondria in tumor cells activated the pyroptosis pathway, leading to a robust antitumor response, as evidenced in xenograft tumor models. Thus, this triple-response theranostic prodrug offers a new platform for precise in vivo cancer diagnosis and anticancer chemotherapy.

Metabolic Acidity/H2O2 Dual-Cascade-Activatable Molecular Imaging Platform Toward Metastatic Breast Tumor Malignancy

Fluorescence imaging in the second near-infrared window (NIR-II) is crucial for accurate tumor diagnosis, offering superior resolution and penetration capabilities. Current NIR-II probes are limited by either being "always on" or responding to one stimulus, leading to low signal-to-noise ratios and potential false positives. We introduced a dual-lock-controlled probe, HN-PBA, activated by both H2O2 and tumor acidic environment. This dual response ensures bright fluorescence at tumor sites, leading to higher tumor-to-normal tissue ratios (T/NT) compared to conventional "always on" probes and probes activated only by H2O2. This strategy allows precise tumor identification and removal of primary and metastatic tumors, achieving superior T/NT ratios (24.3/6.4 for orthotopic and lung metastasis, respectively). Our probe also effectively detected lung metastatic foci as small as≤0.7 mm and showed the capability for accurate lesion localization in clinical breast cancer specimens. This dual-stimuli-responsive strategy could aid future diagnostic probe design.

Safirinium Fluorescent "Click" Molecular Probes: Synthesis, CuAAC Reactions, and Microscopic Imaging

Fluorescent labeling utilizing Cu(I)-catalyzed azide-alkyne cycloaddition reactions (CuAAC) is among the leading applications of the "click" chemistry strategy. Fluorescent probes for this approach can be constructed by linking an azide or alkyne group to a fluorophore, such as the recently developed Safirinium derivatives. These compounds are water-soluble, highly fluorescent heterocycles based on 1,2,4-triazolium, with significant potential for various labeling applications, although they have not yet been converted to azide or alkyne probes. Herein, we report the synthesis of Safirinium-based azide and alkyne functionalized molecular probes for "click" chemistry labeling. We also describe their CuAAC reactions with model compounds, including a lipid mimetic long-chain azide, an azido sugar derivative, and azidothymidine, as well as two model alkynes. We demonstrate that the Safirinium-based probes and their derivatives are chemically stable, suitable for fluorescent microscopy observations, and safe to use. Most of these probes show no toxic effects on CHO-K1 and NIH-3T3 cells.

A novel cyanine photosensitizer for sequential dual-site GSH depletion and ROS-potentiated cancer photodynamic therapy

The efficacy of photodynamic therapy (PDT) is often limited by the reductive microenvironment in tumor cells due to the high level of glutathione (GSH) and glutathione peroxidase 4 (GPX4), which maintain redox homeostasis. Therefore, designing a GSH-responsive photosensitizer that depletes intracellular GSH is a promising strategy to enhance PDT selectivity and efficacy. Herein, we present a GSH-selective sequentially responsive theranostic photosensitizer, Cy-Res. This cyanine agent targeting mitochondria effectively depletes two GSH molecules, leading to the generation of abundant ROS and exacerbating oxidative stress. Additionally, it achieves an 80-fold fluorescence enhancement upon response to GSH, enabling selective imaging of tumor cells. By mitigating GSH's impact on PDT, Cy-ResNPs achieves synergistic and efficient PDT treatment of invasive melanoma under low-power irradiation (808 nm, 80 mW/cm2). The inhibitory processes downregulate GPX4, increase apoptotic proteins like Bax, and promote mixed cell death involving both ferroptosis and apoptosis. Overall, this study offers new insights and strategies for the development of GSH-responsive theranostic agents, highlighting their potential for application in tumor diagnosis and therapy.

Application of a near-infrared viscosity-responsive fluorescent probe for lysosomal targeting in fatty liver mice

Viscosity is a fundamental property in biological systems, influencing organelle function and molecular diffusion. Abnormal viscosity is associated with diseases such as metabolic disorders, neurodegeneration, and cancer. Lysosomes, central to cellular degradation and recycling, are sensitive to viscosity changes, which can disrupt enzymatic activity and cellular homeostasis. Monitoring lysosomal viscosity provides essential information on lysosomal health, helping to uncover underlying mechanisms in various diseases. Recognizing the need for effective monitoring of lysosomal viscosity changes in living cells, we have developed a near-infrared (NIR) viscosity-responsive fluorescent probe, VFLyso, specifically designed for lysosomal targeting. Based on the twisted intramolecular charge transfer (TICT) mechanism, VFLyso exhibits strong NIR fluorescence, a fast response, and a notable fluorescence response to viscosity variations (F/F0 = 65.5-fold), along with excellent selectivity and stability under physiological conditions. Our studies demonstrated that VFLyso could accurately monitor lysosomal viscosity changes in both cell cultures and animal models, including zebrafish and mouse models of fatty liver. This work not only provides a powerful tool for real-time monitoring of lysosomal viscosity but also offers valuable insights into the role of viscosity in disease progression, paving the way for potential diagnostic applications in related disorders.

Integration of Motion and Stillness: A Paradigm Shift in Constructing Nearly Planar NIR-II AIEgen with Ultrahigh Molar Absorptivity and Photothermal Effect for Multimodal Phototheranostics

The two contradictory entities in nature often follow the principle of unity of opposites, leading to optimal overall performance. Particularly, aggregation-induced emission luminogens (AIEgens) with donor-acceptor (D-A) structures exhibit tunable optical properties and versatile functionalities, offering significant potential to revolutionize cancer treatment. However, trapped by low molar absorptivity (ε) owing to the distorted configurations, the ceilings of their photon-harvesting capability and the corresponding phototheranostic performance still fall short. Therefore, a research paradigm from twisted configuration to near-planar structure featuring a high ε is urgently needed for AIEgens development. Herein, by introducing the strategy of "motion and stillness" into a highly planar A-D-A skeleton, we successfully developed a near-infrared (NIR)-II AIEgen of Y5-2BO-2BTF, which boasts an impressive ε of 1.06 × 105 M-1 cm-1 and a photothermal conversion efficiency (PCE) of 77.8%. The modification of steric hindrance on the benzene ring in the acceptor unit of the aggregation-caused quenching counterpart Y5-2BO, to a meta-CF3-substituted naphthyl, leads to reversely staggered packing and various intermolecular noncovalent conformational locks in Y5-2BO-2BTF ("stillness"). Furthermore, the -CF3 moiety acted as a flexible motion unit with an ultralow energy barrier, significantly facilitating the photothermal process in loose Y5-2BO-2BTF aggregates ("motion"). Accordingly, Y5-2BO-2BTF nanoparticles enabled tumor eradication and pulmonary metastasis inhibition through NIR-II fluorescence-photoacoustic-photothermal imaging-navigated type I photodynamic-photothermal therapy. This work provides the first evidence that the highly planar conformation with a reversely staggered stacking arrangement could serve as a novel molecular design direction for AIEgens, shedding new light on constructing superior phototheranostic agents for bioimaging and cancer therapy.

APE1-Activated and NIR-II Photothermal-Enhanced Chemodynamic Therapy Guided by Amplified Fluorescence Imaging

The development of intelligent nanotheranostic technology that integrates diagnostic and therapeutic functions holds great promise for personalized nanomedicine. However, most of the nanotheranostic agents exhibit "always-on" properties and do not involve an amplification step, which may largely limit imaging contrast and restrict therapeutic efficacy. Herein, we construct a novel nanotheranostic platform (Hemin/DHPs/PDA@CuS nanocomposite) by assembling DNA hairpin probes (DHPs) and hemin on the surface of PDA@CuS nanosheets that enables amplified fluorescence imaging and activatable chemodynamic therapy (CDT) of tumors. The cancer-relevant APE1 triggers nucleic acid amplification with DHPs to generate activatable and amplified fluorescence signals for discriminating cancer cells from normal cells. Meanwhile, excessive G-quadruplex/hemin-based DNAzyme are also activated, and they function as Fenton-like catalysts to catalyze the production of highly toxic hydroxyl radicals (•OH) for CDT. Moreover, owing to the excellent photothermal conversion efficiency in the near-infrared-II (NIR-II) window, the PDA@CuS not only improves the catalytic performance of CDT but also furnishes PTT. A remarkable antitumor therapeutic effect is demonstrated both in vitro and in vivo. Therefore, the Hemin/DHPs/PDA@CuS nanocomposite is expected to provide a promising avenue for precise imaging-guided antitumor therapy.

Sequential self-assembly and release of a camptothecin prodrug for tumor-targeting therapy

Chemotherapy is the most commonly used method to treat malignant tumors with a wide range of drugs. However, chemotherapeutic drugs are characterized by poor solubility, low stability and specificity, as well as drug resistance, which led to their limited bioavailability and severe adverse effects. Therefore, most researches focus on one or two strategies while a few researches focus on three strategies to improve the efficacy of drugs. Herein, we combined three strategies (targeted therapy, prodrug design and drug delivery) to exploit a self-assembled camptothecin (CPT) prodrug (CPT-SS-FFEYp-Biotin) for enhancing therapeutic efficacy and reducing side effects of CPT. CPT-SS-FFEYp-Biotin enters into tumor cells following the recognition between biotin and biotin receptors. Moreover, the over-expressed alkaline phosphatase (ALP) on cell membranes specifically dephosphorylates CPT-SS-FFEYp-Biotin to CPT-SS-FFEY-Biotin, which self-assembles into a CPT hydrogel with the local enrichment of CPT. Subsequently, excess glutathione (GSH) in tumor cells can reduce the disulfide bond of CPT-SS-FFEY-Biotin to slowly release CPT for sustained tumor therapy. Cell experiments demonstrated that CPT-SS-FFEYp-Biotin enhances therapeutic efficacy of CPT on tumor cells while being safer to normal cells than CPT. Moreover, CPT-SS-FFEYp-Biotin effectively improved anti-tumor treatment of CPT in vivo. We envision that the integration of these three strategies is helpful to exploit a variety of prodrugs for effective anti-tumor treatment in the future.

Modular Design and Scaffold-Synthesis of Multi-Functional Fluorophores for Targeted Cellular Imaging and Pyroptosis

Fluorophores are essential tools for optical imaging and biomedical research. Their synthetic modification to incorporate new functions, however, remains a challenging task. Conventional strategies rely on linear synthesis in which a parent framework is gradually extended. We here designed and synthesized a versatile library of multi-functional fluorophores via a scaffold-based Ugi four-component reaction (U-4CR). The adaptability of the scaffold is achieved through modification of starting materials. This allows to use a small range of starting materials for the creation of fluorogenic probes that can detect reactive-oxygen species and where the localization into subcellular organelles or membranes can be controlled. We present reaction yields ranging from 60 % to 90 % and discovered that some compounds can even function as imaging and therapeutic agents via Fenton chemistry inducing pyroptosis in living cancer cells. Our study underlines the potential of scaffold-based synthesis for versatile creation of functional fluorophores and their applications.

A novel BODIPY-based fluorescent probe for naked-eye detection of the highly alkaline pH

A novel alkaline pH-responsive probe based on an asymmetric aza-BODIPY was synthesized in a one-pot Schiff base formation reaction. This pH-sensitive probe comprises an asymmetric aza-BODIPY as the luminescent core, with a benzothiazole moiety connected via an imine bond serving as the recognition site. The probe exhibits a turn-off fluorescence response upon exposure to alkaline pH (9.6-12.4), while a bathochromic band in the absorption emerges due to its extended π-conjugation system, accompanied by a visible colorimetric change from yellow to orange to red. Furthermore, the probe responds linearly in the highly alkaline region, with a pKa of 11.65. The recognition mechanism of the probe towards alkaline pH relies on the deprotonation of the imine group on the aza-BODIPY core, leading to an enhanced degree of π-electron conjugation. The quenched fluorescence intensity is attributed to the increased non-radiative decay of the deprotonated form of the probe. The probe demonstrates high reliability for practical applications due to its photostability and reversibility. This study provides new insights into the design of probes for detecting high alkaline pH levels.

An Ultrasound-Activated Supramolecular Modulator Enhancing Autophagy to Prevent Ventricular Arrhythmias Post-Myocardial Infarction

Ventricular arrhythmias (VAs) triggered by myocardial infarction (MI) are the leading cause of sudden cardiac mortality worldwide. Current therapeutic strategies for managing MI-induced VAs, such as left stellate ganglion resection and ablation, are suboptimal, highlighting the need to explore safer and more effective intervention strategies. Herein, we rationally designed two supramolecular sonosensitizers RuA and RuB, engineered through acceptor modification to generate moderate reactive oxygen species (ROS) to modulate VAs. Both RuA and RuB demonstrated high ultrasound (US)-activated ROS production efficiency, with singlet oxygen (1O2) quantum yield (ΦΔ) of 0.70 and 0.88, respectively, surpassing ligand IR1105 and the conventional sonosensitizer ICG (ΦΔ=0.40). In vitro, RuB, at a modest concentration and under US intensity notably boosts pro-survival autophagy in microglia BV2 cell. To improve in vivo stability and biocompatibility, RuB was further encapsulated into DSPE-PEG5000 to prepare RuB nanoparticles (RuB NPs). In vivo studies after microinjection of RuB NPs into the paraventricular nucleus (PVN) and subsequent US exposure, demonstrated that RuB NPs-mediated US modulation effectively suppresses sympathetic nervous activity (SNA) and inflammatory responses, thereby preventing VAs. Importantly, no tissue injury was observed post RuB NPs-mediated US modulation. This work pioneers the design of long-wave emission supramolecular sonosensitizers, offering new insights into regulating cardiovascular diseases.

As Aggregation-Induced Emission Meets with Noncovalent Conformational Locks: Subtly Regulating NIR-II Molecules for Multimodal Imaging-Navigated Synergistic Therapies

Phototheranostics is growing into a sparking frontier in disease treatment. Developing single molecular species synchronously featured by powerful absorption capacity, superior second near-infrared (NIR-II) fluorescence and prominent photothermal conversion ability is highly desirable for phototheranostics, yet remains formidably challenging. In this work, we propose a molecular design philosophy that the integration of noncovalent conformational locks (NoCLs) with aggregation-induced emission (AIE) in a single formulation is able to boost multiple photophysical properties for efficient phototheranostics. The introduction of NoCLs skeleton with conformation-locking feature in the center of molecular architecture indeed elevates the structural planarity and rigidity, which simultaneously promotes the absorption capacity and bathochromic-shifts the emission wavelength centered in NIR-II region. Meanwhile, the AIE tendency mainly originated from flexibly propeller-like geometry at the ends of molecular architecture eventually endows the molecule with satisfactory emission intensity and photothermal conversion in aggregates. Consequently, by utilizing the optimized molecule, unprecedented performance on NIR-II fluorescence-photoacoustic-photothermal trimodal imaging-guided photothermal-chemo synergistic therapy is demonstrated by the precise tumor diagnosis and complete tumor ablation.