Dual-locking nanoprobe based on hemicyanine for orthogonal stimuli-triggered precise cancer imaging and therapy

De novo design of dual-detection fluorescent sensors for bisulfite and copper (II) ion based on cascade activation

BACKGROUND

Cascade activated probes have received extensive attention due to their sequence-dependent detection of multiple markers in pathologic pathways. HSO3- and Cu2+ are biomarkers of intracellular mitochondrial activity, and their simultaneous detection is of great significance. Until now, probes that detect them simultaneously were all based on displacement mechanism with "ON-OFF-ON" switches in an emission channel. In other words, using HSO3- and Cu2+ as two inputs in logic sensing, the inputs of (0,0), (0,1), or (1,1) gave the same "1" output. Therefore, they suffered from the false positive signals in clinical application.

RESULTS

The de novo design of fluorescent probes with a more advanced sensing mechanism was explored. The four dyes, CM-Cu, CMA-Cu, R1, and R2, have similar structures, but their sensing behaviors are quite different. For dual detection of HSO3- and Cu2+, CM-Cu showed emission "ON-OFF-ON" switches based on IMP logic gate; while CMA-Cu, having one more aldehyde, was cascade activated based on AND gate for the first time. Noteworthily, unlike most dual-locked probes, which usually involve a complex synthesis process, here, cascade activation by HSO3- and Cu2+ is achieved by adjusting the electron distribution of a ready-made structure. Coupled with its low toxicity, high specificity, strong solid emission, and anti-diffusion ability, the sensing property of CMA-Cu have been validated in digital encryption and cell imaging.

SIGNIFICANCE

We exhibited how to adjust the dual recognition from displacement to cascade activation by fine-tuning the molecular structure. This study may provide a new idea for the simple design of dual-locked probe, which is helpful for the sequential detection of multiple biomarkers with physiological correlation and could improve the accuracy of disease diagnosis.

Dual-Locked Enzyme-Activatable Fluorescence Probes for Precise Bioimaging

Real-time visualization of endogenous enzymes not only helps reveal the underlying biological principles but also provides pathological information for cancer/disease diagnosis and even treatment guidance. To this end, enzyme-activatable fluorescence probes are frequently fabricated that turn their fluorescence signals "on" exclusively at the enzyme-rich region, thus enabling noninvasive and real-time imaging of enzymes of interest at the molecular level with superior sensitivity and selectivity. However, in a complex biological context, commonly used single enzyme-activatable (i.e., single-locked) probes may suffer from "false positive" signals at healthy tissues and be insufficient to accurately indicate the occurrence of certain diseases. Therefore, dual-locked fluorescence probes have been promoted to address these issues. Using dual enzymes (or an enzyme with another stimulus) as "keys", they permit simultaneous detection of distinct biomarkers, offering significantly enhanced imaging precision toward certain biological events. Considering that recent reviews on these probes remain scarce, we thus provide this review. We summarize the recent progress, particularly highlighting the breakthroughs in the last three years, and discuss the challenges in this field.

Activatable Molecular Probes With Clinical Promise for NIR-II Fluorescent Imaging

The second near-infrared window (NIR-II) fluorescence imaging has been widely adopted in basic scientific research and preclinical applications due to its exceptional spatiotemporal resolution and deep tissue penetration. Among the various fluorescent agents, organic small-molecule fluorophores are considered the most promising candidates for clinical translation, owing to their well-defined chemical structures, tunable optical properties, and excellent biocompatibility. However, many currently available NIR-II fluorophores exhibit an "always-on" fluorescence signal, which leads to background noise and compromises diagnostic accuracy during disease detection. Developing NIR-II activatable organic small-molecule fluorescent probes (AOSFPs) for accurately reporting pathological changes is key to advancing NIR-II fluorescence imaging toward clinical application. This review summarizes the rational design strategies for NIR-II AOSFPs based on four core structures (cyanine, hemicyanine, xanthene, and BODIPY). These NIR-II AOSFPs hold substantial potential for clinical translation. Furthermore, the recent advances in NIR-II AOSFPs for NIR-II bioimaging are comprehensively reviewed, offering clear guidance and direction for their further development. Finally, the prospective efforts to advance NIR-II AOSFPs for clinical applications are outlined.

A novel viscosity sensitive hemicyanine fluorescent dye for real-time imaging of amyloid-β aggregation

Alzheimer's Disease (AD) is a neurodegenerative disease, of which β-amyloid (Aβ) deposition is one of the most important pathological features. It has been reported that during Aβ aggregation, the microenvironment around the Aβ protein is altered in terms of viscosity and polarity. In this work, we developed five novel hemicyanine fluorescent probes (MZs). After screening the photochemical properties, MZ-2 and 3 were found to enable the rapid detection of Aβ42 aggregates, which were also sensitive to ambient viscosity. After comparison the structure of probes, we also observed that extensions of conjugated π-systems effectively cause redshifts of excitation wavelength. In the meanwhile, hydroxyl groups with weaker ionization strengths are more responsive to Aβ42 aggregates than sulfonate groups, probably due to the small size of the hydroxyl group and the acidity. Overall, MZ-2 showed the best response to Aβ42 aggregates (15.35-fold) and viscosity (17.6-fold). MZ-2 can quickly cross the blood-brain barrier (BBB), enabling high-fidelity imaging of Aβ42 aggregates in the mice brain.

Recent Advances in Nanomaterial-Mediated Cell Death for Cancer Therapy

Nanomedicine has shown great anticancer potential by disrupting redox homeostasis and increasing the levels of oxidative stress, but the therapeutic effect is limited by factors including the intrinsic self-protection mechanism of tumors. Cancer cell death can be induced by the exploration of different cell death mechanisms, such as apoptosis, pyroptosis, necroptosis, cuproptosis, and ferroptosis. The merging of nanotechnology with biomedicine has provided tremendous opportunities to construct cell death-based nanomedicine for innovative cancer therapy. Nanocarriers are not only used for the targeted delivery of cell death inducers, but also as therapeutic components to induce cell death to achieve efficient tumor treatment. This review focuses on seven cell death modalities mediated by nanomaterials, such as apoptosis, pyroptosis, necroptosis, ferroptosis, cuprotosis, immunogenic cell death, and autophagy. The mechanisms of these seven cell death modalities are described in detail, as well as the preparation of nanomaterials that induce them and the mechanisms, they used to exert their effects. Finally, this work describes the potential future development based on the current knowledge related to cell death induced by nanomaterials.

Enzyme-responsive, multi-lock optical probes for molecular imaging and disease theranostics

Optical imaging is an indispensable tool for non-invasive visualization of biomolecules in living organisms, thereby offering a sensitive approach for disease diagnosis and image-guided disease treatment. Single-lock activatable optical probes (SOPs) that specifically switch on optical signals in the presence of biomarkers-of-interest have shown both higher detection sensitivity and imaging quality as compared to conventional "always-on" optical probes. However, such SOPs can still show "false-positive" results in disease diagnosis due to non-specific biomarker expression in healthy tissues. By contrast, multi-lock activatable optical probes (MOPs) that simultaneously detect multiple biomarkers-of-interest could improve detection specificity towards certain biomolecular events or pathological conditions. In this Review, we discuss the recent advancements of enzyme-responsive MOPs, with a focus on their biomedical applications. The higher detection specificity of MOPs could in turn enhance disease diagnosis accuracy and improve treatment efficacy in image-guided disease therapy with minimal toxicity in the surrounding healthy tissues. Finally, we discuss the current challenges and suggest future applications of MOPs.

Dual-locked fluorescent probes for precise diagnosis and targeted treatment of tumors

Cancer continues to pose a significant threat to global health, with its high mortality rates largely attributable to delayed diagnosis and non-specific treatments. Early and accurate diagnosis is crucial, yet it remains challenging due to the subtle and often undetectable early molecular changes. Traditional single-target fluorescent probes often fail to accurately identify cancer cells, relying solely on single biomarkers and consequently leading to high rates of false positives and inadequate specificity. In contrast, dual-locked fluorescent probes represent a breakthrough, designed to enhance diagnostic precision. By requiring the simultaneous presence of two specific tumor-associated biomarkers or microenvironmental conditions, these probes significantly reduce non-specific activations typical of conventional single-analyte probes. This review discusses the structural designs, response mechanisms, and biological applications of dual-locked probes, highlighting their potential in tumor imaging and treatment. Importantly, the review addresses the challenges, and perspectives in this field, offering a comprehensive look at the current state and future potential of dual-locked fluorescent probes in oncology.

Dual-stimuli responsive theranostic agents based on small molecules

Stimuli-responsive theranostic agents represent a class of molecules that integrate therapeutic and diagnostic functions, offering the capability to respond to disease-associated biomarkers. Dual-stimuli responsive agents, particularly those based on small molecules, have shown considerable promise for precise imaging-guided therapeutic applications. In this Highlight, we summarize the progress of dual-stimuli responsive theranostic agents based on small molecules, for diagnostic and therapeutic studies in biological systems. The Highlight focuses on comparing different responsive groups and chemical structures of these dual-stimuli responsive theranostic agents towards different biomarkers. The potential future directions of the agents for further applications in biological systems are also discussed.

Site-Specific Cascade-Activatable Fluorogenic Nanomicelles Enable Precision and Accuracy Imaging of Pulmonary Metastatic Tumor

The precise localization of metastatic tumors with subtle growth is crucial for timely intervention and improvement of tumor prognosis but remains a paramount challenging. To date, site-specific activation of fluorogenic probes for single-stimulus-based diagnosis typically targets an occult molecular event in a complex biosystem with limited specificity. Herein, we propose a highly specific site-specific cascade-activated strategy to enhance detection accuracy, aiming to achieve the accurate detection of breast cancer (BC) lung metastasis in a cascade manner. Specifically, cascade-activatable NIR fluorogenic nanomicelles HPNs were constructed using ultra-pH-sensitive (UPS) block copolymers as carriers and nitroreductase (NTR)-activated fluorogenic reporters. HPNs exhibit programmable cascade response characteristics by first instantaneous dissociating under in situ tumor acidity, facilitating deep tumor penetration followed by selective fluorescence activation through NTR-mediated enzymatic reaction resulting in high fluorescence ON/OFF contrast. Notably, this unique feature of HPNs enables high-precision diagnosis of orthotopic BC as well as its lung metastases with a remarkable signal-to-background ratio (SBR). This proposed site-specific cascade activation strategy will offer opportunities for a specific diagnosis with high signal fidelity of various insidious metastatic lesions in situ across different diseases.

Functional Materials for Subcellular Targeting Strategies in Cancer Therapy: Progress and Prospects

Neoadjuvant and adjuvant therapies have made significant progress in cancer treatment. However, tumor adjuvant therapy still faces challenges due to the intrinsic heterogeneity of cancer, genomic instability, and the formation of an immunosuppressive tumor microenvironment. Functional materials possess unique biological properties such as long circulation times, tumor-specific targeting, and immunomodulation. The combination of functional materials with natural substances and nanotechnology has led to the development of smart biomaterials with multiple functions, high biocompatibilities, and negligible immunogenicities, which can be used for precise cancer treatment. Recently, subcellular structure-targeting functional materials have received particular attention in various biomedical applications including the diagnosis, sensing, and imaging of tumors and drug delivery. Subcellular organelle-targeting materials can precisely accumulate therapeutic agents in organelles, considerably reduce the threshold dosages of therapeutic agents, and minimize drug-related side effects. This review provides a systematic and comprehensive overview of the research progress in subcellular organelle-targeted cancer therapy based on functional nanomaterials. Moreover, it explains the challenges and prospects of subcellular organelle-targeting functional materials in precision oncology. The review will serve as an excellent cutting-edge guide for researchers in the field of subcellular organelle-targeted cancer therapy.

Dual stimulus-triggered bioorthogonal nanosystem for spatiotemporally controlled prodrug activation and near-infrared fluorescence imaging

In this study, we combined low pH and cathepsin B dual-stimulus-triggered delivery carriers with a bioorthogonal reaction-activated prodrug to achieve regulated activation of the prodrug. A workable method for precise tumor therapy and imaging is provided by the bioorthogonal reaction, which activates the prodrug and fluorescent probe.

A biotin-modified and H2O2-activatable theranostic nanoplatform for enhanced photothermal and chemical combination cancer therapy

Although synergistic effects of photothermal therapy (PTT) and chemotherapy for cancer have been extensively investigated in previous studies, more potential strategies need to be exploited to alleviate severe adverse effects. In this study, a biotin-modified and activatable nanotheranostic system is developed. This system (BPSP/DOX-CyBA) composed of H₂O₂-sensitive thioketal (TK) linker, hydrophilic biotin-decorated polyethylene glycol (PEG) segment, hydrophobic polycaprolactone (PCL) segment, could self-assemble into (99±1.3) nm nanoparticles and co-deliver H₂O₂-triggered photosensitizer CyBA and cytotoxic drugs DOX to tumor site. In vitro, DOX and CyBA could release rapidly from nanoparticles, CyBA accumulation in the mitochondria causes mitochondrial damage, leading to mitochondrial dysfunctions,while rising the level of ROS in B16F10 cells, and further to promote the micells to trigger release. CyBA could be activated into CyOH and the photothermal therapy was turn "off" into "on". In BPSP/DOX-CyBA group, the local temperature within tumor reached 50℃ and cell apoptosis rate reached 68.6% under Laser irradiation(650 nm, 1W/cm2). Fluorescence microscopy and flow cytometry analysis further demonstrated the better uptake efficiency on B16F10 cells with biotin decoration. In a mice B16F10 tumor model, the group with co-delivery CyBA and DOX had the best tumor retention effect, the maximal local temperature increasement and the minimum tumor growth with negligible side effects, suggesting the potential of BPSP/DOX-CyBA nanopalteform that synergistic photothermal therapy and chemotherapy and mitochondria damage as an effective melanoma treatment strategy.

Recent advances in dual-target-activated fluorescent probes for biosensing and bioimaging

Fluorescent probes have been powerful tools for visualizing and quantifying multiple dynamic processes in living cells. However, the currently developed probes are often constructed by conjugation a fluorophore with a recognition moiety and given signal-output after triggering with one singly target interest. Compared with the single-target-activated fluorescent probes mentioned above, the dual-target-activated ones, triggering with one target under stimulus (such as photoirradiation, microenvironment) or another targets, have the advantages of advoiding nonspecific activation and "false positive" results in complicated environments. In recent years, many dual-target-activated fluorescent probes have been developed to detect various biologically relevant species. In view of the importance of a comprehensive understanding of dual-target- activated fluorescent probes, a thorough summary of this topic is urgently needed. However, no comprehensive and critical review on dual target activated fluorescent probes has been published recently. In this review, we focus on the dual-target-activated fluorescent probes and briefly outline their types and current state of development. In each type, the chemical structure, proposed responsive mechanism and application of probes are highlighted. At last, the challenges and prospective opportunities of every type were proposed.