Modular Design Platform for Activatable Fluorescence Probes Targeting Carboxypeptidases Based on ProTide Chemistry

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.

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.

Thio-ProTide strategy: A novel H2S donor-drug conjugate (DDC) alleviates hepatic injury via innate lysosomal targeting

Hydrogen sulfide (H2S) is a gas signaling molecule with versatile bioactivities; however, its exploitation for disease treatment appears challenging. This study describes the design and characterization of a novel type of H2S donor-drug conjugate (DDC) based on the thio-ProTide scaffold, an evolution of the ProTide strategy successfully used in drug discovery. The new H2S DDCs achieved hepatic co-delivery of H2S and an anti-fibrotic drug candidate named hydronidone, which synergistically attenuated liver injury and resulted in more sufficient intracellular drug exposure. The potent hepatoprotective effects were also attributed to the H2S-mediated multipronged intervention in lipid peroxidation both at the whole cellular and lysosomal levels. Lysosomal H2S accumulation and H2S DDC activation were facilitated by the hydrolysis through the specific lysosomal hydrolase, representing a distinct mechanism for lysosomal targeting independent of the classical basic moieties. These findings provided a novel pattern for the design of optimally therapeutic H2S DDC and organelle-targeting functional molecules.

"Zero" Intrinsic Fluorescence Sensing-Platforms Enable Ultrasensitive Whole Blood Diagnosis and In Vivo Imaging

Abnormal physiological processes and diseases can lead to content or activity fluctuations of biocomponents in organelles and whole blood. However, precise monitoring of these abnormalities remains extremely challenging due to the insufficient sensitivity and accuracy of available fluorescence probes, which can be attributed to the background fluorescence arising from two sources, 1) biocomponent autofluorescence (BCAF) and 2) probe intrinsic fluorescence (PIF). To overcome these obstacles, we have re-engineered far-red to NIR II rhodol derivatives that possess weak BCAF interference. And a series of "zero" PIF sensing-platforms were created by systematically regulating the open-loop/spirocyclic forms. Leveraging these advancements, we devised various ultra-sensitive NIR indicators, achieving substantial fluorescence boosts (190 to 1300-fold). Among these indicators, 8-LAP demonstrated accurate tracking and quantifying of leucine aminopeptidase (LAP) in whole blood at various stages of tumor metastasis. Furthermore, coupling 8-LAP with an endoplasmic reticulum-targeting element enabled the detection of ERAP1 activity in HCT116 cells with p53 abnormalities. This delicate design of eliminating PIF provides insights into enhancing the sensitivity and accuracy of existing fluorescence probes toward the detection and imaging of biocomponents in abnormal physiological processes and diseases.

Activity-Based Fluorescence Diagnostics for Cancer

Fluorescence imaging is one of the most promising approaches to achieve intraoperative assessment of the tumor/normal tissue margins during cancer surgery. This is critical to improve the patients' prognosis, and therefore various molecular fluorescence imaging probes have been developed for the identification of cancer lesions during surgery. Among them, "activatable" fluorescence probes that react with cancer-specific biomarker enzymes to generate fluorescence signals have great potential for high-contrast cancer imaging due to their low background fluorescence and high signal amplification by enzymatic turnover. Over the past two decades, activatable fluorescence probes employing various fluorescence control mechanisms have been developed worldwide for this purpose. Furthermore, new biomarker enzymatic activities for specific types of cancers have been identified, enabling visualization of various types of cancers with high sensitivity and specificity. This Review focuses on recent advances in the design, function and characteristics of activatable fluorescence probes that target cancer-specific enzymatic activities for cancer imaging and also discusses future prospects in the field of activity-based diagnostics for cancer.