Theranostic Heterodimeric Prodrug with Dual-Channel Fluorescence Turn-On and Dual-Prodrug Activation for Synergistic Cancer Therapy

Acid-Responsive Polymer Micelles for Targeted Delivery and Bioorthogonal Activation of Prodrug through Ru Catalyst in Tumor Cells

Bioorthogonal reactions present a promising strategy for minimizing off-target toxicity in cancer chemotherapy, yet a dependable nanoplatform is urgently required. Here, we have fabricated an acid-responsive polymer micelle for the specific delivery and activation of the prodrug within tumor cells through Ru catalyst-mediated bioorthogonal reactions. The decomposition of micelles, triggered by the cleavage of the hydrazone bond in the acidic lysosomal environment, facilitated the concurrent release of Alloc-DOX and the Ru catalyst within the cells. Subsequently, the uncaging process of Alloc-DOX was demonstrated to be induced by the high levels of glutathione within tumor cells. Notably, the limited glutathione inside normal cells prevented the conversion of Alloc-DOX into active DOX, thereby minimizing the toxicity toward normal cells. In tumor-bearing mice, this nanoplatform exhibited enhanced efficacy in tumor suppression while minimizing off-target toxicity. Our study provides an innovative approach for in situ drug activation that combines safety and effectiveness in cancer chemotherapy.

Glutathione-triggered prodrugs: Design strategies, potential applications, and perspectives

The burgeoning prodrug strategy offers a promising avenue toward improving the efficacy and specificity of cytotoxic drugs. Elevated intracellular levels of glutathione (GSH) have been regarded as a hallmark of tumor cells and characteristic feature of the tumor microenvironment. Considering the pivotal involvement of elevated GSH in the tumorigenic process, a diverse repertoire of GSH-triggered prodrugs has been developed for cancer therapy, facilitating the attenuation of deleterious side effects associated with conventional chemotherapeutic agents and/or the attainment of more efficacious therapeutic outcomes. These prodrug formulations encompass a spectrum of architectures, spanning from small molecules to polymer-based and organic-inorganic nanomaterial constructs. Although the GSH-triggered prodrugs have been gaining increasing interests, a comprehensive review of the advancements made in the field is still lacking. To fill the existing lacuna, this review undertakes a retrospective analysis of noteworthy research endeavors, based on a categorization of these molecules by their diverse recognition units (i.e., disulfides, diselenides, Michael acceptors, and sulfonamides/sulfonates). This review also focuses on explaining the distinct benefits of employing various chemical architecture strategies in the design of these prodrug agents. Furthermore, we highlight the potential for synergistic functionality by incorporating multiple-targeting conjugates, theranostic entities, and combinational treatment modalities, all of which rely on the GSH-triggering. Overall, an extensive overview of the emerging field is presented in this review, highlighting the obstacles and opportunities that lie ahead. Our overarching goal is to furnish methodological guidance for the development of more efficacious GSH-triggered prodrugs in the future. By assessing the pros and cons of current GSH-triggered prodrugs, we expect that this review will be a handful reference for prodrug design, and would provide a guidance for improving the properties of prodrugs and discovering novel trigger scaffolds for constructing GSH-triggered prodrugs.

Doxorubicin prodrug-based nanomedicines for the treatment of cancer

The chemotherapeutic drug of doxorubicin (DOX) has witnessed widespread applications for treating various cancers. DOX-treated dying cells bear cellular modifications which allow enhanced presentation of tumor antigen and neighboring dendritic cell activation. Furthermore, DOX also facilitate the immune-mediated clearance of tumor cells. However, disadvantages such as severe off-target toxicity, and prominent hydrophobicity have resulted in unsatisfactory clinical therapeutic outcomes. The effective delivery of DOX drug molecules is still challenging despite the rapid advances in nanotechnology and biomaterials. Huge progress has been witnessed in DOX nanoprodrugs owing to their brilliant benefits such as tumor stimuli-responsive drug release capacity, high drug loading efficiency and so on. This review summarized recent progresses of DOX prodrug-based nanomedicines to provide deep insights into future development and inspire researchers to explore DOX nanoprodrugs with real clinical applications.

Activatable fluorescent probes for real-time imaging-guided tumor therapy

Surgery and drug therapy are the two principal options for cancer treatment. However, their clinical benefits are hindered by the difficulty of accurate location of the tumors and timely monitoring of the treatment efficacy of drugs, respectively. Rapid development of imaging techniques provides promising tools to address these challenges. Compared with conventional imaging techniques such as magnetic resonance imaging and computed tomography etc., fluorescence imaging exhibits high spatial resolution, real-time imaging capability, and relatively low costs devices. The advancements in fluorescent probes further accelerate the implementation of fluorescence imaging in tumor diagnosis and treatment monitoring. In particular, the emergence of site-specifically activatable fluorescent probes fits the demands of tumor delineation and real-time feedback of the treatment efficacy. A variety of small molecule probes or nanoparticle-based probes have been developed and explored for the above-mentioned applications. This review will discuss recent advances in fluorescent probes with a special focus on activatable nanoprobes and highlight the potential implementation of activatable nanoprobes in fluorescence imaging-guided surgery as well as imaging-guided drug therapy.

Tumor-Targeting Near-Infrared Dimeric Heptamethine Cyanine Photosensitizers With an Aromatic Diphenol Linker for Imaging-Guided Cancer Phototherapy

Phototherapy is considered a promising alternative to conventional tumor treatments due to its noninvasive modality and effective therapeutic effect. However, designing a photosensitizer with satisfactory therapeutic effect and high security remains a considerable challenge. Herein, a series of dimeric heptamethine cyanine photosensitizers with an aromatic diphenol linker at the meso position is developed to improve the photothermal conversion efficiency (PCE). Thanks to the extended conjugate system and high steric hindrance, the screened 26NA-NIR and 44BP-NIR exhibit high PCE (≈35%), bright near-infrared (NIR) fluorescence, excellent reactive oxygen species (ROS) generation capability, and improved photostability. Furthermore, their outstanding performance on imaging-guided PDT-PTT synergistic therapy is demonstrated by in vivo and in vitro experiments. In conclusion, this study designs a series of dimeric heptamethine cyanine photosensitizers and presents two compounds for potential clinical applications. The strategy provides a new method to design NIR photosensitizers for imaging-guided cancer treatment.

Spatial specific delivery of combinational chemotherapeutics to combat intratumoral heterogeneity

Hypoxia-induced intratumoral heterogeneity poses a major challenge in tumor therapy due to the varying susceptibility to chemotherapy. Moreover, the spatial distribution patterns of hypoxic and normoxic tissues makes conventional combination therapy less effective. In this study, a tumor-acidity and bioorthogonal chemistry mediated in situ size transformable nanocarrier (NP@DOX_DBCO plus iCPPA_N3) was developed to spatially deliver two combinational chemotherapeutic drugs (doxorubicin (DOX) and PR104A) to combat hypoxia-induced intratumoral heterogeneity. DOX is highly toxic to tumor cells in normoxia state but less toxic in hypoxia state due to the hypoxia-induced chemoresistance. Meanwhile, PR104A is a hypoxia-activated prodrug has less toxic in normoxia state. Two nanocarriers, NP@DOX_DBCO and iCPPA_N3, can cross-link near the blood vessel extravasation sites through tumor acidity responsive bioorthogonal click chemistry to enhance the retention of DOX in tumor normoxia. Moreover, PR104A conjugated to the small-sized dendritic polyamidoamine (PAMAM) released under tumor acidity can penetrate deep tumor tissues for hypoxic tumor cell killing. Our study has demonstrated that this site-specific combination chemotherapy is better than the traditional combination chemotherapy. Therefore, spatial specific delivery of combinational therapeutics via in situ size transformable nanocarrier addresses the challenges of hypoxia induced intratumoral heterogeneity and provides insights into the combination therapy.