Aptamer Conjugate-Based Ratiometric Fluorescent Probe for Precise Imaging of Therapy-Induced Cancer Senescence.

Therapy-induced cellular senescence has been increasingly recognized as a key mechanism to promote various aspects of carcinogenesis in a nonautonomous manner. Thus, real-time imaging monitoring of cellular senescence during cancer therapy is imperative not only to further elucidate its roles in cancer progression but also to provide guidance for medical management of cancer. However, it has long been a challenging task due to the lack of effective imaging molecule tools with high specificity and accuracy toward cancer senescence. Herein, we report the rational design, synthesis, and evaluation of an aptamer conjugate-based ratiometric fluorescent probe for precise imaging of therapy-induced cancer senescence. Unlike traditional senescence imaging systems, our probe targets two senescence-associated markers at both cellular and subcellular dimensions, namely, aptamer-mediated membrane marker recognition for active cell targeting and lysosomal marker-triggered ratiometric fluorescence changes of two cyanine dyes for site-specific, high-contrast imaging. Moreover, such a two-channel fluorescence response is activated after a one-step reaction and at the same location, avoiding the diffusion-caused signal decay previously encountered in dual-marker activated probes, contributing to spatiotemporally specific imaging of therapy-induced cancer senescence in living cells and three-dimensional multicellular tumor spheroids. This work may offer a valuable tool for a basic understanding of cellular senescence in cancer biology and interventions.

A denoising method of ECG signal based on variational autoencoder and masked convolution.

Wearable electrocardiogram (ECG) equipment can realize continuous monitoring of cardiovascular diseases, but these devices are more susceptible to interference from various noises, which will seriously reduce the diagnostic correctness. In this work, a novel noise reduction model for ECG signals is proposed based on variational autoencoder and masked convolution. The variational Bayesian inference is conducted to capture the global features of the ECG signals by encouraging the approximate posterior of the latent variables to fit the prior distribution, and we use the skip connection and feature concatenation to realize the information interaction across the channels. To strengthen the connection of local features of the ECG signals, the masked convolution module is used to extract local feature information, which supplement the global features and the noise reduction performance of whole model can be greatly improved. Experiments are carried out on the MIT-BIH arrythmia database, and the results display that the performance metrics of signal-to-noise ratio (SNR) and root mean square error (RMSE) are significantly improved compared with other approaches while causing less signal distortion.

Dual-Parameter Recognition-Directed Design of the Activatable Fluorescence Probe for Precise Imaging of Cellular Senescence.

Specific imaging of cellular senescence emerges as a promising strategy for early diagnosis and treatment of various age-related diseases. The currently available imaging probes are routinely designed by targeting a single senescence-related marker. However, the inherently high heterogeneity of senescence makes them inaccessible to achieve specific and accurate detection of broad-spectrum cellular senescence. Here, we report the design of a dual-parameter recognition fluorescent probe for precise imaging of cellular senescence. This probe remains silent in non-senescent cells, yet produces bright fluorescence after sequential responses to two senescence-associated markers, namely, SA-ß-gal and MAO-A. In-depth studies reveal that this probe allows for high-contrast imaging of senescence, independent of the cell source or stress type. More impressively, such dual-parameter recognition design further allows it to distinguish senescence-associated SA-ß-gal/MAO-A from cancer-related ß-gal/MAO-A, compared to commercial or previous single-marker detection probes. This study offers a valuable molecular tool for imaging cellular senescence, which is expected to significantly expand the basic studies on senescence and facilitate advances of senescence-related disease theranostics.

Engineering Hierarchical Recognition-Mediated Senolytics for Reliable Regulation of Cellular Senescence and Anti-Atherosclerosis Therapy.

Precise regulation of vascular senescence represents a far-reaching strategy to combat age-related diseases. However, the high heterogeneity of senescence, alongside the lack of targeting and potent senolytics, makes it very challenging. Here we report a molecular design to tackle this challenge through multidimensional, hierarchical recognition of three hallmarks commonly shared among senescence, namely, aptamer-mediated recognition of a membrane marker for active cell targeting, a self-immolative linker responsive to lysosomal enzymes for switchable drug release, and a compound against antiapoptotic signaling for clearance. Such senolytic can target and trigger severe cell apoptosis in broad-spectrum senescent endothelial cells, and importantly, distinguish them from the quiescent state. Its potential for in vivo treatment of vascular diseases is successfully illustrated in a model of atherosclerosis, with effective suppression of the plaque progression yet negligible side effects.

Recent Advances in Strategies for Imaging Detection and Intervention of Cellular Senescence.

Cellular senescence is a stable cell cycle arrest state that can be triggered by a wide range of intrinsic or extrinsic stresses. Increased burden of senescent cells in various tissues is thought to contribute to aging and age-related diseases. Thus, the detection and interventions of senescent cells are critical for longevity and treatment of disease. However, the highly heterogeneous feature of senescence makes it challenging for precise detection and selective clearance of senescent cells in different age-related diseases. To address this issue, considerable efforts have been devoted to developing senescence-targeting molecular theranostic strategies, based on the potential biomarkers of cellular senescence. Herein, we review recent advances in the field of anti-senescence research and highlight the specific visualization and elimination of senescent cells. Additionally, the challenges in this emerging field are outlined.

Artificial Nucleobase-Directed Programmable Synthesis and Assembly of Amphiphilic Nucleic Acids as an All-in-One Platform for Cation-Free siRNA Delivery.

Efficient transport of nucleic acid therapeutics into targeted cells is the key step of genetic modulation in disease treatment. Nowadays, delivery systems strongly rely on cationic materials, but how to balance the trade-off between effectiveness and toxicity of these exogenous materials remains incredibly challenging. Here, we take inspiration from nucleic acid chemistry and introduce a new concept of amphiphilic nucleic acids (ANAs), as an all-in-one platform for cation-free nucleic acid delivery, by programmatically conjugating two different artifical nucleobases with sequence-independent activities. Specifically, the hydrophilic artificial nucleobases in ANAs act as both delivery vectors and therapeutic cargos for integrated benefits, while the hydrophobic nucleobases enable molecular self-assembly for improved stability and endosomal membrane oxidation for enhanced endosomal escape. By virtue of these merits, this platform is successfully used for short interference RNA (siRNA) delivery, which demonstrates a high siRNA loading capacity, rapid cellular uptake, and efficient endosomal escape, eliciting remarkable gene silencing and synergistic inhibitory effects on cancer cell proliferation and migration. This work is a case study in exploiting the basis of nucleic acid chemistry to afford new paradigms for advanced cancer theranostics.

Engineering AND-Gate Aptamer-Signal Base Conjugates for Targeted Magnetic Resonance Molecular Imaging of Metastatic Cancer.

In vivo noninvasive molecular imaging requires precise recognition and in situ, real-time imaging of specific cellular and molecular signatures at the site of interest. However, this is often hindered by issues of current imaging probes relating to either the lack of active recognition or the overall nonspecific mechanism of action. Here, we present an aptamer-signal base conjugate (ApSC) concept to engineer AND-gate molecular tools for tumor-targeted molecular imaging. Superior to conventional synthetic methods for imaging probes, our design enables programmable and precise conjugation between recognition and signaling units in a modular synthesis manner with high fidelity for both the conjugating chemistry and binding affinity to the molecular target. Moreover, this design is endowed with simultaneous multivariate activation that readily adapts to tumor microenvironments for signal output, thus providing improved imaging specificity and sensitivity. Such a concept has been successfully shown in magnetic resonance imaging (MRI), the modality of choice for in vivo noninvasive molecular imaging. The engineered ApSC can produce amplified MR signals only after activation by the unique metabolism and dysregulation of redox balance in cancer. In mouse models of xenograft and metastatic breast cancer, the AND-gate molecular MRI probe elicits high imaging contrast in primary tumors and micrometastases. This study promises to provide synthetically accessible scaffolds that can be extended to a large library of advanced molecular imaging tools with varied imaging modalities and mechanisms of action for preventative, predictive, and personalized medicine.

Spatially Confined Intervention of Cellular Senescence by a Lysosomal Metabolism Targeting Molecular Prodrug for Broad-Spectrum Senotherapy.

Specific intervention of senescent cells (SnCs) is emerging as a powerful means to counteract aging and age-related diseases. Canonical methods are generally designed to target SnC-associated signaling pathways, which are however dynamically changing and highly heterogeneous in SnCs, significantly limiting the effectiveness. Here, we present a tailor-made molecular prodrug targeting lysosome dysfunction, a unique feature shared by virtually all types of SnCs. The prodrug comprises three modules all targeting the altered lysosomal programs in SnCs, namely, a recognizing unit towards the elevated lysosome content, a linker cleavable by the activated lysosomal enzyme, and a lysosomotropic agent targeting the increased lysosomal membrane sensitivity. This spatially confined design enables killing broad-spectrum SnCs, with high specificity over non-SnCs. Along with in vivo benefits, this work offers a way to significantly expand the applicability of senotherapy in a wide range of diseases.

Beyond Blocking: Engineering RNAi-Mediated Targeted Immune Checkpoint Nanoblocker Enables T-Cell-Independent Cancer Treatment.

The emergence of immune checkpoint blockade to activate host T cells to attack tumor cells has revolutionized the cancer treatment landscape over the past decade. However, sustained response has only been achieved in a small proportion of patients. This can be attributed to physiological barriers, such as T-cell heterogeneity and immunosuppressive tumor microenvironments. To this can be added obstacles intrinsic to traditional antibody-driven blockade methods, including the inability to inhibit checkpoint translocation from cytoplasm, systemic immune toxicity, and "bite back" effect on T cells. Using non-small cell lung cancer (NSCLC) as the cancer model, here we report an unconventional, yet powerful, tumor-targeted checkpoint blocking strategy by RNAi nanoengineering for T-cell-independent cancer therapy. Unlike antibodies, such nanoblocker silences both membranous and cytoplasmic PD-L1 in cancer cells, thus eliminating the binding step. Moreover, it is demonstrated that silencing of PD-L1 by the nanoblocker can cause the direct programmed cell death of NSCLC H460 cells, without the need of T-cell intervention. In vivo results from xenograft tumor models further demonstrate that tumor-homing peptide modification enables the nanoblocker to accumulate in the tumor tissue, downregulate the PD-L1 expression, and inhibit the tumor growth more efficiently than the nontargeted group. These findings may offer an effective means toward overcoming barriers against traditional checkpoint blockade and provide different insights into the molecular mechanism(s) underlying immunotherapy.

Molecular Self-Assembly of Bioorthogonal Aptamer-Prodrug Conjugate Micelles for Hydrogen Peroxide and pH-Independent Cancer Chemodynamic Therapy.

Chemodynamic therapy (CDT) has demonstrated new possibilities for selective and logical cancer intervention by specific manipulation of dysregulated tumorous free radical homeostasis. Current CDT methods largely rely on conversion of endogenous hydrogen peroxide (H2O2) into highly toxic hydroxyl radicals via classical Fenton or Haber-Weiss chemistry. However, their anticancer efficacies are greatly limited by the requirement of strong acidity for efficient chemical reactions, insufficient tumorous H2O2, and upregulated antioxidant defense to counteract free radical-caused oxidative damage. Here, we present a new concept whereby bioorthogonal chemistry and prodrug are combined to create a new type of aptamer drug conjugate (ApDC): aptamer-prodrug conjugate (ApPdC) micelle for improved and cancer-targeted CDT. The hydrophobic prodrug bases can not only promote self-assembly of aptamers but also act as free radical generators via bioorthogonal chemistry. In depth mechanistic studies reveal that, unlike traditional CDT systems, ApPdC micelles enable in situ activation and self-cycling generation of toxic C-centered free radicals in cancer cells through cascading bioorthogonal reactions, with no dependence on either H2O2 or pH, yet concurrently with diminished cancerous antioxidation by GSH depletion for a synergistic CDT effect. We expect this work to provide new insights into the design of targeted cancer therapies and studies of free radical-related molecular mechanisms.