A nanoparticle probe for the imaging of autophagic flux in live mice via magnetic resonance and near-infrared fluorescence

Advances in Targeted Autophagy Modulation Strategies to Treat Cancer and Associated Treatment-Induced Cardiotoxicity

Autophagy, an evolutionarily conserved process, plays an important role in cellular homeostasis and human diseases. Cardiovascular dysfunction, which presents during cancer treatment or in cancer-free individuals years after treatment, is a growing clinical challenge. Millions of cancer survivors and patients face an unpredictable risk of developing cardiotoxicity. Cardiotoxicity due to cancer treatment, as well as cancer progression, has been linked to autophagy dysregulation. Modulating autophagy has been further proposed as a therapeutic treatment for both cancer and cardiovascular disorders. The safe and effective use of autophagy modulation as a cardioprotective strategy during cancer treatment especially requires careful consideration and experimentation to minimize the impact on cancer treatment. We focus here on recent advances in targeted autophagy modulation strategies that utilize interdisciplinary approaches in biomedical sciences and are potentially translatable to treat cardiotoxicity and improve cancer treatment outcomes. This review highlights non-small molecule autophagy modulators to enhance targeted therapy, nanomedicine for autophagy modulation and monitoring, and in vitro models and future experiments needed to bring novel autophagy discoveries from basic research to clinical translation.

The Reversible and Background-Free Hydrogel-Sensing Platform for Dual-Mode Detection of Acetone in Exhaled Breath

The acetone present in exhaled breath is a promising indicator for diagnosing human health. The fluorescent hydrogel sensor-based portable sensing platform is a highly effective tool for the on-site detection of acetone. However, existing hydrogel sensors are often limited by their irreversibility and autofluorescence. This study constructed an upconversion nanoprobe with reversibility for dual-mode detection of acetone by simply combining upconversion nanoparticles (UCNPs), hydroxylamine sulfate, and thymol blue (TB). The nanoprobe was further embedded into a hydrogel network to construct the background-free hydrogel nanosensor for the portable detection of acetone. The hydrogel nanosensor utilized long-wavelength-excited UCNPs to avoid self-luminescence interference. Hydroxylamine sulfate, as a specific recognition unit, reacted with acetone to induce the protonation of TB, resulting in an increase in absorbance at 548 nm and a decrease in luminescence at 540 nm, enabling visual colorimetric and precise luminescent detection of acetone. Moreover, the hydrogel nanosensor could be restored to its initial state through the deprotonation of TB, thereby achieving reversible detection. Additionally, 3D printing technology was utilized to construct a portable sensing platform for real-time acetone monitoring. The proposed upconversion hydrogel nanosensor in this study paves a new way for developing hydrogel sensors with high sensitivity and reversibility.

Advanced Nanoprobe Strategies for Imaging Macrophage Polarization in Cancer Immunology

Macrophages are ubiquitous within the human body and serve pivotal roles in immune surveillance, inflammation, and tissue homeostasis. Phenotypic plasticity is a hallmark of macrophages, allowing their polarization into distinct phenotypes M1 (pro-inflammatory, anti-tumor) and M2 (anti-inflammatory, pro-tumor) in response to local microenvironmental cues. In tumor tissues, the polarization of tumor-associated macrophages profoundly shapes the tumor microenvironment, influencing tumor progression, immune evasion, and metastasis. Therefore, the ability to image and monitor macrophage polarization is essential for comprehending tumor biology and optimizing therapeutic strategies. With the rapid advancement of nanomedicine, a diverse array of nanoprobes has been engineered to specifically target tumor-associated macrophages, offering new avenues for noninvasive in vivo imaging and real-time monitoring of macrophage dynamics within the tumor microenvironment. This perspective highlights recent advancements in macrophage-targeting nanoprobes for imaging macrophage polarization both in vitro and in vivo. It also addresses the current challenges in the field, such as enhancing probe sensitivity, specificity, and biocompatibility, while outlining the future directions for the development of next-generation nanoprobes aimed at precision oncology.

Decoration of Autophagy Detecting Nanoparticle with an Anionic Fluorochrome Enhances Multispectral Characterization of Autophagosome Location and Flux

Autophagy is a key biological process that has proven extremely difficult to detect noninvasively. To address this, an autophagy detecting nanoparticle (ADN) was recently developed, consisting of an iron oxide nanoparticle decorated with cathepsin-cleavable arginine-rich peptides bound to the near-infrared fluorochrome Cy5.5. Activation of the probe in autophagolysosomes results in the emission of Cy5.5 fluorescence and provides a measure of autophagosome flux. However, in the early autophagosome ADN fluorescence is silent due to fluorochrome stacking. Here, we introduce to ADN a second non-cleavable fluorophore that allows the probe to be tracked through all stages of autophagy. The nature of the secondary/tracking fluorophore has a profound effect on the activation of ADN and the emission of Cy5.5 fluorescence. The lead candidate, ADN2 (featuring AZDye546 as the secondary fluorophore) has the highest activation rate and change in Cy5.5 fluorescence. Absorbance and fluorescence spectrophotometry methods show that the negatively charged AZDye546 interacts with the positively charged polyarginine motifs of the Cy5.5-polyArg activatable fluorophore, resulting in enhanced baseline quenching of the Cy5.5 signal in the nanoprobe. Flow cytometry shows that the activation of ADN2 remains specific for autophagy and is strongly modulated by classical regulators of autophagy (starvation, bafilomycin) and genetic deletion of key autophagy proteins (ATG5, ATG7). ADN2 co-localized strongly with LC3-GFP positive autophagosomes and provided readouts of in vivo probe delivery and activation in the hearts of fed/starved mice. ADN2 enhances the ability to image autophagy without genetic transfection of cells/animals and underscores the possible effects for unanticipated interactions between fluorochromes and other moieties on the surface of decorated nanoparticles.

Review on the role of autophagy in the toxicity of nanoparticles and the signaling pathways involved

As the development of nanotechnology, the application of nanoproducts and the advancement of nanomedicine, the contact of nanoparticles (NPs) with human body is becoming increasingly prevalent. This escalation elevates the risk of NPs exposure for workers, consumers, researchers, and both aquatic and terrestrial organisms throughout the production, usage, and disposal stages. Consequently, evaluating nanotoxicity remains critically important, though standardized assessment criteria are still lacking. The diverse and complex properties of NPs further complicate the understanding of their toxicological mechanisms. Autophagy, a fundamental cellular process, exhibits dual functions-both pro-survival and pro-death. This review offers an updated perspective on the dual roles of autophagy in nanotoxicity and examines the factors influencing autophagic responses. However, no definitive framework exists for predicting NPs-induced autophagy. Beyond the conventional autophagy pathways, the review highlights specific transcription factors activated by NPs and explores metabolic reprogramming. Particular attention is given to NPs-induced selective autophagy, including mitophagy, ER-phagy, ferritinophagy, lysophagy, and lipophagy. Additionally, the review investigates autophagy's involvement in NPs-mediated biological processes such as ferroptosis, inflammation, macrophage polarization, epithelial-mesenchymal transition, tumor cell proliferation and drug resistance, as well as liver and kidney injury, neurotoxicity, and other diseases. In summary, this review presents a novel update on selective autophagy-mediated nanotoxicity and elucidates the broader interactions of autophagy in NPs-induced biological processes. Collectively, these insights offer valuable strategies for mitigating nanotoxicity through autophagy modulation and advancing the development of NPs in biomedical applications.

An HPQ-based near-infrared dye for the detection of ClO- and accurate imaging of cells and mouse tumor sites in situ

A new fluorescent probe (SWJT-32) with a large Stokes shift was designed and synthesized with 2-(2-hydroxyphenyl)-4(1H)-quinazolinone (HPQ) as the skeleton and N,N-dimethylthiocarbamate as the recognition site. It can detect hypochlorite ions (ClO-) through fluorescence spectroscopy based on the excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) mechanism. The probe has the advantages of strong diffusion resistance, good photostability and selectivity, and high imaging contrast, and can be used for the detection of ClO-. Meanwhile, due to its low toxicity and good biocompatibility in living cells, SWJT-32 can be used for the detection of endogenous and exogenous ClO- in HeLa cells as well as for long-term in vivo imaging in tumor mice.

Biological Properties of Arginine-rich Peptides and their Application in Cargo Delivery to Cancer

Cell-penetrating peptides (CPPs) comprise short peptides of fewer than 30 amino acids, which are rich in arginine (Arg) or lysine (Lys). CPPs have attracted interest in the delivery of various cargos, such as drugs, nucleic acids, and other macromolecules over the last 30 years. Among all types of CPPs, arginine-rich CPPs exhibit higher transmembrane efficiency due to bidentate bonding between their guanidinium groups and negatively charged cellular components. Besides, endosome escape can be induced by arginine-rich CPPs to protect cargo from lysosome-dependent degradation. Here we summarize the function, design principles, and penetrating mechanisms of arginine-rich CPPs, and outline their biomedical applications in drug delivery and biosensing in tumors.

The splicing factor hnRNPL demonstrates conserved myocardial regulation across species and is altered in heart failure

Heart failure (HF) is highly prevalent. Mechanisms underlying HF remain incompletely understood. Splicing factors (SF), which control pre-mRNA alternative splicing, regulate cardiac structure and function. This study investigated regulation of the splicing factor heterogeneous nuclear ribonucleoprotein-L (hnRNPL) in the failing heart. hnRNPL protein increased in left ventricular tissue from mice with transaortic constriction-induced HF and from HF patients. In left ventricular tissue, hnRNPL was detected predominantly in nuclei. Knockdown of the hnRNPL homolog Smooth in Drosophila induced cardiomyopathy. Computational analysis of predicted mouse and human hnRNPL binding sites suggested hnRNPL-mediated alternative splicing of tropomyosin, which was confirmed in C2C12 myoblasts. These findings identify hnRNPL as a sensor of cardiac dysfunction and suggest that disturbances of hnRNPL affect alternative splicing in HF.

Let's talk about flux: the rising potential of autophagy rate measurements in disease

Macroautophagy/autophagy is increasingly implicated in a variety of diseases, making it an attractive therapeutic target. However, many aspects of autophagy are not fully understood and its impact on many diseases remains debatable and context-specific. The lack of systematic and dynamic measurements in these cases is a key reason for this ambiguity. In recent years, Loos et al. 2014 and Beesabathuni et al. 2022 developed methods to quantitatively measure autophagy holistically. In this commentary, we pose some of the unresolved biological questions regarding autophagy and consider how quantitative measurements may address them. While the applications are ever-expanding, we provide specific use cases in cancer, virus infection, and mechanistic screening. We address how the rate measurements themselves are central to developing cancer therapies and present ways in which these tools can be leveraged to dissect the complexities of virus-autophagy interactions. Screening methods can be combined with rate measurements to mechanistically decipher the labyrinth of autophagy regulation in cancer and virus infection. Taken together, these approaches have the potential to illuminate the underlying mechanisms of various diseases.Abbreviation MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; R1: rate of autophagosome formation; R2: rate of autophagosome-lysosome fusion; R3: rate of autolysosome turnover.

Application of Nanomaterials and Related Drug Delivery Systems in Autophagy

Autophagy, a lysosomal self-degradation pathway, plays a critical role in cellular homeostasis by degrading endogenous damaged organelles and protein aggregates into recyclable biological molecules. Additionally, it detoxifies extracellular toxic substances, including drugs and toxic materials, thereby preserving the stability of the intracellular environment. The swift progression of nanotechnology has led to an increased focus on understanding the relationship between nanomaterials and autophagy. The effects of various nanomaterials and nano drug delivery systems on autophagy and their biological functions have been preliminarily assessed, revealing that modulation of intracellular autophagy levels by these agents represents a novel cellular response mechanism. Notably, autophagy regulation based on nanomaterials or nano drug delivery systems for a range of diseases is currently the subject of extensive research. Given the close association between autophagy levels and tumors, the regulation of autophagy has emerged as a highly active area of research in the development of innovative tumor therapies. This review synthesizes the current understanding of the application of nanomaterials or nano drug delivery systems on autophagy and their potential biological functions, suggesting a new avenue for nanomaterial-based autophagy regulation.

Recent Progress in Peptide-Based Molecular Probes for Disease Bioimaging

Recent strides in molecular pathology have unveiled distinctive alterations at the molecular level throughout the onset and progression of diseases. Enhancing the in vivo visualization of these biomarkers is crucial for advancing disease classification, staging, and treatment strategies. Peptide-based molecular probes (PMPs) have emerged as versatile tools due to their exceptional ability to discern these molecular changes with unparalleled specificity and precision. In this Perspective, we first summarize the methodologies for crafting innovative functional peptides, emphasizing recent advancements in both peptide library technologies and computer-assisted peptide design approaches. Furthermore, we offer an overview of the latest advances in PMPs within the realm of biological imaging, showcasing their varied applications in diagnostic and therapeutic modalities. We also briefly address current challenges and potential future directions in this dynamic field.

Procalcitonin Detection Using Immunomagnetic Beads-Mediated Surface-Enhanced Raman Spectroscopy

The early detection of procalcitonin (PCT) is crucial for diagnosing bacterial infections due to its high sensitivity and specificity. While colloidal gold colorimetric and immune-chemiluminescence methods are commonly employed in clinical detection, the former lacks sensitivity, and the latter faces challenges with a brief luminescence process and an elevated background. Here, we introduce a novel approach for the quantitative analysis of PCT using surface-enhanced Raman spectroscopy (SERS), leveraging the enhanced properties of metal nanoparticles. Simultaneously, we employed a magnetic nanoparticle coating and surface biofunctionalization modification to immobilize PCT-trapping antibodies, creating the required immune substrates. The resulting magnetic nanoparticles and antibody complexes, acting as carriers and recognition units, exhibited superparamagnetism and the specific recognition of biomarkers. Then, this complex efficiently underwent magnetic separation with an applied magnetic field, streamlining the cumbersome steps of traditional ELISA and significantly reducing the detection time. In conclusion, the exploration of immunomagnetic bead detection technology based on surface-enhanced Raman spectroscopy holds crucial practical significance for the sensitive detection of PCT.

Tumor Microenvironment Activatable Nanoprodrug System for In Situ Fluorescence Imaging and Therapy of Liver Cancer

The development of new imaging and treatment nanoprodrug systems is highly demanded for diagnosis and therapy of liver cancer, a severe disease characterized by a high recurrence rate. Currently, available small molecule drugs are not possible for cancer diagnosis because of the fast diffusion of imaging agents and low efficacy in treatment due to poor water solubility and significant toxic side effects. In this study, we report the development of a tumor microenvironment activatable nanoprodrug system for the diagnosis and treatment of liver cancer. This nanoprodrug system can accumulate in the tumor site and be selectively activated by an excess of hydrogen peroxide (H2O2) in the tumor microenvironment, releasing near-infrared solid-state organic fluorescent probe (HPQCY-1) and phenylboronic acid-modified camptothecin (CPT) prodrug. Both HPQCY-1 and CPT prodrugs can be further activated in tumor sites for achieving more precise in situ near-infrared (NIR) fluorescence imaging and treatment while reducing the toxic effects of drugs on normal tissues. Additionally, the incorporation of hydrophilic multivalent chitosan as a carrier effectively improved the water solubility of the system. This research thus provides a practical new approach for the diagnosis and treatment of liver cancer.

Ultra-photostable small-molecule dyes facilitate near-infrared biophotonics

Long-wavelength, near-infrared small-molecule dyes are attractive in biophotonics. Conventionally, they rely on expanded aromatic structures for redshift, which comes at the cost of application performance such as photostability, cell permeability, and functionality. Here, we report a ground-state antiaromatic strategy and showcase the concise synthesis of 14 cationic aminofluorene dyes with mini structures (molecular weights: 299-504 Da) and distinct spectra covering 700-1600 nm. Aminofluorene dyes are cell-permeable and achieve rapid renal clearance via a simple 44 Da carboxylation. This accelerates optical diagnostics of renal injury by 50 min compared to existing macromolecular approaches. We develop a compact molecular sensing platform for in vivo intracellular sensing, and demonstrate the versatile applications of these dyes in multispectral fluorescence and optoacoustic imaging. We find that aromaticity reversal upon electronic excitation, as indicated by magnetic descriptors, not only reduces the energy bandgap but also induces strong vibronic coupling, resulting in ultrafast excited-state dynamics and unparalleled photostability. These results support the argument for ground-state antiaromaticity as a useful design rule of dye development, enabling performances essential for modern biophotonics.

Impaired autophagy flux contributes to enhanced ischemia reperfusion injury in the diabetic heart

Myocardial ischemia/reperfusion (I/R) injury is exacerbated in diabetic individuals and animal models. We tested whether autophagy is an important cellular determinant of cell death. First, we utilized a cellular model of hypoxia reoxygenation (H/R) in H9c2 cells cultured in low or high glucose (HG) and tested cell death using flow cytometry to detect Annexin-V and propidium iodide, imaging cell viability ReadyProbe and lactate dehydrogenase release. We observed that cell death induced by H/R was enhanced by HG. Kinetic analysis of caspase-3 activity using a fluorescence reporter probe, stable expression of the VC3AI biosensor and western blotting indicated that H/R induced activation of caspase-3 was enhanced by HG. Temporal autophagy flux analysis using DapRed and DalGreen probes indicated an initial increase in response to H/R that was reduced upon prolonged (24h) R. HG suppressed this induction of autophagy. This was verified using LC3 HiBiT reporter assay, tandem-fluorescent LC3, and western blotting. Lysosomal cathepsin activity was also elevated at 6h and suppressed at 24h R. Autophagy-deficient cells were generated via CRISPR-mediated knockout of atg7 and the effect of combined HG and H/R treatment on caspase activation and cell death was elevated in comparison with wild type cells. We then performed coronary artery ligation surgery to induce ischemia, followed by reperfusion, in wild-type or streptozotocin (STZ)-induced hyperglycemic mice. Non-invasive 3-dimensional imaging using fluorescence molecular tomography combined with computerized tomography was employed to monitor spatio-temporal activation of cardiac autophagy and apoptosis. Upon systemic injection of a near infra-red cathepsin activatable probe we found that hyperglycemic mice had lower activity in the infarct region after I/R versus wild type. In parallel, we observed a higher extent of I/R-induced apoptosis, detected with an annexin-V probe, in hyperglycemic mice. Collectively, these results revealed that impaired autophagic flux in the presence of high glucose levels exacerbates I/R injury.Abbreviation: satg7, autophagy-related 7; FMT, fluorescence molecular tomography; HG, high glucose; H/R, hypoxia/reoxygenation; I/R, ischemia/reperfusion; LC3, MAP1LC3; N, normoxia; NG, normal glucose; NIR, near-infrared; p62, SQSTM1; STZ, streptozotocin.

Ischemia-induced cardiac dysfunction is exacerbated in adiponectin-knockout mice due to impaired autophagy flux

Strategies to enhance autophagy flux have been suggested to improve outcomes in cardiac ischemic models. We explored the role of adiponectin in mediating cardiac autophagy under ischemic conditions induced by permanent coronary artery ligation. We studied the molecular mechanisms underlying adiponectin's cardio-protective effects in adiponectin knockout (Ad-KO) compared with wild-type (WT) mice subjected to ischemia by coronary artery ligation and H9c2 cardiomyocyte cell line exposed to hypoxia. Systemic infusion of a cathepsin-B activatable near-infrared probe as a biomarker for autophagy and detection via noninvasive three-dimensional fluorescence molecular tomography combined with computerized tomography to quantitate temporal changes, indicated increased activity in the myocardium of WT mice after myocardial infarction which was attenuated in Ad-KO. Seven days of ischemia increased myocardial adiponectin accumulation and elevated ULK1/AMPK phosphorylation and autophagy assessed by Western blotting for LC3 and p62, an outcome not observed in Ad-KO mice. Cell death, assessed by TUNEL analysis and the ratio of Bcl-2:Bax, plus cardiac dysfunction, measured using echocardiography with strain analysis, were exacerbated in Ad-KO mice. Using cellular models, we observed that adiponectin stimulated autophagy flux in isolated primary adult cardiomyocytes and increased basal and hypoxia-induced autophagy in H9c2 cells. Real-time temporal analysis of caspase-3/7 activation and caspase-3 Western blot indicated that adiponectin suppressed activation by hypoxia. Hypoxia-induced mitochondrial reactive oxygen species production and cell death were also attenuated by adiponectin. Importantly, the ability of adiponectin to reduce caspase-3/7 activation and cell death was not observed in autophagy-deficient cells generated by CRISPR-mediated deletion of Atg7. Collectively, our data indicate that adiponectin acts in an autophagy-dependent manner to attenuate cardiomyocyte caspase-3/7 activation and cell death in response to hypoxia in vitro and ischemia in mice.

Cascade Catalytic Nanoparticles Selectively Alkalize Cancerous Lysosomes to Suppress Cancer Progression and Metastasis

Lysosomes are critical in modulating the progression and metastasis for various cancers. There is currently an unmet need for lysosomal alkalizers that can selectively and safely alter the pH and inhibit the function of cancer lysosomes. Here an effective, selective, and safe lysosomal alkalizer is reported that can inhibit autophagy and suppress tumors in mice. The lysosomal alkalizer consists of an iron oxide core that generates hydroxyl radicals (•OH) in the presence of excessive H+ and hydrogen peroxide inside cancer lysosomes and cerium oxide satellites that capture and convert •OH into hydroxide ions. Alkalized lysosomes, which display impaired enzyme activity and autophagy, lead to cancer cell apoptosis. It is shown that the alkalizer effectively inhibits both local and systemic tumor growth and metastasis in mice. This work demonstrates that the intrinsic properties of nanoparticles can be harnessed to build effective lysosomal alkalizers that are both selective and safe.

The adjacent effect between Gd(III) and Cu(II) in layered double hydroxide nanoparticles synergistically enhances T1-weighted magnetic resonance imaging contrast

Magnetic resonance imaging (MRI) is one key technology in modern diagnostic medicine. However, the development of high-relaxivity contrast agents with favorable properties for imaging applications remains a challenging task. In this work, dual Gd(III) and Cu(II) doped-layered double hydroxide (GdCu-LDH) nanoparticles show significantly higher longitudinal relaxivity compared with sole-metal-based LDH (Gd-LDH and Cu-LDH) nanoparticles. This relaxation enhancement in GdCu-LDH is also much greater than the simple addition of the relaxivity rate of the two paramagnetic ions in Gd-LDH and Cu-LDH, presumably attributed to synergistic T₁ shortening between adjacent Gd(III) and Cu(II) in the LDH host layers (adjacent effect). Moreover, our GdCu-LDH nanoparticles exhibit a pH-ultrasensitive property in MRI performance and show much clearer MR imaging for tumor tissues in mice than Gd-LDH and Cu-LDH at the equivalent doses. Thus, these novel Gd/Cu-co-doped LDH nanoparticles provide higher potential for accurate cancer diagnosis in clinic application. To the best of our knowledge, this is the first report that two paramagnetic metal ions in one nanoparticle synergistically improve the T₁-MRI contrast.