Light/X-ray/ultrasound activated delayed photon emission of organic molecular probes for optical imaging: mechanisms, design strategies, and biomedical applications.

Conventional optical imaging, particularly fluorescence imaging, often encounters significant background noise due to tissue autofluorescence under real-time light excitation. To address this issue, a novel optical imaging strategy that captures optical signals after light excitation has been developed. This approach relies on molecular probes designed to store photoenergy and release it gradually as photons, resulting in delayed photon emission that minimizes background noise during signal acquisition. These molecular probes undergo various photophysical processes to facilitate delayed photon emission, including (1) charge separation and recombination, (2) generation, stabilization, and conversion of the triplet excitons, and (3) generation and decomposition of chemical traps. Another challenge in optical imaging is the limited tissue penetration depth of light, which severely restricts the efficiency of energy delivery, leading to a reduced penetration depth for delayed photon emission. In contrast, X-ray and ultrasound serve as deep-tissue energy sources that facilitate the conversion of high-energy photons or mechanical waves into the potential energy of excitons or the chemical energy of intermediates. This review highlights recent advancements in organic molecular probes designed for delayed photon emission using various energy sources. We discuss distinct mechanisms, and molecular design strategies, and offer insights into the future development of organic molecular probes for enhanced delayed photon emission.

Afterglow/Photothermal Bifunctional Polymeric Nanoparticles for Precise Postbreast-Conserving Surgery Adjuvant Therapy and Early Recurrence Theranostic.

Adjuvant whole-breast radiotherapy is essential for breast cancer patients who adopted breast-conserving surgery (BCS) to reduce the risk of local recurrences, which however suffer from large-area and highly destructive ionizing radiation-induced adverse events. To tackle this issue, an afterglow/photothermal bifunctional polymeric nanoparticle (APPN) is developed that utilizes nonionizing light for precise afterglow imaging-guided post-BCS adjuvant second near-infrared (NIR-II) photothermal therapy. APPN consists of a tumor cell targeting afterglow agent, which is doped with a NIR dye as an afterglow initiator and a NIR-II light-absorbing semiconducting polymer as a photothermal transducer. Such a design realizes precise afterglow imaging-guided NIR-II photothermal ablation of minimal residual breast tumor foci after BCS, thus achieving complete inhibition of local recurrences. Moreover, APPN enables early diagnosis and treatment of local recurrence after BCS. This study thus provides a nonionizing modality for precision post-BCS adjuvant therapy and early recurrence theranostic.

Effects of M currents on the persistent activity of pyramidal neurons in mouse primary auditory cortex.

Neuronal persistent activity (PA) is a common phenomenon observed in many types of neurons. PA can be induced in neurons in the mouse auditory nucleus by activating cholinergic receptors with carbachol (CCh), a dual muscarinic and nicotinic receptor agonist. PA is presumed to be associated with learning-related auditory plasticity at the cellular level. However, the mechanism is not clearly understood. Many studies have reported that muscarinic receptor agonists inhibit muscarinic-sensitive potassium channels (M channels). Potassium efflux through M channels produces potassium currents, called M currents, that play an essential role in regulating neural excitability and synaptic plasticity. Further study is needed to determine whether M currents affect the PA of auditory central neurons and provide additional analysis of the variations in electrophysiological properties. We used in vitro whole cell patch-clamp recordings in isolated mouse brain slices to investigate the effects of M currents on the PA in pyramidal neurons in layer V of the primary auditory cortex (AI-L5). We found that blocking M currents with XE991 depolarized the AI-L5 pyramidal neurons, which significantly increased the input resistance. The active threshold and threshold intensity were significantly reduced, indicating that intrinsic excitability was enhanced. Our results also showed that blocking M currents with XE991 switched the neuronal firing patterns in the AI-L5 pyramidal neurons from regular spiking to intrinsic bursting. Blocking M currents facilitated PA by increasing the plateau potential and enhancing intrinsic excitability. Our results suggested that blocking M currents might facilitate the PA in AI-L5 pyramidal neurons, which underlies auditory plasticity.NEW & NOTEWORTHY Persistent activity (PA) in AI-L5 pyramidal neurons plays an essential role in acoustic information processing. We used in vitro whole cell patch-clamp recordings to investigate the effects of M currents on the PA in AI-L5 pyramidal neurons. Blocking M currents with XE991 facilitated PA by increasing the plateau potential and enhancing intrinsic excitability, causing the firing patterns of AI-L5 pyramidal neurons to become more bursting. These results provide new insight into our understanding of the cellular mechanisms that govern learning-induced auditory plasticity.

Photoacoustic Imaging and Photothermal Therapy of Semiconducting Polymer Nanoparticles: Signal Amplification and Second Near-Infrared Construction.

Photoacoustic (PA) imaging and photothermal therapy (PTT) have attracted extensive attention in disease diagnosis and treatment. Although many exogenous contrast agents have been developed for PA imaging and PTT, the design guidelines to amplify their imaging and therapy performances remain challenging and are highly demanded. Semiconducting polymer nanoparticles (SPNs) composed of polymers with π-electron delocalized backbones can be designed to amplify their PA imaging and PTT performance, because of their clear structure-property relation and versatility in modifying their molecular structures to tune their photophysical properties. This review summarizes the recent advances in the photoacoustic imaging and photothermal therapy applications of semiconducting polymer nanoparticles with a focus on signal amplification and second near-infrared (NIR-II, 1000-1700 nm) construction. The strategies such as structure-property screening, fluorescence quenching, accelerated heat dissipation, and size-dependent heat dissipation are first discussed to amplify the PA brightness of SPNs for in vivo PA. The molecular approaches to shifting the absorption of SPNs for NIR-II PA imaging and PTT are then introduced so as to improve the tissue penetration depth for diagnosis and therapy. At last, current challenges and perspectives of SPNs in the field of imaging and therapy are discussed.

Recent Advances in Cell Membrane-Camouflaged Nanoparticles for Cancer Phototherapy.

Phototherapy including photothermal therapy (PTT) and photodynamic therapy (PDT) employs phototherapeutic agents to generate heat or cytotoxic reactive oxygen species (ROS), and has therefore garnered particular interest for cancer therapy. However, the main challenges faced by conventional phototherapeutic agents include easy recognition by the immune system, rapid clearance from blood circulation, and low accumulation in target sites. Cell-membrane coating has emerged as a potential way to overcome these limitations, owing to the abundant proteins on the surface of cell membranes that can be inherited to the cell membrane-camouflaged nanoparticles. This review summarizes the recent advances in the development of biomimetic cell membrane-camouflaged nanoparticles for cancer phototherapy. Different sources of cell membranes can be used to coat nanoparticles uisng different coating approaches. After cell-membrane coating, the photophysical properties of the original phototherapeutic nanoparticles remain nearly unchanged; however, the coated nanoparticles are equipped with additional physiological features including immune escape, in vivo prolonged circulation time, or homologous targeting, depending on the cell sources. Moreover, the coated cell membrane can be ablated from phototherapeutic nanoparticles under laser irradiation, leading to drug release and thus synergetic therapy. By combining other supplementary agents to normalize tumor microenvironment, cell-membrane coating can further enhance the therapeutic efficacy against cancer.

Novel Pattern Recognition Receptor Protects Shrimp by Preventing Bacterial Colonization and Promoting Phagocytosis.

The recognition of pathogen-associated molecular patterns is accomplished by the recognition modules of pattern recognition receptors (PRRs). Leucine-rich repeats (LRRs) and C-type lectin-like domain (CTLD) represent the two most universal categories of recognition modules. In the current study, we identified a novel soluble and bacteria-inducible PRR comprising LRRs and a CTLD from the hepatopancreas of kuruma shrimp Marsupenaeus japonicus and named it Leulectin. The module arrangement of Leulectin is unique among all organisms. Both modules, together with the whole molecule, protected shrimp against Vibrio infection. By screening the pathogen-associated molecular patterns that shrimp might encounter, Leulectin was found to sense Vibrio flagellin through the LRRs and to recognize LPS through CTLD. The LRR-flagellin interaction was confirmed by pull-down and far-Western assays and was found to rely on the fourth LRR of Leulectin and the N terminus of flagellin. The recognition of LPS was determined by the long loop region of CTLD in a calcium-independent manner. By sensing the flagellin, LRRs could prevent its attachment to shrimp cells, thereby inhibiting Vibrio colonization. With the ability to recognize LPS, CTLD could agglutinate the bacteria and promote hemocytic phagocytosis. Our study clearly showed the division of labor and the synergy between different recognition modules and provided new insights into the concept of pattern recognition and the function of soluble PRRs in the antibacterial response.

Semiconducting Photothermal Nanoagonist for Remote-Controlled Specific Cancer Therapy.

Nanomedicine have shown success in cancer therapy, but the pharmacological actions of most nanomedicine are often nonspecific to cancer cells because of utilization of the therapeutic agents that induce cell apoptosis from inner organelles. We herein report the development of semiconducting photothermal nanoagonists that can remotely and specifically initiate the apoptosis of cancer cells from cell membrane. The organic nanoagonists comprise semiconducting polymer nanoparticles (SPNs) and capsaicin (Cap) as the photothermally responsive nanocarrier and the agonist for activation of transient receptor potential cation channel subfamily V member 1 (TRPV1), respectively. Under multiple NIR laser irradiation at the time scale of seconds, the nanoagonists can repeatedly and locally release Cap to multiply activate TRPV1 channels on the cellular membrane; the cumulative effect is the overinflux of ions in mitochondria followed by the induction of cell apoptosis specifically for TRPV1-postive cancer cells. Multiple transient activation of TRPV1 channels is essential to induce such a cell death both in vitro and in vivo because both free Cap and simple Cap-encapsulated nanoparticles fail to do so. The photothermally triggered release also ensures a high local concentration of the TRPV1 agonist at tumor site, permitting specific cancer cell therapy at a low systemic administration dosage. Our study thus demonstrates the first example of ion-channel-specific and remote-controlled drug-delivery system for cancer cell therapy.

A Semiconducting Polymer Nano-prodrug for Hypoxia-Activated Photodynamic Cancer Therapy.

Photodynamic therapy (PDT) holds great promise for cancer therapy; however, its efficacy is often compromised by tumor hypoxia. Herein, we report the synthesis of a semiconducting polymer nanoprodrug (SPNpd) that not only efficiently generates singlet oxygen (1 O2 ) under NIR photoirradiation but also specifically activates its chemotherapeutic action in hypoxic tumor microenvironment. SPNpd is self-assembled from a amphiphilic polymer brush, which comprises a light-responsive photodynamic backbone grafted with poly(ethylene glycol) and conjugated with a chemodrug through hypoxia-cleavable linkers. The well-defined and compact nanostructure of SPNpd (30 nm) enables accumulation in the tumor of living mice. Owing to these features, SPNpd exerts synergistic photodynamic and chemo-therapy, and effectively inhibits tumor growth in a xenograft tumor mouse model. This study represents the first hypoxia-activatable phototherapeutic polymeric prodrug system with a high potential for cancer therapy.

A Dual-Modal Molecular Probe for Near-Infrared Fluorescence and Photoacoustic Imaging of Peroxynitrite.

Peroxynitrite (ONOO-), a reactive and short-lived biological oxidant, is closely related with many pathological conditions such as cancer. However, real-time in vivo imaging of ONOO- in tumors remains to be challenging. Herein, we develop a near-infrared fluorescence (NIRF) and photoacoustic dual-modal molecular probe (CySO3CF3) composed of a water-soluble hemicyanine dye caged with a trifluoromethyl ketone moiety for in vivo imaging of ONOO-. The trifluoromethyl ketone moiety can undergo a series of ONOO--induced cascade oxidation-elimination reactions, leading to sensitive and specific fluorescence and photoacoustic turn-on responses toward ONOO-; whereas, a zwitterionic structure of the hemicyanine component ensures good water-solubility. Thus, CySO3CF3 not only specifically detects ONOO- in solution and cells with the limit of detection down to 53 nM but also allows for NIRF and photoacoustic dual-modal imaging of ONOO- in the tumors of living mice.

Isoalantolactone Inhibits Esophageal Squamous Cell Carcinoma Growth Through Downregulation of MicroRNA-21 and Derepression of PDCD4.

BACKGROUND: This study was designed to explore the anticancer potential of isoalantolactone, a sesquiterpene lactone, on esophageal squamous cell carcinoma (ESCC) cells and associated molecular mechanisms. METHODS: ESCC cell lines were treated with isoalantolactone or vehicle and tested for viability, proliferation, cell cycle distribution, and apoptosis. Xenograft tumor studies in nude mice were done to examine the in vivo anticancer effect of isoalantolactone. RESULTS: Isoalantolactone treatment reduced ESCC cell viability and proliferation in vitro, which was coupled with induction of G0/G1 cell cycle arrest and apoptosis. In vivo studies confirmed the growth-suppressive effect of isoalantolactone on ESCC cells. Mechanistically, isoalantolactone reversed microRNA-21-mediated repression of programmed cell death 4 (PDCD4). Overexpression of microRNA-21 and knockdown of PDCD4 blocked the growth suppression and apoptosis induction by isoalantolactone in ESCC cells. CONCLUSIONS: Isoalantolactone shows growth-suppressive activity against ESCC cells, which is ascribed to upregulation of PDCD4 via downregulation of microRNA-21.

Temperature-Correlated Afterglow of a Semiconducting Polymer Nanococktail for Imaging-Guided Photothermal Therapy.

Nanoparticles for photothermal therapy: Real-time temperature monitoring is critical to reduce the nonspecific damage during photothermal therapy (PTT); however, PTT agents that can emit temperature-related signals are rare and limited to few inorganic nanoparticles. We herein synthesize a semiconducting polymer nanococktail (SPNCT ) that can not only convert photo-energy to heat but also emit temperature-correlated luminescence after cessation of light excitation. Such an afterglow luminescence of the SPNCT detects tumors more sensitively than fluorescence as a result of the elimination of tissue autofluorescence, while its temperature-dependent nature allows tumor temperature to be optically monitored under near-infrared (NIR) laser irradiation. Thus, SPNCT represents the first organic optical nanosystem that enables optical-imaging guided PTT without real-time light excitation.

Macrotheranostic Probe with Disease-Activated Near-Infrared Fluorescence, Photoacoustic, and Photothermal Signals for Imaging-Guided Therapy.

Theranostics provides opportunities for precision cancer therapy. However, theranostic probes that simultaneously turn on their diagnostic signal and pharmacological action only in respond to a targeted biomarker have been less exploited. We herein report the synthesis of a macrotheranostic probe that specifically activates its near-infrared fluorescence (NIRF), photoacoustic (PA), and photothermal signals in the presence of a cancer-overexpressed enzyme for imaging-guided cancer therapy. Superior to the small-molecule counterpart probe, the macrotheranostic probe has ideal biodistribution and renal clearance, permitting passive targeting of tumors, in situ activation of multimodal signals, and effective photothermal ablation. Our study thus provides a macromolecular approach towards activatable multimodal phototheranostics.

Ternary Chalcogenide Nanosheets with Ultrahigh Photothermal Conversion Efficiency for Photoacoustic Theranostics.

2D materials (TDMs) have been explored for photonic theranostics. To achieve deep-tissue penetration, near-infrared (NIR) light is essential for photoacoustic (PA) theranostics. However, because the absorption profiles of existing TDMs are generally featureless with no obvious NIR absorption peaks, their PA signals and therapeutic efficacies are limited. This paper herein reports the synthesis and application of ternary chalcogenide nanosheets (Ta2 NiS5 -P) for PA theranostics. In contrast to the current TDMs for such application, Ta2 NiS5 -P has a ternary instead of binary composition. This difference brings in the strong and featured NIR for Ta2 NiS5 -P. To the best of the knowledge, this is the first example using ternary chalcogenide nanosheets for such application; moreover, the photothermal conversion efficiency of Ta2 NiS5 -P is the highest (35%) among all the reported TDMs based on the same calculation method. These advantages allow Ta2 NiS5 -P to passively target, effectively delineate, and completely eradicate the tumor of living mice after systemic administration.

Controllable Synthesis of Highly Luminescent Boron Nitride Quantum Dots.

Boron nitride quantum dots (BNQDs), as a new member of heavy metal-free quantum dots, have aroused great interest in fundamental research and practical application due to their unique physical/chemical properties. However, it is still a challenge to controllably synthesize high-quality BNQDs with high quantum yield (QY), uniform size and strong fluorescent. In this work, BNQDs have been successfully fabricated by the liquid exfoliation and the subsequent solvothermal process with respect to its facileness and easy large scale up. Importantly, BNQDs with high-quality can be controllably obtained by adjusting the synthetic parameters involved in the solvothermal process including filling factor, synthesis temperature, and duration time. Encouragingly, the as-prepared BNQDs possess strong blue luminescence with QY as high as 19.5%, which can be attributed to the synergetic effect of size, surface chemistry and edge defects. In addition, this strategy presented here provides a new reference for the controllable synthesis of other heavy metal-free QDs. Furthermore, the as-prepared BNQDs are non-toxic to cells and exhibit nanosecond-scaled lifetimes, suggesting they have great potential biological and optoelectronic applications.

Frontier knowledge and future directions of programmed cell death in clear cell renal cell carcinoma.

Clear cell renal cell carcinoma (ccRCC) is one of the most common renal malignancies of the urinary system. Patient outcomes are relatively poor due to the lack of early diagnostic markers and resistance to existing treatment options. Programmed cell death, also known as apoptosis, is a highly regulated and orchestrated form of cell death that occurs ubiquitously throughout various physiological processes. It plays a crucial role in maintaining homeostasis and the balance of cellular activities. The combination of immune checkpoint inhibitors plus targeted therapies is the first-line therapy to advanced RCC. Immune checkpoint inhibitors(ICIs) targeted CTLA-4 and PD-1 have been demonstrated to prompt tumor cell death by immunogenic cell death. Literatures on the rationale of VEGFR inhibitors and mTOR inhibitors to suppress RCC also implicate autophagic, apoptosis and ferroptosis. Accordingly, investigations of cell death modes have important implications for the improvement of existing treatment modalities and the proposal of new therapies for RCC. At present, the novel modes of cell death in renal cancer include ferroptosis, immunogenic cell death, apoptosis, pyroptosis, necroptosis, parthanatos, netotic cell death, cuproptosis, lysosomal-dependent cell death, autophagy-dependent cell death and mpt-driven necrosis, all of which belong to programmed cell death. In this review, we briefly describe the classification of cell death, and discuss the interactions and development between ccRCC and these novel forms of cell death, with a focus on ferroptosis, immunogenic cell death, and apoptosis, in an effort to present the theoretical underpinnings and research possibilities for the diagnosis and targeted treatment of ccRCC.

Enhancing the tumor penetration of multiarm polymers by collagenase modification.

Tumor penetration is a critical determinant of the therapy efficacy of nanomedicines. However, the dense extracellular matrix (ECM) in tumors significantly hampers the deep penetration of nanomedicines, resulting in large drug-untouchable areas and unsatisfactory therapy efficacy. Herein, we synthesized a third-generation PAMAM-cored multiarm copolymer and modified the polymer with collagenase to enhance its tumor penetration. Each arm of the copolymer was a diblock copolymer of poly(glutamic acid)-b-poly(carboxybetaine), in which the polyglutamic acid block with abundant side groups was used to link the anticancer agent doxorubicin through the pH-sensitive acylhydrazone linkage, and the zwitterionic poly(carboxybetaine) block provided desired water solubility and anti-biofouling capability. The collagenase was conjugated to the ends of the arms via the thiol-maleimide reaction. We demonstrated that the polymer-bound collagenase could effectively catalyze the degradation of the collagen in the tumor ECM, and consequently augmented the tumor penetration and antitumor efficacy of the drug-loaded polymers.

Membrane Disruption-Enhanced Photodynamic Therapy against Gram-Negative Bacteria by a Peptide-Photosensitizer Conjugate.

Photodynamic therapy (PDT) emerges as a promising strategy for combating bacteria with minimal drug resistance. However, a significant hurdle lies in the ineffectiveness of most photosensitizers against Gram-negative bacteria, primarily attributable to their characteristic impermeable outer membrane (OM) barrier. To tackle this obstacle, we herein report an amphipathic peptide-photosensitizer conjugate (PPC) with intrinsic outer membrane disruption capability to enhance PDT efficiency against Gram-negative bacteria. PPC is constructed by conjugating a hydrophilic ultrashort cationic peptide to a hydrophobic photosensitizer. PPC could efficiently bind to the OM of Gram-negative bacteria through electrostatic adsorption, and subsequently disrupt the structural integrity of the OM. Mechanistic investigations revealed that PPC triggers membrane disruption by binding to both lipopolysaccharide (LPS) and phospholipid leaflet in the OM, enabling effective penetration of PPC into the Gram-negative bacteria interior. Upon light irradiation, PPC inside bacteria generates singlet oxygen not only to effectively decrease the survival of Gram-negative bacteria P. aeruginosa and E. coli to nearly zero in vitro, but also successfully cure the full-thickness skin infection and bacterial keratitis (BK) induced by P. aeruginosa in animal models. Thus, this study provides a broad-spectrum antibacterial phototherapeutic design strategy by the synergistic action of membrane disruption and PDT to combat Gram-negative bacteria.

Whole-Genome Sequencing Reveals the Population Structure and Genetic Diversity of Salmonella Typhimurium ST34 and ST19 Lineages.

Salmonella Typhimurium is an invasive gastrointestinal pathogen for both humans and animals. To investigate the genetic framework and diversity of S. Typhimurium, a total of 194 S. Typhimurium isolates were collected from patients in a tertiary hospital between 2020 and 2021. Antimicrobial susceptibility testing was used to confirm the resistance phenotype. Whole-genome sequencing and bioinformatics analysis were performed to determine the sequence type, phylogenetic relationships, resistance gene profiles, Salmonella pathogenicity island (SPI) and the diversity of the core and pan genome. The result showed that 57.22% of S. Typhimurium isolates were multidrug resistant and resistance of total isolates to the first-line drug ciprofloxacin was identified in 60.82%. The population structure of S. Typhimurium was categorized into three lineages: ST19 (20.10%, 39/194), ST34-1 (47.42%, 92/194) and ST34-2 (40.65%, 63/194), with the population size exhibiting increasing trends. All lineages harbored variety of fimbrial operons, prophages, SPIs and effectors that contributed to the virulence and long-term infections of S. Typhimurium. Importantly, ST34-1 lineage might potentially be more invasive due to the possession of SPI1-effector gene sopE which was essential for the proliferation, internalization and intracellular presence of S. Typhimurium in hosts. Multiple antimicrobial resistance genes were characteristically distributed across three lineages, especially carbapenem genes only detected in ST34-1&2 lineages. The distinct functional categories of pan genome among three lineages were observed in metabolism, signaling and gene information processing. This study provides a theoretical foundation for the evolved adaptation and genetic diversity of S. Typhimurium ST19 and ST34, among which ST34 lineages with multidrug resistance and potential hypervirulence need to pay more attention to epidemiological surveillance.

Transcription-replication collision increases recombination efficiency between plasmids.

It has been proposed that the stalling of the replication forks can induce homologous recombination in several organisms, and that arrested replication forks may offer nuclease targets, thereby providing a substrate for proteins involved in double-strand repair. In this article, we constructed a plasmid with the potential for transcription-replication collision (TRC), in which DNA replication and RNA transcription occur on the same DNA template simultaneously. Theoretically, transcription will impede DNA replication and increase homologous recombination. To validate this hypothesis, another plasmid was constructed that contained a homologous sequence with the exception of some mutated sites. Co-transfection of these two plasmids into 293T cells resulted in increased recombination frequency. The ratio of these two plasmids also affected the recombination frequency. Moreover, we found high expression levels of RAD51, which indicated that the increase in the recombination rate was probably via the homologous recombination pathway. These results indicate that mutant genes in plasmids can be repaired by TRC-induced recombination.

Development of organic photosensitizers for antimicrobial photodynamic therapy.

Bacterial infection poses a significant threat to human health, and the emergence of antibiotic-resistant strains has exacerbated the situation. Antimicrobial photodynamic therapy (aPDT) has emerged as a promising antibiotic-free treatment option that employs reactive oxygen species (ROS) to cause oxidative damage to bacteria and surrounding biomolecules for treating microbial infections. This review summarizes the recent progress in the development of organic photosensitizers, including porphyrins, chlorophyll, phenothiazines, xanthenes and aggregation-induced emission photosensitizers, for aPDT. A detailed description of innovative therapeutic strategies that rely on the infection microenvironment or the unique structural properties of bacteria to amplify the therapeutic effects is provided. Moreover, the combination of aPDT with other therapy strategies such as antimicrobial peptide therapy, photothermal therapy (PTT) or gas therapy, is described. Finally, the current challenges and perspectives of organic photosensitizers for clinical antibacterial applications are discussed.