Modular Prodrug-Engineered Oxygen Nano-Tank With Outstanding Nanoassembly Performance, High Oxygen Loading, and Closed-Loop Tumor Hypoxia Relief.

The clinical translation of tumor hypoxia intervention modalities still falls short of expectation, restricted by poor biocompatibility of oxygen-carrying materials, unsatisfactory oxygen loading performance, and abnormally high cellular oxygen consumption-caused insufficient hypoxia relief. Herein, a carrier-free oxygen nano-tank based on modular fluorination prodrug design and co-assembly nanotechnology is elaborately exploited, which is facilely fabricated through the molecular nanoassembly of a fluorinated prodrug (FSSP) of pyropheophorbide a (PPa) and an oxygen consumption inhibitor (atovaquone, ATO). The nano-tank adeptly achieves sufficient oxygen enrichment while simultaneously suppressing oxygen consumption within tumors for complete tumor hypoxia alleviation. Significant, the fluorination module in FSSP not only confers favorable co-assemblage of FSSP and ATO, but also empowers the nanoassembly to readily carry oxygen. As expected, it displays excellent oxygen carrying capacity, favorable pharmacokinetics, on-demand laser-triggerable ATO release, closed-loop tumor hypoxia relief, and significant enhancement to PPa-mediated PDT in vitro and in vivo. This study provides a novel nanotherapeutic paradigm for tumor hypoxia intervention-enhanced cancer therapy.

Visually evaluating drug efficacy in living cells using COF-based fluorescent nanoprobe via CHA amplified detection of miRNA and simultaneous apoptosis imaging.

BACKGROUNDS: Cancer is a highly fatal disease which is close relative of miRNA aberrant expression and apoptosis disorders. Elucidation of the therapeutic efficacy through investigating the changes in miRNA and apoptosis holds immense importance in advancing the development of miRNA-based precision therapy. However, it remains a challenge as how to visually evaluate the efficacy during protocol optimization of miRNA-based anticancer drugs at the cellular level. Therefore, exploring effective and noninvasive methods for real-time monitoring of therapeutic efficacy in living cells is of great significance. RESULTS: Herein, we reported a novel fluorescent nanoprobe COF-H1/H2-Peptide for visually evaluating drug efficacy in living cells through amplified imaging of low-abundant miRNA-221 with catalytic hairpin assembly (CHA) circle amplification, as well as simultaneous caspase-3 imaging. With strong stability and good biocompatibility, this newly fabricated amplified nanoprobe showed high sensitivity and specificity for the detection of miRNA-221 and caspase-3, and the limit of detection (LOD) of miRNA-221 was as low as 2.79 pM. The fluorescent imaging results showed that this amplified nanoprobe could not only detect caspase-3 in living cells, but also effectively detect low levels of miRNA-221 with increasing anticancer drug concentration and treatment time. The smart nanoprobe had effective performance for optimizing miRNA-based drug treatment schedules by dual-color fluorescence imaging. SIGNIFICANCE: This nanoprobe combined CHA amplified detection of intracellular miRNA-221 and synchronous apoptosis imaging, with excellent sensitivity for the detection of cellular low-level miRNA, enabling the realization of real-time assessment of the efficacy of miRNA-based therapy in living cells. This work presents a promising approach for revealing the regulatory mechanisms between miRNAs and apoptosis in cancer occurrence, development, and treatment.

Molecular Basis for RNA Cytidine Acetylation by NAT10.

Human NAT10 acetylates the N4 position of cytidine in RNA, predominantly on rRNA and tRNA, to facilitate ribosome biogenesis and protein translation. NAT10 has been proposed as a therapeutic target in cancers as well as aging-associated pathologies such as Hutchinson-Gilford Progeria Syndrome (HGPS). The ∼120 kDa NAT10 protein uses its acetyl-CoA-dependent acetyltransferase, ATP-dependent helicase, and RNA binding domains in concert to mediate RNA-specific N4-cytidine acetylation. While the biochemical activity of NAT10 is well known, the molecular basis for catalysis of eukaryotic RNA acetylation remains relatively undefined. To provide molecular insights into the RNA-specific acetylation by NAT10, we determined the single particle cryo-EM structures of Chaetomium thermophilum NAT10 ( Ct NAT10) bound to a bisubstrate cytidine-CoA probe with and without ADP. The structures reveal that NAT10 forms a symmetrical heart-shaped dimer with conserved functional domains surrounding the acetyltransferase active sites harboring the cytidine-CoA probe. Structure-based mutagenesis with analysis of mutants in vitro supports the catalytic role of two conserved active site residues (His548 and Tyr549 in Ct NAT10), and two basic patches, both proximal and distal to the active site for RNA-specific acetylation. Yeast complementation analyses and senescence assays in human cells also implicates NAT10 catalytic activity in yeast thermoadaptation and cellular senescence. Comparison of the NAT10 structure to protein lysine and N-terminal acetyltransferase enzymes reveals an unusually open active site suggesting that these enzymes have been evolutionarily tailored for RNA recognition and cytidine-specific acetylation.

Effects of Hydrogenation on the Corrosion Behavior of Zircaloy-4.

Hydrogen plays an important role in the corrosion of zirconium alloys, and the degree of influence highly depends on the alloy composition and conditions. In this work, the effects of hydrogenation on the corrosion behavior of Zircaloy-4 in water containing 3.5 ppm Li + 1000 ppm B at 360 °C/18.6 MPa were investigated. The results revealed that hydrogenation can shorten the corrosion transition time and increase the corrosion rates of Zircaloy-4. The higher corrosion rates can be ascribed to the larger stress in the oxide film of hydrogenated samples, which can accelerate the evolution of the microstructure of the oxide film. In addition, we also found that hydrogenation has little effect on the t-ZrO2 content in the oxide film and there is no direct correspondence between the t-ZrO2 content and the corrosion resistance of the Zircaloy-4.

pH-triggered hydrophility-adjustable fluorescent probes for simultaneously imaging lipid droplets and lysosomes and the application in fatty liver detection.

To study the collaboration between lipid droplets (LDs) and lysosomes, and the lipid change in nonalcoholic fatty liver disease (NAFLD), herein two pH-triggered hydrophility-adjustable fluorescent probes (LD-Lyso and LD-Lyso 1) are designed. The mechanism is based on cyclization and ring-opening with thorough consideration of pH and hydrophilic differences between LDs and lysosomes. Both of the two probes exist in ring-opening form and emit red fluorescence in acidic environment, while they exist in cyclized form and the emission is blueshifted in alkaline environment due to reduced conjugate planes. Moreover, LD-Lyso exhibits near infrared fluorescence at 740 nm under ring-opening form, which facilitates further cell, tissue, and in vivo imaging. The cell imaging results show that LD-Lyso can simultaneously target LDs and lysosomes by two different colors. Impressively, LD-Lyso cannot only detect NAFLD tissues from the normal tissue, but also distinguish different degrees of NAFLD tissues and mice, which provides a very promising tool for timely diagnosis of early NAFLD.

A novel nanoprobe for visually investigating the controversial role of miRNA-34a as an oncogene or tumor suppressor in cancer cells.

MiRNA-targeted therapy has become a hot topic in current cancer research. The key to this treatment strategy is to clarify the specific role of miRNA in cancer. However, the roles of some miRNAs acting as oncogenic or tumor suppressors are still controversial, which are influenced by different tumor types, even in the same cancer type. Hence, we designed a novel fluorescent nanoprobe based on polydopamine nanoparticles (PDA NPs) for simultaneously detecting caspase-3 and miRNA-34a within living cells. The specific role of miRNA-34a in different cancer cells could be further identified by studying the expression alterations of caspase-3 and miRNA-34a. Confocal imaging indicated that miRNA-34a indeed acted as a tumor suppressor in anticancer drug-treated MCF-7 and HeLa cells, where the effect of miRNA-34a remains controversial. The designed nanoprobe can offer a promising approach to ascertain the oncogenic or tumor-suppressing role of miRNA in different cancer cells with a simple visualization method, which has valuable implications for exploring the practicability of precision therapy focused on miRNA and evaluating the efficacy of new miRNA-targeted anticancer medications.

Hydrolysis-Induced Cu2O Networks and the Triggered Peroxidase-Mimic Activity by Cr6+ under Neutral Conditions.

The current small-scale synthesis and relatively large size of Cu2O have limited its practical applications. Herein, we developed a hydrolysis strategy to prepare phase-pure Cu2O networks composed of small granules (ca. 25 nm) on a gram scale. The preparation involves in situ hydrolyzing the Hx[CuxCl2x] complexes prereduced in N,N'-dimethylformamide (DMF). The DMF-soluble Hx[CuxCl2x] complexes are critical for the homogeneous nucleation of CuCl seeds and subsequent hydrolysis, allowing for separate control over the nucleation and growth stages to regulate the formation of Cu2O networks. The novel Cu2O networks possess numerous exposed active sites and hierarchical porosities, conferring high catalytic activity and fast mass transfer capability. The inherent peroxidase-mimic activity of Cu2O is severely inhibited under neutral conditions but can be triggered by Cr6+, enabling the colorimetric assay of Cr6+ with the assistance of the oxidation-induced color change of 3,3',5,5'-tetramethylbenzidine. Through density functional theory calculation, we confirmed that the attachment of Cr6+ on the Cu2O surface reduced the dissociation energy of H2O2, enhancing the enzyme-mimic activity. The colorimetric detection method demonstrated a sensitive and specific assay capability for Cr6+ (LOD = 0.095 µM). Our work offers a straightforward protocol for novel design of metal or metal-based nanomaterials for nanozymes or other applications.

Small molecule-engineered nanoassembly for lipid peroxidation-amplified photodynamic therapy.

Photodynamic therapy (PDT), extensively explored as a non-invasive and spatio-temporal therapeutic modality for cancer treatment, encounters challenges related to the brief half-life and limited diffusion range of singlet oxygen. Lipid peroxides, formed through the oxidation of polyunsaturated fatty acids by singlet oxygen, exhibit prolonged half-life and potent cytotoxicity. Herein, we employed small molecule co-assembly technology to create nanoassemblies of pyropheophorbide a (PPa) and docosahexaenoic acid (DHA) to bolster PDT. DHA, an essential polyunsaturated fatty acid, co-assembled with PPa to generate nanoparticles (PPa@DHA NPs) without the need for additional excipients. To enhance the stability of these nanoassemblies, we introduced 20% DSPE-PEG2k as a stabilizing agent, leading to the formation of PPa@DHA PEG2k NPs. Upon laser irradiation, PPa-produced singlet oxygen swiftly oxidized DHA, resulting in the generation of cytotoxic lipid peroxides. This process significantly augmented the therapeutic efficiency of PDT. Consequently, tumor growth was markedly suppressed, attributed to the sensitizing and amplifying impact of DHA on PDT in a 4T1 tumor-bearing mouse model. In summary, this molecule-engineered nanoassembly introduces an innovative co-delivery approach to enhance PDT with polyunsaturated fatty acids.

Applications of microalga-powered microrobots in targeted drug delivery.

Over the past decade, researchers have proposed a new class of drug delivery systems, bio-hybrid micro-robots, designed with a variety of living cell-driven micro-robots that utilize the unique mobility of natural organisms (bacteria, cells, exosomes, etc.) to transport effective drugs. Microalgae are considered potential drug delivery carriers. Recent studies have shown that microalga-based drug delivery systems exhibit excellent biocompatibility. In addition, microalgae have a large surfactant area, phototaxis, oxygen production, and other characteristics, so they are used as a carrier for the treatment of bacterial infections, cancer, etc. This review summarizes the modification of microalgae including click chemistry and electrostatic adsorption, and can improve the drug loading efficiency through dehydration and hydration strategies. The prepared microalgal drug delivery system can be targeted to different organs by different dosing methods or using external forces. Finally, it summarizes its antibacterial (gastritis, periodontitis, skin wound inflammation, etc.) and antitumor applications.

Secondary metal doped cuprous-cyanoimidazole frameworks for triple-mode detection of dopamine.

BACKGROUNDS: Metal-organic framework-based nanozymes enable several opportunities for designing novel analysis methods for the detection of pesticides, heavy metal ions, and biomolecules; however, practical applications are still limited by a complicated synthesis route, lower catalytic activity, and single detection mode. Dopamine (DA) is a crucial catecholamine substance in the human body that acts as a neurotransmitter regulating a variety of physiological functions of the central nervous system. Therefore, it is highly significant to explore simple nanozymes synthesis methods for constructing a multiple analysis system to detection DA. RESULTS: Herein, we elaborately selected cobalt ions as the secondary metal doping in cuprous-cyanoimidazole frameworks (CuCo-CIFs) with a mass-production strategy. CuCo-CIFs possess intrinsic peroxidase-like activity that can convert hydrogen peroxide into various reactive oxygen species (i.e., 1O2, OH·, O2·-) and thereby oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) and DA to blue oxTMB and orange polydopamine (PDA), respectively. The absorption of the detection system increases at 460 nm while decreases at 652 nm as the concentration of DA increases under near-neutral pH (6.1), resulting in a color transition from blue to orange. Consequently, an unprecedented triple-mode analysis system of DA monitored by naked eyes, ratiometric-absorption, and scanometric was constructed. The limit of detection for the ratiometric-absorption and scanometric mode can reach 20 nM and 28 nM, respectively. CuCo-CIFs were successfully used for the rapid and accurate detection of DA in practical samples. SIGNIFICANCE: As a simple, low-cost, multi-mode colorimetric platform, this kind of nanozyme detection with peroxidase-like activity exhibits significant potential for the detection of DA. Our work not only expands the applications of MOFs in analytical fields but also addresses the general challenges faced by nanozyme-based colorimetric detection systems of DA. This work provides valuable insights for the rational application of nanozyme and the design of new analysis systems.

Rational design of a genetically encoded NMR zinc sensor.

Elucidating the biochemical roles of the essential metal ion, Zn2+, motivates detection strategies that are sensitive, selective, quantitative, and minimally invasive in living systems. Fluorescent probes have identified Zn2+ in cells but complementary approaches employing nuclear magnetic resonance (NMR) are lacking. Recent studies of maltose binding protein (MBP) using ultrasensitive 129Xe NMR spectroscopy identified a switchable salt bridge which causes slow xenon exchange and elicits strong hyperpolarized 129Xe chemical exchange saturation transfer (hyper-CEST) NMR contrast. To engineer the first genetically encoded, NMR-active sensor for Zn2+, we converted the MBP salt bridge into a Zn2+ binding site, while preserving the specific xenon binding cavity. The zinc sensor (ZS) at only 1 µM achieved 'turn-on' detection of Zn2+ with pronounced hyper-CEST contrast. This made it possible to determine different Zn2+ levels in a biological fluid via hyper-CEST. ZS was responsive to low-micromolar Zn2+, only modestly responsive to Cu2+, and nonresponsive to other biologically important metal ions, according to hyper-CEST NMR spectroscopy and isothermal titration calorimetry (ITC). Protein X-ray crystallography confirmed the identity of the bound Zn2+ ion using anomalous scattering: Zn2+ was coordinated with two histidine side chains and three water molecules. Penta-coordinate Zn2+ forms a hydrogen-bond-mediated gate that controls the Xe exchange rate. Metal ion binding affinity, 129Xe NMR chemical shift, and exchange rate are tunable parameters via protein engineering, which highlights the potential to develop proteins as selective metal ion sensors for NMR spectroscopy and imaging.

pH-Triggered Charge Reversible Fluorescent Probe for Simultaneous Imaging of Lipid Droplets and Nucleoli in Living Cells.

Cooperation between organelles is essential to maintain the normal functions of cells. Lipid droplets (LDs) and nucleoli, as important organelles, play an important role in the normal activities of cells. However, due to the lack of appropriate tools, in situ observation of the interaction between them has been rarely reported. In this work, taking into full consideration the pH and charge differences between LDs and nucleoli, a pH-triggered charge reversible fluorescent probe (LD-Nu) was constructed based on a cyclization-ring-opening mechanism. The in vitro pH titration experiment and 1H NMR showed that LD-Nu gradually transferred from the charged form to the electroneutral form with the increase of pH, and thus, the conjugate plane was reduced and its fluorescence blue-shifted. Most importantly, the physical contact between LDs and nucleoli was visualized for the first time. Meanwhile, the relationship between LDs and nucleoli was also further investigated, and the results showed that their interaction was more liable to be affected by the abnormality of LDs than those of nucleoli. Moreover, the cell imaging results displayed that the LDs both in the cytoplasm and nucleus were observed using the probe LD-Nu, and interestingly, the LDs in the cytoplasm were more susceptible to external stimuli than those in the nucleus. In a word, the probe LD-Nu can serve as a powerful tool for further exploration of the interaction mechanism between LDs and nucleoli in living cells.

Caffeic acid protects against atherosclerotic lesions and cognitive decline in ApoE-/- mice.

Caffeic acid has been indicated to benefit cholesterol balance, but the effect of pure caffeic acid on atherosclerosis in vivo has not been tested. Given that atherosclerosis and Alzheimer's disease share common features including distracted lipid balance and chronic inflammation, the concurrent effects of caffeic acid on atherosclerotic lesions and cognitive decline were explored here by using the ApoE-/- mice model. A two months' administration of 20 mg/kg caffeic acid or saline was given once two days intraperitoneally to 5-month-old female ApoE-/- mice. We found that the caffeic acid treatment reduced the atherosclerotic lesions in the whole aorta and aortic sinus of the resulting 7-month-old ApoE-/- mice by roughly 50%, compared with the saline control. Meanwhile, the cognitive decline of treated mice were significantly alleviated, as measured by Y-maze and Morris water maze tasks. A reduced accumulation of ß-amyloid in the hippocampus was also observed. These effects were associated with elevated serum HDL-c concentration, upregulated ABCA1 and ABCG1 mRNA levels, as well as decrease local inflammation and reduced levels of serum pro-inflammatory cytokines including TNF-α, IL-6 and MCP-1. These obtained results suggested the preventive and therapeutic potential of caffeic acid against atherosclerosis and Alzheimer's disease during aging.

Corrosion Behavior of Ti3SiC2 in Flowing Liquid Lead-Bismuth Eutectic at 500 °C.

MAX phases are promising candidate structural materials for lead-cooled fast reactors (LFRs) and accelerator-driven sub-critical systems (ADSs) due to their excellent corrosion resistance in liquid LBE. In this work, one of the typical MAX phases, Ti3SiC2, was exposed to the flowing LBE with a saturated oxygen concentration at 500 °C for up to 3000 h. The corrosion behaviors, including the evolution of the corrosion layer, mechanical properties and wettability, were evaluated via X-ray diffraction, a scanning electron microscope equipped with an energy-dispersive X-ray, a microhardness test and contact angle measurement. The results reveal that a corrosion structure with a duplex layer was formed on the sample surfaces. The outer layer was a diffusion layer, which always remained thin (<3 µm) during the whole test due to the erosion effect caused by the flowing LBE. The inner layer was the stable protective oxide layer, and its thickness increased with exposure time. The growth of the corrosion structure improved the microhardness and reduced the wettability with regard to LBE, which was beneficial to inhibiting further surface corrosion of Ti3SiC2.

Cathode enabled high faradaic efficiency: reduction of imines to amines with H2O as a H-source.

Benefiting from a high overpotential of the competitive hydrogen evolution reaction with a carbon paper cathode, the desired electrochemical reduction of imines was achieved with high faradaic efficiency by using H2O as a H-source. With this sustainable atom-economic strategy, a series of potentially versatile amines were obtained in medium-to-high yields (49-86%).

A Method for Detecting Antioxidant Activity of Antioxidants by Utilizing Oxidative Damage of Pigment Protein.

A simple and effective method for detecting the antioxidant activity by utilizing oxidative damage of pigment proteins was developed. In this method, phycocyanin and bovine hemoglobin pigment proteins were used as substrates attacked by free radicals; AAPH was used as a free radical initiator; and Trolox as a positive control; and the fermentation products of Lactobacillus plantarum 793, phycocyanin hydrolysates, salmon skin collagen hydrolysates, and synthetic peptides PMRGGYHY and FCVLRP are antioxidants inspected in this study. Because of being attacked by free radicals, the absorbance of the pigment proteins at their characteristic absorption peak changes with time. By recording the time-varying curve at the characteristic absorption peak of the pigment protein in the blank/negative control sample, the Trolox positive control sample, and the samples of inspected antioxidants, the antioxidant activity could be calculated by using the specific equation. The linear detection ranges of Trolox in the phycocyanin assay and the bovine hemoglobin assay were 1-4 µM and 4-24 µM, respectively. Compared with the ORAC assay, the antioxidant activities of the samples measured by this method were slightly lower. The method proposed in this study reflects the protective effects of inspected antioxidants on pigment proteins, which could potentially serve as new biomarkers of oxidative damage processes.

Characterization of a Novel Esterase Est33 From an Antarctic Bacterium: A Representative of a New Esterase Family.

Studies of microorganisms from extreme environments can sometimes reveal novel proteins with unique properties. Here, we identified a novel esterase gene (Est33) from an Antarctic bacterium. The protein was expressed and purified for biochemical characterizations. Site-mutation variants including S94A, D205A, and H233A were constructed to explore the structure-function relationship of the catalytic triad of Est33, and we found mutating Ser94, Asp205, and His233 residues lead to a complete loss of enzyme activity. In addition, the catalytic Ser94 located in a conserved pentapeptide motif GVSWG. Phylogenetic analysis showed that Est33 and its closely related homologs belonged to an independent group apart from other known family members, indicating that Est33 represented a new family of esterase. The Est33 enzyme was found to be a cold-active esterase retaining 25%-100% activity from 10°C to 30°C and to have optimal catalytic activity toward p-nitrophenol acetate (30°C and pH7.5). The serine modifying reagent phenylmethylsulfonyl fluoride inhibited the activity of Est33 by 77.34%, while thiol reagents such as dithiol threitol (DTT) activated the enzyme by 3-fold. Metal chelating reagents EDTA had no effects, indicating that Est33 is not a metalloenzyme. Collectively, these results indicate that Est33 constitutes the first member of a novel esterase family XXI that has been identified.

In Situ Alkyl Radical Recycling-Driven Decoupled Electrophotochemical Deamination.

Molecular electrophotocatalysis has emerged as a powerful strategy for the development of sustainable synthetic protocols. With the proof-of-concept, we exploited a versatile electrophotocatalytic deaminative alkylation approach. Mechanistic investigation indicated that in situ recycling of the alkyl radicals was the key point. Notably, ligand modification and late-stage functionalization of pharmaceuticals were also established, highlighting its feasibility in practical utilization.

Mitochondrial Damage in Myocardial Ischemia/Reperfusion Injury and Application of Natural Plant Products.

Ischemic heart disease (IHD) is currently one of the leading causes of death among cardiovascular diseases worldwide. In addition, blood reflow and reperfusion paradoxically also lead to further death of cardiomyocytes and increase the infarct size. Multiple evidences indicated that mitochondrial function and structural disorders were the basic driving force of IHD. We summed up the latest evidence of the basic associations and underlying mechanisms of mitochondrial damage in the event of ischemia/reperfusion (I/R) injury. This review then reviewed natural plant products (NPPs) which have been demonstrated to mitochondria-targeted therapeutic effects during I/R injury and the potential pathways involved. We realized that NPPs mainly maintained the integrality of mitochondria membrane and ameliorated dysfunction, such as improving abnormal mitochondrial calcium handling and inhibiting oxidative stress, so as to protect cardiomyocytes during I/R injury. This information will improve our knowledge of mitochondrial biology and I/R-induced injury's pathogenesis and exhibit that NPPs hold promise for translation into potential therapies that target mitochondria.

Microstructure and Mechanical Properties of TiB2/AlSi7Mg0.6 Composites Fabricated by Wire and Arc Additive Manufacturing Based on Cold Metal Transfer (WAAM-CMT).

Wire and arc additive manufacturing based on cold metal transfer (WAAM-CMT), as a kind of clean and advanced technology, has been widely researched recently. It was analyzed in detail for the microstructure and mechanical properties of WAAM-CMT printed TiB2/AlSi7Mg0.6 samples fore-and-aft heat treatment in this study. Compared with the grain size of casted AlSi7Mg0.6 samples (252 µm), the grain size of WAAM-CMT printed AlSi7Mg0.6 samples (53.4 µm) was refined, showing that WAAM-CMT process could result in significant grain refinement. Besides, the grain size of WAAM-CMT printed TiB2/AlSi7Mg0.6 samples was about 35 µm, revealing that the addition of TiB2 particles played a role in grain refinement. Nevertheless, the grain size distribution was not uniform, showing a mixture of fine grain and coarse grain, and the mechanical properties were anisotropic of the as-printed samples. This study shows that T6 heat treatment is an efficient way to improve the nonuniform microstructure and eliminate the anisotropy in mechanical properties.