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An Anaerobic Biomimetic Metal-free AIE Polymersome Nanozyme as NADH Oxidase Mimic for Photocatalytic Tumor Suppression by Impairing Cancer Cell Energy Metabolism under Hypoxia
No full textInternational audienceThe intracellular balance between nicotinamide adenine dinucleotide and its reduced form (NAD + /NADH) is essential for cell metabolism. The NAD + /NADH redox imbalance strategy using NADH-oxidase-mimic nanozymes has emerged as an attractive antitumor strategy. Here we develop a photocatalytic metal-free nanozyme that is a polymer vesicle (polymersome) self-assembled from PEG-block-poly(amino acid) functionalized by photocatalytic moieties with aggregation-induced emission (AIE). To enhance biocompatibility and tumor-targetability, the vesicle is coated with folate modified red-blood-cell membrane (FA-RBC) to get biomimetic AIE polymersome nanozyme (BV). Unlike conventional photocatalysts, BV can achieve the cyclical photocatalytic process for NADH-NAD + conversion without O₂ or additional electron acceptors. A new mechanism is proposed that suggests adjacent excited triplet molecules in the AIE assembly play the role of electron acceptors for complete NADH-NAD + conversion and catalyst turnover. This O2-independent photocatalysis is appealing in anticancer treatment since the tumor has a hypoxic microenvironment. In vitro and in vivo investigations demonstrate BV induces a severe NAD⁺/NADH imbalance under hypoxia to lead to inhibition of oxidative phosphorylation and 2 glycolysis, which triggers the energy crisis in 4T1 cancer cells and in the 4T1 tumor of a subcutaneous xenograft model. This work presents a novel approach of cancer therapy through the photocatalytic impairment of tumor energy metabolism by metal-free nanozyme
First Row Transition Metals in Olefin Metathesis: The Role of Iron and Manganese
No full textInternational audienceOlefin metathesis has traditionally been dominated by molybdenum and ruthenium-based catalysts, but the pursuit of sustainable and earth-abundant alternatives has driven interest in first-row transition metals particularly iron. While iron is an attractive candidate due to its abundance, low toxicity, and cost-effectiveness, significant challenges hinder its successful implementation in metathesis reactions. This review examines the electronic and structural properties of iron that contribute to its catalytic limitations, including high-spin configurations, weak metal-alkylidene interactions, and a pronounced tendency toward cyclopropanation. Computational and experimental efforts to overcome these obstacles are discussed, focusing on ligand design strategies and mechanistic insights. Additionally, the potential of manganese as an alternative to iron is explored. This work underscores the complexities of first-row transition metal catalysts in olefin metathesis and highlights future directions for achieving practical, efficient iron-based systems. Future research should focus on refining ligand architectures to stabilize key intermediates, leveraging computational insights to predict reactivity trends, and further investigating the role of metal oxidation states in metathesis activity. While the transition to first-row transition metals remains a challenge, ongoing advancements continue to push the boundaries of sustainable catalysis, bringing the dream of practical iron- or manganese-based olefin metathesis closer to reality
Decoding the interstitial/vacancy nature of dislocation loops with their morphological fingerprints in face-centered cubic structure
No full textInternational audienceDislocation loops are critical defects inducing detrimental effects like embrittlement and swelling in materials under irradiation. Distinguishing their nature (interstitial- or vacancy-type) is a long-standing challenge with great implications for understanding radiation damage. Here, we demonstrate that the morphology of radiation-induced Frank loops can unveil their nature in face-centered cubic (fcc) structure: Circular loops are interstitial-type in all fcc materials, while segmented loops are vacancy-type in high stacking fault energy (SFE) alloys but varied-type in low SFE and high-entropy alloys. The polygonal shape is attributed to the dissociation of an a0/3<111> dislocation into an a0/6<112> Shockley partial and an a0/6<110> stair-rod dislocation. The dissociation of vacancy loops is energetically favorable, whereas interstitial loops require external stimuli to promote dislocation propagation. This “morphology-nature” correlation not only highlights the asymmetry of vacancy/interstitial loops but also offers an efficient way to distinguish loop nature for a wide range of materials
An Alternative Method for Preparing Methyl 2-Ferrocenyl-2-oxo-acetate
No full textInternational audienceBecause of the continuous interest in ferrocene chemistry, there is a sustained demand for various ferrocenic building blocks, especially small molecules with useful chemical functional groups, sometimes containing multiple groups. Our interest in ferrocene ketoesters (ω-ferrocenyl-ω-ketoesters) was motivated by the synthesis of esters and subsequently alcohols of ferrociphenols. However, from a bibliographic survey, only one publication dated from 1964 reports the two-step synthesis (six-step synthesis from ferrocene) of methyl 2-ferrocenyl-2-oxoacetate, the simplest member of this family of compounds, with no further developments since. We hypothesized that a simpler method might exist, such as the Friedel-Crafts method. By focusing on our experiments to use aluminum trichloride as the catalyst, we managed to achieve the synthesis of FcCOCOOMe in a single step, albeit with a very low yield, regardless of reaction time, temperature, amount of aluminum chloride and reagents concentration. Nevertheless, considering the time saved, simplicity, and the use of less hazardous and less expensive reagents, this method offers certain advantages for synthesizing this building block
Recent advances in stimuli-responsive framework materials: Understanding their response and searching for materials with targeted behavior
No full textInternational audienceAlthough all molecular assemblies show some degree of flexibility, the past decade has shown that there is a higher propensity among framework materials to display large-scale dynamic behavior. Beyond the seminal discoveries of the important flexibility of metal–organic frameworks (MOFs), covalent organic frameworks (COFs), hydrogen-bonded organic frameworks (HOFs) or supramolecular organic frameworks (SOFs), and many other framework materials, the field has progressed rapidly: the number of known flexible materials is ever growing, and the diversity of the types of manifestation of this flexibility appears endless. In addition, the microscopic mechanism of their behavior has been studied using a growing combination of experimental characterization techniques, in situ and in operando measurements, as well as computational simulation methods.In this Review, we present some of the significant advances in recent studies of stimuli-responsive framework materials. In particular, we highlight the novel responses that have been discovered in the past few years and the toolbox developed by researchers in the field to better understand the materials’ behavior (both experimentally and computationally). We also show some of the latest progress in the discovery of materials with targeted behavior, whether through de novo design or identification of known materials for new properties — similar to what is known in the field of drug discovery as repurposing
A key advance toward practical aqueous Zn/MnO2 batteries via better electrolyte design
No full textInternational audienceRechargeable aqueous devices, such as alkaline Zn/MnO2 batteries, hold strong potential for large-scale energy storage. However, they face limitations related to zinc and electrolyte degradation. Here, in the spirit of practicality, we have addressed these limitations by developing strategies aiming at resolving issues with the electrolyte, anode, and cathode independently at first, and then in synergy. We propose innovative electrolyte designs that incorporate select organic molecules to leverage hydrogen bonding interactions, reducing Zn nuclei reactivity via the formation of a stable solid electrolyte interphase (SEI). Our optimized Zn/MnO2 batteries demonstrate high stability, achieving a gravimetric capacity of '450 mAh/g (MnO2) and 90% capacity retention. Furthermore, we systematically show the scalability of our methods, moving from a Swagelok cell prototype (3-6 mg/cm2 of mass loading) to cylindrical-type cell (30 mg/cm2). These batteries can operate at unprecedentedly high temperatures of up to 55 degrees C, while offering an energy density of 150 Wh/kg
Smartphone-assisted plasmonic biosensors for rapid on-site detection of foodborne pathogens and allergens
No full textInternational audienceWe report the design of a smartphone-assisted plasmonic immunosensor and its application to the detection of several food contaminants, namely staphylococcal enterotoxin A (SEA), bovine β-lactoglobulin (BLG), and hen egg white lysozyme (LYSO). Comprehensive characterization of antibodies was performed by ELISA and surface plasmon resonance imaging (SPR-i), demonstrating high affinity and specificity for each target, which supports their potential application in complex food matrices. The immunosensing platform utilizes gold nanoparticle-conjugated antibodies and inexpensive glass slides as single-use chips. Both qualitative visual detection by the naked eye down to around 1 ng of BLG, and quantitative detection with a portable spectrophotometer connectable to a smartphone are demonstrated. This self-contained device may provide a rapid, sensitive, and cost-effective approach to food contaminants analysis, potentially useful for on-site food safety assessment
Investigating the internal short-circuit in 18650 cells under thermal abuse conditions
No full textInternational audienceThe occurrence of an Internal Short-Circuit (ISC) in 18650 lithium-ion cells under thermal abuse conditions remains elusive. Equipped with Current Interrupt Devices (CID), the cell's voltage drop may introduce ambiguity, and potentially obscure the precise determination of an ISC. Therefore, comprehensive investigations were undertaken to rigorously explore the ISC and thermal runaway (TR) relationship. In this paper, and for the first time, a three-electrode 18650 lab-scale cell is tested in an Accelerated Rate Calorimeter (ARC) to analyze the potentials' variation under adiabatic conditions. Results have shown that the cell's voltage drop coincides with the positive potential drop (Ewe). Furthermore, tests on cells without CID have indicated that the accelerated TR is triggered following the massive ISC. Moreover, for a long time, the ISC has been associated with the melting of the separator. Hence, this study includes tests on identical lab-scale cells utilizing three types of separators: polyethylene, trilayer, and coated polypropylene. TR tests, conducted under adiabatic and ambient conditions, didn't reveal a significant impact of the separators. Given that the novel preliminary test developed in this study has demonstrated that the loss of their mechanical integrity happens at around the same temperature, the outcomes of the TR tests were comparable
Binding mechanism of oligopeptides on solid surface: assessing the significance of single-molecule approach
No full textInternational audienceThis paper addresses the complementarity and potential disparities between single-molecule and ensemble-average approaches to probe the binding mechanism of oligopeptides on inorganic solids. Specifically, we explore the peptide/gold interface owing to its significance in various topics and its suitability to perform experiments both in model and real conditions. Experimental results show that the studied peptide adopts a lying configuration upon adsorption on the gold surface and interacts through its peptidic links and deprotonated thiolate extremities, in agreement with theoretical predictions. Single-molecule force spectroscopy (SMFS) measurements revealed the existence of a wide panel of adhesion forces, resulting from the interaction between individual peptide moieties and the abundant surface sites. We therefore propose methodological developments for sorting the events of interest to understand the peptide adsorption mechanism. Thermodynamic and kinetic aspects of the peptide adsorption are probed using both static and dynamic force spectroscopy measurements. Specifically, we show the possibility of providing a reasonable estimate of the peptide free energy of adsorption ΔadsG° by exploring the fluctuations of the adhesion work, based on the Jarzynski equality, and by using a parametric Gamma estimator. The proposed approach offers a relevant method for studying the different factors influencing the peptide adsorption and evaluating their impact on ΔadsG° as an alternative to exploring adhesion forces that may lead to misinterpretations. This is illustrated by the comparison of the adsorption of two peptides with specific amino acids substitution. Our method provides insights into the overall mechanism by which peptides interact with the surface and allows an integration of the single-molecule versus ensemble-average points of view
AMOEBA Polarizable Molecular Dynamics Simulations of Guanine Quadruplexes: from the c-Kit Proto-oncogene to HIV-1
No full textInternational audienceLong oligomer sequences, rich in guanine and cytosine, such as c-kit1 and the HIV-1 LTR-III sequence, are prevalent in oncogenes and retroviruses and play crucial roles in cancer. Understanding the conformational dynamics of such guanine quadruplexes and identifying druggable regions are therefore essential for developing new inhibition strategies. In this study, we used extensive AMOEBA polarizable force field molecular dynamics simulations combined with data-driven adaptive sampling and clustering algorithms, reaching a cumulative simulation time of 7.5 μs for c-kit1. Such simulations identified novel structural motives and showcased the flexible loop dynamics, as well as the role of polarizable water in transient stabilization of the G-quadruplex. They also identified two druggable pockets in c-kit1. The 400 ns simulation of the HIV-1 LTR-III sequence confirmed its quadruplex stability and uncovered a potentially druggable cryptic pocket