Initial Reactants Research Articles

Chemical Pathways of SO2 with Hydrogen Atoms on Interstellar Ice Analogues

Sulfur dioxide (SO2) is a sulfur-containing molecule expected to exist as a solid in the interstellar medium. In this study, we have performed laboratory experiments and computational studies on the surface reactions of solid SO2 with hydrogen atoms on amorphous solid water (ASW) at low temperatures. After 40 minutes of exposure of SO2 deposited on ASW to H atoms, approximately 80% of the solid SO2 was lost from the substrate at 10–40 K, and approximately 50% even at 60 K, without any definite detection of reaction products. Quantum chemical calculations suggest that H atoms preferentially add to the S atom of solid SO2, forming the HSO2 radical. Further reactions of the HSO2 radical with H atoms result in the formation of several S-bearing species, including HS(O)OH, the S(O)OH radical, HO–S–OH, HS–OH, and H2S. In codeposition experiments involving H and SO2, we have confirmed the formation of H2S, HS(O)OH, and/or HO–S–OH. However, the yields of these S-bearing species are insufficient to account for the complete loss of the initial SO2 reactant. These findings suggest that some products are desorbed into the gas phase upon formation. This study indicates that a portion of the SO2 in ice mantles may remain unreacted, avoiding hydrogenation, while the remainder is converted into other species, some of which may be subject to chemical desorption.

Reaction-controlled triple O-isotope exchange trajectories during experimental alteration of olivine

The measurements and application of triple O-isotope system is a relatively new and powerful tool in tracing water-rock interaction, allowing to distinguish the temperature-dependent fractionation from the water amount that interacted with the rock. While the use of 18O/16O fractionation between minerals and fluids is well-established, most natural mineral-water reactions remain uncharacterized in terms of the triple isotope fractionation (17O/16O and18O/16O). The triple O-isotope approach is especially promising when it comes to natural samples, where an array of exchanged samples constrains the fluid endmembers. However, multiple exchange mechanisms are likely to occur between the reacting rock and water, which has not been investigated for triple O-isotopes. This study examines the triple O-isotope exchange between fluid and olivine experimentally, as this is a common reaction in nature and mechanisms/rates of reaction are societally important for CO2 sequestration. Water-olivine reaction in batch experiments was investigated at 275 °C at the saturated water vapor pressure of 59.5 bar. Reactants were loaded at mass ratios 0.6 to 2 and exchanged for periods of time between 44 and 1048 h. Local meteoric water and mantle olivine were taken as the initial reactants. The mineral products are brucite, serpentine and minor magnetite that occur as coatings on unreacted olivine as well as individual crystals. The progress of this dissolution-precipitation reaction was traced with the δD-δ′18O-Δ′17O values of reacted fluids and mineral products. After 1048 h of reaction, ∼50 wt% of unreacted olivine remained. In general, experimental data conforms with the triple O-isotope fractionation factors calculated for the co-existing secondary minerals forming in equilibrium with fluid. However, there is scatter and deviations in the reacted fluid compositions likely driven by the difference in relative rates of secondary mineral formation and changing modal and chemical mineral composition. We observe that brucite and magnetite form abundant aggregates early in the progress of the reaction, while chrysotile forms fine-grained coatings that become abundant later. Since individual mineral-water fractionation 103ln18/16α range over 10 ‰ with θ ranging between 0.51 and 0.53, the dynamic behavior of dissolution-precipitation mechanism during alteration of olivine is the main factor to the “wandering” triple O-isotope trajectories in our relatively short experiments.

Applications of Diels-Alder Chemistry in Biomaterials and Drug Delivery.

Recent studies, leveraging click chemistry reactions, have significantly advanced the fields of biomaterials and drug delivery. Of these click reactions, the Diels-Alder cycloaddition is exceptionally valuable for synthetic organic chemistry and biomaterial design, as it occurs under mild reaction conditions and can undergo a retrograde reaction, under physiologically relevant conditions, to yield the initial reactants. In this review, potential applications of the Diels-Alder reaction are explored within the nexus of biomaterials and drug delivery. This includes an emphasis on key platforms such as polymers, nanoparticles, and hydrogels which utilize Diels-Alder for drug delivery, functionalized surfaces, bioconjugation, and other diverse applications. Specifically, this review will focus on the use of Diels-Alder biomaterials in applications of tissue engineering and cancer therapies, while providing a discussion of the advantages, platforms, and applications of Diels-Alder click chemistry.

Nd3+-Doped Scheelite-Type Multifunctional Materials-Their Thermal Stability and Magnetic Properties.

New Nd3+-doped cadmium molybdato-tungstates with the chemical formula of Cd1-3x▯xNd2x(MoO4)1-3x(WO4)3x (where x = 0.0283, 0.0455, 0.0839, 0.1430, 0.1875, 0.2000, 0.2500, and ▯ denotes a vacant site in the crystal lattice) were successfully synthesized by the high-temperature solid state reaction method, using CdMoO4 and Nd2(WO4)3 as the initial reactants. The structure and change in their lattice parameters as a function of Nd3+ ion concentration were investigated by the XRD (X-ray diffraction) method. The surface morphology and grain size of the doped materials were characterized by SEM (scanning electron microscopy). Their thermal properties and initial reactants were analyzed by DTA-TG (differential thermal analysis coupled with thermogravimetry) techniques. The optical properties of the Nd3+-doped cadmium molybdato-tungstates, such as optical band gap, were determined by UV-vis-NIR (ultraviolet-visible-near infrared) spectroscopy. The EPR (electron paramagnetic resonance) technique provided information on the type of magnetic interactions between Nd3+ ions.

Recycling Materials for Sustainable DNA Origami Manufacturing.

DNA origami nanotechnology has great potential in multiple fields including biomedical, biophysical, and nanofabrication applications. However, current production pipelines lead to single-use devices incorporating a small fraction of initial reactants, resulting in a wasteful manufacturing process. Here, we introduce two complementary approaches to overcome these limitations by recycling the strand components of DNA origami nanostructures (DONs). We demonstrate reprogramming entire DONs into new devices, reusing scaffold strands. We validate this approach by reprogramming DONs with complex geometries into each other, using their distinct geometries to verify successful scaffold recycling. We reprogram one DON into a dynamic structure and show both pristine and recycled structures display similar properties. Second, we demonstrate the recovery of excess staple strands postassembly and fold DONs with these recycled strands, showing these structures exhibit the expected geometry and dynamic properties. Finally, we demonstrate the combination of both approaches, successfully fabricating DONs solely from recycled DNA components.

Temperature Effects and Activation Barriers in Aqueous Proton-Uptake Reactions.

Aqueous proton transfer reactions are fundamental in biology and chemistry, yet kinetics and mechanisms of strong base-weak acid reactions are not well understood. In this work, we present a temperature-dependent reaction kinetic study of the water-soluble photobase actinoquinol, in the presence and absence of succinimide, a weak acid reaction partner. We study the temperature dependence of the reaction and connect the observed dynamics to the reaction's thermodynamics. We find that actinoquinol reacts in associated complexes with water/succinimide, creating an intermediate complex that can undergo either dissociation to create products, or reverse proton transfer within the complex to recreate the initial reactants. We find that the intermediates' formation is energetically unfavorable with both reaction partners, which impacts the net reaction rates. We also find that the net reaction rate is additionally strongly influenced by the competition between the dissociation of the intermediates and their reverse reaction.

Quantum stereodynamics studies for the Li + HF (v = 0, j = 1) → H + LiF reaction

In reactive collisions, the colliding direction has an important effect on the reaction dynamics, and the study of reaction stereodynamics which controls the initial orientation or alignment of reactants is of great significance for controlling chemical reactions. In this work, the influence of different initial reactant orientations on the Li + HF (v0 = 0, j0 = 1) → LiF + H reaction dynamics are studied by using the quantum wave packet method. We found that the initial orientation of HF molecule has a great influence on the reactivity and scattering direction of product, but has little influence on the product rotational-vibrational state distribution.

Exploring bioenergy prospects from malt bagasse: Insights through pyrolysis with multi-component kinetic analysis and thermodynamic parameter estimation

Malt bagasse is a by-product of little commercial value in the brewing industry. Under this scenario, the current study represents the first investigation aiming to determine the kinetic triplet and thermodynamic parameters for malt bagasse pyrolysis using a multi-component kinetic approach to elucidate its bioenergy prospects. The pyrolysis progress profiles of malt bagasse were obtained through slow pyrolysis experiments on a thermogravimetric scale in an inert atmosphere, employing four distinct heating rates (10, 15, 25, and 40 °C min−1). This investigation also used the Frazer-Suzuki deconvolution function to elucidate the relative contributions of hemicellulose, cellulose, and lignin to malt bagasse pyrolysis. Activation energies for devolatilization reactions were determined by the isoconversional methods of Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and Starink, and revealed the lowest and highest mean values for pseudo-hemicelluloses (158.3−215.3 kJ mol−1) and pseudo-lignin (279.5−294.8 kJ mol−1), respectively. Frequency factors in malt bagasse pyrolysis ranging from 8.9 × 1016 and 2.2 × 1023 min−1 offer evidence of a simplified reaction chemistry pathway in the conversion towards bioenergy production. The integral master plot indicates the involvement of order-based and geometrical contraction-based mechanisms in malt bagasse pyrolysis. After defining multiple kinetic triplets, a differential equation encompassing contributions from all pseudo-components was formulated, and the simulated results aligned closely with experimental data, accurately describing pyrolysis progress profiles with at least 92.8% precision. The thermodynamic analysis reveals positive ΔH and ΔG values, indicating the non-spontaneous nature of malt bagasse pyrolysis. Higher disorder in the resultant products is attributed to volatile release and molecular rearrangement and is signified by positive ΔS values compared to the initial reactants. This study provided valuable insights into the valorization of malt bagasse, offering crucial information for optimizing pyrolysis reactors, scaling, and designing malt bagasse conversion into valuable biofuels, constituting an effort towards bio-circular economy principles based on the zero-waste concept.

Theoretical study on glucose and methylamine Maillard reaction: formation of the Amadori rearrangement products

In the present study, the mechanism of Maillard reaction was investigated using density functional theory calculations. Glucose and aminomethane were used as initial reactants in this study. The calculations show that the Amadori rearrangement reaction is the rate-controlling step with a corresponding energy potential of 402 kJ/mol，the enthalpy change is 219 kJ/mol, which is an endothermic reaction and therefore energy needs to be supplied from outside if the reaction is to proceed. The calculated results are in good agreement with the previous findings and can provide insight into the reaction mechanism of the Maillard reaction. These findings will help further research and find out the correct reaction mechanism.
 KEY WORDS: Food chemistry, Mechanism, Transition State, Computational chemistry
 Bull. Chem. Soc. Ethiop. 2024, 38(2), 539-545. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i2.20

Atomically dispersed nanozyme-based synergistic mild photothermal/nanocatalytic therapy for eradicating multidrug-resistant bacteria and accelerating infected wound healing.

Constructing a synergistic multiple-modal antibacterial platform for multi-drug-resistant (MDR) bacterial eradication and effective treatment of infected wounds remains an important and challenging goal. Herein, we developed a multifunctional Cu/Mn dual single-atom nanozyme (Cu/Mn-DSAzymes)-based synergistic mild photothermal/nanocatalytic-therapy for a MDR bacterium-infected wound. Cu/Mn-DSAzymes with collaborative effects exhibit remarkable dual CAT-like and OXD-like enzyme activities and could efficiently catalyze cascade enzymatic reactions with a low level of H2O2 as an initial reactant to produce reparative O2 and lethal ˙O2-. Moreover, a black N-doped carbon nanosheet supports of Cu/Mn-DSAzymes show superior NIR-II-triggered photothermal performance, endowing them with photothermal-enhanced dual enzyme catalysis. In addition, such enhanced dual enzyme catalysis likely improves the susceptibility and lethality of photothermal effects on MDR bacteria. In vitro and in vivo studies demonstrate that Cu/Mn-DSAzyme-mediated synergistic nanocatalytic and photothermal effects possess dramatic antibacterial outcomes against MDR bacteria and evidently reduced inflammation at wound sites. Moreover, the combined photothermal effect and O2 release mediated by Cu/Mn-DSAzymes promotes macrophage polarization to reparative M2 phenotype, collagen deposition, and angiogenesis, considerably accelerating wound healing. Therefore, Cu/Mn-DSAzyme-based synergetic dual-modal antibacterial therapy is a promising strategy for MDR bacterium-infected wound treatment, owing to their excellent antibacterial ability and significant tissue remodeling effects.

DESIGNING OF A NEW HARDWARE AND TECHNOLOGICAL SCHEME OF THE PROCESS OF ORGANIC SUBSTANCES MIXTURES SULPHING

The article states that surfactants based on higher alcohols fr. C12 - C14 are mainly used in a wide range of personal hygiene products, such as shampoos, foaming agents for baths, toothpastes, dishwashing liquid, and delicate laundry detergents. The use of surfactants based on a mixture of higher alcohols fr. C12 - C14 and monoethanolamides of higher fatty acids of coconut oil makes it possible to significantly improve the quality characteristics of personal hygiene products. It is stated that the main element of the apparatus and technological scheme of the sulfation process of mixtures of organic substances is a tubular film absorber. It is shown that for the sulfation of two-component mixtures of organic substances based on higher alcohols fr. C12 - C14 and monoethanolamides of higher fatty acids of coconut oil must use a tubular film absorber, which has two-stage cooling - the upper part 1/3 of the length of the absorber, the lower part 2/3 of the length of the absorber. The speed of the gasair flow is maintained at Vg = 20 m/s, the molar ratio of reagents is 1.08 : 1.0, the concentration of sulfur trioxide in the gas-air flow is 3.7% vol., the temperature of the initial reactants: liquid phase is 313 K, gas-air flow is 303 K, cooling water - 293 K. Based on such initial data, an industrial tubular absorber was calculated. The data of such a calculation are given. It is stated that the calculation of the industrial tubular film absorber was carried out according to the developed algorithm and program in the MatLab language, the iterative method of calculation was used in the program. The calculation of the number of pipes of an industrial absorber is given. It is shown that the absorber consists of the following main elements - an upper elliptical cover, a gas-air flow distribution plate, a chamber for distributing a mixture of organic substances, film formers, two cooling chambers, and a lower elliptical cover. It is stated that on the basis of an industrial tubular film absorber, a new equipment and technological scheme has been designed and presented. The main technical, economic and environmental indicators of the implementation of such a hardware and technological scheme are presented.

Perovskite/Pyrochlore Composite Mineral-like Ceramic Fabrication for 90Sr/90Y Immobilization Using SPS-RS Technique

A novel solid-phase synthetic approach was developed to produce a mineral-like composite ceramic based on strontium titanate (SrTiO3) and yttrium titanate (Y2Ti2O7) matrices for immobilizing radionuclides such as 90Sr and its daughter product 90Y, as well as lanthanides and actinides, via reactive spark plasma sintering technology (SPS-RS). Using XRD, SEM, and EDS analyses, the sintering kinetics of the initial mixed oxide reactants of composition YxSr1–1.5xTiO3 (x = 0.2, 0.4, 0.6 and 1) and structure-phase changes in the ceramics under SPS-RS conditions were investigated as a function of Y3+ content. In addition, a detailed study of phase transformation kinetics over time as a function of the heating temperature of the initial components (SrCO3, TiO2, and Y2O3) was conducted via in situ synchrotron XRD heating experiments. The composite ceramic achieved relatively high physicomechanical properties, including relative density between 4.92–4.64 g/cm3, Vickers microhardness of 500–800 HV, and compressive strength ranging from 95.5–272.4 MPa. An evaluation of hydrolytic stability and leaching rates of Sr2+ and Y3+ from the matrices was performed, demonstrating rates did not exceed 10−5–10−6 g·cm−2·day−1 in compliance with GOST R 50926-96 and ANSI/ANS 16.1 standards. The leaching mechanism of these components was studied, including the calculation of solution penetration depth in the ceramic bulk and ion diffusion coefficients in the solution. These findings show great promise for radioactive waste conditioning technologies and the manufacturing of radioisotope products.

Effect of anaerobic digestion pretreatment on pyrolysis of distillers’ grain: Product distribution, kinetics and thermodynamics analysis

To systematically examine the effects of anaerobic digestion (AD) pretreatment on product distribution and kinetics of distillers’ grains (DG) and its digestates collected at different AD durations, Py-GC/MS and TG analyses were conducted. Py-GC/MS analysis revealed a reduction in the proportion of oxygenated and nitrogenous compounds in all digestates and increase the share of hydrocarbons: 46.72% (SD-2), 65.53% (SD-4), 43.20% (SD-6) and 50.05% (SD-8) than DG (38.61%). To assess activation energy, Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa models were employed with average values ranging from 159.54 to 170.96 kJ mol−1 for DG, 156.59–165.42 kJ mol−1 for SD-2, 15.67–166.47 kJ mol−1 for SD-4, 153.28-159-45 kJ mol−1 for SD-6, and 156.02–167.37 kJ mol−1 for SD-8, which were lowered than DG. Thermodynamic studies showed positive ΔH and ΔG values, suggesting that the pyrolysis of DG and digestates is non-spontaneous. The negative ΔS values implied that the degree of disorder in products resulting from bond dissociation was lower than initial reactants. These findings provide valuable insight into the potential of AD as a pretreatment method and offer an understanding of the pyrolysis behavior of digestates. This study not only offers practical guidance but also contributes to the theoretical framework for utilizing AD as a pretreatment method for pyrolysis.

Interface and magnetic-dielectric synergy strategy to develop Fe3O4-Fe2CO3/multi-walled carbon nanotubes/reduced graphene oxide mixed-dimensional multicomponent nanocomposites for microwave absorption

Interfacial and/or magnetic-dielectric synergistic effects are important avenues to boost microwave absorption properties. In order to simultaneously utilize these effects, we elaborately designed mixed-dimensional Fe3O4-FeCO3/multi-walled carbon nanotubes (MWCNTs)/reduced graphene oxide (RGO) multicomponent nanocomposites (MCNCs) in large scale via a facile process of hydrothermal and freeze-drying. The microstructural investigation revealed that two-dimensional RGO, one-dimensional MWCNTs and zero-dimensional Fe3O4-FeCO3 nanoparticles were well bounded to generate the typical mixed-dimensional structure. By controlling the amounts of initial reactants, the Fe3O4-FeCO3/MWCNTs/RGO MCNCs displayed improved impedance matching features, polarization and conduction loss abilities, which lead to the evidently improved electromagnetic absorption properties. The Fe3O4-FeCO3/MWCNTs/RGO MCNCs simultaneously exhibited excellent absorption ability, large absorption bandwidth, low density and thin matching thickness. Generally, this work not only proposed an effective route to make the best of magnetic-dielectric synergy and interfacial strategy for exploiting novel microwave absorption materials, but also presented a simple approach to synthesize magnetic MWCNTs/RGO-based mixed-dimensional MCNCs.

Probing reaction channels via reinforcement learning

Chemical reactions are dynamical processes involving the correlated reorganization of atomic configurations, driving the conversion of an initial reactant into a result product. By virtue of the metastability of both the reactants and products, chemical reactions are rare events, proceeding fleetingly. Reaction pathways can be modelled probabilistically by using the notion of reactive density in the phase space of the molecular system. Such density is related to a function known as the committor function, which describes the likelihood of a configuration evolving to one of the nearby metastable regions. In theory, the committor function can be obtained by solving the backward Kolmogorov equation (BKE), which is a partial differential equation (PDE) defined in the full dimensional phase space. However, using traditional methods to solve this problem is not practical for high dimensional systems. In this work, we propose a reinforcement learning based method to identify important configurations that connect reactant and product states along chemical reaction paths. By shooting multiple trajectories from these configurations, we can generate an ensemble of states that concentrate on the transition path ensemble. This configuration ensemble can be effectively employed in a neural network-based PDE solver to obtain an approximation solution of a restricted BKE, even when the dimension of the problem is very high. The resulting solution provides an approximation for the committor function that encodes mechanistic information for the reaction, paving a new way for understanding of complex chemical reactions and evaluation of reaction rates.

Teaching biophysics I. The specific interactions: the sine qua non processes of life

" The manifestation of life, in all its aspects, is the result of an enormous number of specific biophysical and biochemical molecular interactions taking place ceaselessly into cells, in a highly ordered manner both spatially and temporally. Frequently, a product of any reaction, is not a final compound, but the initial reactant of another reaction taking place in a precise location and at right time into the intricate cellular reactions network. In this minireview, we will present, in an accessible manner, the nature and paramount importance of the specific interactions which constitute the essential basis for all life processes on the Earth"

HOW THE INCORPORATION OF 14C IN LEAD WHITE MAKES ITS ABSOLUTE DATING POSSIBLE

ABSTRACT Known as lead white, lead carbonates were used as white pigment or cosmetics from the 4th century BC to the 20th century AD. Lead white was produced by the corrosion of metallic lead by vinegar and horse manure up to the 19th c. In order to document the incorporation of carbon in the corrosion mechanism, lead carbonates were produced in the laboratory under monitored experimental conditions using materials with different isotope signatures in 14C and 13C. Six experimental setups were defined combining vinegar, acetic acid, horse manure and fossil CO2 gas. The corrosion products were characterized by X-ray diffraction. 14C content and δ13C values of the initial reactants and the final products were measured by accelerator and isotopic ratio mass spectrometry (AMS and IRSM). The reaction between lead and vinegar or acetic acid resulted in lead acetates with a carbon isotopic signature close to that of the corrosive reagent. In the presence of CO2, the carbonatation reaction occurred and the cerussite produced had a predominant 14C signature of the carbon dioxide source. These experiments demonstrate that the CO2 produced by horse manure fermentation is incorporated into the corrosion products, allowing the absolute dating of lead white by the radiocarbon method.

Rapid Colorimetric Determination of Biologically Active Organic Analytes

Four types of reactions (azo coupling, protolytic and oxidative condensation, ion association), accompanied by the formation of hydrophobic colored analytical forms of corresponding organic analytes, are proposed on an example of biologically active substances (aromatic amines, α-amino acids, antibiotics of aminoglycoside and β-lactam series, anionic surfactants). It is shown that, in these systems, the hydrophobicity of both the initial reactants, e.g., tetrafluoroborates of diazonium salts, and analytical forms (azo compounds, Schiff bases, Ruemann’s purpura, ion associates with surfactants) can be increased. Possibilities of various methods for the derivatization of organic analytes with the formation of colored analytical forms with increased hydrophobicity for the best fixation on solid matrices and the development of test systems on their basis, which can be used to control the quality of various samples with rather good performance characteristics, are considered.

Be13 cluster adsorbs water molecules splitting to produce H2 based on density functional theory

Research on the production of hydrogen from water by catalytic decomposition using metal clusters is of great significance in addressing the global energy crisis. Due to the quantum size effect, tunability, and ultra-high surface area, metal clusters exhibit many unique properties, including catalytic performance and optical properties. In this work, the lowest energy structure of Be13 cluster and intermediate states, as well as the hydrogen production mechanism of Be13 cluster and intermediate states + single water molecule were studied by DFT calculations at the PBE0-D3/DEF2TZVP level. The results show that both Be13 cluster and intermediate states release energy during water molecules adsorption and both Be13 cluster and its intermediate state + single water molecule reactions are exothermic. The electronic structures of the original and adsorbed structures were analyzed by ESP method, and their DOS plots were drawn. We investigated the chemical bonding and interactions of the initial structure, reactants and products using IRI analysis. Our results help to provide a basis for developing a more effective method for generating hydrogen from water molecules.

Collaborative CuMn diatomic nanozyme to boost nanocatalytic/mild photothermal/chemo-therapy through overcoming therapeutic resistance

The combined mild-temperature photothermal/chemo-therapy has emerged as a promising approach to complement traditional tumor treatment and enhance therapeutic effects while reduce side effects. However, therapeutic resistance caused by up-regulation of heat shock proteins (HSPs) and P-glycoprotein (P-gp) drastically compromises the synergetic therapeutic effect. Herein, we develop a multifunctional CuMn dual-atom nanozyme loaded with the chemotherapeutic agent doxorubicin (DOX@CuMn-DAzymes) for P-gp and HSPs simultaneous silencing induced synergistic trimodal therapy. The resulting CuMn double-atom pairs with significant synergistic effects can efficiently catalyze cascade reactions of catalase (CAT)-like and oxidase (OXD)-like with endogenous H2O2 as the initial reactant to produce highly reactive singlet oxygen (1O2) under the trigger of acidic tumor microenvironment, destroying the P-gp and HSPs in tumor cells. Benefitting from their black polyporous nanocarbon support, DOX@CuMn-DAzymes not only show superior 1064 nm laser triggered photothermal performance, but also possess high DOX encapsulation efficiency and dual pH- and NIR-responsive DOX release properties. Moreover, in vitro and in vivo study results demonstrate that DOX@CuMn-DAzymes effectively overcome therapeutic resistance by boosting intracellular 1O2 level to simultaneously silence P-gp and HSPs, thereby achieving an impressive synergetic therapeutic efficacy.