A selection from Stockholm University publication database

• Functional Nanostructured Cu-based Alloys with Shape Memory Effect and Tunable Magnetic Properties

  2024. Lesya Demchenko (et al.). Proceedings of the 2024 IEEE 14^th International Conference “Nanomaterials: Applications & Properties” (IEEE NAP-2024)

  Conference

  We demonstrate a method of obtaining tunable magnetic anisotropy in Cu−Al−Mn shape memory alloys, consisting of aging the material in a magnetic field of 1.5 KOe at elevated temperature of T=200^∘C for the precipitation of ferromagnetic nanoparticle of an elongated shape. Using a combination of magnetic and structural measurements, the structural phase transformations of a martensitic type and paramagnetic-superparamagnetic-spin glass transitions were studied in a wide temperature range. On magnetic field aging, a decrease in magnetization and an increase in coercivity are observed, accompanied by a slight shift in the temperature of the magnetic and martensitic phase transition. The observed changes in the magnetic properties of the nanostructured material are explained by additional induced magnetic anisotropy resulting from such thermomagnetic treatment.

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• Structural Features and Mechanical Behavior of Pseudo-β-Ti–Mo–Sn Alloys As-Quenched and As-Aged for Biomedical Application

  2024. Anatoliy Titenko (et al.). Nanooptics and Nanoelectronics, Nanobiotechnology, and Their Applications, 79-98

  Conference

  The paper considers in detail the structural and deformation behavior of ternary metastable β-Ti–(10,12,14)Mo–(1 ÷ 8)Sn (wt.%) alloys under uniaxial tension depending on the concentration of doping elements (Mo and Sn) and heat treatment (quenching and aging). Low-temperature aging allows a significant increase in strength up to 1.5 ÷ 2 times while preserving ductility. The optimal combination of mechanical properties: high values of yield strength σY = 680 MPa and ultimate tensile strength σUT = 1125 MPa along with high ductility of 43% has been achieved in Ti–12Mo–4Sn alloy (wt.%) after aging at 473 K for 60 s. A high strength of the alloys, accompanied by a high rate of strain hardening, without loss of ductility, is a result of the complex nature of deformation with a predominance of TRIP/TWIP mechanisms, i.e. the simultaneous processes of induction of strain martensite and twinning. Record values of strain hardening are reached for Ti–10Mo–(2 ÷ 6)Sn (wt.%) alloys, where the predominant deformation mechanism according to powder XRD and metallography is the TRIP effect, which significantly exceeds the TWIP effect, prevailing in alloys with higher Mo and Sn contents. The mechanical properties of these alloys (high strength and ductility) make them potentially suitable for commercial biomedical applications.

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• Structural and Magnetic Transitions in Aged Shape Memory Cu-Al-Mn and Cu-Al-Mn-Fe Alloys

  2023. Lesya Demchenko (et al.). 2023 IEEE 13th International Conference Nanomaterials: Applications & Properties (NAP), NMM04-1-NMM04-4

  Conference

  A comparative analysis of the structural and magnetic behavior of Cu-Al-Mn and Cu-Al-Mn-Fe alloys depending on their heat treatment is carried out. The influence of low-temperature aging on the behavior of temperature induced martensitic transformation was established. The difference in magnetic behavior of alloys is a consequence of the formation of the ferromagnetic (Cu,Mn) 3 Al and (Fe,Mn) 3 Al Heusler phases during isothermal aging and the transition to a superparamagnetic state. In alloys doped with iron, antiferromagnetic ordering can prevail over ferromagnetic. The precipitates create a significant cumulative effect on the character and characteristic temperature of thermoelastic martensite transformation (MT), as well as on mechanical and magnetic behavior.

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• Mn3O4 Nanocrystal-Induced Eryptosis Features Ca2+ Overload, ROS and RNS Accumulation, Calpain Activation, Recruitment of Caspases, and Changes in the Lipid Order of Cell Membranes

  2025. Yuriy Kot (et al.). International Journal of Molecular Sciences 26 (7)

  Article

  Accumulating evidence suggests that manganese oxide nanoparticles (NPs) show multiple enzyme-mimicking antioxidant activities, which supports their potential in redox-targeting therapeutic strategies for diseases with impaired redox signaling. However, the systemic administration of any NP requires thorough hemocompatibility testing. In this study, we assessed the hemocompatibility of synthesized Mn3O4 NPs, identifying their ability to induce spontaneous hemolysis and eryptosis or impair osmotic fragility. Concentrations of up to 20 mg/L were found to be safe for erythrocytes. Eryptosis assays were shown to be more sensitive than hemolysis and osmotic fragility as markers of hemocompatibility for Mn3O4 NP testing. Flow cytometry- and confocal microscopy-based studies revealed that eryptosis induced by Mn3O4 NPs was accompanied by Ca2+ overload, altered redox homeostasis verified by enhanced intracellular reactive oxygen species (ROS) and reactive nitrogen species (RNS), and a decrease in the lipid order of cell membranes. Furthermore, Mn3O4 NP-induced eryptosis was calpain- and caspase-dependent.

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• Effect of TiO₂ Nanoparticles Defect Structure on their ROS Scavenging Ability

  2024. Svetlana Yefimova (et al.). Proceedings of the 2024 IEEE 14^th International Conference “Nanomaterials: Applications & Properties” (IEEE NAP-2024)

  Conference

  Titanium dioxide nanoparticles (TiO₂ NPs) have attracted significant interest for their ability to modulate reactive oxygen species (ROS) levels within cells. These nanoparticles have shown promise in drug delivery, sonodynamic, photodynamic, photothermal, and ionizing radiation-based anti-cancer therapies, as well as antimicrobial and antioxidant applications. In this study, we analyzed the effects of TiO₂ NP defect structures - specifically the presence of stoichiometric (Ti⁴) and non-stoichiometric (Ti³⁺ andTi²⁺) titaniumions within the crystal lattice - and the aggregation state of TiO₂ NPs on their ROS scavenging capabilities in both cell-free conditions and H₂O₂-treated L929 cells. Two types of TiO₂ NPs with varying concentrations ofTi³⁺ andTi²⁺ ions were synthesized and characterized using XRD, TEM, SAXS, and XPS techniques. The antioxidant properties of these TiO₂ NPs were assessed through chemiluminescence and optical spectroscopy using ROS sensors. Results from chemiluminescence and total antioxidant capacity assays indicated that the synthesized TiO₂ NPs possess radical scavenging abilities, with TiO₂ NPs(1), containing a higher amount of non-stoichiometric titanium ions, demonstrating a stronger effect. Concentrations of up to 40mg /L of TiO₂ NPs showed no impact on L929 cell viability or cell death. Moreover, TiO₂ NPs(1) exhibited a tendency to reduce H₂O₂ induced oxidative stress in L929 cells, while TiO₂ NPs(2) had the opposite effect, likely due to their propensity for aggregation in the cell medium.

  Our findings suggest that the synthesized TiO₂ NPs have potential as agents for modulating intracellular ROS levels at concentrations that do not compromise cell viability.

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• Microscopic mechanisms of luminescence quenching in Eu3+-doped GdVO4 nanoparticles under hydrogen peroxide decomposition

  2024. P. O. Maksimchuk (et al.). Journal of Molecular Liquids 400

  Article

  Sensing intracellular level of hydrogen peroxide (H2O2) is an extremely important task, because the overproduction of H2O2 causes cell mutations and the development of various pathologies. Eu3+-doped GdVO4 NPs has a great potential as multifunctional theranostic agent, as well as a sensor of intracellular H2O2. Therefore, detailed studies of all factors affecting their catalytic and luminescence properties, including the impact of H2O2 on their luminescent properties, are required. In present study, we have analyzed the effects of H2O2 on Eu3+ luminescence intensity in GdVO4:Eu3+ NPs synthesized in a water solution. As-synthesized NPs were characterized by XRD, HR-TEM, XPS and optical spectroscopy techniques. To analyze the surface modification of GdVO4:Eu3+ NPs after H2O2 exposure, XPS analysis and time-resolved luminescence spectroscopy were also used. Two mechanisms responsible for the observed Eu3+ luminescence quenching in GdVO4:Eu3+ NPs were found: (i) the decrease in the efficiency of non-radiative resonance energy transfer through the vanadate VO4 3- groups to Eu3+ ions due to the scattering effect of V4+ ions and (ii) the direct quenching of Eu3+ luminescence by –OH groups formed at the surface of NPs as a result of H2O2 decomposition.

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• Oxidative stress-modifying effects of TiO2 nanoparticles with varying content of Ti3+(Ti2+) ions

  2024. Viktor Kireev (et al.). Nanotechnology 35 (50)

  Article

  Nanoparticles (NPs) with reactive oxygen species (ROS)-regulating ability have recently attracted great attention as promising agents for nanomedicine. In the present study, we have analyzed the effects of TiO2 defect structure related to the presence of stoichiometric (Ti4+) and non-stoichiometric (Ti3+ and Ti2+) titanium ions in the crystal lattice and TiO2 NPs aggregation ability on H2O2- and tert-butyl hydroperoxide (tBOOH)-induced ROS production in L929 cells. Synthesized TiO2-A, TiO2-B, and TiO2-C NPs with varying Ti3+(Ti2+) content were characterized by x-ray powder diffraction, transmission electron microscopy, small-angle x-ray scattering, x-ray photoelectron spectroscopy, and optical spectroscopy methods. Given the role of ROS-mediated toxicity for metal oxide NPs, L929 cell viability and changes in the intracellular ROS levels in H2O2- and tBOOH-treated L929 cells incubated with TiO2 NPs have been evaluated. Our research shows that both the amount of non-stoichiometric Ti3+ and Ti2+ ions in the crystal lattice of TiO2 NPs and NPs aggregative behavior affect their catalytic activity, in particular, H2O2 decomposition and, consequently, the efficiency of aggravating H2O2- and tBOOH-induced oxidative damage to L929 cells. TiO2-A NPs reveal the strongest H2O2 decomposition activity aligning with their less pronounced additional effects on H2O2-treated L929 cells due to the highest amount of Ti3+(Ti2+) ions. TiO2-C NPs with smaller amounts of Ti3+ ions and a tendency to aggregate in water solutions show lower antioxidant activity and, consequently, some elevation of the level of ROS in H2O2/tBOOH-treated L929 cells. Our findings suggest that synthesized TiO2 NPs capable of enhancing ROS generation at concentrations non-toxic for normal cells, which should be further investigated to assess their possible application in nanomedicine as ROS-regulating pharmaceutical agents.

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• Reentrant polar phase induced by the ferroionic coupling in B⁢i_1−𝑥⁢S⁢m_𝑥⁢Fe⁢O₃ nanoparticles

  2024. Anna N. Morozovska (et al.). Physical Review B 110 (22)

  Article

  Using the model of four sublattices, the Landau-Ginzburg-Devonshire-Kittel phenomenological approach and the Stephenson-Highland ionic adsorption model for the description of coupled polar and antipolar long-range orders in ferroics, we analytically calculated the phase diagrams and polar properties of B⁢i_1−𝑥⁢S⁢m_𝑥⁢Fe⁢O₃ nanoparticles covered by surface ions with dependence on their size, surface ions density, samarium content 𝑥, and temperature. The size effects and ferroionic coupling govern the appearance and stability conditions of the long-range ordered ferroelectric, reentrant ferrielectric, and antiferroelectric phases in B⁢i_1−𝑥⁢S⁢m_𝑥⁢Fe⁢O₃ nanoparticles. Calculated phase diagrams are in qualitative agreement with the x-ray diffraction phase analysis, electron paramagnetic resonance, infrared spectroscopy, and electrophysical measurements of B⁢i_1−𝑥⁢S⁢m_𝑥⁢Fe⁢O₃ nanopowders sintered by the solution combustion method. The combined theoretical-experimental approach allows us to explain the influence of the ferroionic coupling and size effects in B⁢i_1−𝑥⁢S⁢m_𝑥⁢Fe⁢O₃ nanoparticles on their polar properties.

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• Stable nanometer-size beta-cyclodextrin-CeO2-x colloidal nanoparticles with high free radical scavenging activity

  2024. Ganna Grygorova (et al.). Journal of Molecular Liquids 396

  Article

  Cyclodextrin (CD) molecules are well-known for their ability to form inclusion complexes with hydrophobic molecules, including small drug molecules and lipophilic antioxidants. The combination of nanoparticles (NPs) with antioxidant properties (so-called nanozymes) and hydrophobic antioxidant molecules using CD@NP complexes can increase sufficiently the antioxidant efficiency of both components due to synergistic effect. Here we propose the new method of obtaining beta-CD@CeO2-x complexes with addition of beta-CD on the stage of syntheses of NPs. As a result, highly stable colloidal solutions of nanometer-size (2-3 nm) beta-CD@CeO2-x nanoparticles were obtained. The stabilization effect of beta-CD molecules was shown. Obtained beta-CD@CeO2-x complexes reveal high antiradical activity in the number of experiments (including center dot OH and O2- scavenging) related to Ce3+/Ce4+ redox switching in nanoceria. The aggregation behavior of beta-CD@CeO2-x complexes in various biological media was studied and the ways to improve their stability were proposed.

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• Catalytic Effect of GdVO4: Eu³⁺Nanocrystals Over H2O2 Decomposition Reaction

  2023. Svetlana Yefimova (et al.). 2023 IEEE 13th International Conference Nanomaterials: Applications & Properties (NAP), NRA06-1-NRA06-5

  Conference

  Hydrogen peroxide (H₂O₂) is a member of the reactive oxygen species (ROS) family and participates in numerous redox metabolism reactions and cellular processes. H₂O₂ is regarded as a pivotal component in the homeostatic metabolism of cells, acting as a mediator in various physiological processes including cell differentiation, proliferation, survival, and immune response. Nevertheless, the Fenton reaction between H₂O₂ and Fe ²⁺ ions serves as the primary trigger for biomolecule oxidation reactions, resulting in the formation of highly reactive hydroxyl radicals (⋅OH). Hence, there is a great interest in preventive antioxidants that can react with H₂O₂ without generating free radicals, such as ⋅OH.

  In the present work, we analyze the mechanism of H₂O₂ decomposition by GdVO₄:Eu³⁺ nanoparticles (NPs) in aqueous solutions using optical spectroscopy technique. The synthesized NPs were characterized by TEM, HR-TEM, XRD, and XPS methods. The possibility of Fenton- and catalase-like reactions of H₂O₂ decomposition in aqueous solutions containing GdVO₄:Eu³⁺ NPs has been analyzed. Obtained results indicate that the Fenton-like reaction with the participation of V ⁴⁺/V³⁺ ions detected in a high amount at the surface of GdVO₄:Eu³⁺ NPs, and ⋅OH generation is not a likely scenario in the system under study. At the same time, it has been revealed that H₂O₂ likely acts as a reductant donating electron to V⁵⁺ ions in GdVO₄:Eu³⁺ NPs that was confirmed by increasing the amount of V⁴⁺ and V³⁺ ions and decreasing V⁵⁺ ions content and the transformation of the GdVO₄:Eu³⁺ absorption spectrum, as well. Thus, GdVO₄:Eu³⁺ NCs could be prospective as an effective preventive antioxidant for H₂O₂ decomposition by catalase-like reaction.

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• Oxide Nanocrystals with Variable Valence Ions for Hydroxyl Radical Neutralization

  2023. Pavel Maksimchuk (et al.). 2023 IEEE 13th International Conference Nanomaterials: Applications & Properties (NAP), NRA05-1-NRA05-5

  Conference

  Cellular respiration in living cells generates biologically active molecules known as reactive oxygen species (ROS). Among these ROS, superoxide anions, hydrogen peroxide, and hydroxyl radicals are produced within mitochondria and play pivotal roles in cellular metabolism. However, an elevation in hydroxyl radical (.OH) levels, the most potent oxidants among ROS, can instigate various pathological processes within cells, ranging from heightened lipid peroxidation of cell membranes to DNA damage. Hydroxyl radicals are generated through water radiolysis during X-ray or gamma irradiation of cells. Their extremely high reactivity, coupled with an average lifespan of only a few nanoseconds in a biological environment, poses a considerable challenge for the cell's internal defense mechanisms in effectively neutralizing them. In response, we propose the utilization of three distinct types of oxide nanocrystals—containing variable valence ions (CeO₂, TiO₂, and GdVO₄)—as promising materials for the efficient neutralization of hydroxyl radicals.

  These nanocrystals, CeO₂, TiO₂, and GdVO₄, exhibit remarkable capabilities in scavenging hydroxyl radicals generated in water solutions during X-ray irradiation. Their hydroxyl radical-neutralizing properties are intricately linked to the high concentration of reduced variable valence ions (such as Ce³⁺ in CeO₂, Ti³⁺ in TiO₂, and V⁴⁺ /V³⁺ in GdVO₄), which possess the ability to donate electrons during hydroxyl radical neutralization reactions. Small oxide nanocrystals, characterized by the presence of structural imperfections like oxygen vacancies, enable the reduction of neighboring variable valence ions, as validated by XPS experiments for all three types (CeO₂, TiO₂, and GdVO₄).

  The proficiency of these small oxide nanocrystals containing variable valence ions (CeO₂, TiO₂, and GdVO₄) in efficiently neutralizing hydroxyl radicals in aqueous solutions highlights their potential as effective antioxidants and radioprotectors within living cells. This promising avenue opens new possibilities for cellular defense and therapeutic applications.

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• Reversible CeO_2-x and CeO_2-x : Eu³⁺ Luminescent Hydrogen Peroxide Sensors with Recovery Rates Controlled by Temperature and UV Irradiation

  2023. Vladyslav Seminko (et al.). The Journal of Physical Chemistry C 127 (22), 10662-10669

  Article

  Hydrogen peroxide (HP) plays an indispensablerole in living organisms,being both an intracellular messenger and a substrate or byproductof a number of enzymes. In this way, HP sensing is important for monitoringthe activity of various cell systems and assessing the redox balanceof the cell as whole. HP sensors based on luminescent inorganic nanoparticlescan be considered as a prospective alternative to traditional dye-and enzyme-based sensors, which usually are unstable and nonreversible.The undoped (CeO2-x ) and Eu3+-doped (CeO2-x :Eu3+) colloidal ceria nanoparticles studied in the paper provideHP detection by reversible quenching of Eu3+ (590 nm) andCe(3+) (430 nm) luminescence bands. The dynamics of Eu3+ and Ce3+ luminescence quenching and recoveryduring HP-nanoceria interaction provides an insight into the microscopicmechanisms of HP sensing by CeO2-x and CeO2-x :Eu3+ nanoparticles.Both CeO2-x and CeO2-x :Eu3+ luminescent sensors are reversibleand their recovery rates can be sufficiently increased by temperatureand continuous UV irradiation. At the same time, Eu3+ ionsdeteriorate the catalase-mimetic activity of CeO2-x NPs and worsen their antioxidant properties, whichshould be kept in mind while using these sensors in biological media.

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• ·OH-Free Catalytic Decomposition of H₂O₂ by GdVO₄:Eu³⁺ Nanoparticles

  2023. Pavel O. O. Maksimchuk (et al.). The Journal of Physical Chemistry C 127 (31), 15206-15214

  Article

  H₂O₂ is known to be one of the initiators provoking biomolecules (lipids and proteins) oxidation and cell mutation and death. In this context, molecules, which can react with H₂O₂ without generating free radicals such as hydroxyl radicals (·OH), are of special interest as effective preventive antioxidants. In the present study, we report on GdVO₄:Eu³⁺ nanoparticles (NPs) as prospective preventive nanozymes. Synthesized GdVO₄:Eu³⁺ NPs were characterized by TEM, HR-TEM, XRD, SAXS, and XPS methods. It has been revealed that in water solutions GdVO₄:Eu³⁺ NPs are in the form of individual crystalline spheroids with 𝑙 = 12.1 ± 1.23 nm and d = 5.76 ± 0.68 nm. Using the optical spectroscopy technique, the possibility for Fenton- and CAT-like reactions in water solutions containing GdVO₄:Eu³⁺ NPs has been analyzed. The protective effect of GdVO₄:Eu³⁺ NPs from H₂O₂-induced oxidative stress has been estimated using rat hepatocytes and analyzing changes in cells’ mitochondrial potential. It was concluded that the main mechanism of H₂O₂ decomposition both in aqueous solutions and biological milieu is rather associated with CAT-like reactions that ensure the V⁴⁺/V⁵⁺ and V³⁺/V⁴⁺ redox cycling.

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Show all publications by Lesya Demchenko at Stockholm University