Multifunctionalized Mesostructured Silica Nanoparticles Containing Mn2 Complex for Improved Catalase-Mimicking Activity in Water

Hybrid multifunctionalized mesostructured stellate silica nanoparticles loaded with β-diketonate Tb3+/Eu3+ complexes as efficient ratiometric emissive thermometers working in water

Despite the great effort made in recent years on lanthanide-based ratiometric luminescent nanothermometers able to provide temperature measurements in water, their design remains challenging. We report on the synthesis and properties of efficient ratiometric nanothermometers that are based on mesoporous stellate nanoparticles (MSN) of ca. 90 nm functionalized with an acetylacetonate (acac) derivative inside the pores and loaded with β-diketonate-Tb3+/Eu3+ complexes able to work in water, in PBS or in cells. Encapsulating a [(Tb/Eu)9(acac)16(μ3-OH)8(μ4-O)(μ4-OH)] complex (Tb/Eu ratio = 19/1 and 9/1) led to hybrid multifunctionalized nanoparticles exhibiting a Tb3+ and Eu3+ characteristic temperature-dependent luminescence with a high rate Tb3+-to-Eu3+ energy transfer. According to theoretical calculations, the modifications of photoluminescence properties and the increase in the pairwise Tb3+-to-Eu3+ energy transfer rate by about 10 times can be rationalized as a change of the coordination number of the Ln3+ sites of the complex from 7 to 8 accompanied by a symmetry evolution from Cs to C4v and a slight shortening of intramolecular Ln3+-Ln3+ distances upon the effect of encapsulation. These nanothermometers operate in the 20-70 °C range with excellent photothermal stability, cyclability and repeatability (>95%), displaying a maximum relative thermal sensitivity of 1.4% °C-1 (at 42.7 °C) in water. Furthermore, they can operate in cells with a thermal sensitivity of 8.6% °C-1 (at 40 °C), keeping in mind that adjusting the calibration for each system is necessary to ensure accurate measurements.

One-Pot Synthesis of MnOx-SiO2 Porous Composites as Nanozymes with ROS-Scavenging Properties

The development of nanomaterials that mimic the activity of enzymes is a topic of interest, for the decomposition of reactive oxygen species (ROS). We report the preparation of a novel nanocomposite of MnO_x needles covered with SiO₂ porous material. The material was prepared in one pot with a two-step procedure. The material was characterized by EDX, SEM, TEM, XRD, nitrogen adsorption-desorption isotherms, and XPS. The synthesis protocol took advantage of the atrane method, favoring the nucleation and initial growth of manganese oxide needles that remained embedded and homogeneously dispersed in a mesoporous silica matrix. The final composite had a high concentration of Mn (Si/Mn molar ratio of ca. 1). The nanozyme presented bimodal porosity: intraparticle and interparticle association with the surfactant micelles and the gaps between silica particles and MnO_x needles, respectively. The porosity favored the migration of the reagent to the surface of the catalytic MnO_x. The nanozyme showed very efficient SOD and catalase activities, thus improving other materials previously described. The kinetics were studied in detail, and the reaction mechanisms were proposed. It was shown that silica does not play an innocent role in the case of catalase activity, increasing the reaction rate.

Intrinsic Multienzyme-like Activities of the Nanoparticles of Mn and Fe Cyano-Bridged Assemblies

This study investigates the intrinsic multienzyme-like properties of the non-stabilized nanocrystalline nanoparticles of manganese-doped Prussian blue (Mn-PB) nanozymes and Prussian blue (PB) nanozymes in chemical and electrocatalytic transformations of reactive oxygen species. The effect of manganese doping on the structural, biomimetic, and electrocatalytic properties of cyano-bridged assemblies is also discussed.