β-N-acetylglucosaminidase grafted on mesoporous silica nanoparticles. A bionanoantibiotic system against Staphylococcus aureus bacteria

A bionanoantibiotic system based on beta-N-acetylglucosaminidase (Ami) and Lysozyme (Lyz) enzymes grafted on the external surface of amino functionalized mesoporous silica nanoparticles, having a radial arrangement of pores (MSNr-NH2), was prepared and fully characterized. Before the enzyme grafting the nanoparticles were also loaded with the antibiotic drug levofloxacin (Levo) to explore the possible synergic effect with the enzymes. MSNr-NH2-Lyz-Levo and MSNr-NH2-Ami-Levo did not show any activity against S. aureus. On the contrary, in the absence of the antibiotic, both Lyz and Ami immobilized on MSNr were able to destroy S. aureus cells, suggesting an inhibiting action of the antibiotic on the enzymes. Although the loading of immobilized Lyz was higher than that of Ami (76 vs. 20 mg/g, respectively), the highest antibacterial efficacy was found for MSNr-NH2-Ami nanoantibiotic. Moreover, MSNr-NH2-Ami was active against S. aureus even at very low concentration (12.5 mu g/ mL) with a bactericidal activity (79%), higher than that determined for MSNr-NH2 loaded with levofloxacin (54%). These results suggest the possibility of using enzyme grafted MSNr as a bionanoantibiotic drug with high efficiency even at low nanoparticles concentration

Beyond Traditional Hyperthermia: In Vivo Cancer Treatment with Magnetic-Responsive Mesoporous Silica Nanocarriers

In this study, we present an innovation in the tumor treatment in vivo mediated by magnetic mesoporous silica nanoparticles. This device was built with iron oxide magnetic nanoparticles embedded in a mesoporous silica matrix and coated with an engineered thermoresponsive polymer. The magnetic nanoparticles act as internal heating sources under an alternating magnetic field (AMF) that increase the temperature of the surroundings, provoking the polymer transition and consequently the release of a drug trapped inside the silica pores. By a synergic effect between the intracellular hyperthermia and chemotherapy triggered by AMF application, significant tumor growth inhibition was achieved in 48 h after treatment. Furthermore, the small magnetic loading used in the experiments indicates that the treatment is carried out without a global temperature rise of the tissue, which avoids the problem of the necessity to employ large amounts of magnetic cores, as is common in current magnetic hyperthermia

Experimental Evidence of the Origin of Nanophase Separation in Low Hole-Doped Colossal Magnetoresistant Manganites

While being key to understanding their intriguing physical properties, the origin of nanophase separation in manganites and other strongly correlated materials is still unclear. Here, experimental evidence is offered for the origin of the controverted phase separation mechanism in the representative La_1–<i>x</i>Ca_<i>x</i>MnO₃ system. For low hole densities, direct evidence of Mn⁴⁺ holes localization around Ca²⁺ ions is experimentally provided by means of aberration-corrected scanning transmission electron microscopy combined with electron energy loss spectroscopy. These localized holes give rise to the segregated nanoclusters, within which double exchange hopping between Mn³⁺ and Mn⁴⁺ remains restricted, accounting for the insulating character of perovskites with low hole density. This localization is explained in terms of a simple model in which Mn⁴⁺ holes are bound to substitutional divalent Ca²⁺ ions