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Beneficial effects in bone cell growth and antibacterial action are currently attributed to Ga3+ ions. Thus, they can be used to upgrade mesoporous bioactive glasses (MBGs), investigated for tissue engineering, whenever they released therapeutic amounts of gallium ions to the surrounding medium. Three gallium-enriched MBGs with composition (in mol %) xSiO2-yCaO-zP2O5-5Ga2O3, being x = 70, y = 15, z = 10 for Ga_1; x = 80, y = 12, z = 3 for Ga_2; and x = 80, y = 15, z = 0 for Ga_3, were investigated and compared with the gallium-free 80SiO2-15CaO-5P2O5 MBG (B). 29Si and 31P MAS NMR analyses indicated that Ga3+ acts as network modifier in the glass regions with higher polymerization degree and as network former in the zones with high concentration of classical modifiers (Ca2+ ions). Ga_1 and Ga_2 exhibited a quick in vitro bioactive response because they were coated by an apatite-like layer after 1 and 3 days in simulated body fluid. Although we have not conducted biological tests in this paper (cells or bacteria), Ga_1 released high but non-cytotoxic amounts of Ga3+ ions in Todd Hewitt Broth culture medium that were 140 times higher than the IC90 of Pseudomonas aeruginosa bacteria, demonstrating its potential for tissue engineering applications. [ABSTRACT FROM AUTHOR]

The ability of Ce-containing bioactive glasses, based on 45S5 Bioglass, to inhibit oxidative stress in terms of reduction in hydrogen peroxide and superoxide (O ), by mimicking the catalase and superoxide dismutase activity is reported in this work. The characterization is performed on the powders of pristine glasses and after the soaking in HO solutions and simulated body fluid. The glass samples are analysed by XPS, XRD, UV-Vis and FT-IR. The best catalyst activities are obtained for the glass with the highest content of cerium (H_5.3 = 5.3 mol% of CeO in the nominal glass composition), and the best Ce/Ce ratio in terms of catalase mimetic activity is found to be a function of HO concentration. Moreover, the detailed study of the surface during the mimic enzymatic activity tests shows the formation of a Ca-P-rich layer on the glass surface, where the presence of Ce ions favours the formation of CePO. The phosphate in turn inhibits the formation of hydroxyapatite, decreasing the bioactivity of the glass with the highest of CeO in the glass composition. This work shows the effect of Ce/Ce ratio towards the catalase mimetic activity and for the first time the superoxide dismutase mimetic activity of Ce-containing 45S5-derived glasses. [ABSTRACT FROM AUTHOR]

In this paper, we report the study of the loading and the release of curcuminoids by bioactive glasses (BG) and mesoporous bioactive glasses (MBG). Through a detailed spectroscopic study, it was possible to determine the amount and the type of molecules released in water and in simulated body fluid (SBF). In particular, curcumin and K2T21 show a good ability to be released in di-keto and keto-enolic form, depending from the pH. However, after 24 h, the amount of pristine curcumin release is very low with a consequent increment of degradation products derived by curcuminoids. The presence of -OH groups on curcuminoids is a fundamental pre-requisite in order to obtain a high loading and release in polar solution such as water and SBF. The substrate on which we loaded the drugs does not seem to affect significantly the loading and the release of the drugs. The environment, instead, affects the release: for all the drugs, the release in SBF, buffered at pH of 7.4, is slightly worse than the release in water (basic pH values). [ABSTRACT FROM AUTHOR]

Zn2[sup +] ions exhibit osteogenic, angiogenic and antimicrobial properties. For this reason, they are often added in small amounts to bioceramics being investigated for bone tissue engineering. In this paper, the cytocompatibility and antibacterial properties of 80% SiO[sub 2]-15% CaO-5% P[sub 2]O[sub 5] (mol%) mesoporous bioactive glass (MBG) scaffolds substituted with 4.0% and 7.0% of ZnO were studied and compared with the Zn-free scaffold. Cell proliferation, morphology, differentiation and cytotoxic effects of Zn2[sup +] ions released from the samples were examined by culturing human osteoblast-like cells (HOS) osteoblasts both in the presence of sample extracts and on the scaffold surface. The bacterial inhibition capacity of the scaffolds was explored by using Gram-positive Stapylococcus aureus bacteria, responsible for numerous infections in orthopedic surgery, to simulate a severe infection. Our results show that the Zn-MBG scaffolds possess a hierarchical meso-macropore structure suitable for osteoblast growth. Furthermore, the amount of Zn2[sup +] released from the scaffold with 4.0% ZnO was found to be more favorable for HOS cell development than that released from the scaffold including 7.0% ZnO. Zn2[sup +] released to the medium from both scaffolds exhibited antibacterial properties against S. aureus. Thus, the cytocompatibility and the antibacterial ability exhibited by the MBG scaffold containing 4.0% ZnO make it a suitable candidate for bone regeneration applications. [ABSTRACT FROM AUTHOR]

In the field of implantation, the delivery and/or immobilization of biomolecules developing a specific action on bone mineralization has attracted great attention in the last few years. In fact, a wide spectrum of enzymes and proteins have been grafted with different methods onto/within implanted materials. Bioactive glasses and glass-ceramics, due to their tailorable properties in terms of chemical composition, reactivity, and easiness of manufacturing, represent good scaffolds for enzyme immobilization. These biomaterials are well known for their peculiar surface reactivity promoting, when contacted with real or simulated body fluids, the formation of an hydroxy-carbonate apatite layer. The aim of the present contribution has been to immobilize, viaa covalent linkage, an enzyme on the glass surface through the formation of self-assembled monolayers (SAMs), in order to obtain a stable bio-conjugate useful as a material bio-implantable into the human body. The innovation of this study resides in the use of a new method of protein immobilization on the glass surface. Unlike other works, in which a preliminary silanization process has often been used, the introduction of gold nanoparticles (AuNPs) in the glass composition allowed us to exploit the easy SAMs formation process on the AuNPs dispersed in the bioactive glass matrix and, consequently, to immobilize an enzyme (soybean peroxidase, SBP, in the present case) on the SAMs. A thorough characterization of the materials, at different steps of the functionalization process, has been also reported, together with in vitroactivity tests of immobilized SBP, compared with merely adsorbed SBP, and cytotoxicity tests using human osteoblast (MG-63) cells. Overall, a new bio-conjugate material, able to maintain its activity over time and to decrease the oxidative stress when in contact with MG-63 cells, has been obtained. [ABSTRACT FROM AUTHOR]

Curcumin, an active ingredient in the traditional Ayurvedic herbal remedy [Curcuma longaL.], is nowadays also employed in western medicine for its pleiotropic activities, ranging from anticancer to its free radical scavenger ability. These features are related to curcumin's function as a metal chelator, especially being selective for hard Lewis acids, such as Ga3+which has interesting pharmacological activities. We report the synthesis and characterization of bioactive gel and mesoporous Ga-containing phospho-silicate glasses loaded with curcumin, in which, for the first time, the design of novel drug delivery systems takes advantage of coordination chemistry. In particular, it was found that: (i) there is a direct correlation between the external surface area and the amount of loaded curcumin; (ii) the presence of Ga3+species on the surface increases the quantity of drug molecules uploaded and slows down their release in the biological medium (SBF), hinting a coordination-like interaction between curcumin and the surface metal ions; (iii) curcumin molecules released in the SBF solution stabilize Ga3+ions, avoiding their precipitation. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work was to study the behaviour of zinc-doped phosphosilicate glasses based on Bioglass® 45S5. In vitro (in simulated body fluid), the reactivity was analysed by means of inductively coupled plasma spectrometry, environmental scanning electron microscopy–energy-dispersive spectroscopy (ESEM–EDS) and X-ray diffraction. In vivo (a rat implanted with glass), the reactivity and the tissue behaviour were analysed by conventional histology, histochemistry, microradiography and ESEM–EDS. The in vivo behaviour matches that in vitro perfectly; they show comparable glass degradation processes and rates, ruled by the amount of zinc in the glass. The reaction mechanism for the formation of a polymerized silica layer superimposed with a peripheral calcium phosphate layer is clearly substantiated by ESEM–EDS investigations. The crystallization of a biologically active hydroxyapatite (HA) layer is observed in both cases; the in vitro experiment shows the presence of HA after 4 days. [Copyright &y& Elsevier]

Tetrahalometallates of the type (Etmorphl1)21MX4 (M = Co, Ni or Zn and with X = Cl, Br or l; M = Cu with X = CI or Br) and mixed tetrahalocuprates, Etmorphll)[CUXY] (X = Cl; N' = 13r; m = 1,2,3) of the N-ethylmorpholinium cation were prepared and investigated by means of spectroscopic and magnetic measurements. While the cobalt(II), nickel(II) and zinc(II) complexes appear to be essentially, tetrahedral, the copper(II) complexes are discussed on the basis of a distorted ('flattened') tetrahedral symmetry. The electronic spectra of the complexes are assigned on this basis. The far i.r. spectra of the complexes show bands which are unambiguously assignable to the metal-halogen stretching modes. The effects of the counter cation on the geometry around the metal ion, compared with that of the morpholinium and piperidinium cations, are discussed in relation to the pK of the amine. [ABSTRACT FROM AUTHOR]