Crystal Chemistry and Antibacterial Properties of Cupriferous Hydroxyapatite.

Copper-doped hydroxyapatite (HA) of nominal composition Ca10(PO4)6[Cux(OH)2-2xOx] (0.0 ≤ x ≤ 0.8) was prepared by solid-state and wet chemical processing to explore the impact of the synthesis route and mode of crystal chemical incorporation of copper on the antibacterial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) strains. Apatites prepared by solid-state reaction showed unit cell volume dilation from 527.17 Å3 for copper-free HA to 533.31 Å3 for material of the putative composition Ca10(PO4)6[Cu0.8(OH)0.4O0.8] consistent with Cu+ insertion into the [001] hydroxyapatite channel. This was less pronounced (528.30 Å3 to 529.3 Å3) in the corresponding wet chemical synthesised products, suggesting less complete Cu tunnel incorporation and partial tenancy of Cu in place of calcium. X-ray absorption spectroscopy suggests fast quenching is necessary to prevent oxidation of Cu+ to Cu2+. Raman spectroscopy revealed an absorption band at 630 cm-1 characteristic of symmetric O-Cu+-O units tenanted in the apatite channel while solid-state 31P magic-angle-spinning nuclear magnetic resonance (MAS NMR) supported a vacancy-Cu+ substitution model within the apatite channel. The copper doping strategy increases antibacterial efficiency by 25% to 55% compared to undoped HA, with the finer particle sizes and greater specific surface areas of the wet chemical material demonstrating superior efficacy.

Effects of manganese incorporation on the morphology, structure and cytotoxicity of spherical bioactive glass nanoparticles.

Bioactive glass nanoparticles (BGNPs) are of great interest in tissue engineering as they possess high dissolution rate and capability of being internalized by cells, releasing their dissolution products with therapeutic benefits intracellularly. A modified Stöber process can be applied to obtain different BGNPs compositions containing therapeutic ions while maintaining controllable particle morphology, monodispersity and reduce agglomeration. Here, BGNPs containing Mn, an ion that has been shown to influence the osteoblast proliferation and bone mineralization, were evaluated. Particles with up to 142.3 ±â€¯10.8 nm and spherical morphology were obtained after MnO incorporation in the SiO2 - CaO system. X-ray photoelectron spectroscopy (XPS) indicated the presence of Mn2+ species and also a reduction in the number of bridging oxygen bonds due to the Ca and Mn. The Ca and Mn network modifier role on the silica network was also confirmed by magic-angle spinning 29Si solid-state nuclear magnetic resonance (MAS NMR). MTT evaluation showed no reduction in the mitochondrial metabolic activity of human mesenchymal stem cells exposed to the glass ionic products. Thus, evaluation showed that Mn could be incorporated into BGNPs by the modified Stöber method while maintaining their spherical morphology and features as a promising strategy for tissue regeneration.

Ring-Opening Polymerization of Cyclic Phosphonates: Access to Inorganic Polymers with a PV-O Main Chain.

We describe a new class of inorganic polymeric materials featuring a main chain consisting of PV-O bonds and aryl side groups, which was obtained with >70 repeat units by ring-opening polymerization of cyclic phosphonates. This monomer-polymer system was found to be dynamic in solution enabling selective depolymerization under dilute conditions, which can be tuned by varying the substituents. The polymers show high thermal stability to weight loss and can be easily fabricated into self-standing thin films. Structural characterizations of the cyclic 6- and 12-membered ring precursors are also described.

Antibacterial Copper-Doped Calcium Phosphate Glasses for Bone Tissue Regeneration.

Calcium phosphate glasses are a promising new generation of biomaterials that can simultaneously induce tissue regeneration and controlled release of therapeutic molecules. In this work, novel calcium phosphate glasses containing 0, 2, 4, and 6 mol % Cu2+ were synthesized via room temperature precipitation reaction in aqueous solution. The effect of Cu2+ addition on the glass properties and structure was investigated using thermal analysis, 31P solid-state MAS NMR, Raman spectroscopy, and X-ray diffraction. All glasses crystallize at temperature >500 °C and are mainly formed by Q1 groups. The release of P, Ca, and Cu in solution over time was monitored via inductively coupled plasma-optical emission spectroscopy. It was found that with increasing Cu content, the amount of P and Ca released decreases whereas the amount of Cu released increases. The effect of Cu2+ release on the antibacterial activity against S. aureus, a bacterial strain commonly found in postsurgery infections, has been investigated. The addition of copper has been shown to infer the glasses antibacterial properties. As expected, the antibacterial activity of the glasses increases with increasing Cu2+ content. Cytocompatibility was assessed by seeding human osteoblast-like osteosarcoma cells Saos-2 (HTB85) on the glass particles. A significant increase in cell number was observed in all the glasses investigated. The copper-doped calcium phosphate glasses have proven to be multifunctional, as they combine bone regenerative properties with antibacterial activity. Therefore, they have great potential as antibacterial bioresorbable materials for hard tissue regeneration.

Facile silane functionalization of graphene oxide.

The facile silane functionalization of graphene oxide (GO) was achieved yielding vinyltrimethoxysilane-reduced graphene oxide (VTMOS-rGO) nanospheres located in the inter-layer spacing between rGO sheets via an acid-base reaction using aqueous media. The successful grafting of the silane agent with pendant vinyl groups to rGO was confirmed by a combination of Fourier-transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The structure and speciation of the silane-graphene network (nanosphere) and, the presence of free vinyl groups was verified from solid-state magic angle spinning (MAS) and solution 13C and 29Si nuclear magnetic resonance (NMR) measurements. Evidence from Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and TEM-High-Angle Annular Dark-Field (TEM-HAADF) imaging showed that these silane networks aided the exfoliation of the rGO layers preventing agglomeration, the interlayer spacing increased by 10 Å. The thermal stability (TGA/DTA) of VTMOS-rGO was significantly improved relative to GO, displaying just one degradation process for the silane network some 300 °C higher than either VTMOS or GO alone. The reduction of GO to VTMOS-rGO induced sp2 hybridization and enhanced the electrical conductivity of GO by 105 S m-1.