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This contribution reviews the existing data on lawsonite stability and trace element geochemistry, and provides new data for metabasaltic and metasedimentary (quartzite) rocks from New Caledonia, Turkey and California. Lawsonite is a major host of REE, Sr, U, Th and Pb in basaltic compositions. Trace element-rich lawsonite also occurs in metasedimentary rocks, in which comparatively fewer phases compete for trace elements than in metabasaltic rocks. Trace element patterns in lawsonite are influenced by the coexistence or breakdown of allanite, titanite, apatite and garnet that compete for these elements in high-P metamorphic rocks. Lawsonite is restricted to cool geotherms and therefore is an indicator mineral for subduction-zone metamorphism. The lawsonite stability field shows a strong dependence on temperature and composition and it is largest in rocks with a high normative anorthite content and, in basaltic systems, carbon content. Along cold geotherms, lawsonite can transport water and trace elements to great depths, providing a source for these elements in the deep mantle. Along warmer geotherms, lawsonite disappears on a continuous reaction, gradually releasing water over a temperature interval of several tens of degrees. During lawsonite breakdown in complex systems, Th and LREE remain trapped in newly formed accessory allanite. However, owing to extreme LREE content, allanite has lower Pb/Ce and Sr/Nd than lawsonite, resulting in a relative enrichment of Sr and Pb compared with Ce and Nd in the fluids produced during lawsonite breakdown. Existing experimental data on the solidus of altered oceanic crust suggest that the lawsonite-breakdown reaction is within 50 °C of the solidus at sub-arc pressures of 3–4 GPa.

In Alpine Corsica (France), deeply subducted metabasalts are well preserved as lawsonite-bearing eclogite (Law-Ecl), occurrence of which is restricted to similar to 10 localities worldwide. The Corsican Law-Ecl, consisting of omphacite + lawsonite + garnet + phengite + titanite, occurs as both single undeformed metabasaltic pillows surrounded by lawsonite blueschist (Law-Bs), and carbonate-bearing eclogitic veins. Law-Bs are found as variably deformed metabasaltic pillows locally cross-cut by eclogitic veins and consist of glaucophane + actinolite + lawsonite + garnet + phengite + titanite. Field evidence and microstructures reveal that both Law-Ecl and Law-Bs are stable at the metamorphic peak in the lawsonite-eclogite stability field. Isochemical phase diagrams (pseudosections) calculated for representative Law-Ecl and Law-Bs samples indicate that both lithologies equilibrated at the same conditions of similar to 520 +/- 20 degrees C and 2.3 +/- 0.1 GPa. Therefore, the coexistence at the same peak metamorphic conditions of Law-Ecl and Law-Bs implies that different portions of deeply subducted oceanic crust may store significantly different H2O contents, depending on bulk-rock chemical composition. In addition, thermodynamic modelling of phase equilibria indicates that the occurring progressive dehydration reactions, which are significantly depending on bulk-rock chemical composition, strongly influence rock densification and eclogite formation in subducting slabs.

In the field of bone tissue engineering, monosized MCM-41 spheres have been incorporated inside a bioactive glass-ceramic macroporous scaffold belonging to the Si0 2 -CaO-K 2 0 (SCK) system so obtaining a multiscale hierarchical composite. The MCM-41-SCK system was prepared by dipping the glass-ceramic scaffold into the MCM-41 synthesis solution and was characterized by means of XRD, micro-XRD, N 2 sorption and scanning electron microscopy. The MCM-41 spheres inside the scaffold are highly uniform in diameter, as those synthesized in powder form. The adsorption capacity of the composite toward ibuprofen is three times higher than that of the MCM-41-free scaffold, because of the presence of the ordered mesoporous silica. Also the release behavior in SBF at 37 °C is strongly affected by the presence of MCM-41 inside the scaffold macropores.

Different cleaning and silanization methods have been applied to bioactive glasses with the aim of covalently bonding bone morphogenetic proteins (BMP-2) to the surface. Several glasses, with different bioactivity index, were cleaned with acidic, basic, or neutral aqueous media to investigate the role of pH in the formation of silanols on glass surfaces of different reactivity. The cleaned glasses were then functionalized using 3-aminopropyl-triethoxysilane (APTS). After the optimization of the silanization procedure, proteins of different complexity were immobilized on the functionalized glasses. To optimize the protein immobilization, a model protein (carnosine) was first used, and the procedure was then used to bind human BMP-2. The glass surfaces were characterized during each step of the treatment by water contact angles and X-ray photoelectron analyses. The APTS functionalization was then used to immobilize bone morphogenetic protein on the bioactive glasses. This result suggested that such a treatment could be successfully used as an efficient alternative to systemic administration of transforming growth factors for the development of local delivery vehicle implants.

Prevention and successful treatment of implant infection following bone surgery are critical challenges to avoid additional stress, disease, and any extra-surgery to patients. We investigated the feasibility of a new synthesis method to prepare a bioactive glass-ceramic scaffolds doped with silver, an antibacterial element. Scaffolds were fabricated by sponge replication method and silver was incorporated in the glass-based slurry that infiltrates the template using silver nitrate as a precursor. The silver-doped scaffolds mimic closely the cancellous bone in terms of 3-D trabecular architecture and mechanical properties, were highly bioactive as demonstrated by the in vitro formation of a surface hydroxyapatite layer upon soaking in simulated body fluids, and exhibited good antibacterial properties against Staphylococcus aureus, a common bacterial strain involved in postsurgical infections

The results of a surface analysis performed on a fluoroapatite-based glass ceramic (SAF) also coating a full-density alpha-alumina substrate (SAF-alumina coating) are presented. These two materials have also been evaluated after soaking in simulated body fluid to understand their ability to induce hydroxyapatite growth on them. Aiming to understand the fluoroapatite glass-ceramic interaction with some plasma proteins, in the second part of this study, fibronectin, albumin, immunoglobulin G, IgA, and complement factor C3c SAF binding have been evaluated; surface activity on complement activation has also been quantified. SAF-alumina coating provides good sites for the nucleation and growth of an apatite layer, equivalent to the mineral component of bone and binds preferentially plasma fibronectin, which is well known to enhance cell adhesion and spreading. Moreover, SAF-alumina coating reduces alumina complement activation directly or via reduced IgA binding. Alumina was shown to bind the same C3 fragments as Zymosan, used as complement activating control, and to induce increased levels of serum soluble iC3b and Bb. A mechanical resistant material with enhanced bioactivity, bone integration, and reduced inflammatory potential respect to alumina has been obtained.