Design of 3D Scaffolds for Hard Tissue Engineering: From Apatites to Silicon Mesoporous Materials

Advanced bioceramics for bone regeneration constitutes one of the pivotal interests in the multidisciplinary and far-sighted scientific trajectory of Prof. Vallet Regí. The different pathologies that affect osseous tissue substitution are considered to be one of the most important challenges from the health, social and economic point of view. 3D scaffolds based on bioceramics that mimic the composition, environment, microstructure and pore architecture of hard tissues is a consolidated response to such concerns. This review describes not only the different types of materials utilized: from apatite-type to silicon mesoporous materials, but also the fabrication techniques employed to design and adequate microstructure, a hierarchical porosity (from nano to macro scale), a cell-friendly surface; the inclusion of different type of biomolecules, drugs or cells within these scaffolds and the influence on their successful performance is thoughtfully reviewed.

Formation of giant iron oxide-copper-gold deposits by superimposed, episodic hydrothermal pulses

Iron oxide-copper-gold deposits are a globally important source of copper, gold and critical commodities. However, they possess a range of characteristics related to a variety of tectono-magmatic settings that make development of a general genetic model challenging. Here we investigate micro-textural and compositional variations in actinolite, to constrain the thermal evolution of the Candelaria iron oxide-copper-gold deposit in Chile. We identify at least two mineralization stages comprising an early 675–800 °C iron oxide-apatite type mineralization overprinted by a later copper-rich fluid at around 550–700 °C. We propose that these distinct stages were caused by episodic pulses of injection of magmatic-hydrothermal fluids from crystallizing magmas at depth. We suggest that the mineralisation stages we identify were the result of temperature gradients attributable to changes in the magmatic source, rather than variations in formation depth, and that actinolite chemistry can be used as a proxy for formation temperature in iron oxide-copper-gold systems.

The features of aliovalent substitution in anionic and cationic sublattices of apatite-related calcium phosphate

We investigated the features of complex substitution in anionic (PO43–CO32–) and cationic (Ca2+M+, M+ – Na, K) sublattices of apatite-type calcium phosphate during wet precipitation. The nanoparticles (10–35 nm) of apatite-related calcium phosphates were prepared from the aqueous solutions of the system М+–Ca2+–CO32––PO43––NO3– at determined molar ratios Ca2+/PO43–=1.67, CO32–/PO43–=1.0 and М+/PO43–=3.0 and 6.0 at the temperature of 250C. The positions of characteristic vibrations of carbonate groups in the FTIR spectra of the prepared samples in the regions of 1500–1400 cm–1 and 880–870 cm–1 confirmed the realization of partial substitution of РО43– by CО32– (B-type) in apatite-type structure. Results of elemental analysis indicated that the presence of potassium cations in the initial solution promoted the anionic substitution in calcium phosphate structure. The study of the activity of the synthesized carbonate-containing calcium phosphates in vitro revealed their tendency to gradual dissolution without a significant effect on the pH of the medium, which indicates the prospects of the synthesized samples in bone engineering.