Papers by Author: Maria Vallet-Regí

Abstract: Dendrimers are a relatively new class of molecules that display a variety of potentially useful architecture-induced properties. In this chapter, we firstly present a general description of this interesting class of macromolecules, making special emphasis in their current biomedical applications. The combination of dendrimers with ceramics, traditionally used in the biomedical field, provides synergistic features and functions to the resulting hybrid materials. After the dendrimers introduction, an overall description of mesoporous silicas, iron oxide nanoparticles and carbon nanotubes bioceramics, is presented. Finally, recent research examples of dendrimer-functionalized ceramics, both from the synthetic and biomedical applicative points of view, are reviewed.

Abstract: In the recent years the driving force for technological change in many respects has shifted towards the design and process of materials that offer a set of responses to external stimuli or environmental conditions. These materials are called “smart materials”. Such responses are designed to fulfil the range of scenarios to which a material or structure may be exposed providing them with a particular functionality. These materials are not only useful because of their structural, chemical, physical or mechanical properties; they can also perform an action within a process. It has been described that smart structures exhibit one or more of the following features; they can act as sensors or actuators within a structural material or bonded in the surface; or they have controllable capabilities that permit to respond to the stimuli according to a prescribed function. These materials become intelligent when they have the ability to respond intelligently and autonomously to changing conditions. There are lots of possibilities within the term functional “smart materials” but in all of them, the term is used to describe systems which respond to a stimulus in a useful and predictable manner. Nowadays it is widely known the useful capability of, piezoelectric, electro-optic, magnetic, electro-mechanic materials, etc…that respond to stimuli such as, electric or magnetic fields, stress, temperature, moisture or pH. These multifunctional character and capability of biomaterials makes them suitable for a big number of applications in every order of human activity, from photochromic lenses for sunglasses to military and aerospace uses. They are already a big part of the market in the engineering industry.

Abstract: Sol–gel synthesis is used for the fabrication of new materials with technological applications including ceramics for implants manufacturing, usually termed bioceramics. Many bioactive and resorbable bioceramics, that is, calcium phosphates, glasses and glass–ceramics, have been improved by using the sol–gel synthesis. In addition, the soft thermal conditions of sol–gel methods made possible to synthesize more reactive materials than those synthesized by traditional methods. Moreover, new families of bioactive materials such as organic–inorganic hybrids and inorganic compounds with ordered mesostructure can be produced. In hybrid materials, the inorganic component ensures the bioactive response whereas the organic polymeric component allows modulating other properties of the resulting biomaterial such as mechanical properties, degradation, etc. On the other hand, the sol–gel processes also allow the synthesis of silica ordered mesoporous materials, which are bioactive and exhibit – as an added value – a possible application as matrices for the controlled release of biologically active molecules (drugs, peptides, hormones, etc.). Finally, by combining the bioactive glasses composition with synthesis strategies of mesoporous materials, template glasses with ordered mesoporosity can be obtained. In this chapter, the advances that sol–gel technology has brought to the silica-based bioactive bioceramics are presented.

Abstract: Towards the design of bioceramics with control over both macroscopic shape and mesoporosity, silica based mesoporous materials have been synthesized using evaporation-induced self-assembly method by two different routes: room temperature (RT) and aerosol-assisted synthesis (A-A). Two series varying surfactant/silica precursor ratio have been synthesized in order to check the mesopore ordering as a function of the structure directing agent amount in both preparation procedures. The A-A method leads to spherical microparticles, which exhibit mesopore ordering for a wider surfactant/silica range compared with room temperature method, which yield irregular shaped particles. Textural properties values show that for the same surfactant amount, aerosol-assisted method develops higher porosity values in the obtained silica microparticles.

Abstract: Much research effort has been committed to the development of bioceramics that promote bone tissue regeneration and this is still one of the greatest challenges for the scientific community. In this sense, silica-based ordered mesoporous materials constitute a new generation of bioceramics that combine the intrinsic properties of bioceramics, such as bioactive behavior, together with the capability to host and controlled release biologically active molecules that promote new bone formation, i.e. drug delivery systems. In this chapter, the recent advances aimed at tailoring ordered mesoporous materials for biomedical applications will be tackled and critically discussed.

Abstract: The research on ceramic scaffolds for bone tissue engineering is, nowadays, one of the newest and most attractive topics in the field of materials for biomedical applications. These scaffolds are aimed to provide supporting or even enhance the reparative capacity of body. Biphasic calcium phosphates (BCPs) and silicon doped BCP are very interesting candidates to be used as materials for scaffolds fabrication in bone tissue engineering. BCPs and silicon doped BCP consist of a mixture of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) or HA and α-tricalcium phosphate (α-TCP), respectively. For the regenerative purposes BCPs show better performance than HA because of the higher solubility of β-TCP compound, which facilitate the subsequent bone ingrowth in the implant. On the other, silicon doped BCP involve silicon that substituted into the apaptite crystal lattice for phosphorous with the subsequent charge imbalance. HA/α-TCP based bioceramics exhibits an important improvement of the bioactive behaviour with respect to non-substituted apatites. This work reviews the procedures to synthesise and fabricate scaffolds based on HA/β-TCP and silicon stabilised HA/α-TCP. Special attraction has been paid in the different synthesis methods and to the shaping of final scaffolds. By knowing the scaffold features at the crystallinity and macrostuctural level, the biocompatibility and clinical performance can be better understood, which will be also considered in this review.

Abstract: Two materials with potential application in bone tissue repair have been developed: 1) a non-biodegradable composite based in a new methacrylic-co-acrylic matrix; and 2) a biodegradable composite based in a chitosan (Ch) matrix. Both matrices were reinforced with glass-ceramic particles of composition (mol%) 70 SiO2 – 30 CaO. The in vitro bioactivity of composites was assessed by soaking in simulated body fluid (SBF) for periods of up to 7 days at 37º C. X-ray diffraction (XRD) and scanning electron microscopy coupled with X-ray energy dispersive spectroscopy (SEM-EDS) were used for deposit identification after different soaking periods. Calcium phosphate particulate deposits were detected after 3 days of immersion, followed by growth and maturation towards apatite.