Biomedical subjects

M Vallet-Regí

Publications and source records attributed to M Vallet-Regí.

At least 19 recordsLinked to original sources

PubMed2007

Bioactive glass as precursor of designed-architecture scaffolds for tissue engineering.

In this work, the conditions to obtain concentrated and fluid suspensions from a bioactive glass (55-SiO(2); 41-CaO; 4-P(2)O(5); mol %) were investigated. The influence of the heat treatment of the glass on the specific surface area, solubility, bioactivity, and finally on their dispersion characteristics was studied. Zeta potential and viscosity measurements were carried out, and based on the obtained results, the best dispersant was selected. The optimum concentration of dispersant, maximum content of solid and time of mixing were also investigated. Slurries containing 50 vol % could be obtained calcining the glass at 1100 degrees C and using Darvan 811 (sodium polyacrylate) as dispersant. Scaffolds with designed architecture were prepared from these suspensions combining the gelcasting method and the stereolithography technique. A polymeric negative (replica of the desired structure) was previously obtained by stereolithography. The slurry was cast into the molds and then polymerized (gelcasting method). The negative was eliminated by heat treatment. After sintering at 1300 degrees C, scaffolds with interconnected porosity and three-dimensional channels of 400-470 microm and macropores of 1.4 microm were obtained.

Ceramics↗

PubMed2007

Microstructure and macroscopic properties of bioactive CaO-SiO2-PDMS hybrids.

CaO-SiO2-PDMS (polydimethylsiloxane) hybrid materials were synthesized as crack-free monoliths presenting in vitro bioactivity, i.e. able to be coated with a calcium phosphate-rich layer after having been soaked in simulated body fluid (SBF). A wide physical-chemical characterization of these materials was carried out to relate their microscopic structure and macroscopic properties. The effect of PDMS and the amounts of water used for the tetraethoxysilane (TEOS) hydrolysis on the mechanical properties of hybrid materials was investigated by three-point bending tests. For a given amount of water, as PDMS content in hybrids increased, the elastic modulus decreased. Furthermore, keeping the PDMS content constant, when the amount of H2O decreased, the elastic modulus increased. Regarding in vitro bioactivity and mechanical properties, the hybrid material obtained with molar ratios H2O/TEOS = 2 and TEOS/PDMS = 3.5 proved to be the best candidate for either soft tissue substitution or metallic implant coating since the hybrid material would promote bond to bone formation, simultaneously dampening the mechanical charges.

Biocompatible Materials↗

PubMed2006

Glass-glass ceramic thermoseeds for hyperthermic treatment of bone tumors.

Implantable thermoseeds are synthesised from mixtures of a melt-derived glass with composition SiO(2) (40)-CaO(40)-Fe(2)O(3)(20) (mol%) and a sol-gel glass with composition SiO(2)(58)-P(2)O(5)(6)-CaO(36) (mol%). Structural, textural and magnetic properties of the samples are evaluated. In vitro bioactivity is assessed in order to determine the potential capability to bond to living bone. In spite of the low textural properties of the material, a bioactive behavior is observed as a result of the sol-gel glass content. Although the crystallization of the glass ceramic provides the magnetic phase, the presence of sol-gel glass modifies the magnetic properties, improving the heating power. For the first time, hyperthermia heating experiments as well as preliminary biocompatibility assays have been carried out for this kind of material. The ability to reach hyperthermic temperature range together with the bioactive behavior makes this biomaterial a very promising candidate for bone cancer treatment.

Adsorption↗

PubMed2006

Crystallochemistry, textural properties, and in vitro biocompatibility of different silicon-doped calcium phosphates.

Three silicon-doped calcium phosphates (Si-CaPs) were synthesized by heating precipitated silicon-doped apatite via different thermal treatments. Temperatures of 700 degrees C, 900 degrees C, and 1100 degrees C led to an apatite-glass biphasic material, nanocrystalline Si-doped apatite (SiHA), and Si-doped apatite-alpha tricalcium phosphate biphasic material, respectively. Structure, microstructure, textural properties, and chemical differences were determined for the three bioceramics. Biocompatibility tests were carried out by seeding osteblast-like cells onto the three substrates. Si-CaP treated at 700 degrees C and 900 degrees C led to Ca decrease in the culture media, partially impeding the cell proliferation over them. However, the proliferation capability is restored when additional culture medium is added. Finally, cytotoxicity results indicated that cell damage is much lower in osteblast-like cells seeded onto SiHA and SiHA-alpha tricalcium phosphate samples than in plastic culture control.

Biocompatible Materials↗

PubMed2006

Room temperature synthesis of agarose/sol-gel glass pieces with tailored interconnected porosity.

An original shaping technique has been applied to prepare porous bodies at room temperature. Agarose, a biodegradable polysaccharide, was added as binder of a sol-gel glass in powder form, yielding an easy to mold paste. Interconnected tailored porous bodies can be straightforwardly prepared by pouring the slurry into a polymeric scaffold, previously designed by stereolitography, which is subsequently eliminated by alkaline dissolution at room temperature. The so obtained pieces behave like a hydrogel with an enhanced consistency that makes them machinable and easy to manipulate. These materials generate an apatite-like layer when immersed in a simulated body fluid, indicating a potential in vivo bioactivity. The proposed method can be applied to different powdered materials to produce pieces, at room temperature, with various shapes and sizes and with tailored interconnected porosity.

Biocompatible Materials↗

PubMed2006

Vitreous SiO2-CaO coatings on Ti6Al4V alloys: reactivity in simulated body fluid versus osteoblast cell culture.

Vitreous coatings of the SiO(2)-CaO system have been prepared on Ti6Al4V substrates by the sol-gel method. The textural parameters (porosity and roughness) and thickness of the films obtained increase when the concentration of the precursor solutions is raised. In vitro studies of these coatings have been performed using two approaches: soaking in simulated body fluid, and by growing osteoblasts on these materials. The results of both studies show differences in terms of chemical reactivity. While in simulated body fluid the coatings were dissolved without forming a bioactive surface, when osteoblast-like cells grew on the coatings they were more stable. Furthermore, cell culture assays show biocompatible behavior of these coatings making them of potential interest for clinical applications. The effect of the textural parameters of the obtained coatings on the cell functions (attachment, spreading, proliferation and differentiation) has also been studied. The results show an increase in these cell parameters as the roughness and porosity of the coatings increase.

Alkaline Phosphatase↗

PubMed2006

Hydroxyapatite/SiO(2)-CaO-P(2)O(5) glass materials: in vitro bioactivity and biocompatibility.

Materials obtained by the heat treatment of mixtures of hydroxyapatite (HA) and a silicate-based glass of the system SiO(2)-CaO-P(2)O(5) have been investigated. The influence of the glass content on the porosity, microstructure and on the constituent phases of the final materials was studied. The influence of these factors on the in vitro bioactive behaviour of the obtained materials was also investigated. In addition, an in vitro biocompatibility assay with osteoblastic-like cells was carried out. The addition of the glass to HA induced different solid-state reactions that yield the transformation of HA into alpha- and beta-tricalcium phosphate as well as the formation of silicon-containing phases (silicocarnotite or pseudowollastonite). In these mixtures an enhancement in the porosity, pore size and a heterogeneous microstructure was observed, compared with the precursors. As the sol gel glass content increased, the previous effects were higher. The materials showed the formation of an apatite-like layer on their surface when soaked in simulated body fluid, being faster in the sample with a higher content of glass. The formation of the new layer began in preferential zones in both samples, depending on the different reactivity of the crystalline phases formed. A synergistic effect between HA and glass was observed, showing in the mixtures a faster bioactive behaviour than in HA and glass themselves. The obtained materials allow a good attachment, spread and proliferation of the osteoblastic-like cells and no cytotoxic effect was observed.

Biocompatible Materials↗

PubMed2006

A bioactive sol-gel glass implant for in vivo gentamicin release. Experimental model in Rabbit.

Biomaterial pieces with osteogenic properties, suitable for use in the treatment of bone defects, were synthesized. The materials, which avoid bone infections, are exclusively composed of gentamicin sulfate and bioactive SiO2-CaO-P2O5 sol-gel glass (synthesized previously), and were manufactured by means of uniaxial and isostatic pressure of the mixed components. After implanting the pieces into rabbit femur, we studied (1) antibiotic release, determining the concentration in proximal and distal bone, liver, kidney, and lung as a function of time, and (2) bone growth as a consequence of the glass reactivity in the biological environment. The results demonstrated that the implants are good carriers for local gentamicin release into the local osseous tissue, where they show excellent biocompatibility and bone integration. Moreover, these implants are able to promote bone growth during the resorption process.

Animals↗

PubMed2005

Bioactive and biocompatible pieces of HA/sol-gel glass mixtures obtained by the gel-casting method.

Hydroxyapatite (HA)/glass mixtures have shown a faster bioactive behaviour than HA itself. On the other hand, the gel-casting method is a simple and reproducible colloidal method to produce ceramic pieces with complex shapes. In this work, pieces of HA/glass mixtures were prepared by the gel-casting method. A study for obtaining concentrated slurries of these mixtures is reported; the bioactivity and biocompatibility of the obtained pieces have been studied also. The influence of pH, dispersant concentration, the content and milling of glass, and the way to prepare the suspensions were investigated. The lowest viscosity and better rheological properties were achieved with the lowest glass content, when the glass was added after the dispersion of the HA powder and when the glass was not milled after calcination. Fluid suspensions with a high solid content (50 vol.%) could be prepared and well-shaped pieces were obtained from these slurries. These pieces showed in vitro bioactive behavior in simulated body fluid; additionally, the proliferation and spreading assays with osteoblastic cells (HOS) showed that the pieces are biocompatible. The results obtained indicate that the gel-casting of HA/glass mixtures produces bioactive and biocompatible pieces with the required shapes. Therefore, these materials could be good candidates for clinical applications and scaffolds for tissue engineering.

Biocompatible Materials↗

PubMed2005

The influence of the phosphorus content on the bioactivity of sol-gel glass ceramics.

The aim of this work was to study the influence of the phosphorus on the crystallization and bioactivity of glass-ceramics obtained from sol-gel glasses. For this purpose two sol-gel glasses with a similar composition but one of them containing P2O5 (70% SiO2; 30% CaO and 70% SiO2; 26% CaO; 4% P2O5, mol%) were prepared. Pieces of these glasses were treated at temperatures ranging between 700 degrees C and 1400 degrees C for 3 h. The obtained materials were characterized by XRD, FTIR, SEM-EDS and the biaxial flexural strength was determined in samples heated at 1100 degrees C. In addition, an in vitro bioactivity study in simulated body fluid (SBF) was carried out. The results showed that phosphorus plays an important role in the crystallization of the glasses: it induced the crystallization of calcium phosphate phases, the stabilization of the wollastonite phase at high temperature as well as the crystallization of SiO2 phases at low temperatures. Moreover, the presence of phosphorus produced a heterogeneous distribution of defects in the pieces and, therefore, the flexural strength of samples containing this element decreased. Finally, glass-ceramics obtained from glasses containing phosphorus showed the fastest formation rate of the apatite layer when soaked in SBF.

Body Fluids↗

PubMed2004

Mesoporous SBA-15 HPLC evaluation for controlled gentamicin drug delivery.

Mesoporous silica SBA-15 was prepared to evaluate its application as gentamicin drug delivery system. Two procedures were used to evaluate the delivery: calcined powder and disk conformed. The samples were charged with gentamicin sulphate and the experiments were carried out in vitro. No significant difference between powder and disk was observed in the tests. The release profiles exhibited a pronounced initial burst release effect of 60%, followed by a very slow release pattern. A new HPLC method was employed for calculated gentamicin amount in the delivery test. This method requires a small amount of sample, very advisable in these kinds of assays.

Chromatography, High Pressure Liquid↗

PubMed2004

Calcium sulphate-based cements containing cephalexin.

Cephalexin containing gypsum and apatite/gypsum cements have been synthesised. The presence of cephalexin into the cements does not alter neither the physico-chemical behaviour of the cements nor produce structural changes on them. These cements behave as drug delivery systems when soaked in simulated body fluid. The release of the drug is different depending on the composition. For gypsum cements, the cephalexin is quickly released, helped by a dissolution process of the matrix, whereas the drug release is more controlled by the hydroxyapatite presence in hydroxyapatite/gypsum samples. Apatite containing cements do not only show a different drug release process, also the paste viscosity is lower and a faster formation "in vitro" of an apatite-type layer on their surface is observed.

Anti-Bacterial Agents↗

PubMed2004

In vitro biocompatibility assessment of poly(epsilon-caprolactone) films using L929 mouse fibroblasts.

Biodegradable and biocompatible materials are the basis for tissue engineering. As an initial step for developing vascular grafts, the in vitro biocompatibility of poly(epsilon-caprolactone) (PCL), recently suggested for several clinical applications, was evaluated in this study using L929 mouse fibroblasts. Different cellular aspects were analyzed in order to know the cell viability during cell culture on PCL films: adhesion, proliferation, morphology, LDH release and mitochondrial function. Since topography and other surface characteristics of materials play an essential part in cell adhesion, PCL membranes with either smooth or rough surface were prepared, characterized and used to carry out cell cultures. During short culture times, PCL produced a significant stimulation of mitochondrial activity evaluated by reduction of the MTT reagent. The results provide evidences of good adhesion, growth, viability, morphology and mitochondrial activity of cells on PCL films. Therefore, it can be concluded that PCL is a suitable and biocompatible material as a scaffold for vascular graft development.

Animals↗

PubMed2003

Localized corrosion of 316L stainless steel with SiO2-CaO films obtained by means of sol-gel treatment.

Sol-gel films on austenitic stainless steel (AISI 316L) polished wafer were prepared from sono-sols obtained from tetraethylorthosilane and hydrated calcium nitrate. However, pitting was observed in different places on the stainless steel surfaces. The corrosion resistance was evaluated by the polarization resistance in simulated body fluid environment at 37 degrees C. The critical current density, the passive current density, the corrosion potential, and the critical pitting potential were studied. The austenitic stainless steel 316L treated presents important electrochemical corrosion and consequently its application as endosseous implants is not possible.

Calcium Compounds↗

PubMed2003

Bioactive glasses as accelerators of apatite bioactivity.

Synthetic carbonatehydroxyapatite is the ceramic closest to the mineral component of human bone and seems, therefore, the optimum material to use in osseous implants. However, in vitro assays performed to determine its bioactivity have shown no positive results after 2 months of assay. With the aim of improving this bioactivity, a new biphasic material was synthesized composed mainly of synthetic carbonatehydroxyapatite and only 5% of a sol-gel bioactive glass. In vitro assays were assessed to determine the bioactive behavior of this new material and revealed that the addition of a minimal amount of bioactive glass is enough to induce bioactivity on synthetic carbonatehydroxyapatites.

Apatites↗

PubMed2003

In vitro bioactivity of silicon-substituted hydroxyapatites.

Silicon-containing hydroxyapatites were synthesized by the controlled crystallization method. Chemical analysis, N(2) adsorption, Hg porosimetry, X-ray diffraction, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used to characterize the hydroxyapatite and to monitor the development of a calcium phosphate layer onto the surface of the substrate immersed in a simulated body fluid, that is, in vitro bioactivity tests. The influence of the silicon content and the nature of the starting calcium and phosphorus sources on the in vitro bioactivity of the resulting materials were studied. A sample of silicocarnotite, whose structure is related to that of hydroxyapatite and contains isolated SiO(4) (4-) anions that isomorphically substitute some PO(4) (3-) anions, was prepared and used as reference material for XPS studies. An increase of the unit cell parameters with the Si content was observed, which indicated that SiO(4) (4-) units are present in lattice positions, replacing some PO(4) (3-) groups. By using XPS it was possible to assess the presence of monomeric SiO(4) (4-) units in the surface of apatite samples containing 0.8 wt % of silicon, regardless the nature of the starting raw materials, either Ca(NO(3))(2)/(NH(4))(2)HPO(4)/Si(OCOCH(3))(4) or Ca(OH)(2)/H(3)PO(4)/Si(OCOCH(3))(4). However, an increase of the silicon content up to 1.6 wt % leads to the polymerization of the silicate species at the surface. This technique shows silicon enrichment at the surface of the three samples. The in vitro bioactivity assays showed that the formation of an apatite-like layer onto the surface of silicon-containing substrates is strongly enhanced as compared with pure silicon-free hydroxyapatite. The samples containing monomeric silicate species showed higher in vitro bioactivity than that of silicon-rich sample containing polymeric silicate species. The use of calcium and phosphate salts as precursors lead to materials with higher bioactivity.

Calcium↗

PubMed2003

A new quantitative method to evaluate the in vitro bioactivity of melt and sol-gel-derived silicate glasses.

Two melt-derived glasses (45S5 and 60S) and four sol-gel glasses (58S, 68S, 77S, and 91S) have been synthesized. The activation energy for the silicon release was determined, and a very close correlation was observed between this value and published results of the bioactive behavior of the glasses. This relationship can be explained in terms of the influence of chemical composition, textural properties, and structural density on the silanol group formation and silicon dissolution. These measurements provide a quantitative method to evaluate the in vitro bioactivity of SiO(2)-based glasses. Preliminary studies suggest an activation energy gap (Ea) of 0.35-0.5 eV as a boundary between bioactive and nonbioactive glasses.

Biocompatible Materials↗

PubMed2003

In vivo bone response to porous calcium phosphate cement.

We conducted an in vivo experiment to evaluate the resorption rate of a calcium phosphate cement (CPC) with macropores larger than 100 microm, using the CPC called Biocement D (Merck Biomaterial, Darmstadt, Germany), which after setting only shows pores smaller than 1 microm. The gas bubble method used during the setting process created macroporosity. Preset nonporous and porous cement implants were inserted into the trabecular bone of the tibial metaphysis of goats. The size of the preset implants was 6 mm and the diameter of the drill hole was 6.3 mm, leaving a gap of 0.3 mm between implant surface and drill wall. After 2 and 10 weeks, the animals were euthanized and cement implants with surrounding bone were retrieved for histologic evaluation. Light microscopy at 2 weeks revealed that the nonporous implants were surrounded by connective tissue. On the cement surface, we observed a monolayer of multinucleated cells. Ten weeks after implantation, the nonporous implants were still surrounded by connective tissue. However, a thin layer of bone now covered the implant surface. No sign of cement resorption was observed. In contrast, the porous cement evoked a completely different bone response. At 2 weeks, bone formation had already occurred inside the implant porosity. Bone formation even appeared to occur as a result of osteoinduction. Also, at their outer surface, the porous implants were completely surrounded by bone. At 2 weeks, about 31% of the initial cement was resorbed. After 10 weeks, 81% of the initial phosphate cement was resorbed and new bone was deposited. On the basis of these observations, we conclude that the creation of macropores can significantly improve the resorption rate of CPC. This increased degradation is associated with almost complete bone replacement.

Animals↗