Synthesis of novel quaternary silica hybrid bioactive microspheres (original) (raw)
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Journal of Biomedical Materials Research Part A, 2013
Bioceramic processing using rapid prototyping technique (RPT) results in a fragile device that requires thermal treatment to improve the mechanical properties. This investigation evaluates the effect of thermal treatment on the mechanical, porosity, and bioactivity properties as well as the cytotoxicity of a porous silica-calcium phosphate nanocomposite (SCPC) implant prepared by RPT. Porous SCPC implant was subject to 3-h treatment at 800 C, 850 C, or 900 C. The compressive strength (s) and modulus of elasticity (E) were doubled when the sintering temperature is raised from 850 to 900 C measuring (s ¼ 15.326 6 2.95 MPa and E ¼ 1095 6 164 MPa) after the later treatment. The significant increase in mechanical properties takes place with minimal changes in the surface area and the percentage of pores in the range 1-356 lm. The SCPC implant prepared at 900 C was loaded with rh-BMP-2 and grafted into a segmental defect in the rabbit ulna. Histology analyses showed highly vascularized bone formation inside the defect. Histopathological analyses of the liver, spleen, kidney, heart, and the lung of rabbits grafted with and without SCPC demonstrated healthy tissues with no signs of toxicity or morphology alterations. Results of the study suggest that it is possible to engineering the mechanical properties of the SCPC implant without compromising its bioactivity. The enhanced bone formation inside the porous SCPC facilitated cell-mediated graft resorption and prohibited any accumulation of the material in the body organs. V
Nanoclays mediate stem cell differentiation and mineralized ECM formation on biopolymer scaffolds
Journal of Biomedical Materials Research Part A, 2013
In this work, novel modified nanoclays were used to mineralize hydroxyapatite (HAP) mimicking biomineralization in bone. This in situ HAPclay was further incorporated into chitosan/polygalacturonic acid (Chi/PgA) scaffolds and films for bone tissue engineering. Differences in microstructure of the scaffolds were observed depending on the changes in processing of in situ HAPclay with ChiPgA biopolymer system. Response of human mesenchymal stem cells (hMSCs) on these scaffolds and films was studied using imaging and assays. SEM micrographs indicate that hMSCs were able to adhere to ChiPgA/in situ HAPclay scaffolds and phase contrast images indicated formation of mineralized nodules on ChiPgA/in situ HAPclay films in absence of osteogenic supplements used for differentiation of hMSCs. The formation of mineralized nodules by hMSCs was confirmed by positive staining of the nodules by Alizarin Red S dye. Viability and differentiation assays showed that ChiPgA/in situ HAPclay scaffolds were favorable for viability and differentiation of hMSCs. Unique two-stage cell seeding experiments were performed as a strategy to enhance tissue formation by hMSCs on ChiPgA/in situ HAPclay composite films. This work showed that biomaterials based on ChiPgA/in situ HAPclay composites can be used for bone tissue engineering applications and in situ nanoclay-HAP system mediates osteoinductive and osteoconductive response from hMSCs. V
Synthesis and in vitro bioactivity of sodium metasilicate-derived silicon-substituted hydroxyapatite
Synthesis and in vitro bioactivity of sodium metasilicate-derived silicon-substituted hydroxyapatite, 2024
Structural alteration of synthetic implants aims to achieve better bioactivity, higher cellular response, and regulated degradability, all of which are critical criteria for a biomaterial to serve as a graft in bone regeneration. The aim of this work was to synthesize silicon-substituted hydroxyapatite and test its bioactivity in simulated body fluid (SBF) by proving the use of sodium metasilicate (Na 2 SiO 3 .9H 2 O) as an affordable precursor of silica. Thus, the study evaluated the in vitro bone-bonding capacity of hydroxyapatite (Ca 10 (PO 4) 6 (OH) 2) (HA) substituted with silicate ion (Ca 10 (PO 4) 6−x (SiO 4) x (OH) 2− x ; Si x HA). The Si x HA with x = 0.4 was synthesized by utilizing a wet precipitation method with sodium metasilicate as a low-cost silica alternative for alkoxysilane precursors. The Si x HA was then examined for properties such as morphology, elemental composition, phase composition, and the nature of chemical bonds using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffractometry (XRD), and Fourier transformed infrared spectroscopy (FTIR), respectively. An in vitro bioactivity experiment was also carried out by incubating the Si x HA in simulated body fluid (SBF) at 36.5 • C for 7 and 14 days. The obtained results revealed the substitution of SiO 4 4− for some PO 4 3− groups in the hydroxyapatite structure. The Si x HA nucleated more apatite crystals on its surface and demonstrated some degradability during the periods of immersion in SBF. The characteristics of the Si x HA imply that it could be used as a graft in bone restoration applications, thus signifying that sodium metasilicate could serve as an economic silica source for silicon-substituted hydroxyapatite production.
Bioactive and biodegradable silica biomaterial for bone regeneration
Bone, 2014
Biosilica, a biocompatible, natural inorganic polymer that is formed by an enzymatic, silicatein-mediated reaction in siliceous sponges to build up their inorganic skeleton, has been shown to be morphogenetically active and to induce mineralization of human osteoblast-like cells (SaOS-2) in vitro. In the present study, we prepared beads (microspheres) by encapsulation of β-tricalcium phosphate [β-TCP], either alone (control) or supplemented with silica or silicatein, into the biodegradable copolymer poly(d,l-lactide-co-glycolide) [PLGA]. Under the conditions used, ≈5% β-TCP, ≈9% silica, and 0.32μg/mg of silicatein were entrapped into the PLGA microspheres (diameter≈800μm). Determination of the biocompatibility of the β-TCP microspheres, supplemented with silica or silicatein, revealed no toxicity in the MTT based cell viability assay using SaOS-2 cells. The adherence of SaOS-2 cells to the surface of silica-containing microspheres was higher than for microspheres, containing only β-...
Journal of Biomedical Materials Research Part B, 2013
This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (Sph Si), whiskers (Wh), silicon-doped whiskers (Wh Si), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and Sph Si groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon-doping have a potential to be part of the filler content of dental composites. V
Microspheres Based on Hydroxyapatite Nanoparticles Aggregates for Bone Regeneration
Key Engineering Materials, 2007
This study concerns the preparation and characterisation of microspheres associating alginate and two different types of hydroxyapatite (HA), which are intended to be used as drug delivery systems and bone regeneration matrices. Hydroxyapatite nanoparticles (HA-1 and HA-2) were prepared using a chemical precipitation synthesis based on H3PO4, Ca(OH)2 and a surfactant, SDS (sodium dodecylsulphate), as starting reagents. These two powders of nanoHA and alginate were used to prepare two different types of microspheres. Both powders and microspheres were characterised using FTIR, TEM, SEM, mercury porosimetry analysis and X-ray diffraction Results show that pure hydroxyapatite (HA) and mixtures of HA/β-TCP in the nanometre range were obtained from both HA syntheses. Microspheres with different characteristics were obtained from these two types of hydroxyapatite. Key Engineering Materials Vols. 330-332 (2007) pp. 243-246 online at http://www.scientific.net
Biomaterials, 2003
In the present work, a new methodology to produce bioactive coatings on the surface of starch-based biodegradable polymers or other polymeric biomaterials is proposed. A sodium silicate gel is employed as an alternative nucleating agent to the more typical bioactive glasses for inducing the formation of a calcium-phosphate (Ca-P) layer. The method has the advantage of being able to coat efficiently both compact materials and porous 3D architectures aimed at being used on tissue replacement applications and as tissue engineering scaffolds. By means of this treatment, it is possible to observe the formation of an apatite-like layer, only after 6 hours of simulated body fluid immersion. For the porous materials, this layer could also be observed inside the pores, clearly covering the cell walls. Furthermore, an increase of the surface hydrophilicity (higher amount of polar groups in the surface) might contribute to the formation of silanol groups that also act as apatite inductors. After 30 days of SBF immersion, the apatite-like films exhibit a partially amorphous nature and the Ca/P ratios became much closer to the value attributed to hydroxyapatite (1.67). The obtained results are very promising for the development of cancellous bone replacement materials and for pre-calcifying bone tissue engineering scaffolds. r
Bioceramics 18, 2006
Bioactive polymeric microspheres can be produced by pre-coating them with a calcium silicate solution and the subsequent soaking in a simulated body fluid (SBF). Such combination should allow for the development of bioactive microspheres for several applications in the medical field including tissue engineering. In this work, three types of polymeric microspheres with different sizes were used: (i) ethylene-vinyl alcohol co-polymer (20-30 µm), (ii) polyamide 12 (10-30 µm) and (iii) polyamide 12 (300 µm). These microspheres were soaked in a calcium silicate solution at 36.5ºC for different periods of time under several conditions. Afterwards, they were dried in air at 100ºC for 24 hrs. Then, the samples were soaked in SBF for 1, 3 and 7 days. Fourier transformed infrared spectroscopy, thin-film X-ray diffraction, and scanning electron microscopy showed that after the calcium silicate treatment and the subsequent soaking in SBF, the microspheres successfully formed a bonelike apatite layer on their surfaces in SBF within 7 days due to the formation of silanol (Si-OH) groups that are quite effective for apatite formation.
Journal of The Royal Society Interface, 2011
The efficient loading and sustained release of proteins from bioactive microspheres remain a significant challenge. In this study, we have developed bioactive microspheres which can be loaded with protein and then have a controlled rate of protein release into a surrounding medium. This was achieved by preparing a bioactive microsphere system with core-shell structure, combining a calcium silicate (CS) shell with an alginate (A) core by a one-step in situ method. The result was to improve the microspheres' protein adsorption and release, which yielded a highly bioactive material with potential uses in bone repair applications. The composition and the core-shell structure, as well as the formation mechanism of the obtained CS -A microspheres, were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectrometer dot and line-scanning analysis. The protein loading efficiency reached 75 per cent in CS -A microspheres with a core-shell structure by the in situ method. This is significantly higher than that of pure A or CS -A microspheres prepared by non-in situ method, which lack a core-shell structure. CS -A microspheres with a core-shell structure showed a significant decrease in the burst release of proteins, maintaining sustained release profile in phosphate-buffered saline (PBS) at both pH 7.4 and 4.3, compared with the controls. The protein release from CS -A microspheres is predominantly controlled by a Fickian diffusion mechanism. The CS -A microspheres with a core-shell structure were shown to have improved apatite-mineralization in simulated body fluids compared with the controls, most probably owing to the existence of bioactive CS shell on the surface of the microspheres. Our results indicate that the core-shell structure of CS -A microspheres play an important role in enhancing protein delivery and mineralization, which makes these composite materials promising candidates for application in bone tissue regeneration.