31-05-2012, 03:36 PM
Improvement of mechanical properties and biocompatibility of forsterite bioceramic addressed to bone tissue engineering materials
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Introduction
Bone tissue engineering proposes a suitable way to repair
and regenerate lost bones. Different materials have been
considered for use in bone tissue engineering (Chim et al.,
2006). The biocompatibility of bioceramics makes them the
most important group of biomaterials. Hydroxyapatite (HA) is
a significant success of bioceramics as a bone tissue repairing
material. HA is osteoconductive; a property that promotes
bone tissue growth (Sprio et al., 2009). Weak mechanical
properties such as low fracture toughness limit the clinical
applications of HA (Hench, 1998). Dense HA has lower fracture
toughness than cortical bone, and higher Youngs modulus
than cortical bone (Hench, 1998).
Preparation of forsterite ceramic
Forsterite nanopowder was prepared according to the
modified solgel process described in our previous report
(Kharaziha and Fathi, 2009). In brief, waterbased solutions
of the magnesium salts and colloidal silica were prepared.
Cell adhesion and growth assay
The method was carried out with nanostructured discs in
contact with osteoblastlike G292 cells in the RPMI1640
medium supplemented with 10% FCS. Prior to cell seeding,
nanostructured forsterite ceramic discs were cleaned in 75%
ethanol solution, sterilized for 20 min under ultraviolet light,
and autoclaved for 30 min at 120 C. After the discs were
placed in a 24well culture plate, 25 L of culture medium
containing 3104 cells were seeded onto the top of the discs.
In order the cells to attach, the plate was incubated for 1 h.
After, 1 mL of fresh culture medium was added to each well
and the cells were incubated for 17 days. Culture media were
refreshed every 2 days.
Cytotoxicity assay
The method was carried out with a dilution of powder extract
in contact with osteoblasts according to the International
Standard Organization (ISO/EN 109935, 1999). A dilution of
forsterite nanopowder extract in contact with osteoblastlike
G292 Cells was used in the RPMI1640 medium supplemented
with 10% FCS (Fetal Calf serum). Prior to testing, the forsterite
nanopowder were washed in 75% ethanol solution, sterilized
for 20 min under ultraviolet light, and autoclaved for 30 min
at 120 C.
Characterization of forsterite ceramic
the TEM micrograph of the forsterite nanopowder
produced via solgel and mechanical alloying methods,
respectively. As seen in Fig. 2(a, b), forsterite particles
produced via the solgel method show a spherical shape
with narrow particle size distribution in the 2545 nm
range (Kharaziha and Fathi, 2009). Fig. 2(c, d) show the
TEM micrograph of forsterite nanopowder produced by
mechanical alloying method (Fathi and Kharaziha, 2009).
Cell adhesion and growth assay
SEM images of the G292 cells cultured for 17 days on the
nanostructured forsterite bulks are presented in Fig. 8. After
1 day, cells attached onto the ceramic and minor filopodia
was observed (Fig. 8a). After 3 days, all of the cells adhered
tightly to the sample surface and spread well (Fig. 8b). After
7 days, the cells formed a flattened sheet and the surface of
all the samples were completely covered by the cells and the
extracellular matrix (Fig. 8c).