Biomedical Engineering Reference
In-Depth Information
manner to all parts of the ceramic pieces, including naturally occurring pores and
channels present on axial (A and C, upper right angles) and longitudinal (B, F)
sections of uncoated (A, B, C) or coated (E, F, G) samples. At this magnifi cation
(1000x), where cell details become more conspicuous, fl attened and spread osteo-
blastlike cells were observed, which began to penetrate and colonise the inner
surface of the existing pores. Rounded cells involved in cellular division events
could be seen attached to the outer surface on the inside of the pores. After six
hours, cells spread out, displaying a fl at confi guration and a normal morphology.
Expansion of the cytoplasm was already visible and completely spread with, in
many cases, the bulge of the nucleus and surface microvilli very apparent, with
profusion of fi lopodia, as well as with larger cytoplasm extensions (lamellipodia).
Neighbouring cells maintained physical contact with one another through cyto-
plasm extensions. No evidence of any major deleterious or cytotoxic responses
was observed. The appearance of the MG-63 cells was the same as the one
observed on two reference materials, namely Ti6Al4V (D) and bulk bioactive
glass (H). Similar results were found for cell attachment and growth on biomor-
phic SiC ceramics coated with hydroxyapatite and silicon substituted apatite by
seeding Saos-2 cells on the material.
11.5.3 In Vivo Biocompatibility Studies
To explore the potentials of the biomorphic silicon carbide and bioactive coat-
ings for medical applications, in vivo biocompatibility studies were carried out
[Borrajo, 2007; González, 2008]. Caution must be increased when comparing
in vitro models to the multi-factorial and multi-cellular in vivo environment. Cells
invariably behave differently in vivo due to the presence of other cell types,
numerous cell signalling factors, the extracellular matrix and physiological differ-
ences in terms of mechanical stress, blood fl ow and 3D growth.
To assess the bioSiC as a biocompatible material, in vivo experiments by
implantation in the femur condyles of twelve rabbits were carried out. The new
bone growth on the periphery of bioSiC cylinders (3.9 mm diameter and 10 mm
length) and inside the pores was evaluated and compared with titanium pieces
implanted as controls. After 12 weeks of implantation, specimens for histological
examination using Optical Microscopy were taken. Samples were fi xed in formal-
dehyde solution, dehydrated by increasingly concentrated alcohols, infi ltrated
with and embedded in Technovit 7200 VLC, and processed by the cutting-
grinding method. Final 30
μ
m sections were stained with Levai-Laczko staining
technique.
Histological (Figure 11.27) examination showed the new bone formation
around the implants and inside the SiC porous matrix, without the appearance of
fi brous tissue on the bone-implant boundary and without any relevant infl amma-
tory reaction. There were no signifi cant differences between the bone density
formed around the SiC implants and Ti controls (Table 11.5).
Additional analysis of SEM micrographs (Figure 11.28) showed the presence
of trabecular bone in the central pores of the ceramics, reaching an average
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