Biomimetic Preparation and Biomineralization of Bioceramics - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 136

phenomenon that involves complex interactions between multiple cellu-
lar and molecular events that regulate the healing process at the interface
(Frayssinet et al. 1993). Calcium phosphate bioceramics have such compo-
sitional resemblance to bone mineral that they induce a biological response
similar to the one generated during bone remodeling. Calcium phosphate
bioceramics are considered to be bioactive and osteoconductive. Bioactivity
would be due to epitaxial nucleation of carbonated apatite crystals at the
surface of ceramic grains. This layer of biological apatite might contain
endogenous proteins and might serve as a matrix for osteoprogenitors cell
attachment and growth (Davies 2003).
Biomimetic precipitation occurs on a variety of bioceramics such as bio-
glass (Leonor et al. 2002), bioactive fiber-reinforced composite implant (Ballo
et al. 2009), sol-gel processed silica, and titania (Uchida et al. 2001). The abil-
ity of a bioceramic material to induce a biomimetic precipitation has been
correlated to the degree of bioceramics dissolution and ions released at the
interface (Ducheyne et al. 1993). This dissolution process is highly dependent
on the nature of the bioceramic phosphate materials (composition, poros-
ity, surface area, and crystallinity) (LeGeros 1993; Christoffersen et al. 1997;
Barrere et al. 2003) and on the composition and supersaturation of the envi-
ronment in vitro (Hyakuna et al. 1990), or the implantation site (Daculsi et al.
1990; Barralet et al. 2000). The morphologies of the surface prepared by the
biomimetic method in a SBF are different from the normal coating derived
from the sol-gel and plasma-spray process. Instead of being dense and
smooth, they are rough and porous and thus have morphology of platelike
particles that may be favorable for the adhesion and proliferation of cells
(Brunette and Chehroudi 1999; Ito 1999).
Biomimetic calcium phosphate materials have previously been evaluated
both in vivo and controllable in vitro experiments. These materials promote
surface adhesion and proliferation, which contributes significantly to good
osteoblastic cell biocompatibility (Vaahtio et al. 2006; Zhang et al. 2009). It
has also been reported that biomimetic calcium phosphate coatings are more
soluble in physiological fluids and more resorbable by osteoclasts than high-
temperature plasma-sprayed hydroxyapatite coatings (Leeuwenburgh et al.
2001; Barrere et al. 2003; Wijenayaka et al. 2009). Thus, these materials might
be useful to enhance favorable bone remodeling, an important process in
bone healing involving osteoclastic resorption and subsequent bone forma-
tion by osteoblasts.
The osseointegration of titanium implants coated with biomimetic calcium
phosphate has been investigated in experimental animal models. These
studies have demonstrated a greater bone-implant contact for biomimetic
calcium phosphate coatings than for uncoated titanium implants (Barrere
et al. 2003; Habibovic et al. 2005). Compared with other surface treatments,
the biomimetic calcium phosphate coating appears to work as an accelerator
of bone ingrowth compared to a conventional titanium plasma spray coat-
ing in a preclinical model (Biemond et al. 2011). Interestingly, it has been