Biomedical Engineering Reference
In-Depth Information
calcification sites in bone and is directly involved in the mineralization pro-
cess of bone growth (Carlisle 1970). Inspired by the bioactive compositions of
silicate-based bioglass and Si function in human body, a new family of bio-
active silicate ceramics with a wide-range composition has been developed
in the past 10 years. It was interesting to find that bioactive silicate ceramics
with specific compositions could significantly stimulate
in vitro
osteogenic
differentiation of several stem cells, and
in vivo
osteogenesis and angiogen-
esis. Bioactive silicate ceramics possess distinct osteostimulation properties.
The study of bioactive silicate ceramics for bone tissue regeneration has been
a hot area of research during the past several years. For this reason, it is of
great importance to review the recent advances for bioactive silicate ceramics
(not the silicate bioactive glasses). By summarizing the research progress in
the field, the categories, mechanical properties, interaction with bone-form-
ing cells, and
in vivo
osteogenesis and angiogenesis of silicate bioceramics
have been mainly highlighted.
2.2 Preparation and Characterization of Silicate Bioceramics
2.2.1 Preparation of Silicate Bioceramics with Different Compositions
A series of silicate bioceramics have been prepared for bone regeneration
and orthopedic coating application. As shown in Table 2.1, silicate bio-
ceramics mainly include binary oxides (CaO-SiO
2
, MgO-SiO
2
, SrO-SiO
2
,
ZnO-SiO
2
), ternary oxides (MgO-CaO-SiO
2
, ZnO-CaO-SiO
2
, SrO-CaO-SiO
2
,
TiO
2
-CaO-SiO
2
, ZrO
2
-CaO-SiO
2
, P
2
O
5
-CaO-SiO
2
, SrO-MgO-SiO
2
, SrO-ZnO-
SiO
2
, and Na
2
O-CaO-SiO
2
) and quaternary oxides (SrO-ZnO-CaO-SiO
2
).
Up to now, more than 20 silicate bioceramics with varied compositions
have been prepared in the past 10 years. Compared to conventional phos-
phate-based bioceramics, silicate bioceramics have more broad chemical
compositions, which may contribute to their adjustable physicochemical
properties, such as mechanical strength, bioactivity, and degradability (Wu
and Chang, forthcoming).
For the preparation of these silicate bioceramics, four main methods were
applied for the synthesis of silicate powder materials, including the sol-gel
method, chemical precipitation, hydrothermal method, and solid-reaction
method. For binary-oxide silicate bioceramics, all the aforementioned meth-
ods can be used, compared to the synthesis of other composition-complex
silicate powders, which often require more specific methods and more accu-
rate control of the reaction conditions. By using the hydrothermal method,
wollastonite (CaSiO
3
) nanowires with high aspect ratios more than 100 and
diameters of 50 to 100 nm were successfully prepared (Figure 2.1) (Li and
Chang 2004). For preparation of pure ternary-oxide and quaternary-oxide
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