Biomedical Engineering Reference
In-Depth Information
TABLE 1.14
Fabrication Methods of Three-Dimensonal Porous Composite Scaffolds
Percentage
of Ceramic
(%)
Biocomposites
Porosity
(%)
Pore Size
(
μ
m)
Fabrication Technique
Ceramic
Polymer
References
Solvent casting/particle
leaching
HA
PLGA
60-75 (wt.)
81-91
800-1800
146
Bioglass
PLLA
20-50 (wt.)
77-80
∼
100 (macro)
∼
10 (micro)
150
Phosphate
glass
PLA-PDLLA
40 (wt.)
93-97
153
A/W
PDLLA
20-40 (wt.)
85.5-95.2
98-154
154
Thermally induced phase
separation/freeze-drying
β-TCP
Chitosan-
gelatin
10-70 (wt.)
322-355
144
HA
PLLA
50 (wt.)
85-95
100
×
300
145
Bioglass
PDLLA
5-29 (wt.)
94
∼
100 (macro)
10-50
(micro)
109-112,
152, 221
Microsphere/sintering
Amorphous
CaP
PLGA
28-75 (wt.)
75
>
100
142, 143
Bioglass
PLGA
75 (wt.)
43
89
149
Polymer foam/ceramic
coating
HA
Bioglass
PLGA
PDLLA
40-85 (vol.)
135, 136
109, 110,
222, 223
Ceramic foam/polymer
coating
HA foam
PDLLA
173,
221-223
two other methods: microsphere sintering and foam coating, which have been considered exten-
sively for the combination of ceramic and polymeric materials, as listed in Table 1.14 and shown
in Figure 1.9. This section will briefl y introduce the processing techniques for polymer-ceramic
composite scaffolds.
1.4.2.1 Solvent Casting
Solvent casting of biocomposite scaffolds involves the dissolution of the polymer in an organic solvent,
mixing it with ceramic granules, and casting the solution into a predefi ned 3-D mold. The solvent is
subsequently allowed to evaporate. The main advantage of this processing technique is the ease of
fabrication without the need of specialized equipment. The primary disadvantages of solvent cast-
ing are (1) the limitation in the shapes (typically fl at sheets and tubes are the only shapes that can
be formed), (2) the possible retention of toxic solvent within the polymer, and (3) the denaturation
of the proteins and other molecules incorporated into the polymer by the use of solvents. The use
of organic solvents to cast the polymer may decrease the activity of bioinductive molecules (e.g.,
protein). The detailed processing steps can be found in Ref. 65.
1.4.2.2
Solvent Casting or Particle Leaching and Microsphere Packing
Polymer-ceramic constructs can be fabricated by the solvent aggregation method. The polymer
microspheres are fi rst formed from traditional water oil/water emulsions. Solvent-aggregated
polymer-ceramic scaffolds can then be constructed by mixing solvent, salt or sugar particles,
ceramic granules, and prehardened microspheres [220]. A 3-D structure of controlled porosity
