Biomedical Engineering Reference
In-Depth Information
Appendix D
Simulated Body Fluids
Numerous sets of solutions are used for in vitro testing of biomaterials. They
simulate at least partially the composition of human body fluids: isotonic (same
osmotic pressure as the body fluid the tested materials are expected to be in contact
with), similar inorganic composition supplemented with some organic compounds
and buffered at an adequate pH. Commonly used solutions are Hanks' and Ringer
but in Table D.2 a recent versions are given. These solutions also serve to grow
hydroxyapatite on substrates. In Table D.1, a summary of the prominent reac-
tions involved in aqueous solution together with their equilibrium constants; the
K
sp
(sp: solubility product) of HA and CaCO
3
are, respectively, 117.0 and
8.6 [
341
,
474
]. For more reliable data on solubility products, see Sect.
10.7
.For
oral materials, a simulation solution of saliva is used: it contains compounds that
are not occurring in plasma or occur only at very low levels (Table D.3). Notice
that the pH range of saliva is below intrabody values. A last example are solu-
tions used for testing artificial heart valves (Table D.4). Minimum Essential Media
(MEM) are very distinct from the SBFs because they contain various combina-
tions of the amino acids: L-arginine, L-cystine, L-glutamine, L-histidine, L-leucine,
L-isoleucine, L-methionine, L-tyrosine, and L-valine, considered essential to allow
growth of cells for which the original Dulbecco version was intended to. Dulbecco's
Eagle Medium (MEM) has about 28 different commercialized compositions for
dedicated applications (ex.:Sigma Aldrich).
log
Tabl e D. 1
Main reactions of carbonate and phosphate;
log of the equilibrium constants are
added in [
]. Data extracted from [
340
,
341
,
474
]
H
2
CO
3
• H
C
C HCO
3
Œ6:31
(D.1)
HCO
3
•
H
C
C
CO
2
3
Œ10:25
(D.2)
Ca
2
C
C
HCO
3
•
CaHCO
3
Œ
1:16
(D.3)
Ca
2
C
C
CO
2
3
•
CaCO
3
Œ
3:38
(D.4)
H
C
C
H
2
PO
4
H
3
PO
4
•
Œ2:20
(D.5)
H
2
PO
4
•
H
C
C
HPO
2
4
Œ7:19
(D.6)
HPO
2
4
H
C
C
PO
3
4
•
Œ12:19
(D.7)
CaH
2
PO
4
Ca
2
C
C
2
H
2
PO
3
4
•
Œ
0:91
(D.8)
Ca
2
C
C
HPO
2
4
•
CaHPO
4
Œ
2:39
(D.9)
