Biomedical Engineering Reference
In-Depth Information
FIGURE 12.14
Conceptual illustration of lizard templating method dense hybridization of alanine residues
in mesopore inside wall. (Reprinted from Zhang, Q., et al.,
J. Am. Chem. Soc.
, 126, 988, 2004. © American
Chemical Society. With permission.)
on protein adsorption onto mesoporous materials [101-106]. Figure 12.15A displays adsorption
isotherm of lysozyme onto three mesoporous silica materials (C
12
-MCM-41, C
16
-MCM-41, and
SBA-15) at pH 10.5 [107]. All the isotherms obeyed Langmuir-type behavior with adsorption
capacity of 13.4, 28.1, and 35.3 µmol g
-
1
for C
12
-MCM-41, C
16
-MCM-41, and SBA-15, respectively.
These values depend signifi cantly on structural parameters of pores: pore volume (C
12
-MCM-41,
0.70 cm
3
g
-
1
; C
16
-MCM-41, 0.86 cm
3
g
-
1
; SBA-15, 1.25 cm
3
g
-
1
) and pore diameter (C
12
-MCM-41,
3.54 nm; C
16
-MCM-41, 4.10 nm; SBA-15, 10.98 nm). The obtained results strikingly demonstrate
the importance of pore structures on the protein adsorption capability. Protein adsorption behaviors
can also be regulated by selection of ambient conditions. Especially, the effect of pH on the protein
adsorption is a subject worthy of detailed investigation, because charged states of both the proteins
and silicate depend signifi cantly on surrounding pH. Figure 12.15B shows adsorption isotherms
of lysozyme onto SBA-15 at various pH conditions [107]. The maximum adsorption capability
of lysozyme to SBA-15 was obtained at pH 10.5, which is very close to the isoelectric point of
lysozyme. Electric repulsion among the protein molecules near the isoelectric point of the protein is
signifi cantly suppressed, which may allow the proteins to pack densely in confi ned spaces. Protein
