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Fig. 5.20
Time-dependent adsorption curves of Cyt C and BSA for the pristine HMPM (
a
)
and the HMPM material after a ball-milling treatment (
b
). Reprinted with permission from Ref.
[
108
]. Copyright 2014, Royal Society of Chemistry
Cyt C adsorption increased sharply at the initial contact time and slowed down
gradually until adsorption equilibrium was reached, demonstrating an adsorption
efficiency of 85.7 %. In contrast, the HMPM hybrid showed much lower adsorp-
tion capability for BSA (13.1 %). This might have resulted from the porous hier-
archy of HMPM. The mesostructured pores with small pore size were distributed
in the shell sections of manganese phosphonate microspheres, which would per-
mit the penetration of small molecules (Cyt C) through the adsorbent and block
BSA molecules with larger size. Thus, the analogous “semipermeable membrane”
effect would favor the separation of proteins with different sizes. Noticeably, the
microspherical morphology with porous hierarchy was destroyed by a ball-mill-
ing technique before adsorbing proteins, leading to a slight decrease of specific
surface area to 48 m
2
g
−
1
and a wide pore size distribution from 0 to 40 nm. As
seen in Fig.
5.20
b, both the protein molecules can be adsorbed and the separa-
tion goal cannot be achieved. Moreover, the resultant adsorption ability of Cyt C
is much lower than that of HMPM, which may be due to the existence of competi-
tive adsorption of the two proteins on the sorbent surface. Therefore, such a good
selectivity is mainly attributable to the peculiar porosity of the manganese phos-
phonate microspheres.
5.4.2 Drug Delivery
The storage capacity and release of drug in porous host materials are governed
by various factors such as pore size, shape, connectivity, and host affinity. As to
traditional porous materials including silica and polymeric matrixes, drug loading
capacity is usually not sufficiently high and encapsulated drug is difficult to be
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