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In-Depth Information
the basis of poly(quaternary ammonium) brushes grown by atom transfer radical
polymerization using an initiator grafted via a phosphonate group to the surface
of magnetite nanoparticles [
120
], recyclable antibacterial magnetic nanoparticles
were successfully synthesized. Given the convenience of separation of the nano-
particles from the bacterial culture tests using an external magnetic field, the
resultant nanoparticles presented high antibacterial activity against
E. coli
even
after eight exposure tests. When cyclodextrin groups were attached to magnetite
nanoparticles using a phosphonic linkage [
121
], the anchored cyclodextrin formed
inclusion complexes with diclofenac sodium salt, a non-steroidal anti-inflamma-
tory drug, demonstrating the potential for targeted drug delivery.
In the past few years, some implant semiconductor biomaterials functionalized
by phosphonic acids, such as In
2
O
3
and TiO
2
, have been investigated for biosensor
applications. In
2
O
3
nanowires were first grafted with 3-phosphonopropionic acid,
and then, the terminal carboxylic acid groups were activated by EDC-NHS aque-
ous solution [
122
], resulting in a nanowire surface reactive toward the amine groups
present on antibodies. After passivation with an amphipathic polymer (Tween 20),
the resultant sensors were found to be capable of performing rapid, label-free, elec-
trical detection of cancer biomarkers directly from human whole blood collected by
a finger prick. However, up to now, detection and treatment of organism diseases
are two consecutive and inseparable processes in clinical diagnostics and medicine,
but their academic studies are often isolated from each other. It is still challeng-
ing and significant to design a “diagnospy” carrier that combines the functions of
biomolecule quantitative detection and bioresponsive drug controlled release [
123
,
124
]. An interesting study pioneered by Li et al. [
125
] was to intentionally design a
smart system on the basis of hybrid phosphonate-TiO
2
mesoporous nanostructures
capped with fluorescein labeled oligonucleotides, which could realize simultane-
ous and highly efficient biomolecule sensing and controlled drug release (Fig.
5.23
).
The incorporation of phosphonate could shift the absorption edge of titania to the
visible light range and introduce positively charged amino groups to interact with
negatively charged fluorescein labeled oligonucleotides, resulting in the closing of
the mesopores and the fluorescence quenching of fluorescein at the same time. The
further addition of complementary single DNA strands or protein target led to the
displacement of the capped DNA due to hybridization or protein-aptamer reactions.
Correspondingly, the pores were opened, causing the release of entrapped drugs as
well as the restoration of dye fluorescence. Moreover, target concentration-depend-
ent fluorescent signal response could be used to monitor treatment effects in real
time, thus providing proof for determining drug dose or adjusting the treatment pro-
gram. The luminescence intensity linearly increased with the increasing of thrombin
concentration, until a plateau was reached. There was a good linearity relationship
between the (
F
/
F
0
- 1) value and thrombin concentration increasing from 5 to 175 nm
with the correlation coefficient of 0.996. The limit of detection (LOD) was 2.3 nm.
Interference experiments exhibited that human serum albumin, collagenase, lysozyme,
cytochrome c, hemoglobin, and trypsin presented much lower fluorescence intensity
restoration and drug release capacities than that of human thrombin due to the almost
unopened aptamer-capped mesopores. This mesoporous hybrid system provides a
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