Biomedical Engineering Reference
In-Depth Information
Fig. 5
Illustration of approaches utilizing ATRP to enhance the release rate of water from ther-
moresponsive hydrogels, including
a
grafting strategy [
177
] and
b
disulfide-thiol chemistry to
generate nanopores [
178
]. Reprinted with permission from American Chemical Society
The development of several degradable hydrogels utilizing ATRP technique has
also been reported; they include preparation of acidic pH-responsive hydrogels
based on thermoresponsive poly(N-isopropylacrylamide-co-5,6-methylene-1,3-di-
oxepane) [
174
], redox-responsive hydrogels based on thiol/disulfide-functional-
ized star polymers [
175
] and radical-responsive gels based on a dynamic covalent
trithiocarbonate cross-linkers [
176
].
6 Nanogels by ATRP
Nanogels are a class of crosslinked hydrogels confined to nanometer-sized parti-
cles. In addition to displaying properties typical for hydrogels, nanogels have tun-
able size varying from submicron to tens of nanometers in diameter with large
surface area, suitable for multivalent bioconjugation, and an interior network for
incorporation of therapeutics. Because of these advantageous properties, they
hold great promise as effective polymer-based drug delivery systems [
179
,
180
].
Several methods have been proposed for the preparation of nanogels incorporat-
ing both chemical and physical crosslinkages. As described in a recent review,
typical methods include photolithographic, micro-molding, and microfluidic meth-
ods, as well as aqueous homogeneous gelation and heterogeneous polymerization
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