Introduction - In-Situ Gelling Polymers: For Biomedical Applications - page 3

a peptide delivery system that retains the bioactivity of the peptides while dis-
charging them at a regulated rate. Here, biodegradable injectable in situ gelling
copolymers offer themselves as ideal peptide delivery agents.
1 Outlook and Perspectives
There are many types of hydrogels, ranging from chemically-, physically- and
supramolecularly-crosslinked hydrogels [ 10 - 22 ]. Of the different types of
crosslinking techniques, supramolecular chemistry is of particular interest for
the formation of in-situ gelling polymers. Although the chemistry for the synthe-
sis of the macrocycles has been discovered more than 100 years ago, the func-
tionalization and application of these macrocycles is still at its infancy. In recent
years, there has been intense research in this direction, including the establish-
ment of standard protocols for the modification of these macrocycles. This has
caught the interest of many researchers globally. The hydrophilic modifications
of these macrocycles have led these materials to be utilized in the formation of
supramolecular structures in the aqueous medium. These are inherently useful
for biomedical targeted applications, particularly for drug and protein deliv-
ery. Indeed, a variety of hierarchical structures, such as hydrogels, micelles
and vesicles, have emerged from the self-assembly of polymer chains brought
about by host-guest interactions. Some of the studies have even made into the
in vivo research settings, showing great promise for these materials. The devel-
opment of biocompatible supramolecular materials remains a big challenge as
most of these materials have not been assessed for long term toxicity effects. For
applications in the biomedical area, interactions of these supramolecular materi-
als with bodily fluids, ionic buffers and protein-containing solutions have to be
further evaluated. The wide use of these materials requires a larger quantity of
materials to be prepared. The scale up production of these materials remains a
major challenge as most of the work is currently done at the intricate labora-
tory scale. Supramolecular host-guest polymeric materials have great potential
to succeed at the biggest stage. Their ability to be manipulated by various stim-
uli, their ease of use by people of disparate technical backgrounds and potential
wide applicability in different biomedical areas as sensors, drug delivery agents,
cell supporting scaffolds and molecular switches make for exciting times for this
unique class of materials in the coming few years.
References
1. Whitesides, G.M., Grzybowski, B.: Self-assembly at all scales. Science 295 (5564), 2418-
2421 (2002). doi: 10.1126/science.1070821
2. Discher, D.E., Eisenberg, A.: Polymer vesicles. Science 297 (5583), 967-973 (2002).
doi: 10.1126/science.1074972