Biodegradable Thermogelling Poly(Organophosphazenes) and Their Potential Biomedical Applications - In-Situ Gelling Polymers: For Biomedical Applications - page 58

dual crosslinked hydrogels can be tuned to the desired extent and may find wide
application, where the gel property and degradation rate are needed to tightly regu-
lated [ 137 ].
5 Summary
Poly(organophosphazenes) with the ability of sol-gel transition at body tem-
perature in aqueous solution have been reviewed. The general molecular
structures of these poly(organophosphazenes) consist of a short hydrophilic
poly(ethyleneglycol) segment and amino acid esters, such as isoleucine ethyl ester
and leucine ethyl ester. The properties of the resultant hydrogels can be simply
controlled by adjusting the composition of cosubstituents or incorporating other
functional side groups. These biodegradable thermosensitive hydrogels with
controlled biodegradability, suitable mechanical strength, and biocompatibility
exhibit tremendous potential as drug delivery carriers or tissue engineering matri-
ces in bon in vitro and in vivo applications. While poly(organophosphazenes) lag
behind many more established polymers for drug delivery application in terms of
on-the-market applications, but most of other thermogelling copolymers are also
at developmental research stage. Therefore, poly(organophosphazenes) are still
competitive in this field, but a practical reality of this biomaterial require the close
cooperation of chemists, chemical engineers, and medical experts on both long-
range fundamental research and workable medical device investigation.
References
1. Hoffman, A.S.: Hydrogels for biomedical applications. Adv. Drug Deliv. Rev. 54 (1), 3-12
(2002). doi: 10.1016/s0169-409x(01)00239-3
2. Bromberg, L.E., Ron, E.S.: Temperature-responsive gels and thermogelling polymer
matrices for protein and peptide delivery. Adv. Drug Deliv. Rev. 31 (3), 197-221 (1998).
doi: 10.1016/s0169-409x(97)00121-x
3. Gil, E.S., Hudson, S.M.: Stimuli-reponsive polymers and their bioconjugates. Prog. Polym.
Sci. 29 (12), 1173-1222 (2004). doi : 10.1016/j.progpolymsci.2004.08.003
4. Jeong, B., Kim, S.W., Bae, Y.H.: Thermosensitive sol-gel reversible hydrogels. Adv. Drug
Deliv. Rev. 54 (1), 37-51 (2002). doi: 10.1016/s0169-409x(01)00242-3
5. Miyata, T., Uragami, T., Nakamae, K.: Biomolecule-sensitive hydrogels. Adv. Drug Deliv.
Rev. 54 (1), 79-98 (2002). doi: 10.1016/s0169-409x(01)00241-1
6. Schmaljohann, D.: Thermo- and pH-responsive polymers in drug delivery. Adv. Drug Deliv.
Rev. 58 (15), 1655-1670 (2006). doi : 10.1016/j.addr.2006.09.020
7. Kwon, I.K., Matsuda, T.: Photo-iniferter-based thermoresponsive block copolymers com-
posed of poly(ethylene glycol) and poly(N-isopropylacrylamide) and chondrocyte immobi-
lization. Biomaterials 27 (7), 986-995 (2006). doi: 10.1016/j.biomaterials.2005.07.038
8. Li, C.M., Buurma, N.J., Haq, I., Turner, C., Armes, S.P., Castelletto, V., Hamley, I.W.,
Lewis, A.L.: Synthesis and characterization of biocompatible, thermoresponsive ABC and
ABA triblock copolymer gelators. Langmuir 21 (24), 11026-11033 (2005). doi: 10.1021/
la0515672