Different poly(2-susbstituted 2-oxazoline)s POxs polymers have been successfully implemented in biomedical applications due to their favorable structural capabilities under certain physical conditions coupled with their ability to produce several functional groups when reacted with their applicable monomers.
The facile introduction of amino groups at the distal chain ends of POxs has not been established despite their attractive features in initiating polymerization of N-carboxy anhydride NCA monomers. The few studies performed additionally takes a longer time for completion of this reaction.
A group of researchers from Japan developed a method of introducing a primary amino group at the distal chain end of POxs through the serial procedure of azido end-capping and Staudinger reactions. The research work is now published in peer-reviewed journal, European Polymer Journal.
They performed a cationic ring-opening polymerization of 2-ethyl-2-oxazoline EtOx, followed by the end-capping reaction with sodium azide, Results from the matrix assisted laser desorption/ionization time-of-flight mass spectroscopy MALDI-TOF-MS measurements confirmed successful polymerization of EtOx and the quantitative introduction of azido group at the distal chain end of the poly(2-ethyl-2-oxazoline) PEtOx. Furthermore, using MALDI-TOF-MS the authors showed successful progress of azide–amine conversion via Staudinger reaction using triphenylphosphine. Introduction of a primary amino group was highly efficient indicative of an amino-functionalization ratio of 96%, determined from gel permeation chromatography GPC with ion exchange column.
Another advantage of this method was the optimized reaction time for the conversion process to amino-functionalized PEtOx, achieving the shortening of time to 1h for the introduction of the azido group and only 3h for the conversion of the azido group to the primary amino group. It should be emphasized that this reaction can proceed in one-pot system, without changing the reactor.
They performed a ring-opening polymerization of L-Lysine (TFA)-NCA from the primary amino group of the synthesized PEtOx-NH2 to obtain PEtOx-b-PLys(TFA). Analysis on the obtained PEtOx-b-PLys(TFA) by size exclusion chromatography SEC and 1H NMR spectroscopy showed a successful block copolymerization of L-Lysine (TFA)-NCA. This end result proves that the amino-functionalized PEtOx can initiate polymerization of NCA monomers.
Apart from the versatility of the procedure in developing functional POx derivatives, the successfully derived block polymer PEtOx-b-PLys(TFA) might have various biomedical applications such as in drug delivery, hydrogel formulation and biological surface coatings.
Shigehito Osawa1, 2, Takehiko Ishii3, Hiroyasu Takemoto4, Kensuke Osada5, 6, , Kazunori Kataoka1, 2, 6 7. A Facile Amino-Functionalization of Poly(2-oxazoline)s’ Distal End Through Sequential Azido End-Capping and Staudinger Reactions, European Polymer Journal (2017) 88, 553-561.
1 Innovation Center of NanoMedicine (iCONM), Kawasaki Institute of Industrial Promotion, 3-25-14, Tonomachi, Kawasaki-ku, Kawasaki 210-0821, Japan
2 Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
3 Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
4 Laboratory for Chemistry and Life Science, Institute of Innovation Research, Tokyo Institute of Technology, R1-11, 4259 Nagatsuka, Midori-ku, Yokohama 226-8503, Japan
5 Japan Science and Technology Agency, PRESTO, 4-1-8 Motomachi, Kawaguchi, Saitama 332-0012, Japan
6 Division of Clinical Biotechnology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
7 Policy Alternatives Research Institute, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
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