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. Author manuscript; available in PMC: 2019 Nov 1.
Published in final edited form as: Adv Ther (Weinh). 2018 Aug 13;1(7):1800058. doi: 10.1002/adtp.201800058

Figure 1.

Figure 1.

Evaluation of hydrogel chemical structure and microstructure. (a) 1H NMR spectrum of chitosan-PEG in D2O at 50°C utilized to determine the percentage of chitosan monomers modified with mPEG. The peak at 3.6 ppm (orange arrow) indicates the methylene group on mPEG. The peak at 3.4 ppm (grey arrow) is associated with a hydrogen present on all chitosan monomers. (b) SEM reveals the microstructure of lyophilized chitosan-PEG samples as synthesized. Scale bar represents 20 μm. (c) The photo shows translucent reconstituted chitosan-PEG in 1× PBS versus the blue hydrogel (CSPG gel) formed after addition and mixing of 0.5 mM genipin and incubation at 37°C overnight. (d) The crosslinked hydrogel was lyophilized and examined under SEM. Scale bar represents 20 μm. The image shows significant structural changes compared to that in (b).