Liquid crystalline composite hydrogels with large pH-triggered anisotropic swelling for embolotherapy

Inspired by the anisotropic structure of biological tissues, anisotropic hydrogels have been developed us-ing various nanofillers, however, it remains a big challenge to synthesize hydrogels with large swelling anisotropy. Herein a single molecule filler, alpha-helical polypeptide, instead of nanoscale fillers, was used to synthesize anisotropic hydrogels. First nematic liquid crystal of poly(gamma-benzyl l-glutamate) (PBLG) was prepared by shearing and stabilized by embedding in a crosslinked polymer matrix. The resulting PBLG composite gels were then converted to poly(L-glutamic acid) (PLGA) composite gels by debenzylation. The rigid rod-like structure of alpha-helical PBLG chains makes them easy to be orientated. The pH-sensitivity of PLGA makes the resulting composite gels pH-sensitive without the need to couple with a stimuli-responsive hydrogel matrix. In response to pH change PLGA composite gels swell anisotropically with a much larger swelling degree in the radial direction than in the axial direction. The swelling anisotropy (3.43) is much higher than most anisotropic hydrogels, particularly the stimuli-responsive ones reported previously. The composite gel also exhibits anisotropic mechanical properties with a larger Young's mod-ulus in the axial direction than that in the radial direction. Preliminary test demonstrated that the com-posite gels have potential in embolotherapy thanks to its large pH-triggered anisotropic swelling.