Optical images and transmission electron micrograph (TEM) of the hydrogels of (A) D-10a (1.5 wt%, pH 4.2), (B) D-10b, (1.5 wt%, pH 4.2, 20U/ml PAP) (C) 12a (0.75 wt%, pH 4.2), and (D) 12b, (0.75 wt%, pH 4.2, 20U/ml PAP) (scale bar is 100 nm). The strain (E) and frequency (F) dependence of dynamic storage modulus G' and loss modulus G" of these hydrogels.