4.4.2 Acid responsive assay of hydrogel
Swelling: A certain weight of hydrogel was immersed in excess pH 5, 6, or 7 phosphate saline buffer. The weight was measured at predetermined time intervals after dried the surface of hydrogel. The swelling ratio was calculated as: Swelling ratio= (Whydrogel- W0)/W0, where Whydrogelis the weight after swelling and W0 is the weight before swelling.
Release: The hydrogel samples of certain weight were put in the pH 6, 7, 8 sterilized phosphate-buffered saline (PBS) at 37 °C, which was shaken at 100 rpm/min. The samples were taken out in the time points to test the corresponding absorption of THB@ANVs. The degradation of hydrogel at different pH was also photographed.