Formation of PVA-TSPBA hydrogels

PVA (72 kDa; 98% hydrolyzed; 5 g) and deionized water (100 ml) were mixed together and stirred at 90°C to acquire a clear solution. TSPBA [5 weight % (wt %) in H₂O, 2 ml] and PVA (5 wt % in H₂O, 2 ml) were mixed together, and a hydrogel was formed instantly. This hydrogel was used for in vitro experiments. For the fabrication of GEM- and aPDL1-loaded gel, predetermined amount of GEM or aPDL1 was added to the PVA aqueous solution. For in vivo application, PVA and TSPBA aqueous solutions were loaded into dual syringes and injected directly toward tumors to form a gel in situ.