Herein, a polysaccharide-based fluorescent hydrogel with multi-responsiveness simply implemented by concurrent effects of ionic crosslinking/rehydration processes is presented. Specifically, the alginate and carboxymethyl chitosan are chosen to prepare the interpenetrating polymer matrix while a pair of metal cations has been selectively sequentially integrated to alter hydrogel mechanical and fluorescent properties. Experimental results indicate the hydrogels show tunable fluorescent emission in response to multiple cations and pH conditions, and display a reversible "ON/OFF" fluorescent response to M