Crosslinking density-programmed poly(acrylamide)/sodium alginate-based emergency hydrogel with asymmetric 3D mass transfer network: spatially vector-targeted release of nitric-oxide for potentiating antibacterial efficacy and wound monitoring and sensing.

In pre-hospital emergency settings, polymicrobial colonization on traumatic wounds readily causes dangerous secondary bacterial infections, an intractable public health issue. Traditional photothermal antibacterial hydrogels suffer from random gas diffusion that lowers gas utilization, slows sterilization and promotes biofilm growth. To solve this problem, this research constructs asymmetric gradient porous PAM/SA photothermal hydrogel via in-situ immersion-driven secondary hierarchical ionic crosslinking, forming unique surface-core gradient pore topology to realize unidirectional targeted nitric oxide (NO) release relying on combined gradient tension, asymmetric pressure and Knudsen flow effects. Compared with ordinary materials, this hydrogel increases local wound NO concentration by 2.1 times in a simulated wound environment and lifts bactericidal rate 4.12-fold; the time to reach nearly full bacteriostasis drops sharply from 29.06 min to only 4 min. The material also owns outstanding mechanical traits with 105.5 kPa tensile strength and 417.9% breaking elongation alongside reliable tissue adhesion, excellent biocompatibility, wound healing capacity and real-time wound tension monitoring function. Benefiting from efficient directional NO delivery, this innovative hydrogel outperforms regular dressings in rapid anti-infection capacity and displays huge practical value for pre-hospital emergency management of open traumatic wounds.