Multiscale Cross-Linking via Polysaccharide-Assisted Robust Zwitterionic Hydrogel Interface Enabling Electrochemical Sensing in Complex Serum

The serious fouling layer from the nonspecific adsorption in complex media would greatly impair the analytical performance and even lead to the complete failure of the electrochemical sensor. Zwitterionic hydrogel has been demonstrated to possess excellent antifouling capability, while it suffers from a weak interface and spontaneous detachment from the electrode surface due to the double-edged hydrophilicity. Here, we found that the anionic polysaccharide coating on the liquid metal (LM) nanoparticle surface, in combination with the cationic chitosan penetrated in the hydrogel network, could synergistically enhance the interface adhesion while retaining antifouling ability, providing an ingenious solution to this issue. Additionally, only ultrasonic treatment was involved for the preparation of this LM-based zwitterionic hydrogel because ultrasonication could easily induce the formation of LM nanoparticles, the self-assembly of anionic polysaccharide on its surface, and simultaneous free radical polymerization of zwitterionic monomer. Finally, an electrochemical immunosensor was successfully fabricated based on this polysaccharide cross-linked LM-based zwitterionic hydrogel, and an ultralow detection limit of 7.17 pg·mL^-1, while a wide linear range from 10 pg·mL^-1 to 10 μg·mL^-1 was obtained in 100% human serum with negligible difference from that in PBS solution. We believe the polysaccharide-stabilized antifouling hydrogel interface presented in this work could inspire more innovative research for biosensing and bioelectronics in the future.