Facile fabrication of liquid metal enabled conductive zwitterionic hydrogel for robust electrochemical sensing in complex serum

Any materials present in complex samples that bind the sensing interface non-specifically will greatly decrease the sensitivity and accuracy of the electrochemical sensor. Zwitterionic hydrogel have exhibited extraordinary antifouling ability, but they are limited by the electrical insulativity and weak interface, resulting in a double-edged strategy. Herein, we proposed a novel approach to resolve this challenge thanks to the liquid metal (LM). It was found that with only ultrasonic treatment, a core–shell nanostructure could be easily formed between LM matrix and sodium alginate (SA) polymer, accompanied with the generation of lots of free radical, which initiated the polymerization of zwitterionic monomer and further crosslinking with methylacrylated bovine serum albumin (MBSA). The whole process involved no synthesis of conductive nanomaterials or addition of initiators. Remarkably, the acquired superhydrophilic hydrogel exhibited a surprisingly favourable adhesion to the electrode surface, attributed to the carboxyl groups and related denser gel network resulting from the LM@SA nanoparticles. Finally, the prepared electrochemical immunosensor possessed excellent repeatability, storage stability, selectivity and meanwhile a wide linear range from 10 pg mL−1–100 ng mL−1, and an ultralow detection limit of 8.23 pg mL−1 for the detection of motilin even in 100 % human serum. Moreover, this was a successful attempt of LM-based nanocomposite hydrogel as an electrochemical sensing matrix, and we believe it could present further opportunities toward more satisfying sensing interface for biosensing and bioelectronics with more research in future.