Highly water-retaining conductive hydrogels based on multi-crosslinked networks for ultrasensitive sensing platform

Hydrogels are widely used in electrochemical sensors due to their unique properties, but their conductivity, influenced by water-content, is highly susceptible to external environment. Therefore, enhancing the water-retention of hydrogels while ensuring stable conductivity and analytical performance is crucial for broadening their application. In this work, a novel polyacrylamide/bacterial cellulose/sulfobetaine methacrylate/sodium alginate composite hydrogel (PBSS)-based multi-crosslinked network hydrogel was designed. The water retention of the PBSS hydrogel was improved by a factor of 1.5 compared to the unreinforced polyacrylamide (PAM) hydrogel (Water loss of hydrogel exposed for 12 h at 37 °C). With the water retention properties of itself, the PBSS hydrogel retained 86 % of its initial conductivity after 12 h of exposure at 60 °C, whereas the PAM hydrogel not only exhibited poor initial conductivity but also lost up to 47 % of its conductivity. PBSS hydrogels were designed as sensing platforms and CaCO₃ spheres were designed as immunoprobes. Ca²⁺ released by the probe rivals Ni²⁺ for the signaling substance on the substrate, enabling the quantification of the target analyte. The sensor exhibited excellent analytical performance and maintained stable performance after four days of storage at 37 °C, offering a promising approach to enhance hydrogel sensor stability for clinical applications.