Conductive ternary MXene-noble metal nanocluster-protein composite hydrogel-based robust, anti-biofouling and ultrasensitive electrochemiluminescence platform for biothiol sensing.

The three-dimensional (3D) hydrophilic network of hydrogels can both load signalling substances and allow the penetration of ions and small molecular targets, while preventing biomacromolecules from contaminating electrode surfaces, making them promising for anti-biofouling electrochemical sensing of complex biological samples. However, the fragile mechanical structure and poor electronic conductivity of hydrogels usually result in low sensitivity of the hydrogel-based biosensing systems, severely limiting their widespread application. Herein, a mechanically robust and conductive ternary MXene/Au-Ag alloy nanocluster (Au-Ag NC)-bovine serum albumin (BSA) composite hydrogel is constructed via a facile "one-pot" route, with ultrathin two-dimensional (2D) MXene nanosheets acting as the reinforced skeleton of the hydrogel network composed of entangled denatured BSA chains and Au-Ag NCs. The incorporation of MXene nanosheets within the hydrogel matrix provides a continuous electronic conductive network, allowing efficient electrochemical excitation of BSA-protected Au-Ag NCs to generate enhanced electrochemiluminescence (ECL) signals. The ternary composite hydrogel also exhibits excellent self-healing and enhanced swelling/deswelling properties, facilitating the construction of a robust hydrogel-based ECL platform for biothiol sensing, and ultrasensitive detection of a specific biothiol, glutathione (GSH), is achieved with a detection limit as low as 340 pM (S/N = 3). The platform can be directly applied for the analysis of complex biological samples, including distinguishing the GSH content in normal cell and cancer cell lysates and the detection of GSH in food samples, demonstrating its potential for future healthcare related applications, such as early diagnosis and food surveillance.