Porphyrin-Decorated Sodium Alginate Hydrogel with Carbon Nanotubes for Confinement-Enhanced Electrochemiluminescence and Antibiotic Resistance Gene Detection

Gel-type electrochemiluminescence (ECL) active materials have attracted attention in sensing applications, where solid-state flexible and robust-response gels are required. Herein, we report a 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin-decorated sodium alginate hydrogel (TPPS-SA hydrogel) as a new-generation ECL cathode luminophore. TPPS-SA hydrogel was synthesized by a facile hydrogen bond interaction. Different from the ECL instability of raw water-soluble TPPS, the ECL emission of the TPPS-SA hydrogel with a space-confined effect gave constantly stable signals with peroxy-disulfate (S₂O₈^2-) as an efficient coreactant. Furthermore, to address the inherent high electrical impedance of the SA hydrogel, carboxyl-functionalized multiwalled carbon nanotubes (MWCNTs-COOH) served as the conductive scaffold to significantly enhance the ECL performance of the TPPS-SA hydrogel. Targeting insufficient detection sensitivity of antibiotic resistance genes (ARGs), we developed a highly selective and sensitive ECL sensing platform to detect ARGs using MWCNTs-COOH-assisted TPPS-SA hydrogels as signal probes coupled with DNA walking machines for target amplification. The proposed ECL sensor demonstrated a low limit of detection (0.42 pM) and excellent selectivity, providing a reliable paradigm for the application of porphyrin-based hydrogels in ECL sensing analysis.