Intelligent food packaging (IFP) is among the key technologies for overcoming global challenges of food safety and food resource waste. Its core lies in monitoring the quality of food in real-time without damage. Sodium alginate (SA), a natural polysaccharide characterized by biodegradability and excellent biocompatibility, can form hydrogels with a 3D network structure, high water content, and functional modification capability, making it an ideal matrix for developing IFP sensing and indicator platforms. Based on the gel chemistry fundamentals of SA, this paper deeply analyzes the structure-activity relationship between sensing mechanism and material structure, and summarizes the existing modification strategies and functional integration paths. The paper also provides a detailed discussion on the application principles and latest advancements of SA-based hydrogels in colorimetric/visual sensing, gas sensing, time-temperature indicator (TTI), and controlled-release carriers for active substances. The current research results show that the detection limit of SA hydrogel beads loaded with anthocyanins for volatile amines can reach 15–25 ppm, and the color difference ΔE can reach 34.2 after 7 days of storage at 4 °C, which is strongly correlated with microbial indicators, total volatile basic nitrogen (TVB-N), pH, etc. The color difference value (ΔE) response of Co-Imd microcrystalline functionalized SA film to ammonia gas reached 23.7 within 60 min, and it had antibacterial activity. The activation energy of Immobilization of laccase on sodium alginate/soluble starch microcapsules to develop a TTI (27.32–61.13 kJ/mol) was highly matched with the activation energy of Agaricus bisporus. The hydrogel microspheres loaded with Cur@Se reduced the total oxidation value of the oils by 53%. The G/SA/nZnOs cryogel pad extended the shelf life of shrimp from 4 days to 6 days at 4 °C. In addition, this paper also discusses the challenges faced by SA-based hydrogels in large-scale production and long-term stability evaluation, and looks forward to future development trends such as integration with artificial intelligence (AI), Internet of Things (IoT), and multi-functional integration, in order to provide theoretical support for in-depth research and industrial application in this field.

A novel sensitive and selective electrochemiluminescence (ECL) sensor using nitrogen-doped graphyne as the platform was proposed for kanamycin (KAN) detection. First, nitrogen-doped graphyne nanomaterial (1N-GY) with high conductivity was synthesized using a high-energy ball milling method. Compared with ordinary graphyne, the addition of nitrogen atoms can improve the conductivity of the material and reduce the electronic migration energy barrier. Then it was used as a substrate material of the ECL sensor, not only increasing the conductivity of the biosensor but also improving the sensitivity of the ECL sensor by providing more immobilization space for the luminescent probe of Nafion-coated mesoporous silica adsorbed Ru(bpy)₃²⁺ (mSiO₂@Nafion@Ru(bpy)₃²⁺). On this basis, mSiO₂@Nafion@Ru(bpy)₃²⁺ functionalized DNA probes were used as luminescent and capture probes to specifically recognize different concentrations of KAN to produce ECL signals. Under optimal conditions, the proposed ECL sensor exhibited good linearity (10⁻¹²–10⁻⁶ M KAN) and a low detection limit of 1.08 pM. The prepared biosensor with good stability and selectivity successfully detected KAN in honey and milk samples, with spiked recovery rates ranging from 98% to 111.79%. This method not only expands the application of 1N-GY as a novel graphitic material in ECL biosensors but also provides an effective way to check antibiotics in dairy products.