DNAzyme-Based Core–Shell Hydrogel Microneedle Arrays for <i>In Situ</i> Live Bacterial Detection on Surfaces

Surface bacterial contamination poses significant risks to public health and food safety, yet conventional detection methods often require complex sample processing and laboratory equipment. Here, we report simple and sensitive DNAzyme-based core–shell hydrogel microneedle arrays (DzCS-HMA) for in situ live bacterial detection on surfaces. DzCS-HMA combines a lysozyme-loaded pullulan shell for on-site live bacterial lysis and a DNAzyme-embedded hydrogel core for bacterial recognition, enabling a straightforward three-step detection process (i.e., surface wetting, microneedle application, and fluorescence readout) within 60 min. DzCS-HMA achieves a detection limit of 71 CFU/mL for Escherichia coli . Validation studies demonstrated excellent performance, with 100% PPA (positive predictive agreement) and 87.5% NPA (negative predictive agreement) on food and environmental surfaces, along with applications in spoilage monitoring and multiplex detection of Burkholderia gladioli pathovar cocovenenans, E. coli, and Staphylococcus aureus . We envision that DzCS-HMA serves as a powerful tool for food safety, clinical diagnostics, and public health surveillance, requiring on-site detection.