Facilely Synthesized Rough Photothermal Gold Nanoparticles for Portable and Rapid Detection of Staphylococcus aureus

Foodborne infections and enterotoxin poisoning caused by S. aureus pose serious threats to food safety and public health. However, conventional detection methods are often time-consuming, technically complex, and typically require relatively large sample volumes. Herein, we report an aptamer-functionalized rough gold nanoparticle (RPG)-based photothermal platform that enables rapid and quantitative detection of S. aureus using a smartphone-compatible thermal imaging system in combination with a laser and an infrared thermal camera. RPGs were synthesized via a facile one-step method, and exhibited uniform particle size and a measured photothermal conversion efficiency of ~73.20%. After optimization of the aptamer concentration, laser irradiation time, and probe concentration, the proposed method exhibited a wide detection range from 1.0 × 102 to 1.0 × 107 cfu/mL, with an operational detection threshold of 100 CFU/mL under the optimized experimental conditions, a total assay time of less than 40 min, and a sample requirement of only 30 μL per assay, while maintaining acceptable reproducibility. Spike-and-recovery experiments in real samples, including orange juice, tap water, and milk, yielded recoveries of 91.8–105.5%, indicating suitable analytical performance in complex matrices. This work provides a rapid, portable, and low-sample-volume detection strategy for S. aureus, offering a practical approach for on-site food safety monitoring.