Hydrogel patch doped with nanoenzyme for SERS detection of hydrogen peroxide in complex body fluids

Abnormally elevated levels of H₂O₂ in body fluids are strongly correlated with various diseases, particularly cancers. Consequently, there is a significant need to develop a simple and efficient method for direct detection of H₂O₂ in body fluids. This study presents an economical and feasible hydrogel patch doped with nanoenzyme, specifically gold nanoparticles assembled on the surface of magnetic nanoparticles (Au@Fe₃O₄ NPs), as a sensing platform for H₂O₂ in complex body fluids. The hydrogel surface-enhanced Raman spectroscopy (SERS) patch demonstrates ultra-high sensitivity for H₂O₂ in vitro with a detection limit of 10 nM, which is attributed to the excellent catalytic efficiency of Au@Fe₃O₄ NPs and the rich distribution of SERS "hot spots" on the nanoenzyme. Notably, the hydrogel SERS patch exhibits superior specificity, repeatability, and background-free detection of H₂O₂ in complex body fluids without pre-treatment. Importantly, the H₂O₂ levels within cancerous cells were observed to gradually increase during the cell death process, as measured using the hydrogel SERS patch developed for practical application. This SERS patch provides a promising, cost-effective strategy for H₂O₂ detection in complex samples such as body fluids, food, and environmental samples in future applications.