Horseradish peroxidase-repeat assay based on tyramine signal amplification for highly sensitive H₂O₂ detection by...

A new and simple surface-enhanced Raman scattering (SERS) biosensor based on the tyramine signal amplification (TSA)-triggered formation of horseradish peroxidase (HRP) repeats on a gold sensing chip was designed for the highly sensitive detection of hydrogen peroxide (H₂O₂). Initially, gold wafers were functionalized with HRP as sensing chips. Then, the HRP immobilized on the chips triggers the TSA reaction to transform the tyramine-HRP conjugate into a tyramine-HRP repeat array. With the aid of the target H₂O₂, the HRP repeats catalyze the oxidation of o-phenylenediamine (OPD) and produce an enzyme catalytic product with a different chemical structure, thus altering the fingerprint of the SERS spectra from that of OPD. H₂O₂ can be quantitatively analyzed according to the change in SERS signal intensity. On the basis of the TSA strategy, the proposed method allows the detection of H₂O₂ with a limit of detection (LOD) of 0.8 × 10^-8 M. The as-prepared SERS sensor can achieve high-sensitivity H₂O₂ detection with a small amount of sample for each analysis. Therefore, this sensor exhibits significant potential for application in bioanalysis.