FGAN@PB NP Nanozyme-Based Colorimetric–Photothermal Dual-Mode Immunosensor for Malachite Green Detection

In this study, a colorimetric–photothermal dual-mode immunosensor based on Fe(Ⅲ)–gallic acid composite Prussian blue nanozyme (FGAN@PB NPs) was developed for the highly sensitive detection of malachite green (MG) in aquatic products. This strategy addresses the stability limitations associated with conventional horseradish peroxidase (HRP). In the colorimetric mode, the immunosensor exhibited an IC50of 7.56 ng/mL with a linear detection range of 2.21–25.84 ng/mL. In the photothermal mode, the linear range was 0.262–25.6 ng/mL, with a detection limit (LOD) of 0.31 ng/mL. The results from the two detection modes were mutually corroborative. Moreover, the detection of the proposed immunosensor was strongly correlated with the LC-MS/MS, offering a promising approach for the rapid on-site screening of MG and improving its applicability in complex sample matrices.