Construction of selectively enhanced MOF-SERS sensor and highly sensitive detection of hCE1 in HepG2 cells

In this paper, a surface-enhanced Raman scattering (SERS) magnetic immunosensor for human carboxylesterase 1 (hCE1) assay was developed using a sandwich structure consisting of a magnetic support substrate, a SERS tag, and a target. The objective was to investigate the correlation between changes in hCE1 levels and liver injury. The utilization of Co-MOF-74@Au@methylene blue (MB) magnetic support substrate facilitated the expedient separation of biological samples while uniformly distributing the AuNPs, thereby enhancing the SERS intensity and improving the reproducibility. The introduction of Co-MOF-74 metal–organic frameworks (MOFs), endowed with its own selective SERS-enhancing properties, into the Co-MOF-74@Au@MB SERS tag further enhances the SERS sensing capability. The proposed SERS sensor exhibited good linearity over the concentration range of hCE1 from 10−2 to 102 μg·mL−1, with a correlation coefficient (R2) of 0.990 and a limit of detection (LOD) of 8.3 ng·mL−1. This demonstrates the potential of this strategy for the detection of trace proteins or enzymes in complex biological samples. In the meantime, the selective SERS enhancement mechanism of MOFs on Raman reporter molecules was preliminarily explored. This provides a new idea for the development of SERS substrates and SERS assays.