Synthesis of Fe₃C@C from Pyrolysis of Fe₃O₄-Lignin Clusters and Its Application for Quick and Sensitive Detection of PrPSc through a Sandwich SPR Detection Assay.

The prion protein (PrPSc) has drawn widespread attention due to its pathological potential to cause prion diseases. Herein, we successfully synthesized Fe₃C@C by carbonizing Fe₃O₄-lignin clusters, which were prepared through a facile hydrogen bonding interaction between ≡Fe-OH and hydroxyl groups of lignin. Our in-depth investigation confirmed that the composites were Fe₃C@C core/shell particles. We constructed a novel sandwich surface plasmon resonance (SPR) detection assay for sensitive PrPSc detection, utilizing bare gold surface and aptamer-modified Fe₃C@C (Fe₃C@C-aptamer). Due to the highly specific affinity of Fe₃C@C-aptamer towards PrPSc, the sandwich type SPR sensor exhibited excellent analytical performance towards the discrimination and quantitation of PrPSc. A good linear relationship was obtained between the SPR responses and the logarithm of PrPSc concentrations over a range of 0.1⁻200 ng/mL. The detection sensitivity for PrPSc was improved by ~10 fold compared with the SPR direct detection format. The required detection time was only 20 min. The specificity of the present biosensor was also confirmed by PrPC and other reagents as controls. This proposed approach could also be used to isolate and detect other highly pathogenic biomolecules with similar structural characteristics by altering the corresponding aptamer in the Fe₃C@C conjugates.