Aptamer Conformation-Cooperated Enzyme-Assisted Surface-Enhanced Raman Scattering Enabling Ultrasensitive Detection of Cell Surface Protein Biomarkers in Blood Samples

Developing novel strategies for sensitive and specific detection of protein biomarkers is a field of active research. Here, we report an ultrasensitive biosensor to detect protein tyrosine kinase-7 (PTK7), an important protein biomarker on the cell surface, by aptamer conformation cooperated enzyme-assisted surface-enhanced Raman scattering (SERS) (ACCESS) technology. Our approach features a synergistic combination of the conformational alteration of the anglerfish aptamer triggered by the recognition of the membrane protein (PTK7) and Exo III enzyme-assisted nucleic acid amplification. It transduces the specific binding events between the aptamer and PTK7 protein into dramatically improved SERS signals. Sensitive and specific detection of PTK7 protein has been demonstrated both in the solution and directly on the surface of live CCRF-CEM cells, with a limit of detection better than the commercial enzyme-linked immunosorbent assay method by nearly 5 orders of magnitude. As a flexible, ultrasensitive, and specific approach, ACCESS promises important applications in clinical diagnostics, where only a very limited amount of the biological sample is available.