SERS and fluorescence detection of circulating tumor cells (CTCs) with specific capture-release mode based on multifunctional gold nanomaterials and dual-selective recognition

Herein, a dual-selective recognition and multi-enhanced surface-enhanced Raman scattering (SERS)-fluorescence dual mode detection platform is designed for the detection of circulating tumor cells (CTCs). The gold nanoflowers (AuNFs) substrate was synthesized and the CTCs were captured on the surface area of AuNFs/ITO substrate by aptamers modified. At the same time, the novel nanoprobe was designed, anti-EpCAM (AE) and trigger DNA were modified onto the surface of gold nanostars (AuNSs) through a PEG linker. The novel nanoprobe identified CTCs through the specific recognition reaction between AE and the cell epithelial adhesion molecule of the CTCs. The dual-recognition cellular mechanism of the aptamers and AE improves selectivity. Then, the complementary sequence (CS) hybridize with aptamers to release the captured CTCs into the culture medium. The number of CTCs released was detected by SERS and fluorescence. The limit of SERS detection was 5 cells/mL with a linear relationship from 5 to 200 cells/mL. The limit of fluorescence detection was 10 cells/mL with a linear relationship from 10 to 200 cells/mL. Thus, the developed CTCs detection platform demonstrates promising applications for clinical diagnosis. First, the uniform polystyrene (PS) monolayer formed by interfacial self-assembly method was implemented on Au/indium tin oxide (ITO) substrate. The area between the bare Au/ITO substrate and PS was occupied by PEG molecules. When the PS mono-layer film was remove, an invisible PEG template was obtained and used to electrochemically deposit AuNFs. Because of the large specific surface area of AuNFs, many DNA aptamers could be incorporated onto the AuNFs/ITO substrate to improve the cell capture efficiency. Simultaneously, nonspecific cell adhesion could be optimally controlled by the PEG molecules. Moreover, AE and the HCR were modified onto the AuNSs as the Raman signal probes. When the CTCs were captured by the aptamer-modified AuNFs substrates, the HCR/AE/PEG/AuNSs complexes were modified on the captured cell membrane surface through the AE recognition of EpCAM. The specificity of cell capture was greatly improved by the dual-recognition mechanism of the aptamer and AE. Rhodamine (ROX)-modified hairpin H1 and hairpin H2 were triggered by the trigger DNA, and a large number of Raman reporter molecules were incorporated into the HCR/AE/PEG/AuNSs complexes by HCR. The Raman signals could be enhanced by the sharp tips of the AuNSs. After that, the compl