Rolling-Circle Amplification Detection of Thrombin Using Surface-Enhanced Raman Spectroscopy with Core-Shell Nanoparticle Probe

Graphical Tagging along : An ultrasensitive surface-enhanced Raman spectroscopy (SERS) sensor based on rolling-circle amplification (RCA)-increased “hot-spot” is developed for the detection of thrombin, with core-shell nanoparticles (see figure; RBITC=Rhodamine B isothiocyanate, MB=magnetic beads) as Raman reporter. An ultrasensitive surface-enhanced Raman spectroscopy (SERS) sensor based on rolling-circle amplification (RCA)-increased “hot-spot” was developed for the detection of thrombin. The sensor contains a SERS gold nanoparticle@Raman label@SiO 2 core-shell nanoparticle probe in which the Raman reporter molecules are sandwiched between a gold nanoparticle core and a thin silica shell by a layer-by-layer method. Thrombin aptamer sequences were immobilized onto the magnetic beads (MBs) through hybridization with their complementary strand. In the presence of thrombin, the aptamer sequence was released; this allowed the remaining single-stranded DNA (ssDNA) to act as primer and initiate in situ RCA reaction to produce long ssDNAs. Then, a large number of SERS probes were attached on the long ssDNA templates, causing thousands of SERS probes to be involved in each biomolecular recognition event. This SERS method achieved the detection of thrombin in the range from 1.0×10 −12 to 1.0×10 −8 M and a detection limit of 4.2×10 −13 M , and showed good performance in real serum samples.