Porous SiO2@Ni@C and Au nanocages as surface-enhanced Raman spectroscopy platform with use of DNA structure switching for sensitive detection of uracil DNA glycolase

In this work, SiO2@Ni@C nanosphere and Au nanocages (AuNCs) platform with use of target-induced DNA structure switching strategy was utilized to construct a surface-enhanced Raman spectroscopy (SERS) biosensor to analyze trace amounts of uracil DNA glycolase (UDG). In details, we utilized NH2-functioned SiO2@Ni@C nanosphere to immobilize abundant hairpin DNA (R) due to the large surface area and abundant adsorption sites. In the presence of the target UDG, they could specifically recognize and hydrolyze the uracil bases, generating apyrimidinic (AP) sites to induce DNA structure switching process, which could reconfigure hairpin DNA (R) to hairpin DNA (R'). Then the generated R' could capture complementary DNA S-1 bonded to the toluidine blue-Au nanocages (AuNCs-TB). With the increasing amount of UDG, more SiO2@Ni@C-NH2-R' would be obtained and coupled with TB-AuNCs-S1 to produce a stronger Raman signal. Based on this simple protocol, the SERS assay could achieve sensitive UDG detection in a concentration range from 5 x 10(-5) U mL(-1) to 1 U mL(-1) with a detection limit down to 3.2 x 10(-5) U mL(-1). Therefore, this SERS-based assay gives a new strategy for SERS detection which may have potential application for ultrasensitive detection of other protein biomarkers.