Figure 4.
Sensing performance. a) Typical EC‐SERS spectra of 3WJ biosensor at +0.2 V before (blue) and after incubation with 100 × 10−12 m single‐mismatched (red) and 100 × 10−12 m complementary miR‐155 (black). b) EC‐SERS spectra obtained at concentrations of miR‐155 from 100 × 10−18 to 1 × 10−9 m. c) Linear correlation between the EC‐SERS signal intensity at 1625 cm−1 and the concentration of miR‐155. d) The corresponding statistical data recorded from the EC‐SERS signal at 1625 cm−1 for the sensors prepared by STV/AuNP–Bio/3WJb monoconjugate (left panel) and STV/AuNP–Bio/3WJb multiconjugate (right panel) after hybridization with 1 × 10−12 m target miR‐155; error bars and distribution curves obtained from ten different samples prepared under identical condition. e) EC‐SERS spectra obtained from multiconjugate biosensor at concentrations of miR‐155 from 100 × 10−18 to 1 × 10−9 m. f) The corresponding correlation curve for (e); error bars calculated based on three identical experiments. g) Representative EC‐SERS spectra of the 3WJ biosensor after being incubated with 100 × 10−12 m miR‐155 in a PBS buffer (black) and human serum (red). h) Statistical analysis and distribution curves of the EC‐SERS signal intensity at 1625 cm−1 of the 3WJ biosensor at +0.2 V before (Probe) and after hybridization with 100 × 10−15 m miR‐155 (Target), 100 × 10−15 m single‐base mismatched miR‐155 (Mismatched), and 1 × 10−12 m noncomplementary miRNA (Nontarget). Data were obtained from 50 random spots on the sensor chip for the PBS and serum samples, respectively. i) Variation in the EC‐SERS signal intensity at 1625 cm−1 upon introduction of different targets of 100 × 10−12 and 100 × 10−18 m perfectly matched miR‐155 and 1 × 10−9 m of nontarget miRNAs (miR‐21, miR‐141, and miR‐143); the inset illustrates typical SERS spectra from three corresponding targets. The signals were collected at 1 s exposure times using a 785 nm laser.