Ultrasensitive SERS detection of nucleic acids via simultaneous amplification of target-triggered enzyme-free recycling and multiple-reporter.

The development of ultrasensitive and specific methods for facile detection of trace nucleic acids is of great significance to human health and safety. In the present work, an ultrasensitive SERS-based strategy for detecting nucleic acids was proposed by integrating the SERS-active AgNRs array with double signal amplifications, i.e. the primary target-triggered enzyme-free amplification recycling and the secondary signal enhancement of multiple-reporter. By comparing two SERS sensing routes, i.e. solid interface recycling (Route A) and solution recycling (Route B), the superior solution recycling was determined first, and then the sensing strategy was optimized by investigating the immobilization time, surface blocking, and number of reporters utilized in the SERS sensing. The experimental results indicate that an ultrasensitive SERS strategy can be achieved via the primary amplification of target-triggered enzyme-free recycling and additional enhancement by the usage of multiple reporters. Under the optimal conditions, the SERS sensing showed good specificity and uniformity, and a linear calibration curve of DNAs in human serum solution, ranging from 1 μM to 1 fM, was obtained with LOD as low as 40.4 aM, and the following recovery rate measurements confirmed that the proposed SERS sensing had good repeatability and reliability, which shows great potential for facile detecting trace DNAs, especially disease-related nucleic acids in the liquid biopsy of early-stage cancer detection.