The background signal is a major factor that restricts the limit of detection of biosensors. Herein, we present a zero-background DNA-sensing approach that utilizes enzyme-guided gold nanoparticle (AuNP) enlargement. This sensing strategy is based on the finding that small nanoparticles are invisible under a darkfield optical microscope, thus completely eliminating the background signal. In the event of target binding, Ag deposition is triggered and enlarges the AuNP beyond its optical diffraction limit, thereby making the invisible AuNP visible. Because the plasmon scattering of Ag is stronger than that of Au, only a thin layer of Ag is required to greatly enhance the scattering intensity of the AuNPs. Our investigation revealed that a target DNA concentration as low as 5.0×10-21M can transform the darkfield image of the nanoparticle from completely dark (invisible) to a blue dot (visible).
Bibliographical noteFunding Information:
The authors gratefully acknowledge the financial support of the Ministry of Science, ICT & Future Planning of Korea ( NRF-2013M3C8A3078512 ). L. Guo acknowledges the financial support of NSFC ( 21277025 and 21205017 ) and the Foundation of Fujian Educational Committee ( JA12039 and JA13024 ). Appendix A
All Science Journal Classification (ASJC) codes
- Biomedical Engineering