posted on 2020-03-18, 16:41authored byJinjie Li, Wenjing Wang, Hao Zhang, Zhicheng Lu, Wenxin Wu, Mingbo Shu, Heyou Han
A DNA
tweezer is a dynamic DNA nanomachine that can reversibly
switch its state between open and closed. Here, we employed a DNA
tweezer for the first time to dynamically control the distance between
plasmonic silver nanoparticles (Ag NPs) for a surface enhanced Raman
scattering (SERS) biosensing application. Two DNA and 4-nitrothiophenol
(4-NTP) modified Ag NPs were linked to the arms of the DNA tweezer
(DNA tweezer-Ag NPs probe) by complementary base pairing. Activation
of the Raman intensity was achieved by the state transformation of
the DNA tweezer-Ag NPs probe from open to closed. The distances between
two Ag NPs in open and closed state were 8.1 ± 2.7 nm and 3.2
± 0.8 nm, respectively. Furthermore, the two Ag NPs were spatially
separated in the open state with a low Raman signal, whereas in the
closed state, Raman intensity was enhanced because of the proximity
of two Ag NPs. The developed biosensing system exhibited a good linear
relationship when the concentration of aflatoxin B1 (AFB1) ranged from 1 ng/mL to 0.01 pg/mL, and the limit of detection
(LOD) was 5.07 fg/mL. In addition, spike recovery and certificated
real foodstuffs were used to examine the feasibility in a real situation.
This protocol provides a potential candidate for SERS detection and
can be used as a promising technology for biological and chemical
sensors.