A label-free resonance light scattering biosensor for nucleic acids using triple-helix molecular switch and G-quadruplex nanowires

In this work, a label-free resonance light scattering (RLS) biosensor based on triple-helix molecular switch (THMS) and G-quadruplex nanowires (G-wires) for HAV DNA and microRNA-31 detection was developed. The target can combine with the loop sequences of triple-helix, and opened the triple-helix structure as well as liberated the G-rich sequences which were self-assembled into G-wires in the presence of K+ and Mg2+ causing an obvious enhancement of RLS intensity. Meanwhile, the RLS signal at 304 nm was linear with the logarithm of target concentration in the range of 50 pM to 300 nM, and the limit of detection is as low as 7.1 pM for HAV DNA and microRNA-31, respectively. Moreover, qualitative analysis of HAV DNA and microRNA-31 was successfully achieved in human serum samples and cancer cell lysates. The biosensor holds a great promise for universal RLS sensing platform for sensitive detection of various targets just by changing the sequence of the THMS in the loop and be a biosensing platform for early clinical diagnosis and biomedical research.