Gold nanoparticle-based optical probes for target-responsive DNA structures

In this work, we report the use of unmodified gold nanoparticles (AuNPs) as an optical probe for the detection of target-responsive structural variations of DNA. By employing two DNA structures, i.e., a pH-responsive i-motif oligonucleotide and a mercury-specific oligonucleotide (MSO), we demonstrated that AuNPs could selectively distinguish target-free and target-bound oligonucleotides via the characteristic surface plasmon resonance-associated red-to-blue color change. Based on these observations, we developed a convenient mix-and-detect approach that could selectively detect environmentally toxic mercury ions.