Reversible structural changes in DNA nanomachines have great potential in the field of bioanalysis. Here, we demonstrate an assembly strategy for quencher-free and tunable DNA tweezers based on 2-aminopurine (2-AP), avoiding the tedious fluorescence labelling step. The conformational state of the tweezers could be controlled by specific oligonucleotides (fuel or anti-fuel). Taking advantage of the local environmental sensitivity of 2-AP, the structural changes of the tweezers were easily tracked, and multiple cyclic switching of the tweezers between the open and closed states was achieved. In addition, the influence of oligonucleotide structure on the fluorescence properties of 2-AP was deeply explored. We figured out that the fluorescence of 2-AP was highly quenched by the base-stacking of natural bases in DNA oligonucleotides. Moreover, by comprehensively regulating the type of bases surrounding the inserted 2-AP site, a sensitive fluorescence response towards dynamic change can be obtained. This principle of quencher-free nanodevices based on 2-AP provides a convenient method for monitoring the structural changes of DNA nanomachines.
Xin-Xin Peng,Tongtong Guo,Hao Lu,Linlin Yue,You Li,Dan Jin,Guo-Jun Zhang,Fan Yang
MicroRNA (MiRNA)-based noninvasive diagnostics are hampered by the challenge in the quantification of circulating miRNAs using a general strategy. Here, we present a base-stacking effect-mediated ultrasensitive electrochemical miRNA sensor (BSee-miR) with a universal sandwich configuration. In the BSee-miR, a short DNA probe (10 nucleotides) self-assembled on a gold electrode surface could effectively capture the target miRNA synergizing with another sequence based on coaxial sandwich base-stacking, which rivals the fully complementary strength. Importantly, such a sandwich structure is flexible to incorporate signal amplification strategies (e.g., biotin–avidin) that are usually difficult to achieve in short sequence detection. Using this design, the BSee-miR achieves a broad dynamic range with a detection limit down to 7.5 fM. Furthermore, we found a high-curvature nanostructuring synergetic base-stacking effect that could improve the sensitivity of the BSee-miR by two orders of magnitude (79.3 aM). Our BSee-miR also has a single-base resolution to discriminate the highly homologous miRNAs. More importantly, this approach is universal and has been used to probe target miRNAs varying in sequences and secondary structures. Our ultrasensitive sensor could detect miRNA in cell lysates and human blood and distinguish cancer patients from normal individuals, promising a versatile tool to measure clinically relevant miRNAs for tumor diagnostics.
危险品化学品经营许可证（带存储）