Signaling probe design for amplification-free detection of bacterial genes using DNA microarray.

DNA microarrays are useful to detect microorganisms for various purposes including clinical testing and food safety. However, conventional DNA microarrays need complicated operations such as amplification, fluorescence labeling, and washing steps. To address this issue, we previously developed the signaling probe-based DNA microarray system that can eliminate these steps, and demonstrated a direct detection of bacterial genes. Nonetheless, this system requires well-designed probe sets due to the fluorescence resonance energy transfer (FRET)-based mode of action. Up to date, the probe design was highly dependent on the trial-and-error processes. In this study, we propose a strategy to rationally design the sequences of signaling probes based on the thermodynamic analysis. This analysis aided to improve the probe performance approximately 2.8 times, without experiments, by suppressing the secondary structure formation of the probes. We successfully demonstrated the specific and amplification-free detection of 5S rRNA from total RNA extracted from Escherichia coli within 30 min.