Primary Designation and Characterization of a Molecular Beacon DNA Sensing Probe

In the current research, a fast, specific, and sensitive sensing probe was designed to detect Toxoplasma gondii DNA based on mechanism of fluorescence resonance energy transfer (FRET), and a magnetic-fluorescent CdTe/Fe₃O₄ quantum dots (mQDs) was utilized as energy donor, and the BHQ-2 was used as energy acceptor, respectively. The mQDs were prepared stepwisely using Fe₃O₄ as magnetic core and CdTe as luminescent shell at ambient temperature. The sensing probe was fabricated through labeling a stem-loop Toxoplasma gondii DNA oligonucleotide with mQDs at the 5´ end and BHQ-2 at 3´ end, respectively. The resulting sensing probe can be simply isolated and purified from the reactant with a common magnet in 5min. Properties of mQDs and sensing probe were investigated by transmission electron microscopy (TEM) and fluorescence spectrum (FS). The TEM data demonstrated that the size of mQDs was ~25 nm. The FS data indicated twice fluorescence recovery (FR) was observed when the complete complimentary target Toxoplasma gondii DNA was introduced. Moreover, the investigation of speicificity of current sensing probe showed that only weak FR was observed when the target DNA with one-mismatch base pair was added, this result revealed the sensing probe has high sensitivity and specificity. The current sensing probe will has great potential applications in the life science and related research.