Analytical Sciences

Fluorescence Imaging of siRNA Delivery by Peptide Nucleic Acid-based Probe

Takaya SATO,* Yusuke SATO,* Kenta IWAI,** Shusuke KUGE,** Norio TERAMAE,* and Seiichi NISHIZAWA*

*Department of Chemistry, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, Japan
**Department of Microbiology, Tohoku Pharmaceutical University, Aoba, Sendai 981-8558, Japan

We report on the use of a peptide nucleic acid (PNA)-based fluorescent probe for the analysis of siRNA delivery to living cells. The probe, Py-AA-TO, possesses thiazole orange (TO) and pyrene moieties in the C- and N-termini of PNA, and can function as a light-up probe capable of selective binding to 3′-overhanging nucleotides of target siRNAs. The affinity-labeling of the siRNAs with Py-AA-TO facilitates fluorescence imaging of cellular uptake of polymer-based carriers encapsulating the siRNAs (polyplexes) through endocytosis and subsequent sequestration into lysosome. In addition, flow cytometric measurements reveal that the monitoring of Py-AA-TO fluorescence inside the cells is successfully applicable to the analysis of the polyplex disassembly. These promising functions of Py-AA-TO are presented and discussed as a basis for the design of molecular probes for fluorescent imaging and quantitative analysis of the siRNA delivery process.

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