ABSTRACT
OBJECTIVE: Therapeutic nucleic acids(siRNA etc.) have unique advantages such as high specificity, safety, and target diversity in the treatment of diseases. However, the naked siRNAs are easily degraded by nucleases(RNase), have short half-lives and low transfection efficiency, which limit their therapeutic application. To construct a mildly acidic microenvironment sensitive liposomal nanocarrier for the efficient localization and delivery of siRNA(small interfering RNA) at the tissue, cell and even organelle levels. METHODS: Blank liposomes were prepared by thin-film hydration using dioleoyl phosphatidylethanolamine(DOPE) and cholesteryl hemisuccinate(CHEMS). The siRNA was compressed with the amphiphilic material SA-R8 to obtain SA-R8/siRNA, which was then incubated with blank liposomes to prepare liposomes encapsulating siRNA. The terminally functionalized phospholipid(DSPE-PEG2000-MAL) was linked to the low pH insertion peptide(pHLIP). The product was then incubated with liposomes encapsulating siRNA to construct pHLIP-modified liposomes encapsulating siRNA. The particle size and distribution of liposomes were characterized by dynamic light scattering principle. The cellular uptake, intracellular transport and distribution were monitored by flow cytometry and confocal laser-scanning technique. RESULTS: The RESULTS showed that the average size of the prepared liposomes encapsulating siRNA was between 150 and 190 nm. The cell uptake of siRNA at pH 6.5 was significantly higher than that of pH 7.4. And the siRNA internalized was well localized in the cytoplasm. CONCLUSION: This carrier shows strong pH sensitivity and can significantly increase the cell uptake of siRNA in the tumor acidic environment.