Feasibility study for efficient delivery of microRNA to the brain using RVG-PEI nanocarrier

Objectives Development of delivery vehicle of microRNA into intracellular organism of cells based on cationic polymer such as PEI (polyethyleneimine) is crucial for the understanding the functional action and role of microRNA in cellular environment. We investigated the feasibility for microRNA delivery to the brain using brain specific RVG-synthesized PEI polymer by examining the delivery of RVG/PEI-coated EGFP reporter gene construct to the brain.

Methods Branched PEI (1.2K) polymer was synthesized with RVG peptide mediated by NHS-PEG-MAL linker. Neuro2a, mouse neuroblastoma was used to test PEI-based internalization into cells. Electrostatic attachment of RVG-PEI polymer with reporter expressing DNA vector was carried out on room temperature condition.

Results Optimal concentration between bPEI polymer and plasmid DNA vector (CMV-luciferase) was determined in two different cell lines, calculated as N:P ratio 10. 125I radioisotope-mixed bPEI polymer which was pre-conjugated with CMV-Gluc vector revealed approximately 2 fold higher radioactivity than 125I radioactivity itself within 3 hr. When PEI polymer was mixed with miR-9 oligomer and gaussia reporter vector containing miR-9 binding sequence, significant reduction of reporter signal was found in dose dependent manner. Specific targeting of the synthesized RVG-PEI was detected in RVG-positive neuro2a cells. The ex vivo validation of isolated several organ after intravenous injection of EGFP expression vector-mixed RVG-PEI polymer showed that higher fluorescence signal in the brain region was found than that in other organs.

Conclusions We successfully delivered the reporter expressing vector to the brain using RVG-synthesized PEI polymer. We expect it would be possible for the specific delivery of interest microRNA into the brain region using RVG-PEI polymer system