Figure 3.

Selection and validation of candidate miRNAs for targeted gene delivery: Depending on the target site (TSs), and nature of application, a few candidate miRNAs are chosen. Generally, miRNAs expressed at high levels in the target cells/tissues whereas at low levels in non-target sites are selected. Generally, the process of optimization of expression cassettes incorporating TSs of candidate miRNAs should include 3–6 TSs separated by 8-10 bps, in case of multiple miRNAs being used in the same cassette, spacing could be decreased. Choosing an appropriate in vitro or ex vivo models expressing candidate miRNAs at a level comparable to target site can bypass the need of in vivo models for preliminary studies. After a successful preliminary evaluation targeted cassettes may be tested in vivo for targeting efficacy, which is followed by the intended application of the targeted delivery system.