Minicircles are small (~4kb) circular plasmid derivatives that have been freed from all prokaryotic vector parts.
For uses as transgene carriers for the genetic modification of mammalia cells, their preparation usually follows a two-step procedure:
- production of a ´parental plasmid´ (bacterial plasmid with eukaryotic inserts) in 'E. coli'
- induction of a site-specific recombinase at the end of this process but still in bacteria. These steps are followed by the
- excision of prokaryotic vector parts via two recombinase-target sequences at both ends of the insert
- recovery of the resulting minicircle (vehicle for the highly-efficient modification of the recipient cell) and the miniplasmid by capillary gel electrophoresis (CGE)
The purified minicircle can be transferred into the recipient cell by transfection or lipofection and into a differentiated tissue, for instance, by jet injection.
A novel addition to the field are self-replicating minicircles, which owe this property to the presence of a S/MAR-Element. Self-replicating minicircles hold great promise for the systematic modification of stem cells the more as the feasibility of such an approach has recently been demonstrated with their precursor form (Ref.)