Reactivation of γ-globin expression using a minicircle DNA system to treat β-thalassemia

•Plasmid-length negatively impacted on the electroporation efficiency of transgenes in HSPCs.•Bacterial backbone-free MC DNA plasmids had advantages over conventional plasmids on gene expression and electroporation efficiency.•γ-globin expression was reactivated in HSPCs by MC SaCas9-sgRNA plasmids.•MC DNA as gene therapy vectors had low insertion frequencies and genotoxicity.