Fe3O4 nanoparticles engineered for plasmid DNA delivery to Escherichia coli

Abstract

Heat shock treatment is the most popular method for transformation of Escherichia coli. We have used 19-nm Fe3O4 nanoparticles for improving heat shock protocol. PGEM-T (3,000 bp) and pCAMBIA (8,428 bp) were used as test plasmids for transformation of competent E. coli cells (strains DH5 alpha and Jm107) obtained from heat shock- and CaCl2-treated bacteria. A combination of heat shock and Fe3O4 nanoparticles led to a significant increase (6-10 fold) in number of transformed colonies in comparison with heat shock alone. The percent increase in transformation efficiency was higher for larger pCAMBIA plasmids compared to PGEM-T. The transformation efficiency decreased in the absence of CaCl2 and increased by addition of glycerol to the bacterial culture.