Spherical and needle shaped magnetic nanoparticles for friction and magnetic stimulated transformation of microorganisms

Abstract

Spherical and needle shaped magnetic nanoparticles (MNPs) were synthesized by thermal decomposition, functionalized with 2-pyrrolidinone for the attachment of pUC19 plasmidic DNA and used in transformations assays of Escherichia coli JM109. Frictional and magnetic stimulation were employed for promoting the translocation of the nanoparticle-pUC19 complexes across the cell envelope. Transformants were obtained through frictional stimulation using needle shaped MNPs achieving a maximum transformation efficiency of 3.1 × 102 CFU/g pUC19. Magnetic stimulation was also performed using both types of nanoparticles under conventional magnetofection conditions on a magnetic bioreactor and did not induce transformation of E. coli JM109, possibly due to the field intensity at the region of the cells (100 mT) not being high enough to overcome the rigidity of the bacterial cell envelope. This work substantiates the need for the delivery agent to have a high aspect ratio in order to achieve transformation of prokaryotes. Moreover, it highlights the limitations of magnetic stimulation for translocation of MNPs across the microbial cell wall, as opposed to magnetofection of eukaryotic cells whereby the entry of genetic material can be readily accomplished using spherical MNPs through an endocytotic uptake mechanism.