Effect of magnetic attraction on gene transfection of bacteria

We propose cells can be descended using magnetic attraction, which leads to shorter experimental time and higher efficiency. We used an electroporation chip with adjustable electromagnetic field as the experimental platform, and tested Escherichia coli and 6-nm magnetic beads combined with DNA plasmid. The magnetic beads were positively charged and easy to bind to the negatively charged cell membrane of E. coli. The magnetic beads and E. coli could be attracted quickly to the bottom because of the electromagnet and could reduce operational time and enhance transfection efficiency. After electroporating and culturing, we obtained the results for E. coli with drug resistance and calculated the number of colony as the transfection efficiency. The achieved transfection efficiency using magnetic beads was seven-fold higher than that without magnetic bead. The following optimum parameter values were determined: 1.4 × 10¹⁴ bead/ml for nano-magnetic bead concentration, 200 Gauss for magnetic flux density, and 40 s for magnetic attraction lasting time. The results will help develop transfection applications for low-descent-velocity cells.