Preparation of Bacterial Magnetite Particles for DNA Carriers

We have investigated the application of bacterial magnetite particles as DNA carriers for microprojectile based gene transfer. The magnetic bacterium, Aquaspirillum sp. AMB-1, can grow aerobically to high cell densities, allowing high yields of bacterial magnetite particles to be sonicated. The optimum sonication conditions were determined and found to be dependent on culture age. Excessive sonication damaged the magnetosome membrane surrounding magnetite particles. This decreased dispersion resulted in a reduced surface area available for DNA adsorption. When compared with gold, tungsten and non membrane coated magnetite, membrane coated magnetite was a better material for DNA binding (5 μg DNA/mg magnetite). The greatest amount of DNA was bound following treatment of membrane coated magnetite with glutaraldehyde-triamine prior to incubation with DNA.