Micrometric periodic assembly of magnetotactic bacteria and magnetic nanoparticles using audio tapes

M. GODOY, A. J. MORENO, G. A. JORGE, H. J. FERRARI, P. S. ANTONEL, L. MIETTA, M. RUIZ, R. M. NEGRI, M. J. PETTINARI, AND V. BEKERIS

JOURNAL OF APPLIED PHYSICS

AMER INST PHYSICS

Lugar: Nueva York; Año: 2012 p. 44905 - 44910

0021-8979

We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillummagneticum AMB-1, which synthesize chains of magnetic nanoparticles inside their bodies, and ofsuperparamagnetic Fe3O4 and ferromagnetic CoFe2O4 nanoparticles in aqueous suspensions usingperiodically magnetized audio tapes. The distribution of the stray magnetic field at the surface of thetapes was determined analytically and experimentally by magneto-optic imaging. Calculationsshowed that the magnetic field close to the tape surface was of the order of 100mT, and the magneticfield gradient was larger than 1 T mm1. Drops of aqueous solutions were deposited on the tapes,and bacteria and particles were trapped at locations where magnetic energy is minimized, asobserved using conventional optical microscopy. Suspensions of M. magneticum AMB-1 treatedwith formaldehyde and kanamycin were studied, and patterns of trapped dead bacteria indicated thatmagnetic forces dominate over self-propelling forces in these experiments, in accordance withcalculated values. The behavior of the different types of samples is discussed.