The measurement of small magnetic signals from magnetic nanoparticles attached to the cell surface and surrounding living cells using a general-purpose SQUID magnetometer.
Magnetic nanoparticles have recently been widely applied in the bio-medical field. Responding to the demand for a simple and sensitive magnetic assay system for bio-liquid samples, we employed a general-purpose superconducting quantum interference device (SQUID) magnetometer. Strips of filter paper were used as a liquid-specimen sample holder possessing a very small magnetic background signal. An aqueous solution of superparamagnetic iron-oxide nanoparticles (Resovist) was dropped in a tiny blot-like spot in the middle of the filter paper and the magnetization was measured. Magnetic moments of a dilution series of Resovist solutions versus the number of particles provided a linear graph, revealing that the magnetic moment per Resovist particle was 8.25 x 10(-17) emu. 1 x 10(5) cancer cells were incubated with Resovist, and the number of Resovist particles attached to the cell surface and surrounding a living cell was calculated to be 1.02 +/- 0.14 x 10(7) particles/cell. Our system using a commercial SQUID magnetometer should be more than enough to determine the number of magnetic nanoparticles biologically reacting with living cells, contributing to the application of magneto nanomaterials to the life-science field.
Hashimoto
S
S
Department of Surgery, Advanced Biomedical Applications, Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
Oda
T
T
Yamada
K
K
Takagi
M
M
Enomoto
T
T
Ohkohchi
N
N
Takagi
T
T
Kanamori
T
T
Ikeda
H
H
Yanagihara
H
H
Kita
E
E
Tasaki
A
A
D002138:Calibration; D045744:Cell Line, Tumor; D002470:Cell Survival; D005374:Filtration; D006801:Humans; D008280:Magnetics; D053758:Nanoparticles; D010209:Paper; D012680:Sensitivity and Specificity