Magnetic particle detection (MPD) for in-vitro dosimetry

In-vitro tests intended for evaluating the potential health effects of magnetic nanoparticles generally require an accurate measure of cell dose to promote the consistent use and interpretation of biological response. Here, a simple low-cost inductive sensor is developed for quickly determining the total mass of magnetic nanoparticles that is bound to the plasma membrane and internalized by cultured cells. Sensor operation exploits an oscillating magnetic field (f0=250 kHz) together with the nonlinear response of particle magnetization to generate a harmonic signal (f3=750 kHz) that varies linearly with particulate mass (R2>0.999) and is sufficiently sensitive for detecting ∼100 ng of carboxyl-coated iron-oxide nanoparticles in under a second. When exploited for measuring receptor-mediated nanoparticle uptake in RAW 264.7 macrophages, results show that the achieved dosimetric performance is comparable with relatively expensive analytical techniques that are much more time-consuming and labor-intensive to perform. The described sensing is therefore potentially better suited for low-cost in-vitro assays that require fast and quantitative magnetic particle detection.

► A simple sensor is described for measuring the mass of magnetic nanoparticles.
► Calibration shows high linearity and sensitivity for inexpensive bioassays.
► Practical use is demonstrated for monitoring nanoparticle delivery and uptake in cultured cells.
► Results highlight known dosimetric effects important for in-vitro toxicology.
► Studied effects include gravitational settling and receptor-mediated interactions.