Characterization data of commercial tracers for magnetic particle imaging

This dataset contains characterization data for various commercially available tracers for magnetic particle imaging (MPI). Currently this includes Synomag-D with plain, NH2, and PEG modified coatings, Perimag, Vivotrax, and Vivotrax Plus. The dataset includes data on particle physical and magnetic properties, like dynamic light scattering, magnetization versus applied field, and zero-field-cooled/field-cooled magnetization measurements, as well as direct evaluations of tracer MPI performance as measured through RELAX and 2D scans on a Magnetic Insight MOMENTUM imager. A table of relevant particle properties is additionally provided as a summary of the processed measurement data for researchers to evaluate directly. All measurements used to generate these values are also provided to allow the evaluation of other analysis methods. Further, this dataset allows for the comparison of several commonly used commercial MPI tracers using a single instrument and consistent procedures. This is useful for researchers aiming to compare performance of newly developed tracers or evaluate the relationship between tracer performance across imaging instruments.

Methods
Dynamic Light Scattering

Hydrodynamic diameter measurements of particles diluted in deionized water were obtained at room temperature using a Brookhaven ZetaPALS as an intensity-weighted lognormal distribution.

Iron Concentration Assay

Iron concentration of all tracers was determined by a colorimetric assay using 1,10-phenanthroline. 10 µL of commercial tracers were digested in 1 mL of 70% nitric acid overnight at 101 °C. The following day, 10 µL of the digested sample was placed in a quartz 96-well plate and dried on a hot plate at 115 °C. The plate was transferred into an OT2 liquid handling robot (Opentrons, Long Island City, NY, US) where 46 µL of DI water followed by 30 µL of hydroxylamine hydrochloride (8.06 M) was added and allowed to react for 1 hour. 49 µL of sodium acetate (1.22 M) and 75 µL of 1,10-phenanthroline monohydrate (13 mM) were then added to complex with the Fe2+. Absorbance measurements at 508 nm were collected in a SpectraMax M5 microplate reader (Molecular Devices, San Jose, CA, US). Concentrations were determined using a calibration curve prepared from a TraceCERT iron solution standard for ICP. All samples were prepared and measured in triplicate.

Magnetometry

Magnetization curves for each sample in liquid at 300 K between -7 T and 7 T were collected using a MPMS-3 SQUID magnetometer.

ZFC and FC curves were collected on the same machine with 10 uL of samples dried on cotton. The sample was heated to 400 K then cooled to 4 K before applying a field of 795.8 A/m (10 Oe). The temperature was then ramped 2 to 400 K and cooled back to 4 K while continuously measuring the magnetization at 2 K intervals.

Magnetic Particle Imaging

MPI performance was evaluated by collecting RELAX (45 kHz, 16 mT in the x axis) and 2D (45 kHz, 16/16 mT for x/z axes, 5.7 T/m) scans in standard mode using a MOMENTUM scanner. 3 uL of commercial tracer solutions at stock concentration were loaded into 0.2 mL microcentrifuge tubes or 0.030” ID capillary tubes for RELAX measurements and 2D images, respectively.