Abstract
Over the last decades, the use of magnetic nanoparticles in research and commercial applications has increased dramatically. However, direct detection of trace quantities remains a challenge in terms of equipment cost, operating conditions and data acquisition times, especially in flowing conditions within complex media. Here we present the in-line, non-destructive detection of magnetic nanoparticles using high performance atomic magnetometers at ambient conditions in flowing media. We achieve sub-picomolar sensitivities measuring ~30 nm ferromagnetic iron and cobalt nanoparticles that are suitable for biomedical and industrial applications, under flowing conditions in water and whole blood. Additionally, we demonstrate real-time surveillance of the magnetic separation of nanoparticles from water and whole blood. Overall our system has the merit of in-line direct measurement of trace quantities of ferromagnetic nanoparticles with so far unreached sensitivities and could be applied in the biomedical field (diagnostics and therapeutics) but also in the industrial sector.
Highlights
Functionalized magnetic nanoparticles have emerged as unique objects for a variety of applications, ranging from usage in life sciences[1] to data storage[2] and industrial wastewater treatment[3]
Nanomag-D - Micromod’s 09-00-132 Nanomag-D dextran coated superparamagnetic iron oxide particles, mean diameter ~130 nm, and saturation magnetization ~45 emu/g. We choose these particular cobalt- and iron-carbide-based ferromagnetic particles because they show larger saturation magnetizations compared to oxide-based particles, and their characteristics and size are suitable for magnetic particle-based blood purification (MPBP)-related applications[9,11]
Using a statistical analysis algorithm we estimate the goodness-of-fit of the observed signals to a normal distribution, from which we obtain the variance of the measured magnetic field signal, which is a measure of the magnetic fluctuations, and which we show is directly related to the concentration of magnetic particles
Summary
Functionalized magnetic nanoparticles have emerged as unique objects for a variety of applications, ranging from usage in life sciences[1] to data storage[2] and industrial wastewater treatment[3]. Magnetic nanoparticles functionalized with capturing moieties (e.g. antibodies) are applied in an extracorporeal circuit where they bind to their targets and are separated by a magnetic field before the blood is recirculated to the patient Several setups utilizing this concept have been proposed and tested in vitro[6,7,8,9,10], as well as in animal trials[11,12]. The detection of the magnetic moment of metallic ferromagnetic nanoparticles is promising and such a direct method could be applied in most media without matrix effects, avoiding sample preparation or destruction. This can be achieved using magnetometric methods, which are not based on optical data acquisition and, can operate in complex media, such as opaque whole blood. The magnetic moments of nanoparticles are extremely small, and any employed measurement methods need to be correspondingly sensitive
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