FeOdots - Superparamagnetic nanoparticles for biomedicine and biotechnology
NIMT FeOdots are superparamagnetic nanoparticles specially designed for use in the fields of biomedicine and biotechnology. FeOdots are engineered nanoparticles of solid iron oxide cores composed mainly of Fe3O4 (Magnetite). Due to non classical synthesis routes size and shape can be controlled. The nanoparticles have a high magnetic saturation (Ms) of about 80 emu/g and are monodispersed (11 nm ± 1 nm).
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| TEM image of NIMT FeOdots and corresponding Number avergage analyzed by Dynamic Light Scattering. |
Coating for extreme conditions
FeOdots are coated with a biocompatible PEG coating using technologies to ensure a much defined coating with high chemical stability and integrity. Variations in coating thickness between individual particles are very small and total coating thickness is 3 nm (seen as a grey area sourrounding the black particles in figure above).
The coating ensures high solubility in all common buffers at pH ranging from 2 to pH 12. Our standard FeOdots are coated with a functionalized PEG containing a primary amino group opening up for possibility of doing bioconjugation to the particles. Coating can also be provided containing unmodified PEG of different molecular weight.
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| Particles incubated for 48 hours in buffers with pH ranging from 2-12. |
Even under extreme salt concentrations (fig below) the particles remain in solution with no observed agglomeration. This has been further confirmed by size measurements using dynamic light scattering (DLS).
The extreme stability of NIMT FeOdots are of importance for in vivo applications or application were complex media is used. The magnetic nanoparticles remain stable in serum and other high protein concentration solutions for a extended period of time. No agglomeration or precipitations are observed upon incubation in human serum (see fig below). This has been further confirmed by size measurements using dynamic light scattering (DLS). Even after more than 3 months in room temperature the particles remain their colloidal stability in human serum.
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| NIMT FeOdots incubated with 1-5 M NaCl for 48 hours (left) and NIMT FeOdots suspended in humas serum for 48 hours (right). |
Poly ethylene glycol (PEG) coating further assures low unspecific binding and PEG is generally considered non toxic. Cell culture studies confirm no decrease of proliferation when incubated together with NIMT FeOdots.
Increased relaxivity
Compared to traditional T2-contrast agenst used in clinical applications agents FeOdots have a higher relaxivity. This provides the researcher with a particle having a significantly higher sensitivity in MRI applications.
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Name |
Magnetic core size [nm] |
Total size [nm] |
Coating material |
r2[a] [mM-1S-1] |
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Conventional MNP Agents |
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AMI-25 (Feridex Endorem) |
5-6 |
80–150 |
Dextran |
ca. 100 |
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SHU 555A (Resovist)[52] |
ca. 4,2 |
ca. 62 |
Carbodextran |
151 |
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AMI-227 (Combidex, Sinerem) |
4-6 |
20–40 |
Dextran |
53 |
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CLIO, MION |
ca. 2,8 |
10–30 |
Dextran |
ca. 69 |
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FeOdots |
11±1 |
18-20 |
PEG/Amino-PEG |
400 |
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[a] The r2 values are literature values and can be slightly variable depending on the field strength and MR
pulse sequences. (Cheon et al, Angew. Chem. Int. Ed. 2008, 47, 5122 – 5135) |
Blood Circulation Time
FeOdots have been injected in rats for estimation. 1 mL of FeOdots 2 mg iron oxide/mL coated with amino-PEG was injected via tail vein injection into four rats and blood samples were removed at different time points and the Iron concentration of plasma was measured. Half-life was determine to approximately 2 hour for the amino-PEG coated FeOdots.
Particle data
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NIMT FeOdot PEG-Amine (N1-FA1-020, N1-FA1-050) |
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Iron concentration |
1.5 mg·mL-1 |
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Iron oxide (Fe3O4) concentration |
2.0 mg·mL-1 |
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Number of particles in 1 mL of solution |
~ 5·1014 |
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Molar concentration of particles |
~ 0.75 µM |
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Number of Amino groups / particle |
~ 700 |
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Core diameter (TEM) |
11 ± 1 nm |
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Particle diameter including coating (TEM) |
18 ± 2 nm |
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Hydrodynamic particle diameter including coating (DLS) |
30 nm (Number Average) |
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Magnetic Susceptibility |
80 emu·g-1 |
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r2 relaxivity |
400 mM-1·S-1 |
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