Experimental study on T2 relaxation time of protons in water suspensions of iron-oxide nanoparticles: Effects of polymer coating thickness and over-low

Chen, D.-X.; Sun, Ning; Huang, Z. J.; Cheng, Changming; Xu, Hong; Gu, Hongchen

doi:10.1016/j.jmmm.2009.10.013

Cited by 34 publications

(36 citation statements)

References 31 publications

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“…[10] More recently, magnetic nanospheres composed of many presynthesized MIOPs had higher r 2 values than that of separated nanoparticles. [11][12] Taboada et al synthesized magnetite nanospheres with an r 2 value of 326 mm À1 s À1 ; [13] an r 2 value of roughly 400 mm À1 s À1 was also obtained in our former work; [14] and, in particular, an r 2 value of 500 mm À1 s À1 was realized by Paquet et al [15] In parallel with the development of experimental results, relaxation theory on MIOPs has also made progress in the last decade. The chemical exchange model and the partial refocusing model were proposed by Brooks [16] and the group of Gillis, [17] respectively.…”

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confidence: 60%

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Magnetite Nanocrystal Clusters with Ultra‐High Sensitivity in Magnetic Resonance Imaging

Cheng

Chen

et al. 2011

ChemPhysChem

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Magnetic iron oxide particles are widely used as contrast agents to improve the sensitivity of magnetic resonance imaging (MRI). Their efficiency in MRI is usually quantified by transverse relaxivity (r(2)) in solution. Herein, we synthesized a series of magnetite nanocrystal clusters (MNCs) with ultra-high transverse relaxivity by a polyol process and studied the relationship between r(2) and size of the MNCs. The sizes of MNCs can be tuned over a wide range from 13 to 179 nm. The r(2) of MNC suspensions as a function of the size of the cluster was analyzed and compared with a theoretical model. We found that MNCs of 64 nm had an r(2) value of 650 mM(-1) s(-1), which was more than three times that of the commercial contrast agent and was among the highest reported for iron oxide materials. Compared with the theoretical model, the r(2) value of the MNC suspension is approximately 0.93 of the theoretical prediction. Imaging of the MNC suspensions was performed in a clinical 1.5 T MRI instrument and a comparison was made between MNCs and commercial contrast agents. MRI indicated that the decrease of signal intensity induced by MNCs was in proportion to the r(2) value, which was in accordance with theoretical predictions. These results demonstrate that MNCs with ultra-high transverse relaxivity and tunable size are promising candidates for molecular imaging and clinical diagnosis in MRI.

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confidence: 60%

“…Monte Carlo simulations [18] and experimental validation [19][20] were used to substantiate these models of relaxation theory. According to relaxation theory, [14,19] the theoretical maximum of r 2 should be around 730 mm À1 s À1 for…”

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confidence: 99%

Magnetite Nanocrystal Clusters with Ultra‐High Sensitivity in Magnetic Resonance Imaging

Cheng

Chen

et al. 2011

ChemPhysChem

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“…For spin-echo (SE) sequences (large particles) and as the echo-time (τ CP ) is reduced the refocusing RF pulses become more effective and partial refocusing occurs and R 2 decreases compared to R * 2 . This is the echo-limited regime (ELR) [32][33][34] valid for τ D > 2τ CP , the relaxation time is given by…”

Section: Methodsmentioning

confidence: 99%

Reduction of T2 Relaxation Rates due to Large Volume Fractions of Magnetic Nanoparticles for All Motional Regimes

Issa

2018

Applied Sciences

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Abstract:The effect of high volume fraction of magnetic nanoparticles (MNP) on Magnetic Resonance Imaging (MRI) transverse relaxation rates (R 2 = 1/T 2 and R 2 * = 1/T 2 *) is investigated using Monte Carlo (MC) simulations. Theoretical models assume that particles occupy a small volume fraction of the sample space. Results presented in this work show that models based on both motional averaged (MAR) and static dephasing (SDR) regimes respectively underestimate and overestimate relaxation rates at large volume fractions. Furthermore, both R 2 * and R 2 * become echo-time dependent. This suggests that diffusion is involved with larger echo-times producing smaller relaxation rates due to better averaging of the magnetic field gradients. Findings emphasize the need for the models to be modified to take account of high particle concentration especially important for application involving clustering and trapping of nanoparticles inside cells. This is important in order to improve the design process of MNP Contrast Agents.

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“…[20][21][22] This fact explains the drastic reduction of the transversal relaxivity value taking place after coating the commercial nanoparticles by a SiO 2 layer, even though in the case of silica coatings, a certain thickness of this silica shell is water permeable. [19,20] The decrease of r 2 observed in the S3 suspension, indicates that this permeability is reduced after gold coating to obtain the SPION-SiO 2 -Au particles. In the case of the PH3 suspension, the observed decrease in r 2 can be ascribed to the before mentioned etching of the SPION core, leading to a loss of magnetic material.…”

Section: Relaxivity and Optical Propertiesmentioning

confidence: 99%

“…Different coatings are being studied including SiO 2 , biomolecules or polymers, Au, dextran, polyethylene glycol (PEG), peptides and protein shells, and the coating influence in T 2 and r 2 has also been thoroughly studied. [17][18][19] Finally, SiO 2 is widely applied as coating material on SPIONs because the silica shell protects the core from the environment avoiding agglomeration, providing colloidal stability and allowing simple and direct biofunctionalization using a well establish silane-based chemistry. Different authors have reported the strong influence of the silica shell thickness in the nanoparticle efficiency as MRI contrast agent.…”

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confidence: 99%

Magneto-plasmonic nanoparticles as theranostic platforms for magnetic resonance imaging, drug delivery and NIR hyperthermia applications

et al. 2014

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PEGylated magneto-plasmonic nanoparticles with a hollow or semi-hollow interior have been successfully synthesized and their physico-chemical characteristics investigated. The hollow interior space can be used to store drugs or other molecules of interest whereas magnetic characterization shows their potential as contrast agents in magnetic resonance imaging (MRI) applications. In addition, their plasmonic characteristics in the near infrared (NIR) region make them efficient in photothermal applications producing high temperature gradients after short irradiation times.We show that by controlling the etching conditions the inner silica shell can be selectively dissolved to achieve a hollow or semi-hollow interior without compromising the magnetic or plasmonic characteristics of the resulting nanoparticles. Magnetic measurements and transmission electron microscopy observations have been used to demonstrate the precise control during the etching process and to select an optimal concentration of etching reagent and contact time to preserve the inner superparamagnetic iron oxide-based nanoparticles and the plasmonic properties of the constructs. Drug loading capabilities were also evaluated for both semi-hollow and as-synthesized nanoparticles using Rhodamine B isothiocyanate as a model compound. The nanoparticles produced could be potentially used as "theranostic" nanoparticles with both imaging capabilities and a dual therapeutic function (drug delivery and hyperthermia).

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Experimental study on T2 relaxation time of protons in water suspensions of iron-oxide nanoparticles: Effects of polymer coating thickness and over-low

Cited by 34 publications

References 31 publications

Magnetite Nanocrystal Clusters with Ultra‐High Sensitivity in Magnetic Resonance Imaging

Magnetite Nanocrystal Clusters with Ultra‐High Sensitivity in Magnetic Resonance Imaging

Reduction of T2 Relaxation Rates due to Large Volume Fractions of Magnetic Nanoparticles for All Motional Regimes

Magneto-plasmonic nanoparticles as theranostic platforms for magnetic resonance imaging, drug delivery and NIR hyperthermia applications

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