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MRI Relaxivity Changes of the Magnetic Nanoparticles Induced by Different Amino Acid Coatings.

ABSTRACT: In this study, we analysed the physico-chemical properties of positively charged magnetic fluids consisting of magnetic nanoparticles (MNPs) functionalised by different amino acids (AAs): glycine (Gly), lysine (Lys) and tryptophan (Trp), and the influence of AA-MNP complexes on the MRI relaxivity. We found that the AA coating affects the size of dispersed particles and isoelectric point, as well as the zeta potential of AA-MNPs differently, depending on the AA selected. Moreover, we showed that a change in hydrodynamic diameter results in a change to the relaxivity of AA-MNP complexes. On the one hand, we observed a decrease in the relaxivity values, r1 and r2, with an increase in hydrodynamic diameter (the relaxivity of r1 and r2 were comparable with commercially available contrast agents); on the other hand, we observed an increase in r2* value with an increase in hydrodynamic size. These findings provide an interesting preliminary look at the impact of AA coating on the relaxivity properties of AA-MNP complexes, with a specific application in molecular contrast imaging originating from magnetic nanoparticles and magnetic resonance techniques.

SUBMITTER: Antal I

PROVIDER: S-EPMC7075310 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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MRI Relaxivity Changes of the Magnetic Nanoparticles Induced by Different Amino Acid Coatings.

Antal Iryna I Strbak Oliver O Khmara Iryna I Koneracka Martina M Kubovcikova Martina M Zavisova Vlasta V Kmetova Martina M Baranovicova Eva E Dobrota Dusan D

Nanomaterials (Basel, Switzerland) 20200224 2

In this study, we analysed the physico-chemical properties of positively charged magnetic fluids consisting of magnetic nanoparticles (MNPs) functionalised by different amino acids (AAs): glycine (Gly), lysine (Lys) and tryptophan (Trp), and the influence of AA-MNP complexes on the MRI relaxivity. We found that the AA coating affects the size of dispersed particles and isoelectric point, as well as the zeta potential of AA-MNPs differently, depending on the AA selected. Moreover, we showed that ...[more]

PMID: 32102280

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Project description:The key criteria to optimize the relaxivity of a Gd(III) contrast agent at high fields (defined as the region ? 1.5 T) can be summarized as follows: (i) the occurrence of a rotational correlation time ?R in the range of ca. 0.2-0.5 ns; (ii) the rate of water exchange is not critical, but a ?M < 100 ns is preferred; (iii) a relevant contribution from water molecules in the second sphere of hydration. In addition, the use of macrocycle-based systems ensures the formation of thermodynamically and kinetically stable Gd(III) complexes. Binuclear Gd(III) complexes could potentially meet these requirements. Their efficiency depends primarily on the degree of flexibility of the linker connecting the two monomeric units, the absence of local motions and the presence of contribution from the second sphere water molecules. With the aim to maximize relaxivity (per Gd) over a wide range of magnetic field strengths, two binuclear Gd(III) chelates derived from the well-known macrocyclic systems DOTA-monopropionamide and HPDO3A (Gd2L1 and Gd2L2, respectively) were synthesized through a multistep synthesis. Chemical Exchange Saturation Transfer (CEST) experiments carried out on Eu2L2 at different pH showed the occurrence of a CEST effect at acidic pH that disappears at neutral pH, associated with the deprotonation of the hydroxyl groups. Then, a complete 1H and 17O NMR relaxometric study was carried out in order to evaluate the parameters that govern the relaxivity associated with these complexes. The relaxivities of Gd2L1 and Gd2L2 (20 MHz, 298 K) are 8.7 and 9.5 mM-1 s-1, respectively, +77% and +106% higher than the relaxivity values of the corresponding mononuclear GdDOTAMAP-En and GdHPDO3A complexes. A significant contribution of second sphere water molecules was accounted for the strong relaxivity enhancement of Gd2L2. MR phantom images of the dinuclear complexes compared to GdHPDO3A, recorded at 7 T, confirmed the superiority of Gd2L2. Finally, ab initio (DFT) calculations were performed to obtain information about the solution structure of the dinuclear complexes.

Dataset Information

MRI Relaxivity Changes of the Magnetic Nanoparticles Induced by Different Amino Acid Coatings.

Publications

MRI Relaxivity Changes of the Magnetic Nanoparticles Induced by Different Amino Acid Coatings.

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