High Relaxivity Gadolinium‐Polydopamine Nanoparticles

Abstract

This study reports the preparation of a series of gadolinium-polydopamine nanoparticles (GdPD-NPs) with tunable metal loadings. GdPD-NPs are analyzed by nuclear magnetic relaxation dispersion and with a 7-tesla (T) magnetic resonance imaging (MRI) scanner. A relaxivity of 75 and 10.3 mM s at 1.4 and 7 T is observed, respectively. Furthermore, superconducting quantum interference device magnetometry is used to study intraparticle magnetic interactions and determine the GdPD-NPs consist of isolated metal ions even at maximum metal loadings. From these data, it is concluded that the observed high relaxivities arise from a high hydration state of the Gd(III) at the particle surface, fast rate of water exchange, and negligible antiferromagnetic coupling between Gd(III) centers throughout the particles. This study highlights design parameters and a robust synthetic approach that aid in the development of this scaffold for T -weighted, high relaxivity MRI contrast agents.

Functionalizing NaGdF4:Yb,Er Upconverting Nanoparticles with Bone-Targeting Phosphonate Ligands: Imaging and In Vivo Biodistribution

“…Direct inspection of the images (see Figure 4) clearly showed initial accumulation in the lungs and the liver, probably due to sequestration of the NPs by the mononuclear phagocyte system (MPS) which might be a consequence of aggregation of the NPs under physiologic conditions. At 3 h and 6 h after nanoparticle injection, 18 F radioactivity was also clearly identified in the bones and joints, independently of the ligand coating. These initial results were confirmed by image quantification ( Figure S15).…”

“…The obtained UCNPs had homogeneous distribution in size and shape, displaying an average diameter of 9.5 ± 1.1 nm according to TEM measurements (Figures 1a and S1). The relatively small size of these UCNPs is advantageous for MRI because of their high surface area, increasing the amount of Gd 3+ ions accessible to water molecules and hence the relaxivity per Gd atom [17][18][19]. Conversely, small UCNPs such as the ones prepared in this work have modest upconversion properties due to solvent deactivation processes ( Figure S2) [20].…”

“…Nuclear imaging, and in particular PET, is routinely employed in the clinics to study the whole-body distribution of radiolabeled species with high sensitivity [24]. 18 F-labelling of UCNPs has demonstrated to be an effective strategy to monitor the biodistribution of these nanomaterials in vivo [25][26][27], often in combination with other imaging modalities [28]. In this study, the observation of the UCNPs in vivo adhesion to the bones using MRI was discarded due to the intrinsic low sensitivity of the technique added to the specific characteristics of the bones: low water content, very short T2 relaxation times due to its rigid nature and susceptibility effects.…”

“…However, UCNPs have much more to offer besides their photophysics [8] since they can simultaneously act as multimodal imaging agents and be employed in theranostics. Gd-containing UCNPs are magnetic resonance imaging (MRI) contrast agents, while labelling with radionuclides such as 18 F and 153 Sm yields positron emission and single photon emission tomography (PET and SPECT) probes, respectively [9,10].…”

An Adaptable Nanoplatform for Integrating Anatomic and Functional Magnetic Resonance Imaging under a 3.0 T Magnetic Field

“…To transform the OA‐NaGdF 4 nanoparticles into hydrophily and enhance the biocompatibility, PDA was then modified as Figure b presented using a method of reverse microemulsion . Besides, PDA decorated on OA‐NaGdF 4 nanoparticles could also anchor Gd 3+ to prevent the leakage of Gd 3+ and further ensure the biocompatibility. After the successful modification using NH 2 ‐PEG‐2000 via Schiff base reaction (Figure S3, Supporting Information), the relative aggregated NaGdF 4 @PDA (NP) with the zeta potential of −5.4 mV and hydrated size of 4.9 µm turned into monodispersed NaGdF 4 @PDA@PEG‐2000 (NPP‐2000) with the zeta potential of +14.5 mV and hydrated size of 200 nm, and NPP‐5000/NPP‐10 000 also presented similar results ( Figure ).…”