Grafting of Gd-DTPA onto MOF-808 to enhance MRI performance for guiding photothermal therapy

Gd(III) chelates are important T₁-weighted contrast agents used in clinical magnetic resonance imaging (MRI), but their low longitudinal relaxivity (r₁) results in limited imaging efficiency. In this study, we utilize a geometric confinement strategy to restrict a Gd chelate (Gd-DTPA) within the channels of a porous metal-organic framework material (MOF-808) for increasing its r₁ relaxivity. Moreover, the Gd-DTPA-grafted MOF-808 nanoparticles were further surface modified with polyaniline (PANI) to construct an MRI-guided photothermal therapy platform. The resulting Gd-DTPA-MOF-808@PANI shows a high r₁ relaxivity of 30.1 mM^-1 s^-1 (0.5 T), which is 5.4 times higher than that of the commercial contrast agent Magnevist. In vivo experiments revealed that Gd-DTPA-MOF-808@PANI has good T₁-weighted contrast performance and can effectively guide photothermal ablation of tumors upon 808 nm laser irradiation. This work may shed some light on the design and preparation of high relaxation rate Gd-based contrast agents for theranostic application via utilization of versatile MOF materials.

Magnetic domains orientation in (Fe3O4/γ-Fe2O3) nanoparticles coated by Gadolinium-diethylenetriaminepentaacetic acid (Gd3+-DTPA)

In this work, the magnetic domains (MDs) orientation was evaluated from magnetite/maghemite nanoparticles (Fe3O4/γ-Fe2O3) NPs coated with Gadolinium (Gd3+) chelated with diethylenetriamine pentaacetate acid (Gd–DTPA). The (Fe3O4/γ–Fe2O3) superparamagnetic cores were configured by adding a DTPA organic layer and paramagnetic Gd as (Fe3O4/γ–Fe2O3)@Gd–DTPA NPs. The cores were obtained by coprecipitation and coated with additional modifications to the synthesis with Gd–DTPA. Analysis of properties showed that particles 9–12 nm, with Gd–DTPA layer thickness ∼10 nm increased their magnetisation from 62.72 to 75.82 emu/g. The result showed that the structure, particle size, composition, thickness and interface defects, as well as the anisotropy, play an important role in MDs orientation of (Fe3O4/γ–Fe2O3)@Gd–DTPA NPs. Magnetic force microscopy (MFM) analysis showed an MDs uniaxial orientation of 90° at magnetisation and disorder at zero conditions and demagnetisation. The MDs interactions showed uniaxial anisotropy defined in the direction of the magnetic field. These addressable and rotational features could be considered for potential applications to induce hydrogen proton alignment in water by longitudinal spin-lattice relaxation T 1 and transversal spin-spin relaxation T 2 as a dual contrast agent and as a theranostic trigger.

Fe/Mn Multilayer Nanowires as High-Performance T1-T2 Dual Modal MRI Contrast Agents

A lot of nanomaterials are using T₁-T₂ dual mode magnetic resonance (MR) contrast agents (CAs), but multilayer nanowire (NW) with iron (Fe) and manganese (Mn) as T₁-T₂ dual modal CAs has not been reported yet. Herein, we synthesized a Fe/Mn multilayer NW with an adjustable Fe layer, as T₁-T₂ dual-mode CAs. The relaxation performance of Fe/Mn multilayer NW was studied at 1.5 T. Results show that, when the length of the Fe layer is about 10 nm and the Mn is about 5 nm, the r₁ value (21.8 mM⁻¹s⁻¹) and r₂ value (74.8 mM⁻¹s⁻¹) of the Fe/Mn multilayer NW are higher than that of Mn NW (3.7 mM⁻¹s⁻¹) and Fe NW (59.3 mM⁻¹s⁻¹), respectively. We predict that our Fe/Mn multilayer NW could be used as T₁-T₂ dual mode MRI CAs in the near future.

A biocompatible theranostic nanoplatform based on magnetic gadolinium-chelated polycyclodextrin: in vitro and in vivo studies

A novel theranostic nanoplatform was prepared based on Fe₃O₄ nanoparticles (NPs) coated with gadolinium ions decorated-polycyclodextrin (PCD) layer (Fe₃O₄@PCD-Gd) and employed for Curcumin (CUR) loading. The dissolution profile of CUR indicated a pH sensitive release manner. Fe₃O₄@PCD-Gd NPs exhibited no significant toxicity against both normal and cancerous cell lines (MCF 10A and 4T1, respectively); while the CUR-free NPs showed more toxicity against 4T1 than MCF 10A cells. In vivo anticancer study revealed appropriate capability of the system in tumor shrinking with no tissue toxicity and adverse effect on body weight. In vivo MR imaging of BALB/c mouse showed both T₁ and T₂ contrast enhancement on the tumor cells. Fe₃O₄@PCD-Gd/CUR NPs showed significant features as a promising multifunctional system having appropriate T₁-T₂ dual contrast enhancement and therapeutic efficacy in cancer theranostics.

Ellagic acid-Fe nanoscale coordination polymer with higher longitudinal relaxivity for dual-modality T1-weighted magnetic resonance and photoacoustic tumor imaging

Dual-modality contrast agents for T₁-weighted magnetic resonance imaging (MRI) and photoacoustic imaging have attracted substantial attention as they combine the advantages of unlimited penetration depth and high sensitivity. However, most of the reported agents are Gd-based materials that exhibit nephrotoxicity, and few studies have focused on Fe-based materials owing to their lower relaxivity. This work describes the development of an ellagic acid (EA)-Fe nanoscale coordination polymer with high longitudinal relaxivity and strong near-infrared absorption for dual-modality T₁-weighted MRI and photoacoustic imaging. The longitudinal relaxivity (r₁) of the prepared EA-Fe@BSA nanoparticles was 2.54 mM^-1 s^-1, an increase of 185% compared with previously reported gallic acid-Fe nanoparticles. Furthermore, in vitro and in vivo experiments demonstrate that the EA-Fe@BSA NPs are an excellent T₁-weighted MRI and photoacoustic dual-modality contrast agent with the advantages of convenient synthesis and low toxicity, exhibiting great potential for clinical use in tumor imaging.

Ultrasmall iron oxide nanoparticles: synthesis, surface modification, assembly, and biomedical applications

Ultrasmall iron oxide nanoparticles (USIO NPs) with a size <5nm are a class of emerging nanomaterials. As a result of their intrinsic drawbacks related to poor colloidal stability, low r₁ relaxivity, and lack of functionality, various strategies have been adopted to synthesize USIO NPs with controllable sizes, to surface modify the particles with polymers, and to assemble them in combination with other nanoscale platforms. Here, we review recent progresses in the synthesis, surface modification, and self-assembly of USIO NPs to address key issues in their biomedical application in the field of cancer diagnosis and therapy, in particular magnetic resonance (MR) imaging, dual-modal or multimodal imaging, drug delivery, and theranostics.

Gadolinium-labelled iron/iron oxide core/shell nanoparticles as T 1-T 2 contrast agent for magnetic resonance imaging

Magnetic resonance imaging (MRI) is indispensable and powerful in modern clinical diagnosis and has some advantages such as non-invasiveness and high penetration depth. Furthermore, dual T 1-T 2 MR imaging has attracted crucial interest as it can decrease the risk of pseudo-positive signals in diagnosing lesions. And it's worth nothing that the dual-mode MR imaging displays a vital platform to provide relatively comprehensive diagnosis information and receive accurate results. Herein, we report a dual T 1-T 2 MR imaging contrast agent (CA) grounded on the iron/iron oxide core/shell nanomaterials conjugated with gadolinium chelate. The Gd-labeled Fe@Fe3O4 NPs reveal the feasibility to utilize them to serve as a dual T 1-T 2 MR imaging CA, and the relaxivity results in a 0.5 T MR system showed a longitudinal relaxivity value (r 1) and transverse relaxivity value (r 2) of 7.2 mM-1 s-1 and 109.4 mM-1 s-1, respectively. The MTT results demonstrate the Gd-labeled Fe@Fe3O4 NPs have no obvious cytotoxicity and a good compatibility. The in vitro and in vivo MRI generated a brighter effect and darkening in T 1-weighted MR imaging and T 2-weighted images, respectively. The results clearly indicate that Gd-labeled Fe@Fe3O4 NPs have potential as a magnetic resonance imaging contrast reagent.

LAPONITE®-stabilized iron oxide nanoparticles for in vivo MR imaging of tumors

We report the synthesis, characterization and utilization of LAPONITE®-stabilized magnetic iron oxide nanoparticles (LAP-Fe3O4 NPs) as a high performance contrast agent for in vivo magnetic resonance (MR) detection of tumors. In this study, Fe3O4 NPs were synthesized by a facile controlled coprecipitation route in LAP solution, and the formed LAP-Fe3O4 NPs have great colloidal stability and about 2-fold increase of T2 relaxivity than Fe3O4 NPs (from 247.6 mM(-1) s(-1) to 475.9 mM(-1) s(-1)). Moreover, cytotoxicity assay and cell morphology observation demonstrate that LAP-Fe3O4 NPs display good biocompatibility in the given Fe concentration range, and in vivo biodistribution results prove that NPs can be metabolized and cleared out of the body. Most importantly, LAP-Fe3O4 NPs can not only be used as a contrast agent for MR imaging of cancer cells in vitro due to the effective uptake by tumor cells, but also significantly enhance the contrast of a xenografted tumor model. Therefore, the developed LAP-based Fe3O4 NPs with good colloidal stability and exceptionally high transverse relaxivity may have tremendous potential in MR imaging applications.

Nanomaterials for In Vivo Imaging

In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality's existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality-we stratify nanomaterials on the basis of their (i) magnetic, (ii) optical, (iii) acoustic, and/or (iv) nuclear properties. We evaluate them for their ability to provide relevant information under preclinical and clinical circumstances, their in vivo safety profiles (which are being incorporated into their chemical design), their modularity in being fused to create multimodal nanomaterials (spanning multiple different physical imaging modalities and therapeutic/theranostic capabilities), their key properties, and critically their likelihood to be clinically translated.