Fluorescence-Magnetism Functional EuS Nanocrystals with Controllable Morphologies for Dual Bioimaging

Gadolinium-based bimodal probes to enhance T1-Weighted magnetic resonance/optical imaging

Gd³⁺-based contrast agents have been extensively used for signal enhancement of T₁-weighted magnetic resonance imaging (MRI) due to the large magnetic moment and long electron spin relaxation time of the paramagnetic Gd³⁺ ion. The key requisites for the development of Gd³⁺-based contrast agents are their relaxivities and stabilities which can be achieved by chemical modifications. These modifications include coordinating Gd³⁺ with a chelator such as diethylenetriamine pentaacetic acid (DTPA) or 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), encapsulating Gd³⁺ in nanoparticles, conjugation to biomacromolecules such as polymer micelles and liposomes, or non-covalent binding to plasma proteins. In order to have a coherent diagnostic and therapeutic approach and to understand diseases better, the combination of MRI and optical imaging (OI) techniques into one technique entity has been developed to overcome the conventional boundaries of either imaging modality used alone through bringing the excellent spatial resolution of MRI and high sensitivity of OI into full play. Novel MRI and OI bimodal probes have been extensively studied in this regard. This review is an attempt to shed some light on the bimodal imaging probes by summarizing all recent noteworthy publications involving Gd³⁺ containing MR-optical imaging probes. The several key elements such as novel synthetic strategy, high sensitivity, biocompatibility, and targeting of the probes are highlighted in the review. STATEMENT OF SIGNIFICANCE: The present article aims at giving an overview of the existing bimodal MRI and OI imaging probes. The review structured as a series of examples of paramagnetic Gd³⁺ ions, either as ions in the crystalline structure of inorganic materials or chelates for contrast enhancement in MRI, while they are used as optical imaging probes in different modes. The comprehensive review focusing on the synthetic strategies, characterizations and properties of these bimodal imaging probes will be helpful in a way to prepare related work.

Hollow structural metal-organic frameworks exhibit high drug loading capacity, targeted delivery and magnetic resonance/optical multimodal imaging

Metal-organic frameworks (MOFs) are attractive in designing drug delivery systems for the treatment of cancer because of their unique porous properties. However, the search for multifunctional MOFs with high drug loading and magnetic resonance/fluorescence imaging capacities is still a challenge and they have rarely been reported. In this article, using the intrinsic advantages of MOFs, hollow Fe-MOFs with biomolecular grafting were fabricated and shown to be capable of loading much more drugs and exhibiting targeted drug delivery, pH-controlled drug release and magnetic resonance/fluorescence imaging. Benefiting from their hollow structures, the drug loading capacity is as high as 35%. Due to post-modification with folic acid (FA) and the fluorescent reagent (5-FAM) and the existence of Fe(iii), in vitro experiments indicate that Fe-MOF-5-NH2-FA-5-FAM/5-FU can target cancer cells HepG-2 and display excellent magnetic resonance/fluorescence imaging. Furthermore, in vivo biodistribution indicates that Fe-MOF-5-NH2-FA-5-FAM/5-FU can accumulate in the tumor. Taken together, our work integrates high drug loading and bioimaging into a single MOF successfully and reveals the enormous potential of the functionalized MOF for drug delivery and bioimaging.

Synthesis and Morphological Control of Biocompatible Fluorescent/Magnetic Janus Nanoparticles Based on the Self-Assembly of Fluorescent Polyurethane and Fe₃O₄ Nanoparticles

Functionalized Janus nanoparticles have received increasing interest due to their anisotropic shape and the particular utility in biomedicine areas. In this work, a simple and efficient method was developed to prepare fluorescent/magnetic composite Janus nanoparticles constituted of fluorescent polyurethane and hydrophobic nano Fe₃O₄. Two kinds of fluorescent polyurethane prepolymers were synthesized by the copolymerization of fluorescent dye monomers, and the fluorescent/magnetic nanoparticles were fabricated in one-pot via the process of mini-emulsification and self-assembly. The nanostructures of the resulting composite nanoparticles, including core/shell and Janus structure, could be controlled by the phase separation in assembly process according to the result of transmission electron microscopy, whereas the amount of the nonpolar segments of polyurethane played an important role in the particle morphology. The prominent magnetic and fluorescent properties of the Janus nanoparticles were also confirmed by vibrating magnetometer and confocal laser scanning microscope. Furthermore, the Janus nanoparticles featured excellent dispersity, storage stability, and cytocompatibility, which might benefit their potential application in biomedical areas.

Facile synthesis of highly monodisperse EuSe nanocubes with size-dependent optical/magnetic properties and their electrochemiluminescence performance

We reported a facile and robust method for the synthesis of highly monodisperse EuSe nanocubes (EuSe NCs) with controllable edge lengths in the range of 8-70 nm. The EuSe NCs were formed through the aggregation of EuSe small particles (cores) and then their surface reconstruction under the influence of 1-dodecanethiol (DDT) that acted as a capping surfactant. DDT was not only found to be critical to the nucleation temperature of preparing EuSe NCs, but also played a decisive role in the formation of structurally well-defined nanocubes. The results indicated that the remarkable monodispersity and high shape consistency of EuSe NCs were highly controlled by the change in the DDT concentration. Furthermore, the size-dependent optical/magnetic properties based on the quantum size effect and the influence of edge lengths of EuSe NCs were also investigated and discussed. More importantly, the electrochemiluminescence (ECL) performance of EuSe NCs was first reported. This will make possible more biomedical applications in future.

Facile Synthesis of Lanthanide (Ce, Eu, Tb, Ce/Tb, Yb/Er, Yb/Ho, and Yb/Tm)-Doped LnF3 and LnOF Porous Sub-Microspheres with Multicolor Emissions

Monodisperse YF₃ and YOF porous sub-microspheres were synthesized by using a novel sacrificing template method with amorphous Y(OH)CO₃ ⋅x H₂ O as the precursors and the template. It was found that the size and shape were well maintained, and the condensed precursor was transformed into uniform porous structures after fluoridation. By fine-tuning the feed of the fluorine source, the final product could be converted from YF₃ to YOF. A possible growth mechanism is proposed for the uniform porous YF₃ structure and the porous yolk-shell-like YOF structure. The luminescence properties showed that the as-synthesized YF₃ :Ln³⁺ (Ln=Eu, Tb, Ce, Ce/Tb, Yb/Er, Yb/Ho, and Yb/Tm) products exhibited strong multicolor emissions, which included down-/upconversion and energy-transfer processes. Additionally, YOX (X=Cl and Br) could be obtained if a different halogen source was used during calcination. However, the spheres were almost completely destroyed. Our novel synthetic route can also be extended to other lanthanide fluorides (REF₃ , RE=Gd, Lu), which may open a facile way to fabricate novel porous nanostructures.

Controllable Synthesis of a Smart Multifunctional Nanoscale Metal-Organic Framework for Magnetic Resonance/Optical Imaging and Targeted Drug Delivery

As a result of their extraordinarily large surfaces and well-defined pores, the design of a multifunctional metal-organic framework (MOF) is crucial for drug delivery but has rarely been reported. In this paper, a novel drug delivery system (DDS) based on nanoscale MOF was developed for use in cancer diagnosis and therapy. This MOF-based tumor targeting DDS was fabricated by a simple postsynthetic surface modification process. First, magnetic mesoporous nanomaterial Fe-MIL-53-NH₂ was used for encapsulating the drug and served as a magnetic resonance contrast agent. Moreover, the Fe-MIL-53-NH₂ nanomaterial exhibited a high loading capacity for the model anticancer drug 5-fluorouracil (5-FU). Subsequently, the fluorescence imaging agent 5-carboxyfluorescein (5-FAM) and the targeting reagent folic acid (FA) were conjugated to the 5-FU-loaded Fe-MIL-53-NH₂, resulting in the advanced DDS Fe-MIL-53-NH₂-FA-5-FAM/5-FU. Owing to the multifunctional surface modification, the obtained DDS Fe-MIL-53-NH₂-FA-5-FAM/5-FU shows good biocompatibility, tumor enhanced cellular uptake, strong cancer cell growth inhibitory effect, excellent fluorescence imaging, and outstanding magnetic resonance imaging capability. Taken together, this study integrates diagnostic and treatment aspects into a single platform by a simple and efficient strategy, aiming for facilitating new possibilities for MOF use for multifunctional drug delivery.