Facile preparation of multifunctional uniform magnetic microspheres for T1-T2 dual modal magnetic resonance and optical imaging

Manganese-based hollow nanoplatforms for MR imaging-guided cancer therapies

Theranostic nanoplatforms integrating diagnostic and therapeutic functions have received considerable attention in the past decade. Among them, hollow manganese (Mn)-based nanoplatforms are superior since they combine the advantages of hollow structures and the intrinsic theranostic features of Mn²⁺. Specifically, the hollow cavity can encapsulate a variety of small-molecule drugs, such as chemotherapeutic agents, photosensitizers and photothermal agents, for chemotherapy, photodynamic therapy (PDT) and photothermal therapy (PTT), respectively. After degradation in the tumor microenvironment (TME), the released Mn²⁺ is able to act simultaneously as a magnetic resonance (MR) imaging contrast agent (CA) and as a Fenton-like agent for chemodynamic therapy (CDT). More importantly, synergistic treatment outcomes can be realized by reasonable and optimized design of the hollow nanosystems. This review summarizes various Mn-based hollow nanoplatforms, including hollow Mn_xO_y, hollow matrix-supported Mn_xO_y, hollow Mn-doped nanoparticles, hollow Mn complex-based nanoparticles, hollow Mn-cobalt (Co)-based nanoparticles, and hollow Mn-iron (Fe)-based nanoparticles, for MR imaging-guided cancer therapies. Finally, we discuss the potential obstacles and perspectives of these hollow Mn-based nanotheranostics for translational applications.

Self-Confirming Magnetosomes for Tumor-Targeted T1 /T2 Dual-Mode MRI and MRI-Guided Photothermal Therapy

Nanomaterials as T₁ /T₂ dual-mode magnetic resonance imaging (MRI) contrast agents have great potential in improving the accuracy of tumor diagnosis. Applications of such materials, however, are limited by the complicated chemical synthesis process and potential biosafety issues. In this study, the biosynthesis of manganese (Mn)-doped magnetosomes (MagMn) that not only can be used in T₁ /T₂ dual-mode MR imaging with self-confirmation for tumor detection, but also improve the photothermal conversion efficiency for MRI-guided photothermal therapy (PTT) is reported. The MagMn nanoparticles (NPs) are naturally produced through the biomineralization of magnetotactic bacteria by doping Mn into the ferromagnetic iron oxide crystals. In vitro and in vivo studies demonstrated that targeting peptides functionalized MagMn enhanced both T₁ and T₂ MRI signals in tumor tissue and significantly inhibited tumor growth by the further MRI-guided PTT. It is envisioned that the biosynthesized multifunctional MagMn nanoplatform may serve as a potential theranostic agent for cancer diagnosis and treatment.

Synthesis of Fe3O4@Gd2O3:Tb3+@SiOx multifunctional nanoparticles and their luminescent, magnetic and hyperthermia properties

Multifunctional Fe₃O₄@Gd₂O₃:Tb³⁺@SiOx nanoparticles were successfully synthesized by co-precipitation and polyol methods. The synthesized nanoparticles were composed by cubic phase as core of Fe₃O₄ and Gd₂O₃:Tb³⁺ and the shell of amorphous SiOx. The composites exhibited a spherical shape with a diameter of 10-15 nm and highly uniform dispersion. They showed not only excellent fluorescence under excitation at a wavelength of 278 nm, but also strong magnetic responsiveness (M_S = 24.040 emu g^-1). The results of magnetic resonance imaging in vitro (r₁ = 6.00 mm^-1 s^-1, r₂ = 63.95 mm^-1 s^-1) showed that the samples could be used as T₁-positive and T₂-negative contrast agents. In addition, it was found that Fe₃O₄@Gd₂O₃:Tb³⁺@SiOx attains hyperthermia temperature (43 °C) in 90 s under the alternating current magnetic field, and their specific absorption rate (229.9 w g^-1) was higher than that of Fe₃O₄ (183.92 w g^-1). Hence, the multifunctional nanoparticle could be used for the diagnosis and therapy of cancer.

Multifunctional Magnetic Resonance Imaging Probes

Magnetic resonance imaging is characterized by high spatial resolution and unsurpassed soft tissue discrimination. Development and characterization of both intrinsic and extrinsic magnetic resonance (MR) imaging probes in the last decade has further strengthened the pivotal role MR imaging holds in the assessment of cancer in preclinical and translational settings. Sophisticated chemical modifications of a variety of nanoparticulate probes hold the potential to deliver valuable multifunctional tools applicable in diagnostics and/or treatment in human oncology. MR imaging suffers from a lack of sensitivity achievable by, e.g., nuclear medicine imaging methods. Advantages of including additional functionality/functionalities in a probe suitable for MR imaging are thus numerous, comprising the addition of fundamentally different imaging information (diagnostics), drug delivery (therapy), or the combination of both (theranostics). In recent years, we have witnessed a plethora of preclinical multimodal or multifunctional imaging probes being published mainly as proof-of-principle studies, yet only a handful are readily applicable in clinical settings. This chapter summarizes recent innovations in the development of multifunctional MR imaging probes and discusses the suitability of these probes for clinical transfer.

H2O2/near-infrared light-responsive nanotheronostics for MRI-guided synergistic chemo/photothermal cancer therapy

Aim: To develop a H₂O₂/near-infrared (NIR) laser light-responsive nanoplatform (manganese-doped Prussian blue@polypyrrole [MnPB@PPy]) for synergistic chemo/photothermal cancer theranostics. Materials & methods: Doxorubicin (DOX) was loaded onto the surface of polypyrrole shells. The in vitro and in vivo MRI performance and anticancer effects of these nanoparticles (NPs) were evaluated. Results: The MnPB@PPy NPs could not only generate heat under NIR laser irradiation for cancer photothermal therapy but also act as an excellent MRI contrast agent. The loaded DOX could be triggered to release by both NIR light and H₂O₂ to enhance synergistic therapeutic efficacy. The antitumor effects were confirmed by in vitro cellular cytotoxicity assays and in vivo treatment in a xenograft tumor model. Conclusion: The designed H₂O₂/NIR light-responsive MnPB@PPy-DOX NPs hold great potential for future biomedical applications.

Plant tannin immobilized Fe3O4@SiO2 microspheres: A novel and green magnetic bio-sorbent with superior adsorption capacities for gold and palladium

In this paper, a new core-shell nanostructured magnetic bio-based composite was prepared by immobilizing persimmon tannin (PT) onto Fe₃O₄@SiO₂ microspheres, and the as designed Fe₃O₄@SiO₂@PT was utilized for adsorptive recovery of Au(III) and Pd(II). The preparation, morphology, composition and magnetic property of Fe₃O₄@SiO₂@PT were characterized. Adsorption parameters of Fe₃O₄@SiO₂@PT towards Au(III) and Pd(II) including initial pH, reaction time, initial concentration of metal ions, effect of acidity and interference of coexisting metal ions were investigated. It is sufficiently confirmed that silica was coated on Fe₃O₄ and persimmon tannin was immobilized on aminated Fe₃O₄@SiO₂. The thickness of silica and loaded persimmon tannin are around 18 nm and 14 nm, respectively. With only 1.00 wt% of persimmon tannin, however, the maximum adsorption capacities of Fe₃O₄@SiO₂@PT for Au(III) and Pd(II) were as high as 917.43 and 196.46 mg·g^-1, respectively. In addition, after adsorption of Au(III) and Pd(II), the magnetization saturation values (Ms) of Fe₃O₄@SiO₂@PT were high enough to guarantee efficient magnetic seperation. Metallic gold could be facilely recovered from wastewaters containing Au(III).

Dual T1/ T2 Nanoscale Coordination Polymers as Novel Contrast Agents for MRI: A Preclinical Study for Brain Tumor

In the last years, extensive attention has been paid on designing and developing functional imaging contrast agents for providing accurate noninvasive evaluation of pathology in vivo. However, the issue of false-positives or ambiguous imaging and the lack of a robust strategy for simultaneous dual-mode imaging remain to be fully addressed. One effective strategy for improving it is to rationally design magnetic resonance imaging (MRI) contrast agents (CAs) with intrinsic T₁/ T₂ dual-mode imaging features. In this work, the development and characterization of one-pot synthesized nanostructured coordination polymers (NCPs) which exhibit dual mode T₁/ T₂ MRI contrast behavior is described. The resulting material comprises the combination of different paramagnetic ions (Fe³⁺, Gd³⁺, Mn²⁺) with selected organic ligands able to induce the polymerization process and nanostructure stabilization. Among them, the Fe-based NCPs showed the best features in terms of colloidal stability, low toxicity, and dual T₁/ T₂ MRI contrast performance overcoming the main drawbacks of reported CAs. The dual-mode CA capability was evaluated by different means: in vitro phantoms, ex vivo and in vivo MRI, using a preclinical model of murine glioblastoma. Interestingly, the in vivo MRI of Fe-NCPs show T₁ and T₂ high contrast potential, allowing simultaneous recording of positive and negative contrast images in a very short period of time while being safer for the mouse. Moreover, the biodistribution assays reveals the persistence of the nanoparticles in the tumor and subsequent gradual clearance denoting their biodegradability. After a comparative study with commercial CAs, the results suggest these nanoplatforms as promising candidates for the development of dual-mode MRI CAs with clear advantages.

Bevacizumab and near infrared probe conjugated iron oxide nanoparticles for vascular endothelial growth factor targeted MR and optical imaging

Vascular endothelial growth factor (VEGF) plays a pivotal role in the cascade of development and progression of cancers. Targeting this cancer hallmark is a logical strategy for imaging based cancer detection and monitoring the anti-angiogenesis treatment. Using Bevacizumab (Avastin®), which is a recombinant humanized monoclonal antibody directly against VEGF and an angiogenesis inhibitor, as a targeting ligand, a multimodal VEGF targeted molecular imaging probe was developed by conjugating near infrared dye (NIR830) labeled bevacizumab to magnetic iron oxide nanoparticles (IONP) for optical and magnetic resonance (MR) imaging of cancers over-expressing VEGF. The targeting effect of NIR830-bevacizumab-IONPs on VEGF over-expressing cells was investigated by receptor mediated cell uptake experiments and a blocking assay using VEGF over-expressing 4T1 breast cancer cells. Systemic administration of VEGF-targeted NIR830-bevacizumab-IONPs into mice bearing 4T1 breast tumors resulted in higher accumulation of targeting IONPs in tumors compared to non-targeted IONPs. Quantitative analysis of T2-weighted MRI at 48 h post-injection revealed that the averaged percentage of signal intensity change in tumors treated with NIR830-bevacizumab-IONPs was 52.4 ± 11.0% compared to 26.9 ± 12.4% in controls treated with non-targeted IONPs. The results demonstrated the feasibility and efficacy of NIR830-bevacizumab-IONPs as a VEGF targeting dual-modality molecular imaging probe that can be potentially used for imaging of cancers with VEGF over-expression and delivery of bevacizumab for imaging guided anti-cancer treatment.

Microwave-assisted preparation of paramagnetic zwitterionic amphiphilic copolymer hybrid molybdenum disulfide for T1-weighted magnetic resonance imaging-guided photothermal therapy

Magnetic resonance imaging (MRI)-guided photothermal therapy (PTT) has recently attracted tremendous attention.

Europium-phenolic network coated BaGdF5 nanocomposites for tri-modal computed tomography/magnetic resonance/luminescence imaging

Multifunctional nanocomposites based on BaGdF₅ nanoparticles (NPs) and metal phenolic network (MPN) have been engineered as novel contrast agents for potential applications in X-ray computed tomography, magnetic resonance and luminescence imaging. The BaGdF₅@MPN nanocomposites were synthesized at room temperature by coating BaGdF₅ NPs with europium-phenolic network, which was obtained by the coordination of europium (III) with tannic acid (TA). The in vitro cytotoxicity assays against HepG2 cells revealed that the BaGdF₅@MPN nanocomposites presented better cytocompatibility and lower cytotoxity than pure BaGdF₅ NPs. In addition, vivid red and green luminescence can be observed by confocal laser scanning microscope (CLSM) from the BaGdF₅@MPN nanocomposites laden HepG2 cells under the excitation of UV (390 nm) and visible light (440 nm), respectively. The longitudinal relaxivity value (r₁) of the nanocomposites was 2.457 mM^-1s^-1. Moreover, the nanocomoposites exhibited X-ray computed tomography (CT) and T₁-weighted magnetic resonance (MR) imaging capacities, and the intensities of the enhanced signals of in vitro CT and MR images were proportional to the concentrations of the nanocomposites. These results indicated that the as-prepared BaGdF₅@MPN nanocomposites are promising contrast agents for CT/MR/luminescence imaging.

Bio-inspired synthesis of PEGylated polypyrrole@polydopamine nanocomposites as theranostic agents for T1-weighted MR imaging guided photothermal therapy

Polypyrrole nanoparticle (PPy) based theranostic agents for magnetic resonance imaging (MRI) guided photothermal therapy (PTT) have received increasing attention in recent years.