Effect of Ho3+ Substitution on Magnetic Properties of ZnCr2Se4

A series of ZnCr2-xHoxSe4 microcrystalline spinels (where x = 0.05, 0.075, and 0.10) containing holmium ions in octahedral coordination were obtained by sintering of adequate reactants at high temperatures. The obtained doped materials were characterized by X-ray diffraction, Scanning Electron Microscopy, UV-Vis-NIR, molecular field approximation, and XPS spectroscopies. Their thermal properties were also investigated. The doping of the ZnCr2S4 matrix with paramagnetic Ho3+ ions with a content of not more than 0.1 and a screened 4f shell revealed a significant effect of orbital and Landau diamagnetism, a strong reduction in short-range ferromagnetic interactions, and a broadening and shift of the peak of the first critical field by simultaneous stabilization of the sharp peak in the second critical field. These results correlate well with FPLO calculations, which show that Cr sites have magnetic moments of 3.19 µB and Ho sites have significantly larger ones with a value of 3.95 µB. Zn has a negligible magnetic polarization of 0.02 µB, and Se induces a polarization of approximately -0.12 µB.

Core-multi-shell design: unlocking multimodal capabilities in lanthanide-based nanoparticles as upconverting, T2-weighted MRI and CT probes

Multimodal bioimaging probes merging optical imaging, magnetic resonance imaging (MRI), and X-ray computed tomography (CT) capabilities have attracted considerable attention due to their potential biomedical applications. Lanthanide-based nanoparticles are promising candidates for multimodal imaging because of their optical, magnetic and X-ray attenuation properties. We prepared a set of hexagonal-phase (β)-NaGdF4:Yb,Er/NaGdF4/NaDyF4 core/shell/shell nanoparticles (Dy-CSS NPs) and demonstrated their optical/T2-weighted MRI/CT multimodal capabilities. A known drawback of multimodal probes that merge the upconverting Er3+/Yb3+ ion pair with magnetic Dy3+ ions for T2-weighted MRI is the loss of upconversion (UC) emission due to Dy3+ poisoning. Particular attention was paid to controlled nanoparticle architectures with tuned inner shell thicknesses separating Dy3+ and Er3+/Yb3+ to shed light on the distance-dependent loss of UC due to Yb3+ → Dy3+ energy transfer. Based on the Er3+ UC spectra and the excited state lifetime of Yb3+, a 4 nm thick NaGdF4 inner shell did not only restore but enhanced the UC emission. We further investigated the effect of the outer NaDyF4 shell thickness on the particles' magnetic and CT performance. MRI T2 relaxivity measurements in vitro at a magnetic field of 7 T performed on citrate-capped Dy-CSS NPs revealed that NPs with the thickest outer shell thickness (4 nm) exhibited the highest r2 value, with a superior T2 contrast effect compared to commercial iron oxide and other Dy-based T2 contrast agents. In addition, the citrate-capped Dy-CSS NPs were demonstrated suitable for CT in in vitro imaging phantoms at X-ray energies of 110 keV, rendering them interesting alternatives to clinically used iodine-based agents that operate at lower energies.

Diagnostic and Therapeutic Approaches for Glioblastoma and Neuroblastoma Cancers Using Chlorotoxin Nanoparticles

Glioblastoma multiforme (GB) and high-risk neuroblastoma (NB) are known to have poor therapeutic outcomes. As for most cancers, chemotherapy and radiotherapy are the current mainstay treatments for GB and NB. However, the known limitations of systemic toxicity, drug resistance, poor targeted delivery, and inability to access the blood-brain barrier (BBB), make these treatments less satisfactory. Other treatment options have been investigated in many studies in the literature, especially nutraceutical and naturopathic products, most of which have also been reported to be poorly effective against these cancer types. This necessitates the development of treatment strategies with the potential to cross the BBB and specifically target cancer cells. Compounds that target the endopeptidase, matrix metalloproteinase 2 (MMP-2), have been reported to offer therapeutic insights for GB and NB since MMP-2 is known to be over-expressed in these cancers and plays significant roles in such physiological processes as angiogenesis, metastasis, and cellular invasion. Chlorotoxin (CTX) is a promising 36-amino acid peptide isolated from the venom of the deathstalker scorpion, Leiurus quinquestriatus, demonstrating high selectivity and binding affinity to a broad-spectrum of cancers, especially GB and NB through specific molecular targets, including MMP-2. The favorable characteristics of nanoparticles (NPs) such as their small sizes, large surface area for active targeting, BBB permeability, etc. make CTX-functionalized NPs (CTX-NPs) promising diagnostic and therapeutic applications for addressing the many challenges associated with these cancers. CTX-NPs may function by improving diffusion through the BBB, enabling increased localization of chemotherapeutic and genotherapeutic drugs to diseased cells specifically, enhancing imaging modalities such as magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), optical imaging techniques, image-guided surgery, as well as improving the sensitization of radio-resistant cells to radiotherapy treatment. This review discusses the characteristics of GB and NB cancers, related treatment challenges as well as the potential of CTX and its functionalized NP formulations as targeting systems for diagnostic, therapeutic, and theranostic purposes. It also provides insights into the potential mechanisms through which CTX crosses the BBB to bind cancer cells and provides suggestions for the development and application of novel CTX-based formulations for the diagnosis and treatment of GB and NB in the future.

Recent development of contrast agents for magnetic resonance and multimodal imaging of glioblastoma

Glioblastoma (GBM) as the most common primary malignant brain tumor exhibits a high incidence and degree of malignancy as well as poor prognosis. Due to the existence of formidable blood–brain barrier (BBB) and the aggressive growth and infiltrating nature of GBM, timely diagnosis and treatment of GBM is still very challenging. Among different imaging modalities, magnetic resonance imaging (MRI) with merits including high soft tissue resolution, non-invasiveness and non-limited penetration depth has become the preferred tool for GBM diagnosis. Furthermore, multimodal imaging with combination of MRI and other imaging modalities would not only synergistically integrate the pros, but also overcome the certain limitation in each imaging modality, offering more accurate morphological and pathophysiological information of brain tumors. Since contrast agents contribute to amplify imaging signal output for unambiguous pin-pointing of tumors, tremendous efforts have been devoted to advances of contrast agents for MRI and multimodal imaging. Herein, we put special focus on summary of the most recent advances of not only MRI contrast agents including iron oxide-, manganese (Mn)-, gadolinium (Gd)-, ¹⁹F- and copper (Cu)-incorporated nanoplatforms for GBM imaging, but also dual-modal or triple-modal nanoprobes. Furthermore, potential obstacles and perspectives for future research and clinical translation of these contrast agents are discussed. We hope this review provides insights for scientists and students with interest in this area.

Recent Advances in Lanthanide Based Nano-Architectures as Probes for Ultra High-Field Magnetic Resonance Imaging

Paramagnetic Lanthanide ions incorporated into nano- architectures are emerging as a versatile platform for Magnetic Resonance Imaging (MRI) contrast agents due to their strong contrast enhancement effects combined with the platform capability to include multiple imaging modalities. This short review examines the application of lanthanide based nanoarchitectures (nanoparticles and nano- assemblies) in the development of multifunctional probes for single and multimodal imaging involving high field MRI as one imaging modality.

A novel green emitting NaGdF4:Dy3+,Ho3+ phosphor with tunable photoluminescence

Dy³⁺,Ho³⁺ co-doped β-NaGdF₄ nanomaterials emitted different shades of green light, which varies from the light blue area towards the blue-green area and ultimately to the green area with the increase of Ho³⁺ ions.

nanocrystals (0 ≤ x ≤ 1): growth, size control and shell formation on β-NaCeF4:Tb core particles

is an interesting shell material for β-NaREF₄ particles of the lighter lanthanides (RE = Ce, Pr, Nd), as variation of its strontium content x allows to vary its lattice parameters and match those of the core material.

Facile synthesis and functionalization of color-tunable Ln3+-doped KGdF4 nanoparticles on a microfluidic platform

Hyaluronic acid (HA)-functionalized lanthanide-doped KGdF₄ nanoparticles were synthesized through two steps on a microfluidic platform. This microfluidic synthesis method allows better control of experimental conditions with lower labor and energy input than traditional beaker synthesis methods for large-scale production of nanoparticles with higher uniformity. First, Ln³⁺-doped KGdF₄ nanoparticles were ultrafast (in minutes) and continuously synthesized using a four-inlets microfluidic chip at room temperature. Then, HA is continuously functionalized on the surface of Ln³⁺-doped KGdF₄ nanoparticles using a T-shape chip through electrostatic adsorption. The synthesized nanoparticles show good uniformity, high biocompatibility, targeted cellular uptake, photoluminescence (PL) and magnetic resonance (MR) properties. This work highlights the potential of microfluidic platform for the development of multifunctional nanoparticles in biomedicine.

Recent advances in the development of nanoparticles for multimodality imaging and therapy of cancer

This review explores recent work directed toward the development of nanoparticles (NPs) for multimodality cancer imaging and targeted cancer therapy. In the growing era of precision medicine, theranostics, or the combined use of targeted molecular probes in diagnosing and treating diseases is playing a particularly powerful role. There is a growing interest, particularly over the past few decades, in the use of NPs as theranostic tools due to their excellent performance in receptor target specificity and reduction in off-target effects when used as therapeutic agents. This review discusses recent advances, as well as the advantages and challenges of the application of NPs in cancer imaging and therapy.

PMAO coated Na(Gd0.5Lu0.5)F4:Nd3+ nanocrystals as multifunctional contrast agent with NIR optical, X-ray and magnetic imaging properties

Nanomaterials with multiple imaging functionalities are nowadays getting tremendous attention due to their several superior features compared to existing contrast agents. By developing a nanomaterial that exhibit multiple functionalities, the possibility to increase the amount of imaging information obtained in a short amount of time is becoming more and more a reality. In this work, we developed a multifunctional nanocrystals (NCs), Na(Gd0.5Lu0.5)F4:Nd3+, that combines multiple rare-earth features as an all-in-one imaging agent comprised of optical imaging, magnetic imaging, and X-ray imaging by utilizing the superparamagnetic features of Gd3+, the high X-ray absorption cross section of Lu3+, and the NIR fluorescence of Nd3+. Morphology, optical properties, and cell viability are shown in detail where the utility of this multifunctional imaging agent was confirmed by optical, X-ray and magnetic imaging experiments. Surface functionalization of the NCs is also presented to highlight the potential application of the NCs as contrast agents in biological imaging.

Polydopamine-coated NaGdF4:Dy for T1/T2-weighted MRI/CT multimodal imaging-guided photothermal therapy

T₁/T₂-weighted MRI/CT imaging-guided PTT agent NaGdF₄:Dy@PPF was prepared and demonstrated its promising application for early diagnosis and therapy of tumors.

Chlorotoxin-A Multimodal Imaging Platform for Targeting Glioma Tumors

Chlorotoxin (CTX) is a 36-amino-acid disulfide-containing peptide derived from the venom of the scorpion Leiurus quinquestriatus. CTX alters physiology in numerous ways. It interacts with voltage gated chloride channels, Annexin-2, and matrix metalloproteinase-2 (MMP-2). CTX-based bioconjugates have been widely subjected to phase I/II clinical trials and have shown substantial promise. Many studies have demonstrated that CTX preferentially binds to neuroectodermal tumors, such as glioblastoma, without cross-reactivity to normal brain cells. With its ability to penetrate the blood-brain-barrier (BBB) and its tyrosine residue allows covalent conjugation with functional moieties, CTX is an attractive platform to explore development of diagnostic and therapeutic agents for gliomas. In this review, we outline CTX structure and its molecular targets, summarize molecular variations of CTX developed for glioma imaging, and discuss future trends and perspectives for CTX conjugates as a theranostic agent.

Comparative toxicity and contrast enhancing assessments of Gd2O3@BSA and MnO2@BSA nanoparticles for MR imaging of brain glioma

The albumin-templated Gd₂O₃ and MnO₂ nanoparticles (NPs) have been developed as a new type of magnetic resonance (MR) T₁ contrast agents. However, their potential toxicity and applicability for MR imaging of brain gliomas has not been fully explored so far. In this study, we prepared Gd₂O₃@BSA and MnO₂@BSA nanoparticles (NPs) and investigated their toxicity comprehensively and comparatively by H&E staining, blood biochemical analysis, and adverse outcome pathways testing. It is revealed that both Gd₂O₃@BSA and MnO₂@BSA NPs are biocompatible at a rational dose level. Although the relaxivity of MnO₂@BSA NPs is less than that of Gd₂O₃@BSA NPs, the MnO₂@BSA NPs lead to a greater contrast enhancement in the brain glioma due to the controlled release of Mn ions under the acidic tumor microenvironmental conditions. These comparative toxicity and contrast enhancement data are of fundamental importance for the clinical translation of Gd₂O₃@BSA and MnO₂@BSA NPs as MR contrast agents for brain glioma diagnosis.

NIR-to-NIR UCL/T1-weighted MR/CT multimodal imaging by NaYbF4:Tm@NaGdF4:Yb-PVP upconversion nanoparticles

Multimodal imaging nanoprobes are urgently sought because they can integrate different imaging function into individual nanoplatform and provide more comprehensive and accurate information for the diagnosis of early-stage tumor. Lanthanide-based upconversion nanoparticles (UCNPs) are regarded as promising nanoplatforms to fabricate these probes. Herein, we firstly developed the active core-active shell structured NaYbF₄:Tm@NaGdF₄:Yb-PVP UCNPs with the average diameter of 13.23±0.96nm as multimodal imaging probes. These water-dispersible nanoprobes presented excellent near-infrared to near-infrared (NIR-to-NIR) upconversion luminescence (UCL) performance, which is favorable for optical bioimaging due to deeper tissue penetration and autofluorescence reduction. After coated with the NaGdF₄:Yb active shell, the UCL emission intensity at 800nm increased by 7.2times. These nanoprobes exhibited a desirable longitudinal relaxivity (r₁=3.58L/(mmols)) and strong X-ray attenuation property (58.84HUL/g). The cytotoxicity assessment, histology analysis and biodistribution study revealed that NaYbF₄:Tm@NaGdF₄:Yb-PVP UCNPs had relatively low cytotoxicity and negligible organ toxicity. These UCNPs were applied for NIR-to-NIR UCL imaging in vivo. More importantly, the detection of small tumor was successfully achieved under T₁-weighted MRI and CT imaging modalities after intravenous injection of these UCNPs. These results revealed that NaYbF₄:Tm@NaGdF₄:Yb-PVP UCNPs could serve as promising NIR-to-NIR UCL/MRI/CT trimodal imaging probes.

Gadolinium-based nanoscale MRI contrast agents for tumor imaging

Gadolinium-based nanoscale magnetic resonance imaging (MRI) contrast agents (CAs) have gained significant momentum as a promising nanoplatform for detecting tumor tissue in medical diagnosis, due to their favorable capability of enhancing the longitudinal relaxivity (r₁) of individual gadolinium ions, delivering to the region of interest a large number of gadolinium ions, and incorporating different functionalities. This mini-review highlights the latest developments and applications, and simultaneously gives some perspectives for their future development.

Optical nanoprobes for biomedical applications: shining a light on upconverting and near-infrared emitting nanoparticles for imaging, thermal sensing, and photodynamic therapy

Shining a light on spectrally converting lanthanide (Ln³⁺)-doped nanoparticles: progress, trends, and challenges in Ln³⁺-nanoprobes for near-infrared bioimaging, nanothermometry, and photodynamic therapy.

Aqueous synthesis of dual-targeting Gd-doped CuInS2/ZnS quantum dots for cancer-specific bi-modal imaging

CIGS/ZnS@FA|APBA q-dots were synthesized in an aqueous phase; these quantum dots exhibited great potential as dual-modal nanoprobes for optical/MR imaging.

Citrate-stabilized lanthanide-doped nanoparticles: brain penetration and interaction with immune cells and neurons

Aim: To unravel key aspects of the use of lanthanide-doped nanoparticles (NPs) in biomedicine, the interaction with immune and brain cells. Materials & methods: Effects of citrate-stabilized CaF2 and SrF2: Yb, Er NPs (13–15 nm) on human dendritic cells and neurons were assessed in vitro. In vivo distribution was analyzed in mice at tissue and ultrastructural levels, and with glia immunophenotyping. Results: The NPs did not elicit dendritic cell activation and were internalized by cultured neurons, without viability changes. After intravenous injection, NPs were found in the brain parenchyma, without features of glial neuroinflammatory response. Conclusion: Lanthanide-doped NPs do not activate cells protagonists of systemic and brain immune responses, are endocytosed by neurons and can cross an intact blood–brain barrier.

Fabrication of RGD-conjugated Gd(OH)3:Eu nanorods with enhancement of magnetic resonance, luminescence imaging and in vivo tumor targeting

The development of multimodal probes with magnetic resonance imaging (MRI) and intraoperative fluorescence imaging is the most challenging task in the field of tumor diagnosis. Herein, a simple one-pot hydrothermal method is used to prepare Eu-doped Gd(OH)₃ nanorods (Gd(OH)₃:Eu NRs) with good fluorescence and the longitudinal relaxivity r₁ value of 4.78 (Gd mM s^-1). After dual-functionalized maleimide-polyethylene glycol-succinimide (Mal-PEG-NHS) macromolecules are coated on the surface of Gd(OH)₃:Eu NRs (PEG-NRs), the results of a lower degradation ratio in newborn calf serum (NCS), reactive oxygen species (ROS) generation in L929 cells and the hemolytic rate of PEG-NRs show their good cyto-compatibility and longer blood circulation time. Moreover, the actively tumor-targeting properties are endowed to NRs through the conjugation of cyclic arginine-glycine-aspartic acid (cRGD) (denoted RGD-NRs). The bio-distributions of RGD-NRs in tumor-bearing nude mice via tail-vein injection indicate that RGD-NRs are specifically taken-up by gliomas. The tests of in vivo T₁-weighted MR imaging via tail-vein injection confirm that RGD-NRs possess a higher positive signal-enhancement ability in gliomas. Besides, the better luminescence imaging of living cells under a fluorescence microscope and the clear in vivo fluorescence imaging further confirm the targeting properties and better in vivo optical imaging behavior of RGD-NRs.

Eu3+ doped α-sodium gadolinium fluoride luminomagnetic nanophosphor as a bimodal nanoprobe for high-contrast in vitro bioimaging and external magnetic field tracking applications

Herein, we introduce a novel strategy for the synthesis of Eu3+ doped α-sodium gadolinium fluoride (α-NaGd0.88F4:Eu0.123+) based luminomagnetic nanophosphors using hydrothermal route. The synthesized nanophosphor has exceptional luminescent and paramagnetic properties in a single host lattice, which is highly desirable for biomedical applications. This highly luminescent nanophosphor with an average particle size ∼ 5±3 nm enables high-contrast fluorescent imaging with decreased light scattering. In vitro cellular uptake is shown by fluorescent microscopy that envisages the characteristic hypersensitive red emission of Eu3+ doped α-sodium gadolinium fluoride centered at 608 nm (5D0-7F2) upon 465 nm excitation wavelength. No apparent cytotoxicity is observed. Furthermore, time- resolved emission spectroscopy and SQUID magnetic measurements successfully demonstrate a photoluminescence decay time in microseconds and enhanced paramagnetic behavior respectively, which promises the applications of nanophosphors in biomedical studies. Hence, the obtained results strongly suggest that this nanophosphor could be potentially used as a bimodal nanoprobe for high-contrast in vitro bio-imaging of HeLa cells and external magnetic field tracking applications of luminomagnetic nanophosphors using permanent magnet.

Bio-inspired nano tools for neuroscience

Research and treatment in the nervous system is challenged by many physiological barriers posing a major hurdle for neurologists. The CNS is protected by a formidable blood brain barrier (BBB) which limits surgical, therapeutic and diagnostic interventions. The hostile environment created by reactive astrocytes in the CNS along with the limited regeneration capacity of the PNS makes functional recovery after tissue damage difficult and inefficient. Nanomaterials have the unique ability to interface with neural tissue in the nano-scale and are capable of influencing the function of a single neuron. The ability of nanoparticles to transcend the BBB through surface modifications has been exploited in various neuro-imaging techniques and for targeted drug delivery. The tunable topography of nanofibers provides accurate spatio-temporal guidance to regenerating axons. This review is an attempt to comprehend the progress in understanding the obstacles posed by the complex physiology of the nervous system and the innovations in design and fabrication of advanced nanomaterials drawing inspiration from natural phenomenon. We also discuss the development of nanomaterials for use in Neuro-diagnostics, Neuro-therapy and the fabrication of advanced nano-devices for use in opto-electronic and ultrasensitive electrophysiological applications. The energy efficient and parallel computing ability of the human brain has inspired the design of advanced nanotechnology based computational systems. However, extensive use of nanomaterials in neuroscience also raises serious toxicity issues as well as ethical concerns regarding nano implants in the brain. In conclusion we summarize these challenges and provide an insight into the huge potential of nanotechnology platforms in neuroscience.

Characterization of multifunctional β-NaEuF4/NaGdF4 core-shell nanoparticles with narrow size distribution

The properties of β-NaEuF4/NaGdF4 core-shell nanocrystals have been thoroughly investigated. Nanoparticles with narrow size distribution and an overall diameter of ∼22 nm have been produced with either small β-NaEuF4 cores (∼3 nm diameter) or large β-NaEuF4 cores (∼18 nm diameter). The structural properties and core-shell formation are investigated by X-ray diffraction, transmission electron microscopy and electron paramagnetic resonance, respectively. Optical luminescence measurements and X-ray photoelectron spectroscopy are employed to gain information about the optical emission bands and valence states of the rare earth constituents. Magnetic characterization is performed by SQUID and X-ray magnetic circular dichroism measurements at the rare earth M(4,5) edges. The characterization of the core-shell nanoparticles by means of these complementary techniques demonstrates that partial intermixing of core and shell materials takes place, and a significant fraction of europium is present in the divalent state which has significant influence on the magnetic properties. Hence, we obtained a combination of red emitting Eu(3+) ions and paramagnetic Gd(3+) ions, which may be highly valuable for potential future applications.

Improving the MR Imaging Sensitivity of Upconversion Nanoparticles by an Internal and External Incorporation of the Gd(3+) Strategy for in Vivo Tumor-Targeted Imaging

Gd(3+)-ion-doped upconversion nanoparticles (UCNPs), integrating the advantages of upconversion luminescence and magnetic resonance imaging (MRI) modalities, are capturing increasing attention because they are promising to improve the accuracy of diagnosis. The embedded Gd(3+) ions in UCNPs, however, have an indistinct MRI enhancement owing to the inefficient exchange of magnetic fields with the surrounding water protons. In this study, a novel approach is developed to improve the MR imaging sensitivity of Gd(3+)-ion-doped UCNPs. Bovine serum albumin (BSA) bundled with DTPA-Gd(3+) (DTPA(Gd)) is synthesized both as the MR imaging sensitivity synergist and phase-transfer ligand for the surface engineering of UCNPs. The external Gd(3+) ion attachment strategy is found to significant improve the MR imaging sensitivity of Gd(3+)-ion-doped UCNPs. The relaxivity analysis shows that UCNPs@BSA·DTPA(Gd) exhibit higher relaxivity values than do UCNPs@BSA without DTPA(Gd) moieties. Another relaxivity study discloses a striking message that the relaxivity value does not always reflect the realistic MRI enhancement capability. The high concentration of Gd(3+)-ion-containing UCNPs with further surface-engineered BSA·DTPA(Gd) (denoted as UCNPs-H@BSA·DTPA(Gd)) exhibits a more pronounced MRI enhancement capability compared to the other two counterparts [UCNPs-N@BSA·DTPA(Gd) and UCNPs-L@BSA·DTPA(Gd) (-N and -L are denoted as zero and low concentrations of Gd(3+) ion doping, respectively)], even though it holds the lowest r1 of 1.56 s(-1) per mmol L(-1) of Gd(3+). The physicochemical properties of UCNPs are essentially maintained after BSA·DTPA(Gd) surface decoration with good colloidal stability, in addition to improving the MR imaging sensitivity. In vivo T1-weighted MRI shows potent tumor-enhanced MRI with UCNPs-H@BSA·DTPA(Gd). An in vivo biodistribution study indicates that it is gradually excreted from the body via hepatobiliary and renal processing with no obvious toxicity. It could therefore be concluded, with improved MR imaging sensitivity by an internal and external incorporation of Gd(3+) strategy, that UCNPs-H@BSA·DTPA(Gd) presents great potential as an alternative in tumor-targeted MR imaging.

Mesoporous silica coated Gd2(CO3)3:Eu hollow nanospheres for simultaneous cell imaging and drug delivery

The efficient optical/MR imaging capabilities, and the hollow structure make Gd₂(CO₃)₃:Eu@mSiO₂ a promising platform for simultaneous bioimaging and drug delivery.

Ultra-small and size tunable PVP-NaGdF4:Dy nanoparticles with high biocompatibility for multimodal tumor imaging

Ultra-small PVP-NaGdF₄:Dy nanoprobes were prepared and they could induce obvious signal enhancement in T₁/T₂-weighted MRI and CT imaging.

An ultrasmall and metabolizable PEGylated NaGdF4:Dy nanoprobe for high-performance T(1)/T(2)-weighted MR and CT multimodal imaging

Lanthanide-based multimodal probes with high sensitivity, simple synthesis strategy, and good biocompatibility promise new applications for clinical diagnosis. However, today's challenge is not only to develop high-performance multimodal probes for more accurate and reliable diagnosis, but also to understand the fate of these probes in vivo. In this context, a novel PEGylated Dy-doped NaGdF4 nanoprobe (PEG-NaGdF4:Dy) was designed and fabricated as a T1/T2-weighted MRI/CT imaging agent. This nanoprobe has a distinct longitudinal relaxivity (r1 = 5.17 mM(-1) s(-1)), relatively high transverse relaxivity (r2 = 10.64 mM(-1) s(-1)), and exhibits strong X-ray attenuation properties (44.70 HU L g(-1)) in vitro. Furthermore, T1/T2-weighted MRI/CT imaging in vivo confirmed that this PEG-NaGdF4:Dy nanoprobe could lead to a significant contrast enhancement effect on liver, spleen and kidney at 24 h post injection. The MTT assay, histological analysis, and biodistribution investigation demonstrated that this multifunctional nanoprobe possessed relatively low cytotoxicity, negligible tissue damage and could be completely excreted out of the body of mice as time prolonged. Therefore, the present PEG-NaGdF4:Dy nanoprobe has the potential for the development of multifunctional T1/T2-weighted MRI/CT imaging to provide more comprehensive and accurate diagnosis information.

NaGdF4:Yb(3+)/Er(3+)@NaGdF4:Nd(3+)@Sodium-Gluconate: Multifunctional and Biocompatible Ultrasmall Core-Shell Nanohybrids for UCL/MR/CT Multimodal Imaging

Multimodal bioimaging nanoparticles by integrating diverse imaging ingredients into one system, represent a class of emerging advanced materials that provide more comprehensive and accurate clinical diagnostics than conventional contrast agents. Here monodisperse and biocompatible core-shell nanoparticles, NaGdF4: Yb(3+)/Er(3+)@NaGdF4:Nd@sodium-gluconate (termed as GNa-Er@Nd), with about 26 nm in diameter were successfully prepared by a facile two step reactions in high boiling solvents, and followed a ligand exchange process with sodium gluconate. The resulting GNa-Er@Nd nanoparticles were well characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), and zeta potentials. These nanohybrids present brightly dual-wavelength excited upconversion luminescence (UCL) under both 980 and 793 nm laser because of the synergistic effect of Yb(3+)/Er(3+) and Nd(3+). They also exhibited excellent relaxivity parameters (r1) in magnetic resonance imaging (MRI) and Hounsfield units (HU) in X-ray computed tomography (CT) that are comparable to the clinical contrast agents. Therefore, these small and monodisperse nanoparticles provide options to construct a unique platform for potential multimodal UCL/CT/MRI imaging simultaneously.

Nanostructured magnetic nanocomposites as MRI contrast agents

Magnetic resonance imaging (MRI) has become an integral part of modern clinical imaging due to its non-invasiveness and versatility in providing tissue and organ images with high spatial resolution. With the current MRI advancement, MRI imaging probes with suitable biocompatibility, good colloidal stability, enhanced relaxometric properties and advanced functionalities are highly demanded. As such, MRI contrast agents (CAs) have been an extensive research and development area. In the recent years, different inorganic-based nanoprobes comprising inorganic magnetic nanoparticles (MNPs) with an organic functional coating have been engineered to obtain a suitable contrast enhancement effect. For biomedical applications, the organic functional coating is critical to improve colloidal stability and biocompatibility. Simultaneously, it also provides a building block for generating a higher dimensional secondary structure. In this review, the combinatorial design approach by a self-assembling pre-formed hydrophobic inorganic MNPs core (from non-polar thermolysis synthesis) into various functional organic coatings (e.g. ligands, amphiphilic polymers and graphene oxide) to form water soluble nanocomposites will be discussed. The resultant magnetic ensembles were classified based on their dimensionality, namely, 0-D, 1-D, 2-D and 3-D structures. This classification provides further insight into their subsequent potential use as MRI CAs. Special attention will be dedicated towards the correlation between the spatial distribution and the associated MRI applications, which include (i) coating optimization-induced MR relaxivity enhancement, (ii) aggregation-induced MR relaxivity enhancement, (iii) off-resonance saturation imaging (ORS), (iv) magnetically-induced off-resonance imaging (ORI), (v) dual-modalities MR imaging and (vi) multifunctional nanoprobes.

Targeted imaging of brain gliomas using multifunctional Fe3O4/MnO nanoparticles

The CTX-conjugated Fe₃O₄/MnO hybrid nanoparticles were synthesized and their feasibility for targeted dual-modality T₁–T₂ MR imaging of brain gliomas was demonstrated.

Upconversion nanophosphors for solar cell applications

This review focuses on the various synthetic approaches to upconversion nanocrystals and recent developments in the photovoltaic applications of upconversion nanomaterials.