GdVO4:Eu3+,Bi3+ Nanoparticles as a Contrast Agent for MRI and Luminescence Bioimaging

Multifunctional Poly(Acrylic Acid)-Coated EuBiGd2O3 Nanocomposite as an Effective Contrast Agent in Spectral Photon Counting CT, MRI, and Fluorescence Imaging

Introduction

Recently, diagnostic methods based on multimodal and non-invasive imaging, such as MRI and CT scanners, have been developed for accurate cancer diagnosis. A key limitation of these imaging systems is their low contrast. Therefore, developing stable, non-toxic, and efficient multimodal imaging contrast agents is desirable. In this work, we demonstrated the synthesis of a poly(acrylic acid) (PAA) - coated nanoparticles (NPs), PAA@EuBiGd2O3-NPs as an imaging agent for contrast enhancement in spectral photon-counting computed tomography (SPCCT), magnetic resonance imaging (MRI) and fluorescence imaging (FL).

Methods

We synthesized PAA-coated EuBiGd2O3-NPs using a polyol method by dissolving metal nitrates and PAA in triethylene glycol. NaOH solution was added under constant heating at 180°C. The nanoparticles were precipitated with the addition of ethanol, then washed, dried, calcined at 600°C, and redispersed in water for further studies. The nanoparticles were characterized using TEM, SEM, XRD, XPS, FTIR, and PL spectroscopy. PAA@EuBiGd2O3-NPs were tested in vitro for their cytocompatibility with lung cancer epithelial cells (A549). The nanocomposite image contrast enhancement was evaluated using SPCCT, MRI, and FL imaging.

Results

The cell viability study showed that PAA@EuBiGd2O3-NPs is safe up to 250 µg/mL, exhibiting IC50 values of 365.8 and 337.8 µg/mL after 24 and 48 hours, respectively. The NPs have strong X-ray attenuation with a slope of ~61 HUmL/mg, as determined from the SPCCT concentration-dependent analysis. The MRI of the NPs reveals a high T1 contrast with a relaxivity of 11.77 mM-1s-1. Fluorescence imaging of cells incubated with PAA@EuBiGd2O₃-NPs shows strong red luminescence.

Conclusion

The new nanocomposite has proven to be an effective trimodal contrast agent with high attenuation in CT, enhanced T1 signal in MRI, and strong red luminescence in FL imaging with promising diagnostic capabilities.

Development of Biocompatible, UV and NIR Excitable Nanoparticles with Multiwavelength Emission and Enhanced Colloidal Stability

The development of functional nanoprobes for biomedical applications is highly important in the field of modern nanotechnology. Due to strict requirements, such as the ability to be excited using irradiation, which allows deep tissue penetration, nonblinking behavior, and good optical and colloidal stability, the choice of nanoparticles is limited, and their synthesis is challenging. Among all of the functional nanoprobes for biomedical purposes, upconverting nanoparticles, especially those with more complex architectures (e.g., core-shell or core-shell-shell), are the most promising candidates. This study demonstrates advanced synthetic routes for constructing biocompatible nanoprobes with tunable optical properties and colloidal stability. The core-shell-shell architecture of the nanoprobes allows excitation from at least four sources, such as 272 and 394 nm of near-ultraviolet (near-UV) irradiation and 980 and 808 nm near-infrared (NIR) lasers. Furthermore, Gd-matrix-based nanoprobes doped with lanthanide ions (Nd3+, Yb3+, Tm3+, and Eu3+) are known for their paramagnetic properties for magnetic resonance imaging (MRI) imaging as well as upconversion luminescence with diverse emission bands across the entire visible spectrum. This feature is highly desirable for photodynamic therapy applications, as the upconversion emission of the proposed nanoprobes could overlap with the absorption band of commonly used photosensitizers and could potentially result in an efficient energy transfer process and enhanced generation of reactive oxygen species or singlet oxygen.

Recent advances of lanthanide nanomaterials in Tumor NIR fluorescence detection and treatment

Lanthanide nanomaterials have garnered significant attention from researchers among the main near-infrared (NIR) fluorescent nanomaterials due to their excellent chemical and fluorescence stability, narrow emission band, adjustable luminescence color, and long lifetime. In recent years, with the preparation, functional modification, and fluorescence improvement of lanthanide materials, great progress has been made in their application in the biomedical field. This review focuses on the latest progress of lanthanide nanomaterials in tumor diagnosis and treatment, as well as the interaction mechanism between fluorescence and biological tissues. We introduce a set of efficient strategies for improving the fluorescence properties of lanthanide nanomaterials and discuss some representative in-depth research work in detail, showcasing their superiority in early detection of ultra-small tumors, phototherapy, and real-time guidance for surgical resection. However, lanthanide nanomaterials have only realized a portion of their potential in tumor applications so far. Therefore, we discuss promising methods for further improving the performance of lanthanide nanomaterials and their future development directions.

Pegylated Eu-enabled submicron alumina spheres as potential theranostics agent RD cell line as model

Objectives

This study is aimed to synthesis and evaluate PEGylated Eu enabled spherical alumina submicron particles (s-Al₂O₃:Eu) for potential theranostic applications.

Methods

This study is bisected into two parts, a) synthesis of PEGylated Eu enabled spherical alumina submicron particles (s-Al₂O₃:Eu), and b) characterization of the synthesized particles to determine their efficacy for potential theranostic applications.

The synthesis of the particles involved the following steps. In the first step, s-Al₂O₃:Eu is synthesized using solvothermal synthesis. In the next step, the particles undergo post synthesis water–ethanol treatment and calcination. The surface of the synthesized s-Al₂O₃:Eu particles is then coated by PEG to increase its biocompatibility.

Once the particles are prepared, they are characterized using different techniques. The microstructure, composition and structure of the particles is characterized using SEM, EDX and XRD techniques. The detection of the functional groups is done using FTIR analysis. The photoluminescence emission spectrum of s-Al₂O₃:Eu is studied using Photoluminescence spectroscopy. And, finally, the biocompatibility is studied using MTT assay on RD cell lines.

Results

The microstructure analysis, from the micrographs obtained from SEM, shows that the spherical alumina particles have a submicron size with narrow size distribution. The compositional analysis, as per EDX, confirms the presence of Oxygen, Aluminum and Europium in the particles. While, XRD analysis of s-Al₂O₃:Eu confirms the formation of alpha alumina phase after calcination at 700 °C. Emission peaks, obtained by Photoluminescence emission spectroscopy, show that the optimum emission intensities correspond to the transition from ⁵D₀ to ⁷F_j orbital of Eu⁺³. FTIR analysis confirms the successful coating of PEG. Finally, a cell viability of more than 86% is observed when the biocompatibility of the particles is studied, using MTT assay on RD cell lines.

Conclusions

s-Al₂O₃:Eu with narrow distribution are successfully synthesized. Structural and functional characterizations support the suitability of s-Al₂O₃:Eu as potential theranostic agent.

Influence of GdVO4:Eu3+ Nanocrystals on Growth, Germination, Root Cell Viability and Oxidative Stress of Wheat (Triticum aestivum L.) Seedlings

The increasing application of lanthanide-doped nanocrystals (LDNCs) entails the risk of a harmful impact on the natural environment. Therefore, in the presented study the influence of gadolinium orthovanadates doped with Eu³⁺ (GdVO₄:Eu³) nanocrystals on wheat (Triticum aestivum L.), chosen as a model plant species, was investigated. The seeds were grown in Petri dishes filled with colloids of LDNCs at the concentrations of 0, 10, 50 and 100 µg/mL. The plants’ growth endpoints (number of roots, roots length, roots mass, hypocotyl length and hypocotyl mass) and germination rate were not significantly changed after the exposure to GdVO₄:Eu³⁺ nanocrystals at all used concentrations. The presence of LDNCs also had no effect on oxidative stress intensity, which was determined on the basis of the amount of lipid peroxidation product (thiobarbituric acid reactive substances; TBARS) in the roots. Similarly, TTC (tetrazolium chloride) assay did not show any differences in cells’ viability. However, root cells of the treated seedlings contained less Evans Blue (EB) when compared to the control. The obtained results, on the one hand, suggest that GdVO₄:Eu³⁺ nanocrystals are safe for plants in the tested concentrations, while on the other hand they indicate that LDNCs may interfere with the functioning of the root cell membrane.

Vanadium-based nanomaterials for cancer diagnosis and treatment

In the past few decades, various vanadium compounds have displayed potential in cancer treatment. However, fast clearness in the body and possible toxicity of vanadium compounds has hindered their further development. Vanadium-based nanomaterials not only overcome these limitations, but take advantage of the internal properties of vanadium in photics and magnetics, which enable them as a multimodal platform for cancer diagnosis and treatment. In this paper, we first introduced the basic biological and pharmacological functions of vanadium compounds in treating cancer. Then, the synthesis routes of three vanadium-based nanomaterials were discussed, including vanadium oxides, 2D vanadium sulfides, carbides and nitrides: V_mX_n (X = S, C, N) and water-insoluble vanadium salts. Finally, we highlighted the applications of these vanadium-based nanomaterials as tumor therapeutic and diagnostic agents.

Effect of Cationic Brush-Type Copolymers on the Colloidal Stability of GdPO4 Particles with Different Morphologies in Biological Aqueous Media

In this study, we present the synthesis of cationic brush-type polyelectrolytes and their use in the stabilization of GdPO4 particles in aqueous media. Polymers of various compositions were synthesized via the RAFT polymerization route. SEC equipped with triple detection (RI, DP, RALS, and LALS) was used to determine the molecular parameters (Mn, Mw, Mw/Mn). The exact composition of synthesized polymers was determined using NMR spectroscopy. Cationic brush-type polymers were used to improve the stability of aqueous GdPO4 particle dispersions. First, the IEPs of GdPO4 particles with different morphologies (nanorods, hexagonal nanoprisms, and submicrospheres) were determined by measuring the zeta potential of bare particle dispersions at various pH values. Afterward, cationic brush-type polyelectrolytes with different compositions were used for the surface modification of GdPO4 particles (negatively charged in alkaline media under a pH value of ∼10.6). The concentration and composition effects of used polymers on the change in particle surface potential and stability (DLS measurements) in dispersions were investigated and presented in this work. The most remarkable result of this study is redispersible GdPO4 nanoparticle colloids with increased biocompatibility and stability as well as new insights into possible cationic brush-type polyelectrolyte applicability in both scientific and commercial fields.