Europium-Doped Gd2O3 Nanotubes Increase Bone Mineral Density in Vivo and Promote Mineralization in Vitro

Biomedical Applications of Gadolinium-Containing Biomaterials: Not Only MRI Contrast Agent

The potential applications of rare earth elements (REEs) in biomedical fields have been intensively investigated. Numerous studies have shown that doping biomaterials with REEs can enhance their properties. Gadolinium (Gd) is a biocompatible REE that holds promise in biomedical applications. This review examines the use of Gd-doped biomaterials in osteogenic, antimicrobial, anticancer applications, and in bioimaging and bioprobes, as reported in the literature until December 2024. The included studies demonstrate that Gd-containing biomaterials promote osteogenesis, enhance antimicrobial properties, and perform well in anticancer applications and bioimaging. Taken together, they point to the considerable potential of Gd-doped biomaterials and thus to avenues for future research.

Eu-Doped TiO2 Coatings via One-Step In Situ Preparation Enhance Macrophage Polarization and Osseointegration of Implants

The controllable regulation of immune and osteogenic processes plays a critical role in the modification of biocompatible materials for tissue regeneration. In this study, titanium dioxide-europium coatings (MAO/Eu) were prepared on the surface of a titanium alloy (Ti-6Al-4V) via a one-step process combining microarc oxidation (MAO) and in situ doping. The incorporation of Eu significantly improved the hydrophilic and mechanical properties of the TiO2 coatings without altering their morphology. The presence of Eu effectively stimulated calcium influx in macrophages and activated β-catenin through the wnt/β-catenin signaling pathway. Consequently, macrophage M2 polarization was accelerated through the overexpression of prostaglandin E2 (PGE2). Additionally, Ca2+ promoted the osteogenic differentiation of MC3T3-E1 cells through the synergistic upregulation of transcription factors (e.g., AP-1, BMP-2). In vivo studies demonstrated that MAO/Eu coatings significantly enhanced osseointegration compared with the titanium alloy group. Therefore, MAO/Eu shows promising potential as an ideal coating for implants that offers effective immunomodulatory strategies and improves bone integration.

Mangiferin- and GNPs/ECPP-loaded platform of UH with dual bi-directional dynamic modulation of stem cells/macrophages and osteoblasts/osteoclasts for the prevention of aseptic loosening

Aseptic inflammation and osteolysis triggered by the phagocytosis of implant wear particles by macrophages are important reasons for aseptic loosening (AL) in total joint replacement, which ultimately leads to implant failure. Therefore, the development of implants with long-term effectiveness in preventing AL is a pressing issue. In contrast to the conventional idea of reducing the occurrence of AL through anti-inflammatory treatment, we prepared implants based on a novel concept: to prevent AL by returning the dynamic balance of osteogenesis/osteolysis through dynamic modulation, which is expected to completely resolve the problem of AL. In this study, a natural polyphenol, mangiferin (MAN), and a composite filler (GNPs/ECPP) were loaded into ultrahigh-molecular-weight polyethylene (UH) to construct a hip implant component with the ability to prevent AL. This modified implant was able to improve the oxidation resistance and wear resistance of implants, which could reduce the production of wear particles, recruit BMSCs as well as promote their proliferation/osteogenic differentiation and inhibit macrophage activity and RANKL-induced macrophage osteoclast differentiation in vitro. These effects suggest that this modified implant has achieved the dual bi-directional dynamic modulation of stem cells/macrophages and osteoblasts/osteoclasts for the prevention of aseptic loosening. Notably, in vivo experiments for implantation of wear-particle-coated titanium rods demonstrated that wear particles from the prepared implant significantly promoted the osseointegration capacity of implanted prosthesis (titanium rod) and effectively inhibited peri-prosthesis osteolysis. This work provides a new concept and presents a promising way for the development of durable implant components with long-term protection against AL.

Heterothermic Cataluminescence Sensor System for Efficient Determination of Aldehyde Molecules

A simple and stable cataluminescence (CTL) sensing platform based on a single sensing material for effective and rapid detection of aldehydes is an urgent need due to growing concerns for the environment, security, and health. Here, an effective and user-friendly identification method is successfully proposed to determine six common aldehydes of homologous compounds via a heterothermic CTL sensor system. Using Gd2O3 with excellent catalytic activity as a sensing material, thermodynamic and kinetic insights into the interactions between Gd2O3 and aldehydes at different temperatures were extracted and integrated to generate a unique constellation profile for each tested aldehyde, whereby achieving their effective and prompt determination. Moreover, the sensor system allowed the quantitative analysis of aldehydes with detection limits of 0.001, 0.009, 0.011, 0.011, 0.007, and 0.003 μg mL-1. Significantly, the sensor system had an excellent stability of up to 30 days. The CTL sensing platform was constructed based on a thermal regulation strategy that can provide a new approach to chemical agent identification.

Systematic review of the osteogenic effect of rare earth nanomaterials and the underlying mechanisms

Rare earth nanomaterials (RE NMs), which are based on rare earth elements, have emerged as remarkable biomaterials for use in bone regeneration. The effects of RE NMs on osteogenesis, such as promoting the osteogenic differentiation of mesenchymal stem cells, have been investigated. However, the contributions of the properties of RE NMs to bone regeneration and their interactions with various cell types during osteogenesis have not been reviewed. Here, we review the crucial roles of the physicochemical and biological properties of RE NMs and focus on their osteogenic mechanisms. RE NMs directly promote the proliferation, adhesion, migration, and osteogenic differentiation of mesenchymal stem cells. They also increase collagen secretion and mineralization to accelerate osteogenesis. Furthermore, RE NMs inhibit osteoclast formation and regulate the immune environment by modulating macrophages and promote angiogenesis by inducing hypoxia in endothelial cells. These effects create a microenvironment that is conducive to bone formation. This review will help researchers overcome current limitations to take full advantage of the osteogenic benefits of RE NMs and will suggest a potential approach for further osteogenesis research.

Doped Multiple Nanoparticles with Hydroxyapatite Coating Show Diverse Health Effects in vivo

Introduction

The lack of osteoinductive, angiogenic and antimicrobial properties of hydroxyapatite coatings (HA) on titanium surfaces severely limits their use in orthopedic and dental implants. Therefore, we doped SiO2, Gd2O3 and CeO2 nanoparticles into HA to fabricate a HASiGdCe coating with a combination of decent antibacterial, angiogenic and osteogenic properties by the plasma spraying technique.

Methods

The HASiGdCe coating was analyzed by SEM (EDS), surface roughness tests, contact angle tests, XRD, FTIR spectroscopy, tensile tests and electrochemical dynamic polarization tests. Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO-1) were used as representative bacteria to verify the antibacterial properties of the HASiGdCe coating. We evaluated the cytocompatibility and in vitro osteoinductivity of the HASiGdCe coating by investigating its effect on the cell viability and osteogenic differentiation of MC3T3-E1 cells. We assessed the in vitro angiogenic activity of the HASiGdCe coating by migration assay, tube formation assay, and RT‒PCR analysis of angiogenic genes in HUVECs. Finally, we used infected animal femur models to investigate the biosafety, antimicrobial and osteointegration properties of the HASiGdCe coating in vivo.

Results

Through various characterization experiments, we demonstrated that the HASiGdCe coating has suitable microscopic morphology, physical phase characteristics, bonding strength and bioactivity to meet the coating criteria for orthopedic implants. The HASiGdCe coating can release Gd3+ and Ce4+, showing strong antibacterial properties against MRSA and PAO-1. The HASiGdCe coating has been shown to have superior osteogenic and angiogenic properties compared to the HA coating in in vitro cellular experiments. Animal implantation experiments have shown that the HASiGdCe coating also has excellent biosafety, antimicrobial and osteogenic properties in vivo.

Conclusion

The HASiGdCe coating confers excellent antibacterial, angiogenic and osteogenic properties on titanium implants, which can effectively enhance implant osseointegration and prevent bacterial infections, and it accordingly has promising applications in the treatment of bone defects related to orthopedic and dental sciences.

The biological functions of europium-containing biomaterials: A systematic review

The biological functions of rare-earth elements (REEs) have become a focus of intense research. Recent studies have demonstrated that ion doping or alloying of some REEs can optimize the properties of traditional biomaterials. Europium (Eu), which is an REE with low toxicity and good biocompatibility, has promising applications in biomedicine. This article systematically reviews the osteogenic, angiogenic, neuritogenic, antibacterial, and anti-tumor properties of Eu-containing biomaterials, thereby paving the way for biomedical applications of Eu. Data collection for this review was completed in October 2022, and 30 relevant articles were finally included. Most articles indicated that doping of Eu ions or Eu-compound nanoparticles in biomaterials can improve their osteogenic, angiogenic, neuritogenic, antibacterial, and anti-tumor properties. The angiogenic, antibacterial, and potential neuritogenic effects of Eu(OH)₃ nanoparticles have also been demonstrated.

Surface Functionalization of Hydroxyapatite Scaffolds with MgAlEu-LDH Nanosheets for High-Performance Bone Regeneration

Although artificial bone repair scaffolds, such as titanium alloy, bioactive glass, and hydroxyapatite (HAp), have been widely used for treatment of large-size bone defects or serious bone destruction, they normally exhibit unsatisfied bone repair efficiency because of their weak osteogenic and angiogenesis performance as well as poor cell crawling and adhesion properties. Herein, the surface functionalization of MgAlEu-layered double hydroxide (MAE-LDH) nanosheets on porous HAp scaffolds is reported as a simple and effective strategy to prepare HAp/MAE-LDH scaffolds for enhanced bone regeneration. The surface functionalization of MAE-LDHs on the porous HAp scaffold can significantly improve its surface roughness, specific surface, and hydrophilicity, thus effectively boosting the cells adhesion and osteogenic differentiation. Importantly, the MAE-LDHs grown on HAp scaffolds enable the sustained release of Mg2+ and Eu3+ ions for efficient bone repair and vascular regeneration. In vitro experiments suggest that the HAp/MAE-LDH scaffold presents much enhanced osteogenesis and angiogenesis properties in comparison with the pristine HAp scaffold. In vivo assays further reveal that the new bone mass and mineral density of HAp/MAE-LDH scaffold increased by 3.18- and 2.21-fold, respectively, than that of pristine HAp scaffold. The transcriptome sequencing analysis reveals that the HAp/MAE-LDH scaffold can activate the Wnt/β-catenin signaling pathway to promote the osteogenic and angiogenic abilities.

Rare earth smart nanomaterials for bone tissue engineering and implantology: Advances, challenges, and prospects

Bone grafts or prosthetic implant designing for clinical application is challenging due to the complexity of integrated physiological processes. The revolutionary advances of nanotechnology in the biomaterial field expedite and endorse the current unresolved complexity in functional bone graft and implant design. Rare earth (RE) materials are emerging biomaterials in tissue engineering due to their unique biocompatibility, fluorescence upconversion, antimicrobial, antioxidants, and anti-inflammatory properties. Researchers have developed various RE smart nano-biomaterials for bone tissue engineering and implantology applications in the past two decades. Furthermore, researchers have explored the molecular mechanisms of RE material-mediated tissue regeneration. Recent advances in biomedical applications of micro or nano-scale RE materials have provided a foundation for developing novel, cost-effective bone tissue engineering strategies. This review attempted to provide an overview of RE nanomaterials' technological innovations in bone tissue engineering and implantology and summarized the osteogenic, angiogenic, immunomodulatory, antioxidant, in vivo bone tissue imaging, and antimicrobial properties of various RE nanomaterials, as well as the molecular mechanisms involved in these biological events. Further, we extend to discuss the challenges and prospects of RE smart nano-biomaterials in the field of bone tissue engineering and implantology.

Graphene Oxide/Chitosan/Hydroxyapatite Composite Membranes Enhance Osteoblast Adhesion and Guided Bone Regeneration

Two-dimensional materials provide a secluded space for bone formation and preserve the growth of surrounding tissues, thus playing a crucial role in guided bone regeneration (GBR). Graphene oxide (GO) has been widely employed in GBR due to its good mechanical and hydrophilic properties. A single GO membrane, however, does not provide a friendly environment for osteogenic cell adhesion. With their adjustable mechanical properties and excellent biocompatibility, composite membranes can simulate the multicomponent structure of an extracellular matrix for cell adhesion. To obtain two-dimensional membranes with appropriate mechanical strength and sufficient biocompatibility, GO-based composite membranes simultaneously containing chitosan (CS) and hydroxyapatite (HAP) were first prepared using one-step vacuum filtration and a biomimetic mineralization method. CS and HAP improved the mechanical strength and surface hydrophilicity of the membranes. In addition, moderate addition of HAP enhanced the adhesion, differentiation, and mineralization of osteoblasts. The prepared composite membranes were then implanted into a calvarial defect model to evaluate their osteogenic induction effects in vivo. Microcomputed tomography observation and histological analysis indicate that GO/CS/HAP composite membranes can accelerate bone regeneration without the contribution of endogenous cytokines. GO/CS/HAP composite membranes with unique biomimetic porous structures, superior mechanical properties, and excellent bone regeneration capacity are potential materials for application in GBR.

Doping gadolinium versus lanthanum into hydroxyapatite particles for better biocompatibility in bone marrow stem cells

Lanthanide ions (Ln³⁺) doped hydroxyapatite (HAP) particles are well established in biomedical areas. Although Ln elements are closely located in the periodic table and have plenty of similar characteristics, the minor differences in the effective ionic radii could cause alterations in the physicochemical and biological properties of HAP substitutes. The present study synthesized lanthanum-(La-) and gadolinium-(Gd-) doped HAP particles (La-HAP and Gd-HAP). And the effects of two types of particles on bone marrow stem cells (BMSCs) viability were also measured and compared in vitro. The results indicated that the Gd-HAP adsorbed more serum proteins from culture media and inhibited the new layer of apatite formation on its surface when comparing to La-HAP with a similar crystalline structure, particle size, and Zeta potential. These surface modifications can significantly reduce the cell adhesion of Gd-HAP, simultaneously decreasing the Gd-HAP particle uptake efficiency. Moreover, the cell viability of Gd-HAP remained higher than that of La-HAP in culture periods. We concluded that a slight variation in the effective ionic radii between Gd³⁺ and La³⁺ could alter the adsorption of serum proteins on the particles' surface, modulating subsequent cellular responses. The present work provides an interesting view that Gd-HAP is endowed with better cellular biocompatibility than La-HAP.

Multicolor tunable luminescence and energy transfer of core-shell structured SiO2@Gd2O3 microspheres co-activated with Dy3+/Eu3+ under single UV excitation

Optimizing structure and varying doped ions are two main strategies to obtain excellent luminescence performance. Spherical morphology is considered to be the most ideal phosphor structure due to the least surface defects. Herein, a series of spherical and monodispersed Dy³⁺/Eu³⁺ co-activated SiO₂@Gd₂O₃ core-shell phosphors with multicolor tunable luminescence were successfully prepared via a facile urea assisted precipitation method. Related chemical reactions and the possible growth mechanism of Gd₂O₃:Ln³⁺ directional deposition on the surface of SiO₂ microspheres were put forward. Upon 273 nm UV radiation excitation, SiO₂@Gd₂O₃:Dy³⁺ and SiO₂@Gd₂O₃:Eu³⁺ samples exhibited characteristic yellow (⁴F_9/2-⁶H_13/2) and blue (⁴F_9/2-⁶H_15/2) emissions of Dy³⁺ and red (⁵D₀-⁷F₂) emission of Eu³⁺, respectively. Meanwhile, multicolor emissions (warm white, yellow and orange) could be easily obtained by modulating the relative content of Dy³⁺ and Eu³⁺ in SiO₂@Gd₂O₃:Ln³⁺ samples under a single excitation wavelength. Moreover, it was confirmed that Dy³⁺ could transfer energy to Eu³⁺ in the form of quadrupole-quadrupole interaction and further improved the luminescence intensity of Eu³⁺ by comparing experimental data with theoretical calculations. These results imply that tunable luminescence Dy³⁺,Eu³⁺ co-doped SiO₂@Gd₂O₃ microspheres have great potential applications in multicolor displays and biolabeling fields.

Investigation of potential adverse central nervous system effects after long term oral administration of gadolinium in mice

Objectives

To examine potential gadolinium (Gd) accumulation in the brain of healthy mice after long-term oral administration of Gd-containing food pellets and to investigate whether Gd leads to adverse central nervous system (CNS) effects, specifically focussing on locomotor impairment in Gd exposed compared to control animals.

Materials and methods

The local Animal Experimental Ethics Committee approved all procedures and applications. Fifteen female C57Bl/6 mice were orally exposed to a daily intake of 0.57 mmol Gd chloride/ kg body weight over a period of 90 weeks from the age of 4 weeks on. Gd-free, but otherwise equivalent experimental diets were given to the control group (N = 13). The animals were monitored daily by animal caretakers regarding any visible signs of distress and evaluated clinically every four weeks for the first 60 weeks and afterwards every two weeks for a better temporal resolution of potential long-term effects regarding impairment of motor performance and loss of body weight. The individual Gd content was measured using mass spectrometry in a sub-cohort of N = 6 mice.

Results

The absolute brain Gd levels of the Gd-exposed mice were significantly increased compared to control mice (0.033± 0.009 vs. 0.006± 0.002 nmol Gd/ g brain tissue). Long-term oral Gd exposure over almost the entire life-span did not lead to adverse CNS effects including locomotor changes (rotarod performance, p = 0.1467) in healthy mice throughout the study period. Gd-exposed mice showed less increased body weight compared to control mice during the study period (p = 0.0423). Histopathological alterations, such as hepatocellular vacuolization due to fatty change in the liver and a loss of nucleated cells in the red pulp of the spleen, were found in peripheral organs of both groups.

Conclusions

Low levels of intracerebral Gd caused by chronic oral exposure over almost the entire life span of mice did not lead to alterations in locomotor abilities in healthy mice throughout the normal aging process.

Y2O3 Nanoparticles Caused Bone Tissue Damage by Breaking the Intracellular Phosphate Balance in Bone Marrow Stromal Cells

Y₂O₃ nanoparticles (NPs) have become great promising products for numerous applications in nanoscience especially for biomedical application, therefore increasing the probability of human exposure and gaining wide attention in biosecurity. It is well known that rare earth (RE) materials are deposited in the bone and excreted very slowly. Nevertheless, the effect of Y₂O₃-based NPs on bone metabolism has not been exactly known yet. In the present study, the effects of Y₂O₃ NPs on bone marrow stromal cells (BMSCs) and bone metabolism in mice after intravenous injection were studied. The results demonstrated that Y₂O₃ NPs could be taken up into BMSCs and localized in acidifying intracellular lysosomes and underwent dissolution and transformation from Y₂O₃ to YPO₄, which could lead to a break in the intracellular phosphate balance and induce lysosomal- and mitochondrial-dependent apoptosis pathways. Furthermore, after being administered to mice, a higher concentration of yttrium occurred in bone, which caused the apoptosis of bone cells and induced the destruction of bone structure. However, the formation of a YPO₄ coating on the surface of Y₂O₃ NPs by pretreatment of Y₂O₃ NPs in lysosome-simulated body fluid could observably decrease the toxicity in vivo and in vitro. This study may be useful for practical application of Y₂O₃ NPs in the biomedical field.