Rare Earth Oxide Nanoparticles Research Articles

Optical nanomaterials with focus on rare earth doped oxide: A Review

Optical nanomaterials (ONMs) have attracted significant attention of the global research community owing to their several superior advantages. Some of the ONMs depict negligible photobleaching, bright emission, large electron-hole overlap integral, ease of coating on any surface, large Stoke/Antistoke shifts, higher photostabilites, easy to incorporate inside human body etc. These properties make them technologically highly efficient which helps in minimizing the global issue of energy crisis and improving the standard of living of common man. Several aspects of ONMs such as plasmonic nanomaterials, quantum dots, photonic crystals, and rare earth doped nanoparticles have been discussed. For covering various categories of luminescent nanomaterials (LNMs) based on composition, a brief introduction and importance of metal nanoclusters, carbon nano dots, organic-inorganic nanocomposites, and metal doped nanoparticles have been also included. This review article gives very concise overview of rare earth doped oxide nanoparticles covering several important aspects such as rare earth ion (RE) as dopant, oxide-based host, nanophosphors etc. The importance of LNMs, their advantages as well as drawbacks are also highlighted. Technologically important types of RE doped oxide nanoparticles pertaining to downconversion, upconversion, persistence and radioluminescence are also explained and covered in detail in this review article. Several recent applications involving LNMs in bioimaging, solar cell, thermal sensor, biosensor, anti-counterfeiting etc are explained. In the last section of the review, a comparison between nano and bulk rare earth doped oxide LNMs are discussed in terms of several photophysical properties such as dopant local symmetry, Stark splitting, emission intensity, luminescence lifetime, host to dopant energy transfer, quantum yield etc. Finally, this review article is concluded with summary, outlook, challenges, and future scope on the use of LNMs. Several important aspects of LNMs with focus on RE doped oxide nanoparticles have been covered in this review article which will help general readers in their further research, in this important area, for development of both fundamental sciences and applications involving LNMs.

Effect of samarium oxide nanoparticles on degradation and invitro biocompatibility of magnesium

Benefitting from the advantages of being bioresorbable and having an elastic modulus, density and mechanical properties that closely match load-bearing bones, magnesium (Mg)-based materials are emerging as superior alternatives to permanent implants like titanium and stainless steel in orthopedic and craniofacial trauma fixation. To inhibit faster degradation of magnesium in physiological environments that has greatly limited its widespread clinical applicability, thermally stable metal-oxide nanoparticles have been used as a reinforcement to simultaneously improve the biomechanical and corrosion properties. Against this background, the objective of this study was to develop non-toxic magnesium-based nanocomposites incorporating rare earth oxides (REOs) synthesized by powder metallurgy technique followed by microwave sintering. The influence of rare-earth oxide (Sm2O3) nanoparticles on the microstructure, degradation, and biological performance of magnesium was investigated. The immersion test for 28 days revealed the rate of corrosion in Mg/1.5 vol.% Sm2O3 was 1.028 mm/year, reflecting a 25 % improvement compared to Mg. The viabilities of MC3T3-E1 cells for up to 1 vol.% Sm2O3 addition was >70 % indicating good in-vitro cytocompatibility while the lactate dehydrogenase (LDH) assay revealed all the nanocomposites exhibited Level ‘0’ cytotoxicity. The potential of rare-earth oxide reinforced magnesium nanocomposites, as explored in this work, was found to be suitable for temporary implant instead of rare-earth alloying addition to magnesium, which has known to cause potential toxicity.

Synergistic Effect of Aqueous Rare-Earth Salt and Oxide Nanoparticles on PVDF Based Self-Polarized, Piezoelectric Nanogenerators for Energy Harvesting Applications

Synergistic Effect of Aqueous Rare-Earth Salt and Oxide Nanoparticles on PVDF Based Self-Polarized, Piezoelectric Nanogenerators for Energy Harvesting Applications

Downregulation of the photosynthetic machinery and carbon storage signaling pathways mediate La2O3 nanoparticle toxicity on radish taproot formation

The molecular and physiological mechanisms of how rare earth oxide nanoparticles (NPs) alter radish (Raphanus sativus L.) taproot formation and cracking were investigated in the present study. We compared plants that received suspensions of 10, 50, 100, 300 mg L−1 of La2O3 NPs, 300 m L−1 La2O3 bulk-particles (BPs), 0.8 m L−1 La3+, or only water for six days during their tuber formation period. 100 and 300 mg L−1 La2O3 NPs exposure decreased storage root biomass by 38% and 60%, respectively, and they both induced visible root cracking. Physiological analyses showed that La2O3 NPs exposure (>100 mg L−1) significantly inhibited leaf net photosynthetic rate, cell wall pectin synthesis of both storage root epidermis and xylem parenchyma tissues, but increased the contents of cellulose and hemicellulose 1 in root epidermis cell walls. Moreover, transcriptome analysis further found that La2O3 NPs changed root cell wall structure by down-regulating core genes involved in cell wall pectin and IAA biosynthesis, which coincided with the observed La2O3 NPs-induced root cracking. Our results revealed the molecular mechanisms related to cell wall carbohydrate metabolism in response to NPs stress, providing a step forward for understanding the causes of NPs phytotoxicity on edible plant taproot formation and cracking.

Magnetic characterization of rare-earth oxide nanoparticles

High saturation magnetization and hysteresis-less magnetic responses are desirable for nanoparticles in scientific and technological applications. Rare-earth oxides are potentially promising materials because of their paramagnetism and high magnetic susceptibility in the bulk, but the magnetic properties of their nanoparticles remain incompletely characterized. Here, we present full M–H loops for commercial RE2O3 nanoparticles (RE = Er, Gd, Dy, Ho) with radii from 10–25 nm at room temperature and 4 K. The magnetic responses are consistent with two distinct populations of atoms, one displaying the ideal Re3+ magnetic moment and the other displaying a sub-ideal magnetic moment. If all sub-ideal ions are taken to be on the surface, the data are consistent with ≈2−10 nm surface layers of reduced magnetization. The magnetization of the rare-earth oxide nanoparticles at low temperatures (1.3–1.9 T) exceeds that of the best iron-based nanoparticles, making rare-earth oxides candidates for use in next-generation cryogenic magnetic devices that demand a combination of hysteresis-less response and high magnetization.

Phosphate induced surface transformation alleviated the cytotoxicity of Y2O3 nanoparticles to tobacco BY-2 cells

The wide applications of rare earth oxide nanoparticles (REO NPs) in various fields and their subsequent release into the environment have attracted the research of their effects on organisms. In this study, the toxicity of yttrium oxide (Y2O3) NPs to tobacco BY-2 cells was evaluated and the importance of phosphate in the medium on the toxicity of Y2O3 NPs was revealed. 50 mg L−1 Y2O3 NPs induced 52.4% cellular growth inhibition after 24-h exposure. Phosphate inhibited the release of Y3+ from Y2O3 NPs from 6.00 to 0.04 mg L−1 at 24 h, thus reduced the toxicity of Y2O3 NPs. The surface charge of Y2O3 NPs changed from 24.0 mV (in deionized water) to −7.6 mV (in phosphate solution), which induced the aggregation of Y2O3 NPs. The change of surface properties reduced the direct nanotoxicity of Y2O3 NPs. High-resolution transmission electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and X-ray diffraction results demonstrated that phosphate transformed the surface of Y2O3 NPs to amorphous YPO4. This surface transformation decreased phosphate concentration in the medium. The dialysis membrane encapsulation experiment further identified the contribution percentage of direct nanotoxicity and indirect toxicity (i.e., phosphate depletion) of Y2O3 NPs to tobacco BY-2 cells in the presence of phosphate to be 68.3% and 31.7%, respectively. This study highlights the significant role of phosphate in altering the environmental behavior and toxicity of REO NPs.

Negative effects of rare earth oxide nanoparticles of La2O3, Nd2O3, and Gd2O3 on the ammonia-oxidizing microorganisms

Nanoparticles released into soil environment potentially impact microorganisms, which furtherly disturb terrestrial biogeochemical cycles. However, how rare earth oxide nanoparticles affect the functional microorganisms inhabited in natural soil is still unknown. This study was aimed to investigate the effect of different types of rare earth oxide nanoparticles on the ammonia-oxidizing microorganisms. Soil respectively added with 0, 10, 50, and 100 mg kg−1 of La2O3, Nd2O3, or Gd2O3 nanoparticle were incubated at 25 °C in the dark for 60 days. The potential ammonia oxidation (PAO), abundance and communities of ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB) were measured at the 1st, 7th, and 60th day. Our results showed that the PAO in soils with nanoparticles significantly decreased due to nanoparticle toxicity at the 1st day, but it gradually increased to the control level owing to the adaptation of AOA and AOB in soils with nano-Nd2O3 and nano-Gd2O3. Interestingly, the abundance of AOB as reflected by the qPCR analysis was upregulated for the hormesis effect of AOB responding to nano-Nd2O3 or nano-Gd2O3 with 50 mg kg−1 level. Moreover, terminal restriction fragment length polymorphism (T-RFLP) results suggested that the communities for AOA and AOB shifted with nanoparticles type and incubation time. Rare earth oxide nanoparticles could inhibit activities of ammonia-oxidizing microorganisms, and thus they might be used as potential nitrification inhibitors to improve nitrogen use efficiency in the agricultural ecosystems.

Magnetocaloric effect in Tb2O3 and Dy2O3 nanoparticles at cryogenic temperatures

Magnetic refrigeration is a cooling technology based on the magnetocaloric effect, which has greater energy efficiency than conventional refrigeration, and has attracted much attention for low and room temperature cooling applications. Here, we report magnetocaloric effects at cryogenic temperatures in nanostructured rare earth oxides prepared by rare earth nitride formation and successive oxidation that guarantees chemical stabilities and finer particle sizes of rare earth oxide nanoparticles. Tb2O3 and Dy2O3 rare earth oxides with a cubic structure were prepared that undergo a second-order magnetic transition at Néel temperatures of 8 K and 4 K, respectively. Magnetic entropy changes (−ΔSM) were 6.6 and 18.2 J/kg K, respectively, at an applied magnetic field of 6 T.

Abstract C062: The use of nanoparticles to improve tumour radiosensitivity

Abstract Fractionated radiotherapy, administered by high energy external beam X-rays, is the mainstay of several cancer treatment regimens. However, treatment is often required for several weeks, with cure rates limited by radio-resistant hypoxic areas within the tumour, patient compliance due to the frequency of required treatments and cumulatively high total radiation dose that can cause adjacent tissue toxicity. Radiosensitisers are being developed to improve efficacy, but most are still limited by tumour hypoxia. Titanium oxide is a well-known, non-toxic, photoactive material that generates hydroxyl free radicals by water splitting under ultraviolet light. Rare earth doped titanium oxide nanoparticles can be delivered to cancer cells and interact with X-rays and electrons, concentrating free radicals within the cells. Crucially, this response is also effective within hypoxic tumour regions. Proof of concept studies were performed in pancreatic tumour cells PANC-1 irradiated in vitro. Both cell number and clonogenicity were reduced following irradiation in the presence of nanoparticles compared to irradiation alone. This response was then further evaluated in subcutaneously xenografted tumours. Briefly, male CD-1 nude mice were inoculated with either the pancreatic carcinoma, MiaPaCa-2, or the head and neck squamous cell carcinoma, FaDU, cells. Tumours were allowed to grow until palpable and then irradiated with 2Gy daily for 5 days (Mon-Fri) for 1 or 2 weeks (or sham irradiated) to mimic the clinical protocol. Immediately prior to the first irradiation each week tumours were injected with 125μg nanoparticles or vehicle. Tumour growth was then monitored for up to 5 weeks. Injection of the nanoparticles alone had no effect on tumour growth rate, but when combined with irradiation there was up to 65-75% reduction in tumour volume 30 days after the start of treatment. Sections of Carnoy’s fixed tumours taken 3 days (Day 15) after the last irradiation were immunohistochemically labelled with the proliferation marker bromodeoxyuridine (BrdU). Whilst there was a clear radiation response there was little difference in proliferation following co-administration of nanoparticles at this early timepoint, suggesting either surviving radioresistant clones had evolved by two weeks or that the nanoparticle induced tumour growth delay was not simply the result of early cell death/cell cycle interruption but may have delayed effects. These preliminary studies show that titanium oxide nanoparticles are non-toxic and can enhance the efficacy of radiotherapy in pancreatic and head and neck tumour cell lines. Further work will quantify the level of tumour cell death in normal vs hypoxic tumour regions over time, in a range of tumour types with differing levels of radiosensitivity. Citation Format: Ben Reed, Gareth Wakefield, Matt Stock, Gregory Tudor. The use of nanoparticles to improve tumour radiosensitivity [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C062. doi:10.1158/1535-7163.TARG-19-C062

Fabrication and reduction process of dispersive Er2O3 doped Mo super-fine powders comparing with La2O3 doped Mo powders

It is known that uniformly dispersed rare earth oxide (RE2O3) nanoparticles in molybdenum matrix could improve the ductility of Mo. However, it is reported that the agglomeration of La2O3 was quite serious when the addition amount of La2O3 was over 2 wt%, which leaded to a dramatic decrease of the ductility of Mo. In this paper, a new type of uniformly dispersed Er2O3 doped Mo powder was prepared, with the amount of Er2O3 accounting for 4 wt%. It is found that the reduction temperature of MoO3 was higher and the grain size was smaller for the Mo powders doped with Er2O3 than those doped with La2O3. First-principles calculations illustrate that La2O3/Er2O3 had a strong trend to be absorbed on the surface of MoO3, and the inhibition capability for the reduction of MoO3 to MoO2 by Er3+ was larger than La3+ due to the stronger Er-O interactions. It gives a potential explanation of the higher reduction temperature of MoO3 doped with Er2O3 than that doped with La2O3. Furthermore, the formation energies of Er-O and La-O pairs within the bulk Mo were in the sequence: La-O > Er-O > 0 eV, indicating that these systems are unstable and La2O3 is easier to escape from the interior of Mo grains and agglomerate on the Mo surface than Er2O3.

Cytotoxicity, dose-enhancement and radiosensitization of glioblastoma cells with rare earth nanoparticles

Glioblastoma is a heterogeneous disease with multiple genotypic origins. Despite treatment protocols such as surgery, radiotherapy and chemotherapy, the prognosis for patients remains poor. This study investigates the cytotoxic and radiation dose-enhancing and radiosensitizing ability of five rare earth oxide nanoparticles, in two different immortalized mammalian cell lines; U-87 MG and Mo59K. Significant cytotoxicity was observed in U-87 MG cells when exposed to Nd2O3 and La2O3. Autophagy was also detected in cells after incubation with Nd2O3. Radiosensitization was observed in U-87 MG when incubated with Gd2O3, CeO2-Gd and Nd2O3:Si. Importantly, these elements did not cause any intrinsic toxicity in the absence of irradiation and so could be considered biocompatible. The Gd2O3 and CeO2-Gd nanoparticles were also seen to generate ROS in U-87 MG cells after irradiation. Furthermore, the Mo59K and U-87 MG cells responded very differently to exposure to the rare earth nanoparticles. This may indicate the importance of the genotype of cells in the successful use of rare earth oxides for treatment.

Rare earth oxide nanoparticles promote soil microbial antibiotic resistance by selectively enriching antibiotic resistance genes

This study demonstrates that rare earth oxide nanoparticles can enhance soil microbial antibiotic resistance by inducing the enrichment and spread of antibiotic resistance genes in soil microbial communities.

Enhanced Cerenkov luminescence tomography analysis based on Y2O3:Eu3+ rare earth oxide nanoparticles.

Cerenkov luminescence imaging offers a new diagnostic alternative to radiation imaging, but lacks intensity and penetration. In this study, a Cerenkov luminescence signal and its image quality were enhanced using rare earth oxide nanoparticles as a basis for Cerenkov luminescence excited fluorescence imaging and Cerenkov luminescence excited fluorescence tomography. The results also provided 3D-imaging and quantitative information. The approach was evaluated using phantom and mice models and 3D reconstruction and quantitative studies were performed in vitro, showing improved optical signal intensity, similarity, accuracy, signal-to-noise ratio, and spatial distribution information. The method offers benefits for both optical imaging research and radiopharmaceutical development.

Preparation and Catalytic Activity of M2O3/CNTs (M = Y, Nd, Sm) Nanocomposites by Solvothermal Process

The rare-earth oxide nanoparticles along carbon nanotubes (CNTs) (M2O3/CNTs, M = Y, Nd, Sm) were prepared by in situ solvothermal method. Products were characterized by infrared spectroscopy, X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectrometry, scanning electron microscopy, and Brunauer-Emmett-Teller method. M2O3/CNTs presented good morphology and large surface area. Furthermore, catalysis of M2O3/CNTs during the thermal decomposition of ammonium perchlorate (AP) was evaluated by differential thermal analysis (DTA). Compared with Nd2O3/CNTs and Sm2O3/CNTs, Y2O3/CNTs nanocomposites showed the best catalytic effect on the thermal decomposition of AP. With the addition of 2 wt.% Y2O3/CNTs nanocomposite, high decomposition temperature of AP decreased by 125.5°C, and the total DTA heat release increased by 2.027 kJ·g−1.

High inflammogenic potential of rare earth oxide nanoparticles: the New Hazardous Entity

Due to the exponential increase in the development and utilization of rare earth oxide nanoparticles (REO NPs) in various fields, the possibility of exposure in humans by inhalation has increased. However, there are little information about hazards of REO NPs and its mechanisms of toxicity. In this study, we evaluated the acute pulmonary inflammation using 10 REO NPs (Dy2O3, Er2O3, Eu2O3, Gd2O3 La2O3, Nd2O3, Pr6O11, Sm2O3, Tb4O7, and Y2O3) and four well-known toxic particles (CuO, NiO, ZnO, and DQ12). Minimum three doses per NP were instilled into the lungs of female Wistar rats at surface area dose metric and lung inflammation was evaluated at 24 h post-instillation by bronchoalveolar lavage fluid (BALF) analysis and histopathological observation. All types of REO NPs showed common pathological changes including mild to moderate infiltration of neutrophils and activated macrophages in the alveoli, peribronchial, and perivascular region. The inflammogenic potential evaluated by the number of granulocytes divided by the treated surface area dose showed all types of REO NPs has much higher inflammogenic potential than DQ12, ZnO, and NiO NPs. The correlation plot between the number of granulocytes and the potential for reactive oxygen species (ROS) generation showed a good correlation with exception of Pr6O11. The higher inflammogenic potential of REO NPs than that of well-known highly toxic particles imply that REO NPs need special attention for inhalation exposure and more studies are needed. In addition, the potential of ROS generation is one of the key factors producing lung inflammation by REO NPs.

Nanoparticle Augmented Radiotherapy using Titanium Oxide Nanoparticles

Titanium oxide is a photoactive material that generates hydroxyl free radicals via water splitting. When doped with rare earth ions titanium oxide nanoparticles are activated by X-rays and X-ray generated electrons and are used to enhance radiotherapy treatment of solid tumours. As the nanoparticles generate free radicals by water splitting the presence of molecular oxygen is not required and aggressive hypoxic tumours may be targeted. A clonogenic assay of radio resistant pancreatic cancer (PANC- 1) cells shows a radiotherapy dose enhancement factor of 1.9 at clinically relevant nanoparticle loadings. A fast growing oropharyngeal cancer (FaDu) xenograft demonstrates that rare earth doped titanium oxide nanoparticles delivered by intratumoural injection disperse throughout the tumour, being taken up by cancer cells and undergoing passive accumulation in the Golgi apparatus. Incident radiotherapy activates the nanoparticles to produce hydroxyl free radicals, destroying the Golgi apparatus, and inducing tumour cell apoptosis. This results in a reduction in proliferating cancer cells and a consequent reduction in tumour regrowth rate by a factor of 3.8. There is no increase in systemic toxicity when using nanoparticles in addition to radiotherapy. Rare earth doped titanium oxide nanoparticles therefore represent a novel approach to tumour treatment via destruction of the cells Golgi apparatus during radiotherapy.

Bending strength and wear behavior of Fe-Cr-C-B hardfacing alloys with and without rare earth oxide nanoparticles

The aim of this paper was to investigate the effect of rare earth oxide (REO) nanoparticles on the bending strength and wear behavior of Fe-Cr-C-B hardfacing alloys. Fe-based hardfacing alloys with different content of REO nanoparticles were prepared. Optical microscope and scanning electron microscope were used to observe the microstructure of the Fe-based hardfacing alloys. X-ray diffractometer was used to study the phases of the hardfacing alloys. Energy dispersive spectrometer and X-ray photoelectron spectroscopy were used to study the chemical composition. HXA-1000 Vickers micro-hardness tester and Instron universal material test machine were used to study the mechanical properties of the Fe-based hardfacing alloys. Pin-on-disk wear testing machine was used to study the wear behavior of the Fe-based hardfacing alloys. The experimental results showed that REO nanoparticles refined the primary carbide and increased the volume fraction of primary carbide. REO nanoparticles increased the fracture toughness of primary carbide. REO nanoparticles improved the bending strength of the hardfacing alloys. The bending strength of the hardfacing alloy with 0.288wt.% REO nanoparticles increased by 46.4% compared to that of the hardfacing alloy without REO nanoparticles. The wear resistance of the hardfacing alloy was improved significantly by adding 0.288wt.% REO nanoparticles. The main mechanisms were abrasion wear and mild oxidative wear when normal load was 5N. When normal load was 30N, the main mechanisms were abrasion wear and severe oxidative wear accompanied by severe adhesion.

Giant Cellular Vacuoles Induced by Rare Earth Oxide Nanoparticles are Abnormally Enlarged Endo/Lysosomes and Promote mTOR-Dependent TFEB Nucleus Translocation.

Many nanomaterials are reported to disrupt lysosomal function and homeostasis, but how cells sense and then respond to nanomaterial-elicited lysosome stress is poorly understood. Nucleus translocation of transcription factor EB (TFEB) plays critical roles in lysosome biogenesis following lysosome stress induced by starvation. The authors previously reported massive cellular vacuolization, along with autophagy induction, in cells treated with rare earth oxide (REO) nanoparticles. Here, the authors identify these giant cellular vacuoles as abnormally enlarged and alkalinized endo/lysosomes whose formation is dependent on macropinocytosis. This vacuolization causes deactivation of mammalian target of rapamycin (mTOR), a TFEB-interacting kinase that resides on the lysosome membrane. Subsequently, TFEB is dephosphorylated at serine 142 and translocated into cell nucleus. This nucleus translocation of TFEB is observed only in vacuolated cells and it is critical for maintaining lysosome homeostasis after REO nanoparticle treatment, as knock-down of TFEB gene significantly compromises lysosome function and enhances cell death in nanoparticle-treated cells. Our results reveal that cellular vacuolization, which is commonly observed in cells treated with REOs and other nanomaterials, represents a condition of profound lysosome stress, and cells sense and respond to this stress by facilitating mTOR-dependent TFEB nucleus translocation in an effort to restore lysosome homeostasis.

Tissue deposition and toxicological effects of commercially significant rare earth oxide nanomaterials: Material and physical properties.

Rare earth oxide (REO) materials are found naturally in earth's crust and at the nanoscale these REO nanoparticles exhibit unique thermal, electrical, and physicochemical properties. REO nanoparticles are widely used in different industrial sectors for ceramics, glass polishing, metallurgy, lasers, and magnets. Recently, some of these REO nanoparticles have been identified for their potential application in medicine, including therapy, imaging, and diagnostics. Concurrent research into the REO nanomaterials' toxicities has also raised concern for their environmental impacts. The correlation of REO nanoparticles mediated toxicity with their physiochemical properties can help to design nanoparticles with minimal effect on the environment and living organisms. In vitro assay revealed toxicity toward Human squamous epithelial cell line (CCL30) and Human umbilical vascular endothelial cells (HUVEC) at a concentration of 100 µM and higher. In vivo results showed, with the exception of CeO2 and Gd2 O3 , most of the naoparticles did not clear or had minimum clearance (10-20%) from the system. Elevated levels of alanine transferase were seen for animals given each different nanoparticle, however the increases were not significant for CeO2 and Dy2 O3 . Nephrotoxicity was only seen in case of Dy2 O3 and Gd2 O3 . Lastly, histological examination revealed presence of swollen hepatocytes which further confirms toxicity of the commercial REO nanomaterials. The in vivo toxicity is mainly due to excessive tissue deposition (70-90%) due to the commercial REO nanoparticles' poor physical properties (shape, stability, and extent of agglomeration). Therefore, optimization of nanoparticles physical properties is very important. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 904-917, 2017.

Versatile rare-earth oxide nanocomposites: enhanced chemo/photothermal/photodynamic anticancer therapy and multimodal imaging.

The development of novel nanocomposites that combine multiple imaging and therapeutic strategies has recently attracted considerable attention because of their cumulative and synergistic therapeutic effects. In this study, doxorubicin (DOX)- and indocyanine green (ICG)-loaded Gd2O3:Eu3+@P(NIPAm-co-MAA)@THA@cRGD nanocomposites {abbreviated as DOX-ICG-TPNPs@cRGD; P(NIPAm-co-MAA): poly[(N-isopropylacrylamide)-co-(methacrylic acid)]; THA: 4,4-trifluoro-1-(9-pentylcarbazole-3-yl)-1,3-butanedione; cRGD: cyclic(Arg-Gly-Asp-d-Phe-Lys)} were designed, assembled, fully characterized, and successfully applied in multimodal imaging diagnosis and therapy. The designed nanocomposites display a versatile, multifunctional platform that includes (a) simultaneous targeting with cRGD, (b) multimodal imaging, including two-photon luminescence (TPL), magnetic resonance imaging (MRI), computed tomography (CT), and photothermal imaging (PTI), and (c) stimuli-responsive coordinated drug delivery; this results in a highly efficient synergistic chemo/photothermal/photodynamic anticancer therapy (chemo/PTT/PDT). An important feature of the obtained nanocomposites is the enhancement of both the PTT and PDT effects of ICG due to the effective light protection of a two-photon sensitized Eu3+ complex. This integrated strategy shows an excellent synergistic inhibition of tumor growth triggered by NIR laser irradiation, as confirmed by both in vitro and in vivo tests. The present study emphasizes the influence and interaction of every component in the nanocomposites and demonstrates that the systematic design of nanocarriers can lead to an assembly of smart nanomaterials with enhanced antitumor efficacy.