Rare Earth Nanoparticles Research Articles

Great enhancement of relative gain in polymer waveguide amplifier using NaYF4/NaLuF4:Yb,Er-PMMA nanocomposite as gain media

Polymer-based waveguide amplifiers were the key devices in short-distance optical communication systems. However, the low relative gain of these amplifiers hindered their practical applications. Here, we introduced a kind of waveguide amplifier devices affording higher relative gain, which were using a new nanocomposite as gain media. The nanocomposite was synthesized by copolymerization of the methyl methacrylate (MMA) monomers with the unsaturated organic ligand-modified core-shell rare earth nanoparticles (NPs). Due to the formation of chemical bonds between the NPs and the polymer matrix, the dispersion of NPs and the stability of the nanocomposite were both greatly improved. Therefore, using this nanocomposite as gain media, in a 15 mm long embedded rectangular waveguide, a really high relative gain of 27 dB at 1535 nm with the 980 nm laser pump was observed, which was nearly three times higher than that in our previous work. Owing to its good performance, the nanocomposite could play an important role in the future optical communication technology.

Cancer cell membrane-coated rare earth doped nanoparticles for tumor surgery navigation in NIR-II imaging window

With the attractive characteristics of low toxicity, narrow emission spectra, long fluorescence lifetime, and no photobleaching, rare-earth doped nanoparticles (RENPs) have become promising imaging nanoplatforms in the second near-infrared window (NIR-II, 1000–1700 nm). Many studies have been devoted to different surface modification strategies of RENPs to achieve good NIR-II tumor imaging property. However, the tumor imaging efficiency of these approaches remains disappointing. Herein, two methods were pursued to modify RENPs with either polyethylene glycol (PEG) or cancer-cell-membrane to generate PEGylated-RENPs and cancer-cell-membrane camouflaged RENPs (CC-RENPs), respectively. This study demonstrated that cancer-cell-membrane coating of RENPs greatly improved tumor imaging performance in NIR-II window than PEG coating. Besides, CC-RENPs uptakes in liver and spleen significantly decreased. Importantly, CC-RENPs was found to be capable to aid us to pursue precise resection of the tumor. In conclusion, CC-RENPs are capable of targeting tumors and show high tumor NIR-II imaging quality. They are highly promising nanomaterials for future medical applications.

Magnesium nanocomposites reinforced with rare earth element nanoparticles: nanoindentation-driven response

Magnesium (Mg), as the lightest metallic material, is 33% lighter than aluminum which makes it, potentially, a great replacement for aluminum and its alloys. However, Mg in pure and alloyed conditions is brittle at ambient temperature which largely limits their applications. One key solution to enhance the strength and ductility of Mg and its alloys is to embed thermally-stable nano-size reinforcements within the Mg matrix to produce so-called “Mg nanocomposites”. The Mg nanocomposites are considering revolutionizing energy-saving lightweight materials of the future with enhanced strength and ductility properties. Mg nanocomposites are, however, at the initial degrees of improvement and consequently, systematic research is required to set up microstructure/property relationships at distinct potential conditions (i.e. temperatures and strain rates). In the present study, a nanoindentation testing approach is adopted to assess ambient-temperature small scale mechanical properties of a group of Mg nanocomposites reinforced with rare-earth element nanoparticles (NPs), i.e. Sm2O3. This paper tried to assess various nanoindentation-driven properties of the Mg-Sm2O3 nanocomposites and compare them with the pure Mg as the baseline.

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

Emitting/Sensitizing Ions Spatially Separated Lanthanide Nanocrystals for Visualizing Tumors Simultaneously through Up- and Down-Conversion Near-Infrared II Luminescence In Vivo.

Near-infrared lights have received increasing attention regarding imaging applications owing to their large tissue penetration depth, high spatial resolution, and outstanding signal-to-noise ratio, particularly those falling in the second near-infrared window (NIR II) of biological tissues. Rare earth nanoparticles containing Er3+ ions are promising candidates to show up-conversion luminescence in the first near-infrared window (NIR I) and down-conversion luminescence in NIR II as well. However, synthesizing particles with small size and high NIR II luminescence quantum yield (QY) remains challenging. Er3+ ions are herein innovatively combined with Yb3+ ions in a NaErF4 @NaYbF4 core/shell manner instead of being codoped into NaLnF4 matrices, to maximize the concentration of Er3+ in the emitting core. After further surface coating, NaErF4 @NaYbF4 @NaYF4 core/shell/shell particles are obtained. Spectroscopy studies are carried out to show the synergistic impacts of the intermediate NaYbF4 layer and the outer NaYF4 shell. Finally, NaErF4 @NaYbF4 @NaYF4 nanoparticles of 30 nm with NIR II luminescence QY up to 18.7% at room temperature are obtained. After covalently attaching folic acid on the particle surface, tumor-specific nanoprobes are obtained for simultaneously visualizing both subcutaneous and intraperitoneal tumor xenografts in vivo. The ultrahigh QY of down-conversion emission also allows for visualization of the biodistribution of folate receptors.

Size-Dependent Photothermal Conversion and Photoluminescence of Theranostic NaNdF4 Nanoparticles under Excitation of Different-Wavelength Lasers.

The narrow absorption and emission bands, long fluorescence lifetime, and excellent stability of rare earth nanoparticles (referred to as RE NPs) make them very attractive for multimodal imaging and therapy of cancer. Their narrow absorption requires the careful selection of laser wavelength to achieve the best performance, particularly for RE NPs simultaneously having photothermal and photoluminescent properties (e.g., Nd-based nanoparticles), which has not been investigated. Herein, we prepared a series of different-sized NaNdF4 nanoparticles (referred to as NNF NPs) (i.e., 4.7, 5.9, 12.8, and 15.6 nm) from ultrasmall nanoclusters and investigated their in vitro and in vivo size-dependent photothermal conversion and photoluminescence under irradiation by a 793 nm laser and an 808 nm laser, respectively. We find that all nanoparticles exhibited the better photothermal conversion performance under the irradiation of the 808 nm laser than under the 793 nm laser, of which 12.8 nm NNF NPs showed the best performance, and the temperature of their solution can be quickly increased from 30 °C to around 60 °C within 10 min under the irradiation of the 808 nm laser with a power intensity of 0.75 W/cm2. When we used the 793 nm laser to excite these NNF NPs, we found that all nanoparticles exhibited the stronger photoluminescence in the second near-infrared window (NIR-II) than under the excitation by the 808 nm laser, of which 15.6 nm NNF NPs possessed the strongest NIR-II luminescence. We then modified 12.8 nm NNF NPs with phospholipid carboxyl PEG and functionalized with RGD for actively targeted imaging of cancer. The NaNdF4@PEG@RGD nanoparticles (referred to as NNF-P-R NPs) have good biocompatibility, stability, and excellent targeting capability. The in vivo result show that 12.8 nm NNF NPs exhibited better photothermal conversion performance under the irradiation of the 808 nm laser, and stronger NIR-II fluorescence under irradiation of the 793 nm laser, which are consistent with the in vitro result. This work demonstrates the significance of selection of the proper laser wavelength for maximally taking advantage of RE nanoparticles for the diagnosis and treatment of cancer.

Structural and Electronic Characterization Through Spectroscopy Analysis of Gd-Gd₂O₃ Nanoparticles.

Based on the new necessity of residual dispensing of heavy metals (or even more, rare earths) that are part of the composition of multiple electronic components as the cellular phones or computers; this work reports the use of physical processes for taking advantage of elements from the electronic residues. Recycling and processing to generate nanomaterials is an attractive option, because the economic and ecologic perspectives. In this work, Gd-Gd₂O₃ nanoparticles (through a sonic-chemical method at room temperature assisted with Tannic acid as reduction agent), is reported. The structure characterization was performed over the samples using complementary techniques such as transmission electron microscopy, X-ray diffraction, Raman and infrared spectroscopies. The obtained results are related to self-assembling mechanisms. As a complement, Ultraviolet-visible absorbance data was used to determine some electronic properties such as band structure. Therefore, this work has demonstrated the possibility of synthesizing lanthanide nanoparticles without burning the samples.

Enhancing upconversion luminescence of highly doped lanthanide nanoparticles through phase transition delay

Doping of rare earth (RE) ions in a low-phonon-energy host matrix is an effective strategy to enhance the upconversion luminescence (UCL) of lanthanide-doped nanoparticles. However, doping of optically inactive RE ions at high concentrations can cause an undesirable phase transition of the host matrix, with concomitant decrease in luminescence. Herein, we present a phase-transition-delay protocol to effectively preserve the pure orthorhombic phase of a KLu2F7:Yb3+,Er3+ system, even at high RE dopant concentrations. The proposed concept can be realized by incorporating a set of optically inactive RE dopants, i.e., Y3+ or Gd3+, with different ionic radii to replace the Lu3+ ions in the host matrix to overcome the energy barrier of the phase transition. The nanoparticles were synthesized in a high-boiling solvent or at a high reaction temperature. We observed maximal UCL of Er3+ at different Y3+ or Gd3+ dopant concentrations; the optimal Y3+ or Gd3+ concentration at which maximal UCL is observed is 10 mol% for samples prepared by a water-based hydrothermal route, while it is 30 mol% for samples prepared by an oleic acid-based hydrothermal route. Further, this optimal concentration could be increased to as much as 50 mol% by adopting a high reaction temperature. The high doping of Y3+ or Gd3+ can efficiently lead to enhanced upconversion performance of the final materials (as much as 32-fold and 9-fold enhancements in the upconversion intensity and quantum yield, respectively, are achieved). The UCL enhancement is caused by the break-down of the symmetry of lanthanide sites in the crystal lattice induced by Y3+ or Gd3+, which enhances the energy transfer probabilities between Yb3+ and Er3+. Our findings highlight a convenient route to simultaneously tune the phase transition of the host and upconversion output, and this strategy can be applied to other upconversion host materials.

Excretable Lanthanide Nanoparticle for Biomedical Imaging and Surgical Navigation in the Second Near-Infrared Window.

Recently, various second near‐infrared window (NIR‐II, 1000–1700 nm) fluorophores have been synthesized for in vivo imaging with nonradiation, high resolution, and low autofluorescence. However, most of the NIR‐II fluorophores, especially inorganic nanoprobes, are mainly retained in the reticuloendothelial system (RES) such as the liver and spleen, leading to long‐term safety concerns. Herein, a type of lanthanide‐based excretable NIR‐II nanoparticle, RENPs@Lips, which can be quickly cleared out of body after intravenous administration with half‐lives of 23.0 h for the liver and 14.9 h for the spleen, is reported. Interestingly, over 90% of RENPs@Lips can be excreted through a hepatobiliary system within 72 h postinjection. The moderate blood half‐time (T 1/2 = 17.96 min) allows for multifunctional applications in delineating the hemodynamics of vascular disorders (artery thrombosis, ischemia, and tumor angiogenesis) and monitoring blood perfusion in response to acute ischemia. In addition, RENPs@Lips exhibit high performance in identifying orthotopic tumor vessels intraoperatively and embolization surgery under NIR‐II imaging navigation. Moreover, excellent signal‐to‐background ratio (SBR) is successfully achieved to facilitate sentinel lymph nodes biopsy (SLNB) with tumor‐bearing mice. The high biocompatibility, favorable excretability, and outstanding optical properties warrant RENPs@Lips as novel promising NIR‐II nanoparticles for future applications and translation into an interdisciplinary amalgamation of research in diverse fields.

In vivo molecular imaging for immunotherapy using ultra-bright near-infrared-IIb rare-earth nanoparticles.

The NIR-IIb (1500–1700 nm) window is ideal for deep-tissue optical imaging in mammals, but lacks bright and biocompatible probes. Here, we developed biocompatible cubic-phase (α-phase) erbium-based rare-earth nanoparticles (ErNPs) exhibiting bright downconversion luminescence at ~ 1600 nm for dynamic imaging of cancer immune-therapy in mice. We used ErNPs functionalized with cross-linked hydrophilic polymer layers attached to anti-PD-L1 antibody for molecular imaging of PD-L1 in a mouse model of colon cancer and achieved tumor to normal tissue signal ratios of ~ 40. The long luminescence lifetime of ErNPs (~ 4.6 ms) enabled simultaneous imaging of ErNPs and lead sulfide quantum dots (PbS QDs) emitting in the same ~ 1600 nm window. In vivo NIR-IIb molecular imaging of PD-L1 and CD8 revealed cytotoxic T lymphocytes in the tumor microenvironment in response to immunotherapy, and altered CD8 signals in tumor and spleen due to immune activation. The novel crosslinked functionalization layer facilitated 90% ErNPs excretion within two weeks without detectable toxicity in mice.

Nanoceria: A rare-earth nanoparticle as a promising anti-cancer therapeutic agent in colon cancer

The bioactivity and physical characteristics of CeO2 nanoparticles are significantly dependent on the type of the particle, particle size and defects. Herein, a facile and cost effective microwave-assisted combustion route was used to prepare pure CeO2 nanoparticles (NPs). The samples were thoroughly characterized by various techniques and tested as anti-cancer therapeutic agent in colon cancer. The structural investigations (X-ray Powder Diffraction) revealed the formation of single phase cubic fluorite-type structure of CeO2 with Fm-3m space group. Morphological analysis (FESEM), demonstrated the aggregation of irregular nanoparticles with grain size ~ 20–40 nm. To have more knowledge on the sample morphology, TEM and HRTEM images were taken. TEM image showed ceria NPs with squared shape and particle size in 50–95 nm range. Furthermore, HR-TEM micrographs confirmed the crystallinity of the CeO2 sample, which was explored by calculating the distance between the fringes in the corresponding Fourier transformed images. The BET specific surface area (SSA) of as-synthesized ceria nanoparticles, was observed to be 25 m2/g. UV–vis spectral analysis reveals that the direct band gap of CeO2 nanoparticles is about 2.8 eV.It was interesting to observe that, the as prepared NPs exhibit remarkable differential cytotoxicity towards healthy (BHK121, Baby Hamster Kidney cells) and human Colon cancer cells (HCT116). Nuclear fragmentation assay indicated clear DNA fragmentation in HCT116 cells, whereas intact nucleus was observed in normal cells, suggesting ceria induced apoptotic cell death in colon cancer cells. In sum, MACS generated ceria nanoparticles could uncover a new avenue in cancer therapy.

Boosting often overlooked long wavelength emissions of rare-earth nanoparticles for NIR-II fluorescence imaging of orthotopic glioblastoma

Rare-earth nanoparticles (RE NPs) with narrow long wavelength emissions have been recently investigated for their potential application for fluorescence imaging in the second near-infrared window (NIR-II). Previously these RE NPs have a very limited application in the diagnosis and treatment of deep-seated tumors such as brain tumors, due to their weak fluorescence in the range of 1300–1700 nm. Herein, we report a significant enhancement of more than 10 times regular emission of NaNdF4 nanoparticles at 1340 nm wavelength by coating them with an inert layer of NaLuF4, followed by sensitizing with a near-infrared dye (IR-808). We deliver these highly bright nanoparticles into the brain by using focused ultrasound to temporarily open the blood-brain barrier (BBB), and then detect the orthotopic glioblastoma by fluorescence imaging at 1340 nm. The images obtained from long wavelength fluorescence (i.e. 1340 nm) exhibited better resolution and contrast compared to the short wavelength fluorescence (i.e. 1060 nm). Our study not only provides insights for enhancing often overlooked emissions of rare-earth nanoparticles for NIR-II fluorescence imaging of deep-seated tumors, but also demonstrates great potential of focused ultrasound based technology in delivering nanotheranostic agents.

Effect of Y2O3 Nanoparticles on Growth of Maize Seedlings

With the increasing application of rare earth nanoparticles (RENPs), the growing chances of these NPs being released into the environment highlight the importance of understanding the influence of RENPs on plant growth. In this study, we assessed the effect of Y2O3 NPs on the growth of maize seedlings. Germinated buds of maize were planted in pot-cultured farmland soil amended with different concentrations (0–500 mg/kg) of Y2O3 NPs for 25 days. Y2O3 NPs could inhibit root growth. Compared with control treatment, root biomass significantly decreased at high concentrations ( ≥ 100 mg/kg), while root elongation was significantly inhibited at low concentrations ( ≥ 10 mg/kg). However, the growth and photosynthesis of aboveground shoots were not affected by all Y2O3 NPs treatments. This study will help us better understand the phytotoxicity of Y2O3 NPs.

Simultaneous determination of two phosphorylated p53 proteins in SCC-7 cells by an ICP-MS immunoassay using apoferritin-templated europium(III) and lutetium(III) phosphate nanoparticles as labels.

Phosphorylated p53 proteins are biomarkers with clinical utility for early diagnosis of cancer, but difficult to quantify. An inductively coupled plasma mass spectrometry (ICP-MS) based immunoassay is described here that uses uniform lanthanide nanoparticles (NPs) as elemental tags for the simultaneous determination of two phosphorylated p53 proteins. Apoferritin templated europium (Eu) phosphate (AFEP) NPs and apoferritin templated lutetium (Lu) phosphate (AFLP) NPs with 8nm in diameter were used to label two phosphorylated p53 proteins at serine 15 and serine 392 sites (p-p5315 and p-p53392), respectively. The assay has a sandwich format, and p-p5315 and p-p53392 were first captured and then recognized by AFEP and AFLP NPs labelled antibodies, respectively. The Eu and Lu were then released from the immune complexes under acidic condition for ICP-MS measurement. The limits of detection for p-p5315 and p-p53392 are 200 and 20pg·mL-1, with linear ranges of 0.5-20 and 0.05-20ng·mL-1, respectively. The method was further applied to study the response of p-p5315 and p-p53392 in SCC-7 cells exposed to the natural carcinogen arsenite. A significant up-regulation of p-p5315 and p-p53392 can be observed when cells were exposed to arsenite at 5μmol·L-1 level for 24h. Graphical abstract Schematic presentation of the ICP-MS immunoassay using apoferritin templated europium (III) and lutetium (III) phosphate nanoparticles as labels for the simultaneous determination of two phosphorylated p53 proteins. Europium (Eu) phosphate nanoparticles (blue) and lutetium (Lu) phosphate nanoparticles (pink) were synthesized in the size-restricted cavity of apoferritin. They were further coupled with antibodies to prepare Eu and Lu labelled probes for p-p5315 (blue) and p-p53392 (pink), respectively. After formation of aa sandwich, the labelled Eu and Lu were dissociated in acid and then introduced to ICP-MS for the simultaneous determination of two phosphorylated p53 proteins p-p5315 (blue) and p-p53392 (pink).

Light management through up-conversion and scattering mechanism of rare earth nanoparticle in polymer photovoltaics

Primary loss mechanisms in a single junction solar cell are below Eg loss and thermalization loss which limits the maximum achievable cell efficiency. In order to overcome the fundamental loss mechanisms called transmission loss due to the mismatch of the solar spectrum with the photoactive layer absorption spectrum, the up-conversion mechanism was adopted to improve the performance of organic photovoltaics. This mechanism was adopted using rare-earth nanoparticle β-NaYF4:Yb3+/Er3+ in P3HT and PTB7 conducting polymer-based n-i-p organic photovoltaic device. β-NaYF4:Yb3+/Er3+ nanoparticles absorb infrared (IR) photons whose wavelength approximately 980 nm and emit photons in the green wavelength region with the emission intensity maximum occurs at 520 nm and 541 nm. This non-linear optical process (up-conversion mechanism) was used in the polymer solar cell. The polymers used in this study exhibits the absorption range from ~300 nm to 680 nm and 300 nm-800 nm respectively for P3HT and PTB7. Using β-NaYF4:Yb3+/Er3+ in polymer solar cell can reduce the transmission loss through harvesting IR photons. In this study, up-conversion nanoparticles (UCNPs) were embedded between the photoactive layer and anode interface to harvest IR light. Presence of these UCNPs assists in visible photons generation process in the vicinity of the photoactive layer which leads to the increased photo collection. Optimum loading of β-NaYF4:Yb3+/Er3+ nanoparticles in the device interface for improvement in the photocurrent and efficiency were investigated and correlated with the device optical and electrical processes. The optical process suggests that improvement in photocurrent is a synergistic effect of the up-conversion process and light scattering by β-NaYF4:Yb3+/Er3+. The device with UCNPs showed absorbance improvement which suggests that backscattered light at the anode/active layer interface improve the active layer absorption. Detailed investigation of the device properties allows interpreting that the photocurrent improvement is an up-conversion process as well as the scattering. In the optimized up-conversion based device, the photo-current due to up-conversion process and light scattering are of the same order. However, this can vary with respect to photoactive layer absorption properties.

Zirconium metal organic framework for design of tetragonal rare earth-doped zirconia nanoparticles

Zirconium metal–organic frameworks ZrOBDC (where BDC=C6H4(COOH)2, terephthalic acid) doped and co-doped with rare earth ions Ln (ZrOBDC:Ln3+, where Ln3+ = Eu3+ and Tb3+ as well as Er3+ and Yb3+) were used as precursors for the design of tetragonal rare earth doped zirconia nanoparticles (t-ZrO2:Ln3+ NPs) through annealing process. Preparation, characterization and luminescence properties of ZrOBDC:Ln3+ and ZrO2:Ln3+ NPs were investigated. The as-obtained t-ZrO2:Ln3+ NPs have high purity with an average size of 20–30 nm. The luminescence spectra of ZrOBDC:Tb3+ and ZrOBDC:Eu3+ display strong green and red emission at around 544 and 611 nm which correspond to 5D4 → 7F5 and 5D0 → 7F2 transitions of Tb3+ and Eu3+ ions, respectively. The green and red up-conversion emissions of ZrO2:Er3+,Yb3+ NPs due to 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of the Er3+ ions are observed under 976 nm laser excitation.

(Invited) Towards New Near-Infrared Triggered Theranostic Nanoplatforms

Light triggered theranostic (therapy and diagnostic) platforms have gained a considerable attention in recent years. In theranostics, light as an external trigger stands out due to its non-invasiveness, high local precision and temporal resolution. Many such theranostic nanoplatforms employ high-energy (visible or UV) light to initiate the individual therapeutic and diagnostic modalities. However, light at these wavelengths suffers from inherent drawbacks such as having little to no penetration in living tissue, induces autofluorescence from inherent fluorophores or chromophores in tissues and can cause photodamage. The use of NIR light for excitation mitigates such drawbacks associated with high-energy excitation, for example, little to no background autofluorescence from the specimen under investigation as well as no incurred photodamage. Moreover, one of the biggest limitations is of course, that of penetration. As such, NIR light can penetrate tissues much better than high-energy light especially when these wavelengths lie within the three biological windows (BW-I: 700-950, BW-II: 1000-1350, BW-III: 1550-1870 nm) where tissues are optically transparent. At the forefront of NIR excited nanomaterials are rare earth doped nanoparticles, which due to their 4f electronic energy states can undergo conventional (Stokes) luminescence and emit in the three NIR biological windows. However, unlike other classes of nanoparticles, they can also undergo a multiphoton excitation process where the NIR excitation light is converted to higher energies resulting in anti-Stokes luminescence spanning the UV-visible-NIR regions (commonly known as upconversion). Due to the versatility of their optical properties, it now becomes possible to generate upconverted high-energy light (UV or blue) in situ to trigger other light activated therapeutic modalities (i.e. drug release) while using the NIR emission for diagnostics (i.e. bioimaging, nanothermometry). Here, we present the synthesis of various NIR excited (and emitting) rare earth doped core/shell (and multishell) nanoparticles and demonstrate how their luminescence properties can be exploited for potential use in theranostics.

High Affinity to Skeleton Rare Earth Doped Nanoparticles for Near-Infrared II Imaging.

As a newly noninvasive emerging modality, NIR-II fluorescence imaging (1000-1700 nm) has many advantages over conventional visible and NIR-I imaging (700-900 nm). Unfortunately, only a few NIR-II fluorophores are suitable for bone imaging. Here, we report an NIR-II fluorophore based on DSPE-mPEG encapsulated rare earth doped nanoparticles (RENPs@DSPE-mPEG), which shows inherent affinity to bone without linking any targeting ligands, and thus, it provides an alternative noninvasive and nonradiation strategy for skeletal system mapping and bone disease diagnoses. Interestingly, within the NIR-II window, imaging at a longer wavelength (1345 nm) provides a higher resolution and signal-to-noise ratio than imaging at 1064 nm, even though the quantum yield at 1064 nm is 2-fold higher than that at 1345 nm. Besides bone imaging, RENPs@DSPE-mPEG show an imaging application in blood vessels and lymph nodes. Importantly, RENPs@DSPE-mPEG can be internalized by circulating white blood cells. This finding may open a window to increase efficient nanoparticle delivery in the fields such as immunotherapy and improve the diagnostic and therapeutic efficacy of cancer-targeted nanoparticles in clinical applications.

Thermal analysis of erbium charge storage nanoparticles embedded in organic MIS structure

We report on the self-heating characteristics of fabricated organic MIS structures using rare earth erbium nanoparticle as electrical charge storage elements. The organic MIS structure consists of a semiconductive polymer synthesized by means of doping two non-conductive polymers with an ionic liquid, glycerol. SEM images revealed that the rare earth nanoparticles are charging. A Zeta analyzer was used to determine the size of the nanoparticles with an average diameter size of 92 nm. The capacitance versus voltage hysteresis loops of the MIS structure revealed large window gates with a voltage span of 33 V when a ±20 V sweep scan was performed. FLIR thermograph showed an increase in temperature of 1.3 °C of the MIS structure when connected to an AC power generator at 60 Hz. Doing so increased the time constant of the device by 47% when the device is connected the a power source for 15 min. We also assessed on the relationship of increasing the temperature of the Er nanoparticles increases the amount of charges stored in the MIS capacitor.

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.