Upconversion Particles Research Articles

Application of novel targeted molecular imaging probes in the early diagnosis of upper urinary tract epithelial carcinoma.

Imaging techniques of upper tract urothelial carcinoma (UTUC) are presently limited. Upconversion particles (UCPs) could be used to target tumors for imaging. The present study aimed to assess the value of a nano-UCP as a diagnostic probe for deep tumor tissue, including UTUC. Polymer-coated water-soluble UCPs were synthesized. The pH Low Insertion Peptide (pHLIP) polypeptide was synthesized using the solid phase method. The silane shell surface was modified to present amino or carboxyl groups. Succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate was used for the coupling of the polypeptide to the UCPs. An animal model of subcutaneous tumor was established in 4-week old nude mice using UTUC cells. Urinary tract epithelial cancer T24 cells were injected into the diaphragm below the heart. PHLIP-UCP solution (1 ml) was injected into the abdominal cavity of each animal. Optical detection was performed using a small animal living body multispectral imaging system. UCPs dispersed in chloroform emitted no light under natural light, while they emitted a green light when excited with a 980-nm laser. The maximum emission wavelength of Ho3+-doped UCPs was ~550 nm and the red emission region was ~650 nm. As the coated UCPs possessed a tendency to agglomerate and precipitate, the yield of the UCPs in the aqueous phase was reduced. Tumors could be successfully imaged in tumor-bearing mice. NaYF4: Yb, Ho3+ UPCs could be used for the detection of UTUC, thus further studies are required to determine if it could be used in larger animals with deeper tumors.

Security writing application of thermal decomposition assisted NaYF4:Er3+/Yb3+ upconversion phosphor

The authors have synthesized water-dispersible NaYF4:Er3+/Yb3+ upconversion particles via a thermal decomposition route and optimized the green upconversion emission through a concentration variation of the Yb3+ sensitizer. The prepared particles were found to be ellipsoid in shape having an average particle dimension of 600 × 150 nm. It is observed that the sample with 18 mmol% Yb3+ ion concentration and 2 mmol% Er3+ ion gives optimum upconversion intensity in the green region under 980 nm excitation. Colloidal dispersibility of the sample in different solvents was checked and hexane was found to be the best medium for the prepared particles. The particle size of the sample was found to be suitable for the preparation of colloidal ink and security writing on a plain sheet of paper. This was demonstrated successfully using ink prepared in polyvinyl chloride gold medium.

Spectral management and morphology evolution of β-NaGdF4:Yb3+,Er3+ by tuning the concentration of citric acid

β-NaGdF4:Yb3+,Er3+ upconversion (UC) particles were prepared by a facile hydrothermal process with assistance of citric acid (CA). The morphologies of β-NaGdF4 UC particles were controlled by changing the doses of CA in precursor. With an increase CA concentration in precursor, increase sizes of crystals were observed, resulting in the increasing of luminescence intensity. The energy transfer ET mechanism was analyzed in detail.

The use of upconversion microparticles as a novel internal radiation source for fabrication of composite materials

Upconversion (UC) microparticles were used as novel internal radiation sources for composite preparation. These particles emit Ultraviolet‐Visible radiation when exposed to Near‐infrared waves. This radiation causes uniform and deep polymerization. Two types of UC particles were prepared via a facile hydrothermal method, including NaLuF4: Yb 20%, Tm 0.5% and NaLuF4: Yb 40%, Tm 0.5%. The effect of three different photoinitiator systems, including titanocene, bisacylphosphine oxide, and camphorquinone, on the cure depth and the degree of conversion (DC) was investigated. Polymerization reaction rate was also studied. Moreover, the effect of weight percentage of UC particles and laser intensity on the cure depth and the DC were evaluated. Rheological behavior of the composites with different percentage of the particles (1, 3, and 5%) and the effect of temperature were studied. The results showed that the overlap of the UC particles emission spectrum with the photoinitiator absorption spectrum and the intensity of the photoinitiator absorption in the emission range of the particles are of the most important factors affecting cure depth, rate and DC. The cure depth with DC up to approximately 80% was 41 mm. Moreover, the DC was almost constant along the sample. POLYM. COMPOS., 40:884–892, 2019. © 2018 Society of Plastics Engineers

Single 808 nm Laser Treatment Comprising Photothermal and Photodynamic Therapies by Using Gold Nanorods Hybrid Upconversion Particles

Light therapy has become the subject of research on cancer treatment because of its selectivity, low invasive damage, and side effects. Photothermal therapy (PTT) and photodynamic therapy (PDT) are prevalent treatments used to induce cancer cell apoptosis by generating heat and reactive oxygen species (ROS). In this study, mesoporous silica shell-coated gold nanorods (AuNR@mS) are synthesized by seed crystal growth method. AuNR@mS are assembled into nanocomposites through electrostatic adsorption with lanthanide-doped upconversion nanoparticles (UCNP). When controlling the aspect ratio of gold nanorods (AuNRs), the surface plasmon resonance peaks of the short-axis and the long-axis match the maximum absorption cross section at 520 and 660 nm of the fluorescence light released by the UCNPs. The converted fluorescence stimulates AuNRs to generate heat through energy transfer. ROS production is induced by loading the photosensitizer Merocyanine 540 (MC540) in the mesoporous silica layer and is further enhanc...

Upconversion particle@Fe3O4@molecularly imprinted polymer with controllable shell thickness as high-performance fluorescent probe for sensing quinolones

Localized photo-polymerization was ingeniously applied to prepare a multifunctional molecularly imprinted polymer (MIP) fluorescent probe using the “layer-by-layer” assembly of MIP and Fe3O4 nanoparticles on NaYF4: Yb3+, Er3+ upconversion particles (MUCPs@MIP). Enrofloxacin was used as the template and chosen as the target molecular during the investigation of the adsorption property. This ternary probe has magnetic and broad-spectrum molecular recognition capability, fast response, and upconversion fluorescence. The results of the fluorescence quenching analysis showed good linear ranges of 1.03nmol/L to 0.28μmol/L for enrofloxacin, 1.69nmol/L to 0.22μmol/L for fleroxacin, 6.92nmol/L to 0.28μmol/L for levofloxacin, 7.54nmol/L to 0.30μmol/L for ciprofloxacin, and 3.90nmol/L to 0.25μmol/L for enoxacin. This probe was further used to determine five quinolones in fish tissues and the recoveries ranging from 90.33% to 108.43% were obtained with relative standard deviation below 5.53%. This work offers a new and general strategy to synthesize a MUCPs@MIP upconversion fluorescence probe with magnetic and selective molecular recognition capability for rapid and accurate sensing of multiple chemical residues in the environment and agri-food products.

ПЕРСПЕКТИВЫ ПРИМЕНЕНИЯ АПКОНВЕРСИОННЫХ ЧАСТИЦ NaYF4:Er,Yb ДЛЯ ФОТОТЕРАПИИ

ПЕРСПЕКТИВЫ ПРИМЕНЕНИЯ АПКОНВЕРСИОННЫХ ЧАСТИЦ NaYF4:Er,Yb ДЛЯ ФОТОТЕРАПИИ

Precise stimulation of near-infrared light responsive shape-memory polymer composites using upconversion particles with photothermal capability

The incorporation of thermally-induced shape-memory polymer (SMP) with photothermal fillers has been widely used in creating photoresponsive SMP composites (SMPCs). Near-infrared (NIR) light, which is safer for human tissues and naked eyes, has been widely used to trigger such intelligent SMPCs containing carbon nanomaterials, metal nanoparticles, or rare earth organic complexes. There is still a need to aim invisible NIR light beam remotely onto SMPCs to realize the precise shape recovery of their featured areas. Here, NaYF4:99.5%Yb3+, 0.5%Tm3+ particles presenting both upconversion and photothermal capabilities were utilized as multifunctional fillers in a crosslinked copolymer of methyl methacrylate and butyl acrylate, enabling the prepared SMPCs to transfer the NIR light at 980 nm simultaneously into both visible light and heat. The particles with a low content up to 1 phr did not vary the crosslinking level and glass transition temperature of the SMPC. With the aid of upconversion at a relatively low power density, the position of laser beam on SMPC surface was detected easily, facilitating the aim towards the area anticipated to be triggered without inducing a shape deformation. The subsequent increase in power density successfully resulted in the precise shape recovery with the recovery ratio higher than 90%. The concept of precise location before stimulation was demonstrated in the cases of multiple shape deformations, remote activation in the darkness, and microscale structured surfaces. The reported multifunctional nanoparticles truly executed the remote and precise trigger of SMPCs using invisible NIR light, which can be further exploited in other thermally-induced smart polymer composites.

Nanoparticle-Based Immunochemical Biosensors and Assays: Recent Advances and Challenges.

We review the progress achieved during the recent five years in immunochemical biosensors (immunosensors) combined with nanoparticles for enhanced sensitivity. The initial part introduces antibodies as classic recognition elements. The optical sensing part describes fluorescent, luminescent, and surface plasmon resonance systems. Amperometry, voltammetry, and impedance spectroscopy represent electrochemical transducer methods; electrochemiluminescence with photoelectric conversion constitutes a widely utilized combined method. The transducing options function together with suitable nanoparticles: metallic and metal oxides, including magnetic ones, carbon-based nanotubes, graphene variants, luminescent carbon dots, nanocrystals as quantum dots, and photon up-converting particles. These sources merged together provide extreme variability of existing nanoimmunosensing options. Finally, applications in clinical analysis (markers, tumor cells, and pharmaceuticals) and in the detection of pathogenic microorganisms, toxic agents, and pesticides in the environmental field and food products are summarized.

A NIR-responsive up-conversion nanoparticle probe of the NaYF4:Er,Yb type and coated with a molecularly imprinted polymer for fluorometric determination of enrofloxacin

The paper describes the preparation of a fluorescent probe based on the use of up-conversion particles (UCPs) of the type NaYF4: Er, Yb and shelled with a molecularly imprinted polymer (MIP) that is specific for the antibiotic enrofloxacin. The upconverted green luminescence emitted by the UCPs upon photoexcitation at 980 nm was used to locally generate a thin MIP shell around the UCPs via photopolymerization. Enrofloxacin is used as the template, and ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent. It is found that enrofloxacin is well captured by the MIP and then quenches the fluorescence of the UCPs. Fluorescence decreases linearly in the 63 ng·L−1 to 60 μg·L−1 enrofloxacin concentration range, with a 8 ng·L−1 limit of detection. The method was applied to the determination of enrofloxacin in spiked fish samples. Recoveries ranged from 83.7 to 87.7%, with relative standard deviations between 2.0 and 5.5% (for n = 3).

Synthesis of g-C3N4-based NaYF4:Yb,Tm@TiO2 ternary composite with enhanced Vis/NIR-driven photocatalytic activities

Upconversion (UC) NaYF4:Yb,Tm nanocrystals (NCs) are capable of converting low-energy near-infrared (NIR) photons to high-energy ultraviolet (UV) and visible (Vis) photons. Integration of NaYF4:Yb,Tm with graphitic carbon nitride (g-C3N4) can extend the spectral response of g-C3N4 to the NIR range. However, photocatalytic activity of NaYF4:Yb,Tm/g-C3N4 is still severely limited by the high recombination rate of photo-generated (PG) electrons and holes (e–/h+) in the g-C3N4. Herein, we report a facile approach to fabricate a ternary nanocomposite consisting of NaYF4:Yb,Tm, TiO2 and g-C3N4. When NaYF4:Yb,Tm NCs were coated with a TiO2 shell and sequentially assembled with g-C3N4 nanosheets (NSs), a semiconductor heterojunction can be fabricated on the UC particles. The as-prepared nanocomposites possess an enhanced photocatalytic activity under Vis and/or NIR lights due to the formation of heterojunction and UC effect. The ternary nanocomposites have been characterized in detail and their photocatalytic mechanism is proposed. Such kind of ternary nanocomposites may provide a new scenario for the design and synthesis of composite photocatalysts for efficiently utilizing the Vis/NIR lights in environmental remedy.

Ecophotonics: assessment of temperature gradient in aquatic organisms using up-conversion luminescent particles

In the frameworks of developing ecophotonics, we consider the possibility of applying luminescence spectroscopy for monitoring conditions of aquatic organisms, aimed at the study and prognosis of the effect of human activity and climate changes on the environment. The method of luminescence spectroscopy in combination with anti-Stokes luminophores (up-conversion particles) used as optical sensors is used for the noninvasive assessment of the temperature gradient in the internal tissues of aquatic organisms. It is shown that the temperature dependence of the intensity ratio observed in the maxima of the luminescence spectrum bands of the particles Y2O3 : Yb, Er, administered in a biological object, is linear. This fact offers a possibility of using the up-conversion particles for assessing the metabolic activity of different tissues, including those in the framework of ecological monitoring.

Low Efficiency Upconversion Nanoparticles for High-Resolution Coalignment of Near-Infrared and Visible Light Paths on a Light Microscope.

The combination of near-infrared (NIR) and visible wavelengths in light microscopy for biological studies is increasingly common. For example, many fields of biology are developing the use of NIR for optogenetics, in which an NIR laser induces a change in gene expression and/or protein function. One major technical barrier in working with both NIR and visible light on an optical microscope is obtaining their precise coalignment at the imaging plane position. Photon upconverting particles (UCPs) can bridge this gap as they are excited by NIR light but emit in the visible range via an anti-Stokes luminescence mechanism. Here, two different UCPs have been identified, high-efficiency micro540-UCPs and lower efficiency nano545-UCPs, that respond to NIR light and emit visible light with high photostability even at very high NIR power densities (>25 000 Suns). Both of these UCPs can be rapidly and reversibly excited by visible and NIR light and emit light at visible wavelengths detectable with standard emission settings used for Green Fluorescent Protein (GFP), a commonly used genetically encoded fluorophore. However, the high efficiency micro540-UCPs were suboptimal for NIR and visible light coalignment, due to their larger size and spatial broadening from particle-to-particle energy transfer consistent with a long-lived excited state and saturated power dependence. In contrast, the lower efficiency nano-UCPs were superior for precise coalignment of the NIR beam with the visible light path (∼2 μm versus ∼8 μm beam broadening, respectively) consistent with limited particle-to-particle energy transfer, superlinear power dependence for emission, and much smaller particle size. Furthermore, the nano-UCPs were superior to a traditional two-camera method for NIR and visible light path alignment in an in vivo Infrared-Laser-Evoked Gene Operator (IR-LEGO) optogenetics assay in the budding yeast Saccharomyces cerevisiae. In summary, nano-UCPs are powerful new tools for coaligning NIR and visible light paths on a light microscope.

Photostable upconverting and downconverting pH sensors based on combination of a colorimetric NIR indicator and stable inorganic phosphors as secondary emitters

New robust optical pH sensors rely on a combination of a photochemically stable NIR colorimetric aza-BODIPY dye and inorganic phosphors. Inner-filter effect is utilized to convert the colorimetric changes into a luminescence response. Chromium(III)-activated gadolinium aluminium borate and Egyptian Blue were used as inert reference phosphors, enabling two-wavelength ratiometric read-out in the emission and excitation mode, respectively. Additionally, we synthetized dually-emitting upconverting particles (UCPs) based on lanthanide-doped molybdates (NaCaY1−xLax(MoO4)3, La=Yb(III), Ho(III) and Tm(III)) featuring anti-Stokes emission peaks in the red/NIR spectral region (645/800nm). Upon NIR excitation (980nm) the NIR emission of the upconverting particles is modulated by the pH indicator, whereas the red emission serves as a reference. Importantly, the spectral properties of the pH sensor based on UCPs are fully compatible with the biological optical window.

Highly uniform up-converting nanoparticles: Why you should control your synthesis even more

Luminescent β-NaYF4:Yb3+,Er3+ (xYb: 0.17, xEr: 0.03) nanomaterials were synthesized for use as labels for biomedical applications with high temperature co-precipitation synthesis in 1-octadecene and oleic acid. The effect of the synthesis conditions (e.g. argon flow, cooling and stirring rates) on the products’ up-conversion luminescence intensity, particle size and morphology were studied. The factors contributing to these properties were analysed. It was observed that an efficient inert gas flow is essential to the formation of the preferred highly-luminescent hexagonal structure. Furthermore, the flow rate, together with the stirring rate, crucially affect the Er:Yb molar ratio of the products. The optimization of this ratio is essential when strong up-conversion emission is required from small particles, whereas the morphology and uniformity of the nanoparticles can be controlled with the cooling rate. These results emphasize the importance of controlling the synthesis conditions, especially when nanoparticles need to have a specific morphology because of their use e.g. as luminescent labels in medical diagnostics.

Microwave-assisted synthesis of NaYF4:Yb3+/Tm3+ upconversion particles with tailored morphology and phase for the design of UV/NIR-active NaYF4:Yb3+/Tm3+@TiO2 core@shell photocatalysts

Coupling of TiO2 with rare earth (RE) metal-based upconversion particles (UCPs) is a promising strategy to develop near-infrared (NIR)-driven TiO2-based photocatalysts. This, however, requires the controlled synthesis of bright NIR-to-UV UCPs with tailored morphology, size and crystalline phase. Herein, we report a rapid, efficient and reproducible co-precipitation/microwave (MW)-assisted hydrothermal method for the preparation of NaYF4:Yb3+/Tm3+ UCPs which allows tailoring the morphology (spherical nanoparticles, microrods) and crystalline phase (cubic, hexagonal) and hence the optical response of the resulting UCPs by simply varying the MW treatment time or ethylenediaminetetraacetic acid (EDTA) concentration. The EDTA concentration strongly affects the size of the primary UCPs during the co-precipitation step which plays a decisive role in dictating the final particle morphology in the subsequent MW-assisted hydrothermal step. Based on microscopic and XRD analyses, a model for the growth of UCPs with different morphologies has been proposed. Pure hexagonal microrods with strong upconversion (UC) photoluminescence (PL) in the UV (345 nm, 361 nm) and visible (450 nm, 475 nm) regions are obtained using MW treatment times of 30–60 min and EDTA/RE3+ molar ratios above 1.5. The UCPs@TiO2 core@shell composite photocatalysts prepared by coating anatase TiO2 on the surface of UCPs using a sol–gel method showed good photocatalytic activity under both ultraviolet (UV) and NIR light. This efficient and reproducible co-precipitation/MW-assisted approach may be considered as a step forward towards the efficient harvesting of sunlight for photochemical and photoelectrical applications based on TiO2.

Revisiting the optimized doping ratio in core/shell nanostructured upconversion particles.

The development of rare-earth doped upconversion nanoparticles (RE-UCNPs) in various applications is fuelling the demand for nanoparticles with highly enhanced upconversion luminescence (UCL). Although the core/shell structure is proved to enhance the UCL effectively, there is still plenty of room to further improve the UCL by optimizing the doping ratio of the materials. In this article, a general strategy is demonstrated to achieve highly-enhanced visible UCL in core/shell nanostructured NaREF4 by increasing the doping ratio of Yb3+ in the core region. The energy transfer from RE-UCNPs to surface quenching sites through Yb3+-Yb3+ energy migration is demonstrated to be the main reason for restricting the doping ratio of Yb3+. Notable UCL enhancement (ca. 15 times) of core/shell structured α-NaYF4:Yb,Er@CaF2 nanoparticles is observed by increasing the concentration of Yb3+ to 98 mol%. The highly-enhanced visible UCL signal is used to guide the lymphatic vessel resection with the naked eye.

NIR induced photopolymerization of acrylate-based composite containing upconversion particles as an internal miniaturized UV sources

Abstract Inventing a new light source for overcoming the disadvantages of conventional radiation curing technology is essential. Upconversion particles capable of emitting photon span from ultraviolet to NIR region of electromagnetic spectrum under excitation of NIR laser, could play the role of a light source within the formulation. Different amount of these upconversion particles were introduced to TMPTA monomer in order to survey their curing ability. The curing process was performed under various NIR laser intensities. The monomer to polymer conversion was studied using FT-IR and real-time FT-IR analysis. Increasing the filler content leads to better curing of the composite. Furthermore, the feasibility of curing TMPTMA containing camphorquinone as photoinitiator, by the blue upconversion emission was studied. Besides, the ability of these particles as UV and blue source cooperation in dual curing was observed. Increasing the photo-initiator and upconversion particles concentration resulted in higher double bond conversion. Increasing the laser intensity, by enhancing the upconversion emissions leads to better monomer to polymer conversion. The new source passed the inducing of dual curing process.

Erratum to: Luminescence Monitoring of Temporal Changes and Efficiency of Tissue Optical Clearing by NIR-Excited Upconversion Particles

The time history and efficiency of optical clearing of rat skin in vitro have been studied by monitoring the changes in the luminescence signal from [Y2O3:Yb, Er] upconversion particles located under tissue layers. It has been shown that, under the action of immersion agent on the skin, image contrast is increased from zero to 0.36. The structure of the cleared tissue samples becomes more distinct. We have performed a numerical simulation of the experiment using the Monte Carlo method. It has been obtained that the recorded luminescence intensity is proportional to the square of the number of exciting photons. The proportionality coefficient depends on the scattering coefficient of biological tissue. The proposed method of analysis of the temporal dependencies can be used as the basis for the construction of an algorithm of study of the time history of clearing agent’s diffusion into biological tissue by temporal changes of the luminescence of upconversion nanoparticles delivered into the tissue. Visualization of a local object which contained particles and was placed under tissue layers has led to the assumption of the possibility of tracking the movements of encapsulated drugs within the blood vessels by the luminescence of nanoparticles contained in a capsule.

RGDS- and TAT-Conjugated Upconversion of NaYF4:Yb(3+)/Er(3+)&SiO2 Nanoparticles: In Vitro Human Epithelioid Cervix Carcinoma Cellular Uptake, Imaging, and Targeting.

Starting NaYF4:Yb(3+)/Er(3+) nanoparticles with size tuned from 24 to 33 nm were prepared by high-temperature coprecipitation of lanthanide chlorides in high-boiling organic solvents. To enhance colloidal stability in aqueous medium, an aminosilica shell was introduced on the surface by hydrolysis and condensation of tetramethyl orthosilicate and (3-aminopropyl)trimethoxysilane using a reverse microemulsion technique; to form alkyne groups, reaction with 4-pentynoic acid followed. Finally, the cell adhesive and cell penetrating azidopentanoyl-GGGRGDSGGGY-NH2 (RGDS) and azidopentanoyl-GGGRKKRRQRRR-NH2 (TAT) peptides were conjugated to the upconversion particles via Cu(I)-catalyzed alkyne-azide cycloaddition. The concentrations of the peptides bound to the nanoparticle surfaces and amount of adsorbed residual Cu(I) catalyst were determined using an (125)I-radiolabeled RGDS peptide and a (64)Cu(I)-doped catalyst, respectively. Targeting and uptake of the RGDS- and TAT-conjugated NaYF4:Yb(3+)/Er(3+)&SiO2 nanoparticles by human cervix carcinoma HeLa cells were monitored by confocal microscopy. RGDS-conjugated nanoparticle probes were mainly localized on the cell plasma membrane due to specific binding of the peptide to the corresponding integrins. In contrast, the TAT-conjugated nanoparticles were able to cross the cell membrane and accumulate in the cell cytoplasm. Thus, this new peptide bioconjugation approach supported both extra- and intracellular nanoparticle uptake, enabling targeting and imaging of the specific tumor phenotypes.