Poly (acrylic acid)-capped lanthanide-doped BaFCl nanocrystals: synthesis and optical properties

An advancement in the synthesis of nano Pd@magnetic amine-Functionalized UiO-66-NH2 catalyst for cyanation and O-arylation reactions

The magnetic MOF-based catalytic system has been reported here to be an efficient catalyst for synthesis of benzonitriles and diarylethers of aryl halides under optimal conditions. The MOF catalyst was built based on magnetic nanoparticles and UiO-66-NH₂ which further modified with 2,4,6-trichloro-1,3,5-triazine and 5-phenyl tetrazole at the same time and the catalyst structure was confirmed by various techniques. This new modification has been applied to increase anchoring palladium into the support. Furthermore, the products' yields were obtained in good to excellent for all reactions under mild conditions which result from superior activity of the synthesized heterogeneous catalyst containing palladium. Also, the magnetic property of the MOF-based catalyst makes it easy to separate from reaction mediums and reuse in the next runs.

MRBLES 2.0: High-throughput generation of chemically functionalized spectrally and magnetically encoded hydrogel beads using a simple single-layer microfluidic device

The widespread adoption of bead-based multiplexed bioassays requires the ability to easily synthesize encoded microspheres and conjugate analytes of interest to their surface. Here, we present a simple method (MRBLEs 2.0) for the efficient high-throughput generation of microspheres with ratiometric barcode lanthanide encoding (MRBLEs) that bear functional groups for downstream surface bioconjugation. Bead production in MRBLEs 2.0 relies on the manual mixing of lanthanide/polymer mixtures (each of which comprises a unique spectral code) followed by droplet generation using single-layer, parallel flow-focusing devices and the off-chip batch polymerization of droplets into beads. To streamline downstream analyte coupling, MRBLEs 2.0 crosslinks copolymers bearing functional groups on the bead surface during bead generation. Using the MRBLEs 2.0 pipeline, we generate monodisperse MRBLEs containing 48 distinct well-resolved spectral codes with high throughput (>150,000/min and can be boosted to 450,000/min). We further demonstrate the efficient conjugation of oligonucleotides and entire proteins to carboxyl MRBLEs and of biotin to amino MRBLEs. Finally, we show that MRBLEs can also be magnetized via the simultaneous incorporation of magnetic nanoparticles with only a minor decrease in the potential code space. With the advantages of dramatically simplified device fabrication, elimination of the need for custom-made equipment, and the ability to produce spectrally and magnetically encoded beads with direct surface functionalization with high throughput, MRBLEs 2.0 can be directly applied by many labs towards a wide variety of downstream assays, from basic biology to diagnostics and other translational research.

Paper-based biodetection using luminescent nanoparticles

Point-of-care and in-field technologies for rapid, sensitive and selective detection of molecular biomarkers have attracted much interest. Rugged bioassay technology capable of fast detection of markers for pathogens and genetic diseases would in particular impact the quality of health care in the developing world, but would also make possible more extensive screening in developed countries to tackle problems such as those associated with water and food quality, and tracking of infectious organisms in hospitals and clinics. Literature trends indicate an increasing interest in the use of nanomaterials, and in particular luminescent nanoparticles, for assay development. These materials may offer attributes for development of assays and sensors that could achieve improvements in analytical figures of merit, and provide practical advantages in sensitivity and stability. There is opportunity for cost-efficiency and technical simplicity by implementation of luminescent nanomaterials as the basis for transduction technology, when combined with the use of paper substrates, and the ubiquitous availability of cell phone cameras and associated infrastructure for optical detection and transmission of results. Luminescent nanoparticles have been described for a broad range of bioanalytical targets including small molecules, oligonucleotides, peptides, proteins, saccharides and whole cells (e.g., cancer diagnostics). The luminescent nanomaterials that are described herein for paper-based bioassays include metal nanoparticles, quantum dots and lanthanide-doped nanocrystals. These nanomaterials often have broad and strong absorption and narrow emission bands that improve opportunity for multiplexed analysis, and can be designed to provide emission at wavelengths that are efficiently processed by conventional digital cameras. Luminescent nanoparticles can be embedded in paper substrates that are designed to direct fluid flow, and the resulting combination of technologies can offer competitive analytical performance at relatively low cost.

Lectin-conjugated pH-responsive mesoporous silica nanoparticles for targeted bone cancer treatment

A novel multifunctional nanodevice based in doxorubicin (DOX)-loaded mesoporous silica nanoparticles (MSNs) as nanoplatforms for the assembly of different building blocks has been developed for bone cancer treatment. These building blocks consists of: i) a polyacrylic acid (PAA) capping layer grafted to MSNs via an acid-cleavable acetal linker, to minimize premature cargo release and provide the nanosystem of pH-responsive drug delivery ability; and ii) a targeting ligand, the plant lectin concanavalin A (ConA), able to selectively recognize, bind and internalize owing to certain cell-surface glycans, such as sialic acids (SA), overexpressed in given tumor cells. This multifunctional nanosystem exhibits a noticeable higher internalization degree into human osteosarcoma cells (HOS), overexpressing SA, compared to healthy preosteoblast cells (MC3T3-E1). Moreover, the results indicate that small DOX loading (2.5 µg mL^-1) leads to almost 100% of osteosarcoma cell death in comparison with healthy bone cells, which significantly preserve their viability. Besides, this nanodevice has a cytotoxicity on tumor cells 8-fold higher than that caused by the free drug. These findings demonstrate that the synergistic combination of different building blocks into a unique nanoplatform increases antitumor effectiveness and decreases toxicity towards normal cells. This line of attack opens up new insights in targeted bone cancer therapy.

STATEMENT OF SIGNIFICANCE

The development of highly selective and efficient tumor-targeted smart drug delivery nanodevices remains a great challenge in nanomedicine. This work reports the design and optimization of a multifunctional nanosystem based on mesoporous silica nanoparticles (MSNs) featuring selectivity towards human osteosarcoma cells and pH-responsive antitumor drug delivery capability. The novelty and originality of this manuscript relies on proving that the synergistic assembly of different building blocks into a unique nanoplatform increases antitumor effectiveness and decreases toxicity towards healthy cells, which constitutes a new paradigm in targeted bone cancer therapy.

Mechanochemically prepared SrFCl nanophosphor co-doped with Yb3+ and Er3+ for detecting ionizing radiation by upconversion luminescence

We report a novel method for detecting ionizing radiation by employing the phenomenon of upconversion luminescence. Nanocrystalline SrFCl:Yb³⁺/Er³⁺ was prepared by ball-milling and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The photoluminescence properties of nanocrystalline SrFCl:Yb³⁺, SrFCl:Er³⁺ and SrFCl:Yb³⁺/Er³⁺ before and after X-irradiation were investigated. The results demonstrate that both Yb³⁺ and Er³⁺ ions in the SrFCl host are reduced to their divalent state upon X-ray exposure. Under 980 nm infrared excitation, SrFCl:Yb³⁺/Er³⁺ nanocrystals displayed efficient upconversion luminescence. The upconversion luminescence intensity gradually decreased with increasing X-irradiation in a double exponential fashion with rate constants of k₁ = 0.08 Gy^-1 and k₂ = 0.01 Gy^-1. In comparison with other X-ray storage phosphors, the present system shows a much higher stability of stored information since it is not subject to photobleaching in the read-out process. This is the first report on detecting ionizing radiation by upconversion luminescence, with the potential for improved read-out performance over traditional storage phosphors. Possible applications of the present phosphor include bioimaging and in vivo cell-level X-ray dose monitoring.

Ultrasensitive Luminescent In Vitro Detection for Tumor Markers Based on Inorganic Lanthanide Nano-Bioprobes

Ultrasensitive and accurate detection of tumor markers is of vital importance for the screening or diagnosis of cancers at their early stages and for monitoring cancer relapse after surgical resection. Inorganic lanthanide (Ln3+) nanoparticles (NPs), owing to their superior physicochemical characteristics, are regarded as a new generation of luminescent nano-bioprobes in the field of cancer diagnosis and therapy. In this progress report, a focus is set on our recent efforts on the development of inorganic Ln3+-NPs as efficient luminescent nano-bioprobes for the ultrasensitive in vitro biodetection of tumor markers, with an emphasis on the dissolution-enhanced luminescent bioassay (DELBA), an emerging technique recently developed toward practical medical applications.

Sensitive Detection of ssDNA Using an LRET-Based Upconverting Nanohybrid Material

Water-dispersible, optical hybrid nanoparticles are preferred materials for DNA biosensing due to their biocompatibility. Upconverting nanoparticles are highly desirable optical probes in sensors and bioimaging owing to their sharp emission intensity in the visible region. We herein report a highly sensitive ss-DNA detection based on an energy transfer system that uses a nanohybrid material synthesized by doping NaYF4:Tm(3+)/Yb(3+) upconverting nanoparticles (UCNPs) on silica coated polystyrene-co-acrylic acid (PSA) nanoparticles (PSA/SiO2) as the donor, and gold nanoparticles (AuNPs) decorated with Ir(III) complex as the acceptor. UCNPs tagged on PSA/SiO2 and the cyclometalated Ir(III)/AuNP conjugates were then linked through the ss-DNA sequence. Sequential addition of the target DNA to the probe molecular beacon complex resulted in the separation of the optical nanohybrid material and the quencher, leading to a measurable increase in the blue fluorescence emission intensity. Our results have shown a linear relationship between the fluorescence intensity and target DNA concentration down to the picomolar.

Multifunctional LaPO4:Ce/Tb@Au mesoporous microspheres: synthesis, luminescence and controllable light triggered drug release

Uniform LaPO₄:Ce/Tb mesoporous microspheres were prepared by a facile co-precipitation process. Under UV irradiation, a rapid DOX release was derived from the overlap of the green emission of Tb³⁺ and the surface plasmon resonance (SPR) band of Au.

Lanthanide-doped luminescent nano-bioprobes: from fundamentals to biodetection

Trivalent lanthanide (Ln(3+))-doped luminescent inorganic nanoparticles (NPs), characterized by long-lived luminescence, large Stokes and/or anti-Stokes shifts, narrow emission bands and high photochemical stability, are considered to be promising candidates as luminescent bioprobes in biomedicine and biotechnology. In this feature article, we provide a brief overview of the most recent advances in Ln(3+)-doped luminescent inorganic NPs as sensors, which covers from their chemical and physical fundamentals to biodetection, such as controlled synthesis methodology, surface modification chemistry, optical physics, and their promising applications in diverse bioassays, with an emphasis on heterogeneous and homogeneous in vitro biodetection. Finally, some of the most important emerging trends and future efforts toward this active research field are also proposed.

Doxorubicin conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles for therapy and sensing of drug delivery by luminescence resonance energy transfer

In this study, we report an anticancer drug delivery system based on doxorubicin (DOX)-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles. The as-synthesized nanoparticles consist of uniform spherical nanoparticles with an average diameter of 25 nm. The drug delivery system demonstrates the ability to release DOX by cleavage of the hydrazone bond in mildly acidic environments. The spectra overlap between emission of donor NaYF(4):Yb(3+)/Tm(3+) nanoparticles at 452 nm ((1)D(2)→(3)F(4)) and 477 nm ((1)G(4)→(3)H(6)) and the broad absorbance of acceptor DOX centered at around 480 nm enables energy transfer to occur between the nanoparticles and DOX. The quenching and recovery of the up-conversion luminescence of NaYF(4):Yb(3+)/Tm(3+) by DOX due to luminescence resonance energy transfer (LRET) mechanism are applied as optical probe to confirm the DOX conjunction and monitor the release of DOX. The DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles exhibit an obvious cytotoxic effect on SKOV3 ovarian cancer cells via MTT assay. Meanwhile, the endocytosis process of DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles by SKVO3 cells was demonstrated through confocal laser scanning microscopy (CLSM), flow cytometry and ICP-OES. Such drug delivery system, which combines pH-triggered drug-release and up-converting nanoparticles-based LRET property, has excellent potential applications in cancer therapy and smart imaging.

Controlled synthesis and optical spectroscopy of lanthanide-doped KLaF₄ nanocrystals

KLaF(4), as a good host matrix for trivalent lanthanide (Ln(3+)) ions to fabricate upconversion (UC) or downconversion (DC) phosphors, has been rarely reported. Herein, monodisperse (∼10 nm) cubic-phase Ln(3+)-doped KLaF(4) nanocrystals (NCs) were synthesized via a facile thermal decomposition method. Upon excitation at 980 nm, UC luminescence properties of KLaF(4):Ln(3+)/Yb(3+) (Ln = Tm, Ho, Er) NCs were comprehensively surveyed. Particularly, after coating an inert KLaF(4) shell, the green and red UC luminescence intensity of KLaF(4):Er(3+)/Yb(3+) NCs was enhanced ∼35 times, and the corresponding UC lifetimes of (4)S(3/2) and (4)F(9/2) levels of Er(3+) were observed significantly prolonged from 42 and 68 μs in core-only NCs to 87 and 136 μs in core/shell counterparts. Furthermore, intense DC luminescence was also achieved in Ce(3+)/Tb(3+) and Eu(3+) doped KLaF(4) NCs, with absolute quantum yields of 39.8% (Tb(3+)) and 17.3% (Eu(3+)). The luminescence lifetimes of (5)D(0) (Eu(3+)) and (5)D(4) (Tb(3+)) were determined to be 4.2 and 4.7 ms, respectively. Water-soluble Ln(3+)-doped KLaF(4) NCs featuring excellent monodispersion, long luminescence lifetime, and high UC/DC efficiency may have versatile and promising applications as luminescent nano-biolabels.

Morphology and phase control of fluorides nanocrystals activated by lanthanides with two-model luminescence properties

The morphology, size and phase control of luminescent fluoride nanocrystals through doping has become a new research hotspot due to their improved properties. In this work, Yb(3+) ions, as one of the most efficient sensitizers for various lanthanide activators, were doped in NaGd(Y)F(4) nanocrystals. The results show that no obvious influence was observed for Yb(3+)-doped NaYF(4) nanocrystals, while the influence of Yb(3+) doping on NaGdF(4) nanocrystals was remarkable. The NaGd(1-x)Yb(x)F(4) nanocrystals were synthesized by a hydrothermal route and had a morphology of rice-like nanorods. By controlling the synthesis parameters, the average size and slenderness of the nanocrystals increased gradually with addition of Yb(3+) ions. In contrast, the NaGd(1-x)Yb(x)F(4) nanocrystals maintained a hexagonal phase, which is more beneficial for application as a luminescent host, until the content of Yb(3+) ions reached x = 0.9. The growth and transformation mechanism of NaGd(1-x)Yb(x)F(4) nanocrystals was proposed to be a result of the competition between ion diffusion and an Oswald ripening process. Photoluminescence (PL) spectra confirm the efficient up-conversion and near-infrared (NIR) two-model luminescence properties of Er(3+) (Tm(3+)) activated NaGd(Y)(1-x)Yb(x)F(4) nanocrystals. Simulated analysis results indicate that a colloidal solution of mixed luminescent nanocrystals is expected to find application as the activated medium of three dimensional displays and a broadband optical amplifier.

Room temperature synthesis of hydrophilic Ln(3+)-doped KGdF4 (Ln = Ce, Eu, Tb, Dy) nanoparticles with controllable size: energy transfer, size-dependent and color-tunable luminescence properties

In this paper, we demonstrate a simple, template-free, reproducible and one-step synthesis of hydrophilic KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) nanoparticles (NPs) via a solution-based route at room temperature. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the samples. The results indicate that the use of water-diethyleneglycol (DEG) solvent mixture as the reaction medium not only allows facile particle size control but also endows the as-prepared samples with good water-solubility. In particular, the mean size of NPs is monotonously reduced with the increase of DEG content, from 215 to 40 nm. The luminescence intensity and absolute quantum yields for KGdF(4): Ce(3+), Tb(3+) NPs increase remarkably with particle sizes ranging from 40 to 215 nm. Additionally, we systematically investigate the magnetic and luminescence properties of KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) NPs. They display paramagnetic and superparamagnetic properties with mass magnetic susceptibility values of 1.03 × 10(-4) emu g(-1)·Oe and 3.09 × 10(-3) emu g(-1)·Oe at 300 K and 2 K, respectively, and multicolor emissions due to the energy transfer (ET) process Ce(3+)→ Gd(3+)→ (Gd(3+))(n)→ Ln(3+), in which Gd(3+) ions play an intermediate role in this process. Representatively, it is shown that the energy transfer from Ce(3+) to Tb(3+) occurs mainly via the dipole-quadrupole interaction by comparison of the theoretical calculation and experimental results. This kind of magnetic/luminescent dual-function materials may have promising applications in multiple biolabels and MR imaging.

Facile synthesis of an up-conversion luminescent and mesoporous Gd2O3 : Er3+@nSiO2@mSiO2 nanocomposite as a drug carrier

In this paper, we report the facile synthesis of a bifunctional inorganic nanocomposite which is composed of core-shell structured mesoporous silica coated with up-conversion Gd2O3 : Er3+ particles. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption, and photoluminescence (PL) spectra were used to characterize the samples. The results indicate that the nanocomposite with general 50 nm shell thickness and 300 nm core size shows typical ordered mesoporous characteristics (2.3 nm) and has spherical morphology with smooth surface and narrow size distribution. The bifunctional system shows unique green up-conversion emission under 980 nm NIR laser excitation even after loading with drug molecules. In addition, biocompatibility tests on L929 fibroblast cells using an MTT assay reveals low cytotoxicity of the system. Drug release tests suggest that the nanocomposite has a controlled drug release property with ibuprofen (IBU) as the model drug. Interestingly, the up-conversion emission intensity of the bifunctional carrier increases with the released amount of model drug, thus allowing the release process to be monitored and tracked by the change of up-conversion luminescence intensity. This composite can potentially act as a functional drug carrier system.

Progress on lanthanide-based organic-inorganic hybrid phosphors

Research on organic-inorganic hybrid materials containing trivalent lanthanide ions (Ln(3+)) is a very active field that has rapidly shifted in the last couple of years to the development of eco-friendly, versatile and multifunctional systems, stimulated by the challenging requirements of technological applications spanning domains as diverse as optics, environment, energy, and biomedicine. This tutorial review offers a general overview of the myriad of advanced Ln(3+)-based organic-inorganic hybrid materials recently synthesised, which may be viewed as a major innovation in areas of phosphors, lighting, integrated optics and optical telecommunications, solar cells, and biomedicine.