Shell Upconversion Nanoparticles Research Articles

Enhanced NIR-I emission from water-dispersible NIR-II dye-sensitized core/active shell upconverting nanoparticles

Water-dispersible NIR-II dye (IR-1061) sensitized core/active shell upconversion nanoparticles (800 nm emission of Tm3+ ion).

Epitaxial growth of ultrathin layers on the surface of sub-10nm nanoparticles: the case of β-NaGdF4:Yb/Er@NaDyF4 nanoparticles.

Upconversion core–shell nanoparticles have attracted a large amount of attention due to their multifunctionality and specific applications. In this work, based on a NaGdF4 sub-10 nm ultrasmall nanocore, a series of core–shell upconversion nanoparticles with uniform size doped with Yb3+, Er3+ and NaDyF4 shells with different thicknesses were synthesized by a facile sequential growth process. NaDyF4 coated upconversion luminescent nanoparticles showed an obvious fluorescence quenching under excitation at 980 nm as a result of energy resonance transfer between Yb3+, Er3+ and Dy3+. NaGdF4:Yb,Er@NaDyF4 core–shell nanoparticles with ultrathin layer shells exhibited a better T1-weighted MR contrast.

Energy transfer mechanism dominated by the doping location of activators in rare-earth upconversion nanoparticles.

Research on the energy transfer mechanism of rare-earth-doped upconversion nanoparticles (UCNPs) has been an important area due to the increasing demand for tuning multicolor emission and enhancing the upconversion efficiency; however, because of large energy mismatch, many lanthanide activators, such as Eu3+, cannot realize highly efficient near infrared-to-visible upconversion by simple codoping of Yb3+. Therefore, introduction of other ions to assist the energy transfer process is required. Herein, we prepared core-shell nanoparticles with different doping locations to investigate the upconversion energy transfer mechanism. The upconversion luminescence (UCL) of core-shell nanoparticles was investigated by steady-state luminescence and time-resolved luminescence spectra. The UCL behaviors in these different multi-activator core-shell nanoparticles were observed. The results revealed different energy transfer channels influenced by the doping location of activators. This study may open up new avenues of structure design for fine-tuning of multicolor UCL for specific applications.

Design and Synthesis of Core-Shell-Shell Upconversion Nanoparticles for NIR-Induced Drug Release, Photodynamic Therapy, and Cell Imaging.

Novel core-shell-shell structured nanoparticles 75 nm in diameter with all-in-one "smart" functional capabilities for simultaneous photoresponsive drug release, photodynamic therapy, and cell imaging are designed and prepared. These nanoparticles consist of an upconversion (UC) emission core, a photosensitizer-embodied silica sandwich shell, and a β-cyclodextrin (β-CD) gated mesoporous silica outmost shell with drugs (Rhodamine B as a model) loaded inside. We show in this proof-of-concept demonstration that, under 980 nm near-infrared irradiation, UC 540 nm green light emissions were emitted for cell imaging, and 660 nm red light emissions were excited for activating photosensitizers to generate singlet oxygen, which could be exploited directly to kill cancer cells and simultaneously dissociate β-CD gatekeeper to release drugs. The preliminary results reported here will shed new light on the future design and applications of multifunctional platforms for cancer therapy and diagnostic.

Dye-Sensitized Core/Active Shell Upconversion Nanoparticles for Optogenetics and Bioimaging Applications.

Near-infrared (NIR) dye-sensitized upconversion nanoparticles (UCNPs) can broaden the absorption range and boost upconversion efficiency of UCNPs. Here, we achieved significantly enhanced upconversion luminescence in dye-sensitized core/active shell UCNPs via the doping of ytterbium ions (Yb(3+)) in the UCNP shell, which bridged the energy transfer from the dye to the UCNP core. As a result, we synergized the two most practical upconversion booster effectors (dye-sensitizing and core/shell enhancement) to amplify upconversion efficiency. We demonstrated two biomedical applications using these UCNPs. By using dye-sensitized core/active shell UCNP embedded poly(methyl methacrylate) polymer implantable systems, we successfully shifted the optogenetic neuron excitation window to a biocompatible and deep tissue penetrable 800 nm wavelength. Furthermore, UCNPs were water-solubilized with Pluronic F127 with high upconversion efficiency and can be imaged in a mouse model.

794 nm excited core–shell upconversion nanoparticles for optical temperature sensing

Nd3+ sensitized core–shell upconversion nanoparticles (UNCPs) are promising candidates for application in optical temperature sensors at a biocompatible excitation wavelength (794 nm).

Optical temperature sensing with minimized heating effect using core–shell upconversion nanoparticles

Core–shell NaYF4:Yb3+, Tm3+@NaYF4:Yb3+, Nd3+ nanosystem for temperature sensing with a minimized heating effect, which demonstrates a high sensitivity of up to 1.55% K−1 at a temperature range between 313 and 553 K.

Sequential growth of sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core–shell–shell nanoparticles for photodynamic therapy

Upconversion (UC) nanostructures have attracted much interest for their extensive biological applications. In this work, we describe a sequential synthetic route to prepare sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core–shell upconversion nanoparticles. The as-prepared products were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM, JEM 2100F), respectively. The as-prepared core–shell nanoparticles of NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb are composed of elliptical nanoparticles with a length of 80nm and width of 42nm, which show efficient upconversion fluorescence excited at 808nm indicating the formation of core–shell–shell sandwiched nanostructures. In addition, the as-prepared sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core–shell upconversion nanoparticles also show strong upconversion fluorescence excited at 980nm. Amphiphilic mPEG2k-b-PEBEP6K copolymers (denoted as PPE) were chosen to transfer these hydrophobic UCNPs into the aqueous phase for biological application. In vitro photodynamic therapy of cancer cells show that the viability of cells incubated with the nanoparticles loaded with MC 540 was significantly lower as compared to the nanoparticles without photosensitizers exposed to NIR laser.

An imaging-guided platform for synergistic photodynamic/photothermal/chemo-therapy with pH/temperature-responsive drug release

To integrate biological imaging and multimodal therapies into one platform for enhanced anti-cancer efficacy, we have designed a novel core/shell structured nano-theranostic by conjugating photosensitive Au25(SR)18 – (SR refers to thiolate) clusters, pH/temperature-responsive polymer P(NIPAm-MAA), and anti-cancer drug (doxorubicin, DOX) onto the surface of mesoporous silica coated core–shell up-conversion nanoparticles (UCNPs). It is found that the photodynamic therapy (PDT) derived from the generated reactive oxygen species and the photothermal therapy (PTT) arising from the photothermal effect can be simultaneously triggered by a single 980 nm near infrared (NIR) light. Furthermore, the thermal effect can also stimulate the pH/temperature sensitive polymer in the cancer sites, thus realizing the targeted and controllable DOX release. The combined PDT, PTT and pH/temperature responsive chemo-therapy can markedly improve the therapeutic efficacy, which has been confirmed by both in intro and in vivo assays. Moreover, the doped rare earths endow the platform with dual-modal up-conversion luminescent (UCL) and computer tomography (CT) imaging properties, thus achieving the target of imaging-guided synergistic therapy under by a single NIR light.

Lutetium doping for making big core and core–shell upconversion nanoparticles

Fabricating big sized core and core–shell UCNs through lutetium doping.

Near infrared activation of an anticancer Pt(IV) complex by Tm-doped upconversion nanoparticles.

The Pt(IV) complex cis,cis,trans-[Pt(NH3)2(Cl)2(O2CCH2CH2CO2H)2] is photoactivated by near infrared light (980 nm) using NaYF4:Yb(3+)/Tm(3+)@NaYF4 core-shell upconversion nanoparticles. Coupling of this cisplatin precursor with the biocompatible PEGylated phospholipid DSPE-PEG(2000)-NH2 affords a valuable approach to decorate the surface of the nanoparticles, providing novel photoactivatable nanomaterials capable of releasing Pt(II) species upon NIR light excitation.

Temperature sensitivity and stability of NaYF4:Yb3+, Er3+ core-only and core–shell upconversion nanoparticles

Hexagonal (β)-phase NaYF4:Yb3+, Er3+ upconversion nanoparticles (UCNPs) with or without a protection shell are successfully synthesized. Effects of inert (undoped NaYF4) and active (NaYF4:10% Yb3+) shells on their upconversion luminescence (UCL) and temperature sensing properties are studied. Well-fitted exponential relations between the intensity ratio (RHS) of the green fluorescence bands of Er3+ ions (2H11/2→4I15/2 and 4S3/2→4I15/2) and temperature are obtained for core-only and core–shell UCNPs, showing their potential applications as temperature sensing probes. Heating–cooling cycle tests show that all the samples have high thermal stability. Both inert and active shells can obviously improve the UCL properties of UCNPs, and do not affect their RHS values and thermal sensitivity. However, compared with the active shell, the inert shell can significantly reduce the thermal effect of UCNPs caused by laser excitation, which is beneficial for practical applications by avoiding the interference of excitation light and reducing the measuring errors. Temperature sensing properties of UCNPs are insusceptible to different dispersion mediums and show high stability in a broad range of pH values and salt conditions, indicating their availability for temperature sensing in the biomedical field.

Facile Preparation of Well-Defined Hydrophilic Core–Shell Upconversion Nanoparticles for Selective Cell Membrane Glycan Labeling and Cancer Cell Imaging

Molecular imaging enables in situ visualization of biomolecules in living organisms and creates numerous opportunities for basic biological research and early disease diagnosis. As luminescent probes for molecular imaging, lanthanide-doped upconversion nanoparticles (UCNPs) exhibit superior performance compared to conventional fluorescent dyes in many ways, including high tissue penetration depth and minimized autofluorescence and photobleaching, making them particularly advantageous for imaging analysis. Although various synthesis methods have been reported, the preparation of high quality, water-soluble UCNPs remains challenging. For in situ imaging, glycans on the cell surface are particularly attractive due to their key roles in cellular activity and disease occurrence and development. However, glycan imaging is a challenging task due to their diverse structures and incompatibility with genetically encoded fluorescent tagging techniques. Herein, we report a new type of highly water-soluble, lectin-functionalized core-shell UCNP synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) for selective cell membrane glycan labeling and cancer cell imaging. SI-ATRP modification results in controlled growth of hydrophilic polymers on the UCNP surface and well-defined core-shell structure, producing UCNPs with improved biocompatibility and intact luminance property. Furthermore, the numerous functional groups on the polymer brush shell provide a large number of binding sites and 3D support for lectin immobilization. The increased loading density and diversified architecture of the immobilized lectins facilitates multivalent binding between the lectins and the glycans on the cell surface and leads to selective labeling of highly metastatic hepatocellular carcinoma cells (HCCHM3) in vitro and successful in vivo imaging of HCCHM3 inoculated mice.