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Upconversion nanoparticles (UCNPs) convert near-infrared excitation into visible emission with efficiencies far greater than those of two-photon absorption or second harmonic generation, enabling u...

A grand challenge for medicine is to develop tools to selectively image and treat diseased cells. Rare earth doped upconverting nanoparticles (UCNPs) have been extensively studied for imaging applications because of their ability to absorb near infrared radiation (NIR) and emit visible light, but these particles cannot induce therapy alone. Recently, we developed methods to couple the UCNPs to visible and NIR-absorbing gold nanostructures through nucleic acid interactions. Here, we show that gold-UCNP clusters with optimized plasmon resonance and particle compositions provide both in vitro imaging contrast and combination cell killing through simultaneous photothermal (PTT) and photodynamic (PDT) therapy. PDT was induced by embedding singlet oxygen photosensitizers in silica shells on the UCNPs. Upon photoexcitation with 980 nm light, the NIR absorbing gold-UCNP clusters both increased the local temperature and generated singlet oxygen, increasing cell killing relative to either modality alone. The multifunctional polyethylene glycol (PEG) coated gold-NaYF

A grand challenge for medicine is to develop tools to selectively image and treat diseased cells. Rare earth doped upconverting nanoparticles (UCNPs) have been extensively studied for imaging applications because of their ability to absorb near infrared radiation (NIR) and emit visible light, but these particles cannot induce therapy alone. Recently, we developed methods to couple the UCNPs to visible and NIR-absorbing gold nanostructures through nucleic acid interactions. Here, we show that gold–UCNP clusters with optimized plasmon resonance and particle compositions provide both in vitro imaging contrast and combination cell killing through simultaneous photothermal (PTT) and photodynamic (PDT) therapy. PDT was induced by embedding singlet oxygen photosensitizers in silica shells on the UCNPs. Upon photoexcitation with 980 nm light, the NIR absorbing gold–UCNP clusters both increased the local temperature and generated singlet oxygen, increasing cell killing relative to either modality alone. The multifunctional polyethylene glycol (PEG) coated gold–NaYF4:Yb/Er clusters exhibited high biocompatibility without irradiation but synergistic cell killing of MCF-7 cancer cells under light excitation. Finally, we also demonstrate that an optimal gold plasmon resonance is critical for minimizing absorbance overlap with the photosensitizers.

Rare-earth activated upconversion nanoparticles (UCNPs) are receiving renewed attention for use in bioimaging due to their exceptional photostability and low cytotoxicity. Often, these nanoparticles are attached to plasmonic nanostructures to enhance their photoluminescence (PL) emission. However, current wet-chemistry techniques suffer from large inhomogeneity and thus low enhancement is achieved. In this paper, we report lithographically fabricated metal-insulator-metal (MIM) nanostructures that show over 1000-fold enhancement of their PL. We demonstrate the potential for bioimaging applications by dispersing the MIMs into water and imaging bladder cancer cells with them. To our knowledge, our results represent one and two orders of magnitude improvement, respectively, over the best lithographically fabricated structures and colloidal systems in the literature. The large enhancement will allow for bioimaging and therapeutics using lower particle densities or lower excitation power densities, thus increasing the sensitivity and efficacy of such procedures while decreasing potential side effects., Upconversion nanoparticles are already used in bio-imaging but still suffer from low luminescence. Here, metal-insulator-metal nanostructures with 1-2 orders magnitude enhancement in upconversion are introduced enabling bioimaging at reduced particle or excitation power densities, respectively.

We present results on enhanced upconversion of NaYF 4 : Er3+, Yb3+ nanoparticles using a metal-insulator-metal structure that can eventually be dispersed in solution. Enhancement of 1200x in photoluminescence and 3.8x in energy transfer rate is observed.

DNA-mediated assembly of core-satellite structures composed of Zr(IV)-based porphyrinic metal-organic framework (MOF) and NaYF(4),Yb,Er upconverting nanoparticles (UCNPs) for photodynamic therapy (PDT) is reported. MOF NPs generate singlet oxygen ((1)O(2)) upon photoirradiation with visible light without the need for additional small molecule, diffusional photosensitizers such as porphyrins. Using DNA as a templating agent, well-defined MOF-UCNP clusters are produced where UCNPs are spatially organized around a centrally located MOF NP. Under NIR irradiation, visible light emitted from the UCNPs is absorbed by the core MOF NP to produce (1)O(2) at significantly greater amounts than what can be produced from simply mixing UCNPs and MOF NPs. The MOF-UCNP core-satellite superstructures also induce strong cell cytotoxicity against cancer cells, which are further enhanced by attaching epidermal growth factor receptor targeting affibodies to the PDT clusters, highlighting their promise as theranostic photodynamic agents.

Combinations of rare earth doped upconverting nanoparticles (UCNPs) and gold nanostructures are sought as nanoscale theranostics due to their ability to convert near infrared (NIR) photons into visible light and heat, respectively. However, because the large NIR absorption cross-section of the gold coupled with their thermo-optical properties can significantly hamper the photoluminescence of UCNPs, methods to optimize the ratio of gold nanostructures to UCNPs must be developed and studied. We demonstrate here nucleic acid assembly methods to conjugate spherical gold nanoparticles (AuNPs) and gold nanostars (AuNSs) to silica-coated UCNPs and probe the effect on photoluminescence. These studies showed that while UCNP fluorescence enhancement was observed from the AuNPs conjugated UCNPs, AuNSs tended to quench fluorescence. However, conjugating lower ratios of AuNSs to UCNPs led to reduced quenching. Simulation studies both confirmed the experimental results and demonstrated that the orientation and distance of the UCNP with respect to the core and arms of the gold nanostructures played a significant role in PL. In addition, the AuNS-UCNP assemblies were able to cause rapid gains in temperature of the surrounding medium enabling their potential use as a photoimaging-photodynamic-photothermal agent.

We report enhanced up-conversion in NaYF 4 :Yb3+, Er3+ nanoparticles by surface plasmon. Simple grating and MIM grating structures were investigated to target the excitation processes. Photoluminescence spectroscopy showed up to 30x enhancement in up-converted luminescence intensity.