Nanoplasmonic Upconverting Nanoparticles as Orientation Sensors for Single Particle Microscopy.

We showed that the anisotropic disk shape of nanoplasmonic upconverting nanoparticles (NP-UCNPs) creates changes in fluorescence intensity during rotational motion. We determined the orientation by a three-fold change in fluorescence intensity. We further found that the luminescence intensity was strongly dependent on the particle orientation and on polarization of the excitation light. The luminescence intensity showed a three-fold difference between flat and on-edge orientations. The intensity also varied sinusoidally with the polarization of the incident light, with an Imax/Imin ratio of up to 2.02. Both the orientation dependence and Imax/Imin are dependent on the presence of a gold shell on the UCNP. Because the fluorescence depends on the NP's orientation, the rotational motion of biomolecules coupled to the NP can be detected. Finally, we tracked the real-time rotational motion of a single NP-UCNP in solution between slide and coverslip with diffusivity up to 10-2 µm2s-1.

Enhancement of Upconverted Fluorescence by Interference Layers.

Upconverting nanoparticles show potential applications in the field of photovoltaics and array-based detection devices. While fluorescence enhancement using interference of incident radiation is well known in Stokes-shift type systems such as fluorescent dyes; the effect of such interference geometry in nonlinear Anti-Stokes type emission, such as in upconversion rare earth photophysics is demonstrated for the first time. This work describes in detail the influence of the interference modulation on both the excitation (interion energy transfer) and radiative decay with nonradiative decay processes active between emissive levels. These effects are illustrated in the thickness dependence of the decay rate and rise time. Single particle upconverted spectra and time-resolved measurements show concurrent optimization of the infrared absorption and emission at 540 and 650 nm, with an average enhanced emission of 20 times at λ = 540 and 45 times at λ = 650 nm, dependent on the interference layer thickness and on the excitation intensity. The experimental results are correlated with finite element modeling. Both experiments and calculations show emission enhancement at an interference layer thickness of about 740 ± 20 nm, where such tolerance and the planar design, leads to ease in implementation in applications.

Characterization of an injectable chitosan-demineralized bone matrix hybrid for healing critical-size long-bone defects in a rabbit model.

BACKGROUND: The effect of injectable demineralized bone matrix (DBM) on bone repair is not known. Here, we tested the hypothesis that injectable DBM can heal a critical-size diaphyseal radius defect in a rabbit model. MATERIALS AND METHODS: The bone defect was filled with DBM powder, injectable DBM or powdered, freeze-dried powdered allografts. Radiological determination, gross evaluation, histology, and micro-computer tomography was carried out 4, 8, and 12 weeks after the surgery, respectively. RESULTS: The injectable DBM group yielded better when compared with the freeze-dried powder group (p < 0.05). Moreover, biomechanical functionality was restored comparable to normal levels in the injectable DBM group. CONCLUSIONS: The injectable DBM was as effective in structurally and functionally repairing bone defects as the DBM powder and more effective than the freeze-dried bone powder. Thus, our study supports the use of injectable DBM for bone healing.

Treatment of hydrogen molecule abates oxidative stress and alleviates bone loss induced by modeled microgravity in rats.

UNLABELLED: Treatment with molecular hydrogen alleviates microgravity-induced bone loss through abating oxidative stress, restoring osteoblastic differentiation, and suppressing osteoclast differentiation and osteoclastogenesis. INTRODUCTION: Recently, it has been suggested that hydrogen gas exerts a therapeutic antioxidant activity by selectively reducing cytotoxic reactive oxygen species (ROS). The aim of the present study was to elucidate whether treatment with molecular hydrogen alleviated bone loss induced by modeled microgravity in rats. METHODS: Hindlimb suspension (HLS) and rotary wall vessel bioreactor were used to model microgravity in vivo and in vitro, respectively. Sprague-Dawley rats were exposed to HLS for 6 weeks to induced bone loss and simultaneously administrated with hydrogen water (HW). Then, we investigated the effects of incubation with hydrogen-rich medium (HRM) on MC3T3-E1 and RAW264.7 cells exposed to modeled microgravity. RESULTS: Treatment with HW alleviated HLS-induced reduction of bone mineral density, ultimate load, stiffness, and energy in femur and lumbar vertebra. Treatment with HW alleviated HLS-induced augmentation of malondialdehyde content and peroxynitrite content and reduction of total sulfhydryl content in femur and lumbar vertebra. In cultured MC3T3-E1 cells, incubation with HRM inhibited modeled microgravity-induced ROS formation, reduction of osteoblastic differentiation, increase of ratio of receptor activator of nuclear factor kappa B ligand to osteoprotegerin, inducible nitric oxide synthetase upregulation, and Erk1/2 phosphorylation. In cultured RAW264.7, incubation with HRM aggravated modeled microgravity-induced ROS formation, osteoclastic differentiation, and osteoclastogenesis. CONCLUSION: Treatment with molecular hydrogen alleviates microgravity-induced bone loss in rats. Molecular hydrogen could thus be envisaged as a nutritional countermeasure for spaceflight but remains to be tested in humans.

Nanofabricated upconversion nanoparticles for photodynamic therapy.

We present a novel process for the production of three-layer Composite Nanoparticles (CNPs) in the size range 100-300 nm with an up-converting phosphor interior, a coating of porphyrin photosensitizer, and a biocompatible PEG outer layer to prevent clearance by the reticuloendothelial system. We show that these CNPs produce millimolar amounts of singlet oxygen at NIR intensities far less than other two-photon techniques.

Cooperativity and resonances in periodically driven spin-boson systems.

We present an analytical recursive formulation for the quantum transport in symmetric two-level systems under the influence of both dissipation and periodic driving. The rate-matching condition for quantum stochastic resonance despite its different appearance is found to be physically the same as that in the classical case. Analyzed are also the Rabi resonance and its implication to quantum stochastic resonance. We demonstrate that no matter how weak the driving field is, transport can involve about 70% population in the vicinities of the third-harmonic as well as the fundamental-harmonic Rabi resonance. Recovered is also an adiabatic passage condition in which the transport carries a nearly 100% population in the low frequency and strong driving limit.