NIR-Responsive Photocatalytic Activity and Mechanism of NaYF₄:Yb,Tm@TiO₂ Core–Shell Nanoparticles

Core–shell structured nanoparticles for near-infrared (NIR) photocatalysis were synthesized by a two-step wet-chemical route. The core is composed of upconversion luminescence NaYF₄:Yb,Tm prepared by a solvothermal process, and the shell is anatase TiO₂ nanocrystals around NaYF₄ particles formed via a method similar to a Stöber process. Methylene blue compound as a model pollutant was used to investigate the photocatalytic activity of NaYF₄:Yb,Tm@TiO₂ composites under NIR irradiation. To understand the nature of NIR-responsive photocatalysis of NaYF₄:Yb,Tm@TiO₂, we investigated the energy transfer process between NaYF₄:Yb,Tm and TiO₂ and the origin of the degradation of organic pollutants under NIR radiation. Results indicate that the energy transfer route between NaYF₄:Yb,Tm and TiO₂ is an important factor that influences the photocatalytic activity significantly and that the degradation of organic pollutants under NIR irradiation is caused mostly by the oxidation of reactive oxygen species generated in the photocatalytic reaction, rather than by the thermal energy generated by NIR irradiation. The understanding of NIR-responsive photocatalytic mechanism helps to improve the structural design and functionality of this new type of catalytic material

NIR to VUV: Seven-Photon Upconversion Emissions from Gd³⁺ Ions in Fluoride Nanocrystals

Here we show that a near-infrared (NIR) diode laser is capable of generating vacuum ultraviolet (VUV) emissions in fluoride nanocrystals through photon upconversion (UC) processes. By using Yb³⁺ and Tm³⁺ as sensitizers, we successfully obtained the VUV photons with the energy exceeding 6 eV in YF₃: Yb, Tm, and Gd nanocrystals. The seven photon UC fluorescence from the ⁶<i>G</i>_<i>J</i> → ⁸<i>S</i>_7/2 transitions of Gd³⁺ ions and the possible VUV UC mechanism were reported along with the calculation of the branching ratio under different pumping power excitation. Practically, it offers a promising solution for VUV light generation without cryogens and expensive instrumentations. Fundamentally, the extremely high-order UC processes will intrigue great interest in exploring unusual high-energy radiative transitions in rare earth ions

The Signature of MicroRNA Dysregulation in Muscle Paralyzed by Spinal Cord Injury Includes Downregulation of MicroRNAs that Target Myostatin Signaling

<div><p>Spinal cord injury (SCI) results in muscle atrophy, reduced force generation and an oxidative-to-glycolytic fiber type shift. The mechanisms responsible for these alterations remain incompletely understood. To gain new insights regarding mechanisms involved in deterioration of muscle after SCI, global expression profiles of miRs in paralyzed gastrocnemius muscle were compared between sham-operated (Sham) and spinal cord-transected (SCI) rats. Ingenuity Pathways Analysis of the altered miRs identified signaling via insulin, IGF-1, integrins and TGF-β as being significantly enriched for target genes. By qPCR, miRs 23a, 23b, 27b, 145, and 206, were downregulated in skeletal muscle 56 days after SCI. Using FISH, miR-145, a miR not previously implicated in the function of skeletal muscle, was found to be localized to skeletal muscle fibers. One predicted target of miR-145 was Cited2, a transcriptional regulator that modulates signaling through NF-κB, Smad3 and other transcription factors. The 3’ UTR of Cited2 mRNA contained a highly conserved miR-145 seed sequence. Luciferase reporter assays confirmed that miR-145 interacts with this seed sequence. However, Cited2 protein levels were similar between Sham and SCI groups, indicating a biochemical interaction that was not involved in the context of adaptations after SCI. Taken together, the findings indicate dysregulation of several highly expressed miRs in skeletal muscle after SCI and suggest that reduced expression of miR-23a, 145 and 206 may have roles in alteration in skeletal muscle mass and insulin responsiveness in muscle paralyzed by upper motor neuron injuries.</p></div

Europium-Complex-Grafted Polymer Dots for Amplified Quenching and Cellular Imaging Applications

We report on a europium-complex-grafted polymer for preparing stable nanoparticle probes with high luminescence brightness, narrow emission bandwidth, and long luminescence lifetimes. A Eu complex bearing an amino group was used to react with a functional copolymer poly­(styrene-<i>co</i>-maleic anhydride) by the spontaneous amidation reaction, producing the polymer grafted with Eu complexes in the side chains. The Eu-complex-grafted polymer was further used to prepare Eu-complex-grafted polymer dots (Pdots) and Eu-complex-blended poly­(9-vinylcarbazole) composite Pdots, which showed improved colloidal stability as compared to those directly doped with Eu-complex molecules. Both types of Pdots can be efficiently quenched by a nile blue dye, exhibiting much lower detection limit and higher quenching sensitivity as compared to free Eu-complex molecules. Steady-state spectroscopy and time-resolved decay dynamics suggest the quenching mechanism is via efficient fluorescence resonance energy transfer from the Eu complex inside a Pdot to surface dye molecules. The amplified quenching in Eu-complex Pdots, together with efficient cell uptake and specific cell surface labeling observed in mammalian cells, suggests their potential applications in time-resolved bioassays and cellular imaging

mRNAs targets of differentially expressed miRs that lie within the signaling pathways of TGFß family members.

<p>Confirmed targets are identifed by boldface. Numbers in brackets are literature citations for confirmed targets.</p

Cited2 protein expression is maintained at 56 days post-SCI.

<p>Rat gastrocnemius muscle was fractionated into cytosolic (A) and nuclear fractions (B) and probed for Cited2 expression by immunoblotting. There were no differences in either the cytosolic or nuclear expression of Cited2. Data are presented as mean values normalized to tubulin or histone H3. N = 5 per group.</p

qPCR determinations of relative expression levels of selected miRNAs (panels A and B).

<p>Graphs show means ± STD for 8 animals per group. *, p < 0.05. Abbreviations: RQ, fold-change for the comparison between SCI and Sham groups.</p

Body and muscle weights at 56 days after spinal cord transection at T4.

<p>Data are mean values ± STD for: A) body weight; B) gastrocnemius; C) soleus; D) plantaris; E) triceps; F) biceps. Percentages shown within each bar are: gain in body weight relative to pre-operative weight (panel A) and normalized muscle weight relative to Sham (panels B-F). N = 14 for each group.</p

Effect of SCI on expression of the mostly highly expressed miRs in gastrocnemius muscle.

<p>Effect of SCI on expression of the mostly highly expressed miRs in gastrocnemius muscle.</p

miR-145 is localized to muscle fibers.

<p>LNA-FISH was performed on cross sections of (rat gastrocnemius muscle using DIG-labeled LNA-FISH probes for miR-145, scrambled control, and U6 snRNA. A: 20 nM miR-145 probe, B: 40 nM miR-145 probe; C: U6 snRNA probe (1 nM); D: scrambled control probe (40 nM); E: no probe. Scale bar: 30 microns.</p