Oxygen Reduction Reaction with Manganese Oxide Nanospheres in Microbial Fuel Cells.

Operating microbial fuel cells (MFCs) under extreme pH conditions offers a substantial benefit. Acidic conditions suppress the growth of undesirable methanogens and increase redox potential for oxygen reduction reactions (ORRs), and alkaline conditions increase the electrocatalytic activity. However, operating any fuel cells, including MFCs, is difficult under such extreme pH conditions. Here, we demonstrate a pH-universal ORR ink based on hollow nanospheres of manganese oxide (h-Mn3O4) anchored with multiwalled carbon nanotubes (MWCNTs) on planar and porous forms of carbon electrodes in MFCs (pH = 3-11). Nanospheres of h-Mn3O4 (diameter ∼ 31 nm, shell thickness ∼ 7 nm) on a glassy carbon electrode yielded a highly reproducible ORR activity at pH 3 and 10, based on rotating disk electrode (RDE) tests. A phenomenal ORR performance and long-term stability (∼106 days) of the ink were also observed with four different porous cathodes (carbon cloth, carbon nanofoam paper, reticulated vitreous carbon, and graphite felt) in MFCs. The ink reduced the charge transfer resistance (R ct) to the ORR by 100-fold and 45-fold under the alkaline and acidic conditions, respectively. The current study promotes ORR activity and subsequently the MFC operations under a wide range of pH conditions, including acidic and basic conditions.

Peripherally misfolded proteins exacerbate ischemic stroke-induced neuroinflammation and brain injury.

BACKGROUND: Protein aggregates can be found in peripheral organs, such as the heart, kidney, and pancreas, but little is known about the impact of peripherally misfolded proteins on neuroinflammation and brain functional recovery following ischemic stroke. METHODS: Here, we studied the ischemia/reperfusion (I/R) induced brain injury in mice with cardiomyocyte-restricted overexpression of a missense (R120G) mutant small heat shock protein, αB-crystallin (CryABR120G), by examining neuroinflammation and brain functional recovery following I/R in comparison to their non-transgenic (Ntg) littermates. To understand how peripherally misfolded proteins influence brain functionality, exosomes were isolated from CryABR120G and Ntg mouse blood and were used to treat wild-type (WT) mice and primary cortical neuron-glia mix cultures. Additionally, isolated protein aggregates from the brain following I/R were isolated and subjected to mass-spectrometric analysis to assess whether the aggregates contained the mutant protein, CryABR120G. To determine whether the CryABR120G misfolding can self-propagate, a misfolded protein seeding assay was performed in cell cultures. RESULTS: Our results showed that CryABR120G mice exhibited dramatically increased infarct volume, delayed brain functional recovery, and enhanced neuroinflammation and protein aggregation in the brain following I/R when compared to the Ntg mice. Intriguingly, mass-spectrometric analysis of the protein aggregates isolated from CryABR120G mouse brains confirmed presence of the mutant CryABR120G protein in the brain. Importantly, intravenous administration of WT mice with the exosomes isolated from CryABR120G mouse blood exacerbated I/R-induced cerebral injury in WT mice. Moreover, incubation of the CryABR120G mouse exosomes with primary neuronal cultures induced pronounced protein aggregation. Transduction of CryABR120G aggregate seeds into cell cultures caused normal CryAB proteins to undergo dramatic aggregation and form large aggregates, suggesting self-propagation of CryABR120G misfolding in cells. CONCLUSIONS: These results suggest that peripherally misfolded proteins in the heart remotely enhance neuroinflammation and exacerbate brain injury following I/R likely through exosomes, which may represent an underappreciated mechanism underlying heart-brain crosstalk.

Diffusion doping of cobalt in rod-shape anatase TiO2 nanocrystals leads to antiferromagnetism.

Cobalt(ii) ions were adsorbed to the surface of rod-shape anatase TiO2 nanocrystals and subsequently heated to promote ion diffusion into the nanocrystal. After removal of any remaining surface bound cobalt, a sample consisting of strictly cobalt-doped TiO2 was obtained and characterized with powder X-ray diffraction, transmission electron microscopy, UV-visible spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy, SQUID magnetometry, and inductively-coupled plasma atomic emission spectroscopy. The nanocrystal morphology was unchanged in the process and no new crystal phases were detected. The concentration of cobalt in the doped samples linearly correlates with the initial loading of cobalt(ii) ions on the nanocrystal surface. Thin films of the cobalt doped TiO2 nanocrystals were prepared on indium-tin oxide coated glass substrate, and the electrical conductivity increased with the concentration of doped cobalt. Magnetic measurements of the cobalt-doped TiO2 nanocrystals reveal paramagnetic behavior at room temperature, and antiferromagnetic interactions between Co ions at low temperatures. Antiferromagnetism is atypical for cobalt-doped TiO2 nanocrystals, and is proposed to arise from interstitial doping that may be favored by the diffusional doping mechanism.

Intraductal Drug Delivery to the Breast: Effect of Particle Size and Formulation on Breast Duct and Lymph Node Retention.

Drug delivery by direct intraductal administration can achieve high local drug concentration in the breast and minimize systemic levels. However, the clinical application of this approach for breast cancer treatment is limited by the rapid clearance of the drug from the ducts. With the goal of developing strategies to prolong drug retention in the breast, this study was focused on understanding the influence of particle size and formulation on breast duct and lymph node retention. Fluorescent-labeled polystyrene (PS) particles ranging in size from 100 to 1000 nm were used to study the influence of particle size. Polylactic acid-co-glycolic acid (PLGA) was used to develop and test formulations for intraductal delivery. Cy 5.5, a near-IR dye, was encapsulated in PLGA microparticles, nanoparticles, and the in situ gel to study the biodistribution in rats using an in vivo imager. PS microparticles (1 µm) showed longer retention in the duct compared to 100 and 500 nm nanoparticles. The ductal retention half-life was 5-fold higher for PS microparticles compared to the nanoparticles. On the other hand, the free dye was cleared from the breast within 6 h. PLGA nanoparticles sustained the release of Cy 5.5 for >4 days. Microparticles and gel showed a much slower release than nanoparticles. PLGA in situ gel and microparticles were retained in the breast for up to 4 days, while the nanoparticles were retained in the breast for 2 days. PLGA nanoparticles and microparticles drained to the axillary lymph node and were retained for up to 24 and 48 h, respectively, while the in situ gel and the free dye did not show any detectable fluorescence in the lymph nodes. Taken together, the results demonstrate the feasibility of prolonged retention in the breast duct and lymph node by optimal formulation design. The findings can serve as a framework to design formulations for localized treatment of breast cancer.

Bioadhesive Food Protein Nanoparticles as Pediatric Oral Drug Delivery System.

The goal of this study was to develop bioadhesive food protein nanoparticles using zein (Z), a hydrophobic corn protein, as the core and whey protein (WP) as the shell for oral pediatric drug delivery applications. Lopinavir (LPV), an antiretroviral drug, and fenretinide, an investigational anticancer agent, were used as model drugs in the study. The particle size of ZWP nanoparticles was in the range of 200-250 nm, and the drug encapsulation efficiency was >70%. The nanoparticles showed sustained drug release in simulated gastrointestinal fluids. ZWP nanoparticles enhanced the permeability of LPV and fenretinide across Caco-2 cell monolayers. In both ex vivo and in vivo studies, ZWP nanoparticles were found to be strongly bioadhesive. ZWP nanoparticles enhanced the oral bioavailability of LPV and fenretinide by 4 and 7-fold, respectively. ZWP nanoparticles also significantly increased the half-life of both drugs. The nanoparticles did not show any immunogenicity in mice. Overall, the study demonstrates the feasibility of developing safe and effective food protein-based nanoparticles for pediatric oral drug delivery.

Measuring the internal quantum yield of upconversion luminescence for ytterbium-sensitized upconversion phosphors using the ytterbium(iii) emission as an internal standard.

A method is presented for estimating the internal quantum yield (IQY) of NIR-to-NIR and NIR-to-visible upconversion (UC) luminescence for Yb3+-sensitized energy-transfer upconversion (ETU) phosphors. The method does not require an integrating sphere or a secondary standard, but rather uses the 1 µm emission of the Yb3+ sensitizer as an internal standard. The method requires the acquisition of the 1 µm emission decay curve of the UC phosphor using low pulse-energy density, an estimation of the radiative decay constant of the 1 µm emission, and emission spectra corrected for instrument response. This method is valid for UC emission spectra acquired via pulsed or continuous wave (cw) excitation. The method is demonstrated for cw excitation to obtain IQY for UC and downshifted luminescence for ß-phase NaYF4: 0.5%Tm, 25%Yb and NaYF4: 2%Er, 18%Yb nanocrystals (with and without a passivating NaYF4 shell) over a range of excitation irradiance. The corresponding results are consistent with those obtained using integrating spheres and numerical simulations, respectively. For pulsed excitation, an additional alternative method is described which requires acquisition of the 1 µm emission decay curve at each excitation pulse-energy density for which the IQY is to be determined. The proposed methods should be particularly useful for samples having very low absorbance at the excitation wavelength, for which direct determination methods are impractical.

Stable Inks Containing Upconverting Nanoparticles Based on an Oil-in-Water Nanoemulsion.

An oil-in-water nanoemulsion capable of dispersing upconverting nanoparticles (UCNPs) for 7 months was investigated. Negative staining transmission electron microscopy shows that the UCNPs reside in the oil phase of the nanoemulsion. Dynamic light scattering measurements indicate that the majority of the oil volume is contained in droplets less than 1 µm in diameter. The system studied could be used to inkjet print UCNPs at least 7 months after the ink was first formulated. Nanoemulsion stability was tested in the short term, over 11 days, using an ink stability test developed for this research. It was found that after an initial loss of UCNPs, the majority of the UCNPs remained well-dispersed in solution. The UCNP dispersion was stable for longer periods under storage at 333 K compared to storage at 277 K.

Ligand Controlled Morphology Evolution of Active Intermediates for the Syntheses of Gold Nanostars.

Gold nanostars have unique plasmonic properties that are related to the highly branched nanostructures. However, it is challenging to precisely control these branches. Here we studied the reaction kinetics on the seed-mediated growth process of gold nanostars using in situ UV-vis spectroscopy. The impact of hydroquinone ligands on the formation and evolution of active intermediates was systematically explored. In addition, we improved the classical seed-mediated method to achieve a much better control on the final morphology of gold nanostars by a sudden addition of a high concentration ligand solution. Our method can significantly advance the syntheses of gold nanostars and provide numerous opportunities to prepare nanomaterials with unique morphology and plasmonic properties.