Electrochemistry and electrogenerated chemiluminescence of a spirobifluorene-based donor (triphenylamine)-acceptor (2,1,3-benzothiadiazole) molecule and its organic nanoparticles

A new D-A-π-A-D molecule (Spiro-BTA) containing two 2,1,3-benzothiadiazole (BTA) as the acceptor (A) and triphenylamine as the donor (D) bridged by a spirobifluorene moiety has been synthesized. The novel D-A molecule shows intense red emission (612 nm) with a high PL quantum yield (Φ(PL) = 0.51) in a solid film. A cyclic voltammogram of Spiro-BTA in 1:2 MeCN:benzene/0.1 M Bu(4)NPF(6) shows two reversible oxidation waves and one reversible reduction wave. The first oxidation wave and reduction wave were assigned as two successive electron transfer peaks separated by ～50 mV related to the oxidation of the two noninteracting donors and the reduction of the two noninteracting acceptors, respectively. Electrogenerated chemiluminescence (ECL) of Spiro-BTA upon cyclic oxidation and reduction in MeCN:benzene 1:2 shows a very bright and stable red emission that could be seen in a well-lit room. Using a reprecipitation method, well-dispersed organic nanoparticles (NPs) of the Spiro-BTA were prepared in aqueous solution. The nanoparticles were analyzed by dynamic light scattering (DLS) and scanning electron microscopy (SEM), yielding a NP size (without surfactant) of 130 ± 20 nm, while with surfactant, 100 ± 20 nm. Bathochromic shifts of absorption spectra (～16 ± 2 nm), as compared to that of the dissolved Spiro-BTA in THF, were observed for both NPs in water and as a thin film. While blue shifts (14 ± 2 nm) were observed for the photoluminescence (PL). The PL intensity of the Spiro-BTA nanoparticles was slightly enhanced (Φ(PL) of nanoparticles in water = 48%) over that of the dissolved Spiro-BTA in THF. The ECL of the organic Spiro-BTA nanoparticles in aqueous solution could be observed upon oxidation with tri-n-propylamine as a coreactant.     

Effect of Urea on the Morphology of Co3O4 Nanostructures and Their Application for Potentiometric Glucose Biosensor

In this study, an effect of different concentrations of urea on the morphology of cobalt oxide (Co₃O₄) nanostructures was investigated. The Co₃O₄ nanostructures are fabricated on gold coated glass substrate by the hydrothermal method. The morphological and structural characterization was performed by scanning electron microscopy, and X‐ray diffraction techniques. The Co₃O₄ nanostructures exhibit morphology of flowers‐like and have comprised on nanowires due to the increasing amount of urea. The nanostructures were highly dense on the substrate and possess a good crystalline quality. The Co₃O₄ nanostructures were successfully used for the development of a sensitive glucose biosensor. The presented glucose biosensor detected a wide range of glucose concentrations from 1×10^?6 M to 1×10^?2 M with sensitivity of a ?56.85 mV/decade and indicated a fast response time of less than 10 s. This performance could be attributed to the heterogeneous catalysis effect at glucose oxidase enzyme, nanoflowers, and nanowires interfaces, which have enhanced the electron transfer process on the electrode surface. Moreover, the reproducibility, repeatability, stability and selectivity were also investigated. All the obtained results indicate the potential use of the developed glucose sensor for monitoring of glucose concentrations at drugs, human serum and food industry related samples.     

Photo-switchable azobenzene-functionalized block copolymers from atom transfer radical polymerizations

Diblock copolymers composed of monomers of tert-butyl acrylate and a side-chain azobenzenecontaining monomer, 4-[(E)-(4-nitrophenyl)diazenyl]phenyl prop-2-enoate were synthesized using atom transfer radical polymerization technique. Experimental strategy involved synthesis of block of tert-butyl acrylate macroinitiator followed by addition of second block of azobenzene-containing monomer to prepare desired block-copolymer. GPC analysis indicated narrow molecular weight distributions with degree of polymerization found in good agreement with targeted value. Prepared block copolymers of varying chain lengths can potentially be used to obtain morphologies that can find useful applications for biomedical applications including intriguing photo-switchable drug delivery systems.     

Preparation of QP4VP-b-LCP liquid crystal block copolymer and its application as a biosensor

The interface between nematic liquid crystal, 4-cyano-4′-pentylbiphenyl (5CB), and water in a transmission electron microscopy (TEM) grid cell coated with QP4VP-b-LCP (quaternized poly(4-vinylpyridine) (QP4VP) and poly(4-cyanobiphenyl-4′-oxyundecylacrylate) (LCP)) was examined for protein and DNA detection. QP4VP-b-LCP was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Quaternization of P4VP with iodomethane (CH₃I) made it a strong cationic polyelectrolyte and allowed QP4VP-b-LCP to form complexes with oppositely charged biological species. Several proteins, such as bovine serum albumin (BSA), hemoglobin (Hb), α chymotrypsinogen-A (ChTg), and lysozyme (LYZ), were tested for nonspecific protein detection. By injecting the protein solutions into the TEM grid cell, the initial homeotropic orientation of the TEM grid cell changed to a planar orientation above their isoelectric points (PIs) due to electrostatic interactions between QP4VP (+charge) and proteins (?charge), which did not occur below the PIs of the tested proteins. Their minimum concentrations at which the homeotropic to planar configurational change (H-P change) occurred were 0.01, 0.02, 0.03, and 0.04 wt.% for BSA, ChTg, Hb, and LYZ, respectively. One of the strong anionic polyelectrolytes, deoxyribonucleic acid (DNA) (due to the phosphate deoxyribose backbone) was also tested. A H-P change was observed with as little as 0.0013 wt.% salmon sperm DNA regardless of the pH of the cell. A H-P change occurred in 5CB and was observed by polarized optical microscopy. This simple and inexpensive setup for nonspecific biomaterial detection provides the basic idea for developing effective selective biosensors by introducing specific binding groups, such as the aptamer and antibody.     

Random Čech complexes on Riemannian manifolds

In this paper we study the homology of a random ?ech complex generated by a homogeneous Poisson process in a compact Riemannian manifold M. In particular, we focus on the phase transition for “homological connectivity” where the homology of the complex becomes isomorphic to that of M. The results presented in this paper are an important generalization of 7 , from the flat torus to general compact Riemannian manifolds. In addition to proving the statements related to homological connectivity, the methods we develop in this paper can be used as a framework for translating results for random geometric graphs and complexes from the Euclidean setting into the more general Riemannian one.     

An approach to remove alpha amylase for proteomic analysis of low abundance biomarkers in human saliva

Proteomic characterization of human whole saliva for the identification of disease-specific biomarkers is guaranteed to be an easy-to-use and powerful diagnostic tool for defining the onset, progression and prognosis of human systemic diseases and, in particular, oral diseases. The high abundance of proteins, mainly alpha amylase, hampers the detection of low abundant proteins appearing in the disease state and therefore should be removed. In the present study a 2-DE was used to analyze human whole saliva following the removal of alpha amylase by affinity adsorption to potato starch. After alpha amylase removal whole saliva was analyzed by SDS-PAGE showing at least sixfold removal efficiency and by an alpha amylase activity assay showing 97% reduced activity. MS identification of the captured alpha amylase after elution demonstrated specific removal; 2-DE analysis showed the selective removal of alpha amylase and consequently increased gel resolution. MS identification of protein spots in the 60 kDa area revealed 15 proteins, which were masked before alpha amylase removal. In conclusion, treatment of human whole saliva with an alpha amylase removal device increases gel resolution and enables a higher protein sample for analysis.     

Miscellaneous PEDOT:PTS (polythiophenesulfonyl chloride) based conductive binder for silicon anodes in lithium ion batteries

Lithium ion batteries which are an energy storage system have increasing attention owing to suitability and advantages for many applications. Although it has ideal specifications, the capacity properties still have to be developed. In this study, the electrical conductivity of the anode was increased by using a conductive polymer binder and the active material content of the anode was also enhanced without adding carbon additives. Silicon based anodes were manufactured by using poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) and poly(3,4-ethylenedioxythiophene)/polythiophenesulfonyl chloride (PEDOT:PTS) conductive polymer binders. Si/PEDOT:PTS anode showed about 2000 mAh/g specific capacities after 60 cycles with decreasing impedance.     

Chemical Synthesis of Bioactive Proteins

Nature has developed a plethora of protein machinery to operate and maintain nearly every task of cellular life. These processes are tightly regulated via post-expression modifications—transformations that modulate intracellular protein synthesis, folding, and activation. Methods to prepare homogeneously and precisely modified proteins are essential to probe their function and design new bioactive modalities. Synthetic chemistry has contributed remarkably to protein science by allowing the preparation of novel biomacromolecules that are often challenging or impractical to prepare via common biological means. The ability to chemically build and precisely modify proteins has enabled the production of new molecules with novel physicochemical properties and programmed activity for biomedical research, diagnostic, and therapeutic applications. This minireview summarizes recent developments in chemical protein synthesis to produce bioactive proteins, with emphasis on novel analogs with promising in vitro and in vivo activity.     

Effect of sonication and freezing-thawing on the aggregate size and dynamic surface tension of aqueous DPPC dispersions

The effect of sonication and freezing-thawing on the aggregate size and dynamic surface tension of aqueous dipalmitoylphosphatidylcholine (DPPC) dispersions was studied by cryogenic-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), UV-vis spectroturbidimetry, and surface tensiometry. When 1000 ppm (0.1 wt%) DPPC dispersions were prepared with a certain protocol, including extensive sonication, they contained mostly frozen vesicles and were quite clear, transparent, and stable for at least 30 days. The average dispersed vesicles diameter was 80 nm in water and 90 nm in standard phosphate saline buffer. After a freeze-thaw cycle, this dispersion became turbid, and precipitates of coagulated vesicles were observed with large particles of average size of 1.5x10(3) nm. The vesicle coagulation is due to the local salt concentration increase during the freezing of water. This dispersion has much higher equilibrium and dynamic surface tension than those before freezing. When this freeze-thawed dispersion was subjected to a resonication at 55 degrees C, smaller vesicles with sizes of ca. 70 nm were produced, and a lower surface tension behavior was restored as before freezing. Similar behavior was observed at 30 ppm DPPC. These results indicate that the freeze-thaw cycle causes substantial aggregation and precipitation of the vesicles. These results have implications for designing efficient protocols of lipid dispersion preparation and lung surfactant replacement formulations in treating respiratory disease and for effective administration.