One-Step Aqueous Synthesis of Anionic and Cationic AgInS2 Quantum Dots and Their Utility in Improving the Efficacy of ALA-Based Photodynamic Therapy

Silver–indium–sulfide quantum dots (AIS QDs) have potential applications in many areas, including biomedicine. Their lack of regulated heavy metals, unlike many commercialized QDs, stands out as an advantage, but the necessity for alloyed or core–shell structures and related costly and sophisticated processes for the production of stable and high quantum yield aqueous AIS QDs are the current challenges. The present study demonstrates the one-step aqueous synthesis of simple AgInS2 QD compositions utilizing for the first time either a polyethyleneimine/2-mercaptopropionic acid (AIS-PEI/2MPA) mixture or only 2-mercaptopropionic acid (AIS-2MPA) as the stabilizing molecules, providing a AgInS2 portfolio consisting of cationic and anionic AIS QDs, respectively, and tuneable emission. Small AIS QDs with long-term stability and high quantum yields (19–23%) were achieved at a molar ratio of Ag/In/S 1/10/10 in water without any dopant or a semiconductor shell. The theranostic potential of these cationic and anionic AIS QDs was also evaluated in vitro. Non-toxic doses were determined, and fluorescence imaging potential was demonstrated. More importantly, these QDs were electrostatically loaded with zwitterionic 5-aminolevulinic acid (ALA) as a prodrug to enhance the tumor availability of ALA and to improve ALA-induced porphyrin photodynamic therapy (PDT). This is the first study investigating the influence of nanoparticle charge on ALA binding, release, and therapeutic efficacy. Surface charge was found to be more critical in cellular internalization and dark toxicity rather than drug loading and release. Both QDs provided enhanced ALA release at acidic pH but protected the prodrug at physiological pH, which is critical for tumor delivery of ALA, which suffers from low bioavailability. The PDT efficacy of the ALA-loaded AIS QDs was tested in 2D monolayers and 3D constructs of HT29 and SW480 human colon adenocarcinoma cancer cell lines. The incorporation of ALA delivery by the AIS QDs, which on their own do not cause phototoxicity, elicited significant cell death due to enhanced light-induced ROS generation and apoptotic/necrotic cell death, reducing the IC50 for ALA dramatically to about 0.1 and 0.01 mM in anionic and cationic AIS QDs, respectively. Combined with simple synthetic methods, the strong intracellular photoluminescence of AIS QDs, good biocompatibility of especially the anionic AIS QDs, and the ability to act as drug carriers for effective PDT signify that the AIS QDs, in particular AIS-2MPA, are highly promising theranostic QDs

Dimethyl (1-hydr­oxy-1,2-diphenyl­ethyl)phospho­nate

In the mol­ecule of the title compound, C16H19O4P, the coordination around the P atom is distorted tetra­hedral. The aromatic rings are oriented at a dihedral angle of 72.28 (11)°. Intra­molecular C—H⋯O hydrogen bonding result in the formation of five- and six-membered rings. In the crystal structure, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules. There is also a weak C—H⋯π inter­action

Assessment of forest roads and firebreaks in Turkey

No Abstrac

Template-Directed Synthesis of Silica Nanotubes for Explosive Detection

Cataloged from PDF version of article.Fluorescent porous organic-inorganic thin films are of interest of explosive detection because of their vapor phase fluorescence quenching property. In this work, we synthesized fluorescent silica nanotubes using a biomineralization process through self-assembled peptidic nanostructures. We designed and synthesized an amyloid-like peptide self-assembling into nanofibers to be used as a template for silica nanotube formation. The amine groups on the peptide nanofibrous system were used for nucleation of silica nanostructures. Silica nanotubes were used to prepare highly porous surfaces, and they were doped with a fluorescent dye by physical adsorption for explosive sensing. These porous surfaces exhibited fast, sensitive, and highly selective fluorescence quenching against nitro-explosive vapors. The materials developed in this work have vast potential in sensing applications due to enhanced surface area. © 2011 American Chemical Society

Instability tests for air-jet textured yarns

The air-jet texturing process is briefly introduced and its advantages over other texturing processes are summarized. Characteristics of air-jet textured yarns are stated with special reference to the stability of the yarns. Test methods used in industry and research to determine the "stability" or "instability" of air-jet textured yarns are critically reviewed. These methods involve different basic principles and therefore inevitably give different results. There is no consensus on a standard method. Effects of various test parameters, such as specimen length, test duration, and the alternatives of using a single yarn, a hank, or a skein as a test specimen are investigated. An improved test method is suggested as a standard instability test, and various existing methods are compared with it. Results of all the methods show similar trends for varying values of air pressure. Other yarn characteristics such as linear density, breaking elongation, and tenacity are also determined, and their indications of yarn quality are compared with the indications of instability tests. Stability test results alone provide misleading information regarding air-jet textured yarn quality

Dimethyl (2-hydr­oxy-4-phenyl­but-3-en-2-yl)phospho­nate

In the title compound, C12H17O4P, the phenyl­butenyl group is disordered over two sets of sites with an occupancy ratio of 0.755 (12):0.245 (12). In the crystal, inversion dimers linked by pairs of O—H⋯O hydrogen bonds occur, forming R 2 2(10) ring motifs. The packing is consolidated by weak C—H⋯π inter­actions

Self-Assembled Peptide Nanofiber Templated One-Dimensional Gold Nanostructures Exhibiting Resistive Switching

Cataloged from PDF version of article.An amyloid-like peptide molecule self-assembling into one-dimensional nanofiber structure in ethanol was designed and synthesized with functional groups that can bind to gold ions. The peptide nanofibers were used as templates for nucleation and growth of one-dimensional gold nanostructures in the presence of ascorbic acid as reducing agent. We performed multistep seed-mediated synthesis of gold nanoparticles by changing peptide/gold precursor and peptide/reducing agent ratios. Gold nanostructures with a wide range of morphologies such as smooth nanowires, noodle-like one-dimensional nanostructures, and uniform aggregates of spherical nanoparticles were synthesized by use of an environmentally friendly synthesis method. Nanoscale electrical properties of gold-peptide nanofibers were investigated using atomic force microscopy. Bias dependent current (IV) measurements on thin films of gold-peptide nanofiber hybrid revealed tunneling dominated transport and resistive switching. Gold-peptide nanofiber composite nanostructures can provide insight into electrical conduction in biomolecular/inorganic composites, highlighting their potential applications in electronics and optics. © 2012 American Chemical Society

A stochastic spectral analysis of transcriptional regulatory cascades

The past decade has seen great advances in our understanding of the role of noise in gene regulation and the physical limits to signaling in biological networks. Here we introduce the spectral method for computation of the joint probability distribution over all species in a biological network. The spectral method exploits the natural eigenfunctions of the master equation of birth-death processes to solve for the joint distribution of modules within the network, which then inform each other and facilitate calculation of the entire joint distribution. We illustrate the method on a ubiquitous case in nature: linear regulatory cascades. The efficiency of the method makes possible numerical optimization of the input and regulatory parameters, revealing design properties of, e.g., the most informative cascades. We find, for threshold regulation, that a cascade of strong regulations converts a unimodal input to a bimodal output, that multimodal inputs are no more informative than bimodal inputs, and that a chain of up-regulations outperforms a chain of down-regulations. We anticipate that this numerical approach may be useful for modeling noise in a variety of small network topologies in biology

Amyloid-like peptide nanofiber templated titania nanostructures as dye sensitized solar cell anodic materials

Cataloged from PDF version of article.One-dimensional titania nanostructures can serve as a support for light absorbing molecules and result in an improvement in the short circuit current (Jsc) and open circuit voltage (Voc) as a nanostructured and high-surface-area material in dye-sensitized solar cells. Here, self-assembled amyloid-like peptide nanofibers were exploited as an organic template for the growth of one-dimensional titania nanostructures. Nanostructured titania layers were utilized as anodic materials in dye sensitized solar cells (DSSCs). The photovoltaic performance of the DSSC devices was assessed and an enhancement in the overall cell performance compared to unstructured titania was observed. © 2013 The Royal Society of Chemistry