12 research outputs found
The influence of the chain length and the functional group steric accessibility of thiols on the phase transfer efficiency of gold nanoparticles from water to toluene
The papers were published with the financial support from the budget of the West Pomeranian Voivodeship.This paper describes the influence of the chain length and the functional group steric accessibility of thiols modifiers on the phase transfer process efficiency of water synthesized gold nanoparticles (AuNPs) to toluene. The following thiols were tested: 1-decanethiol, 1,1-dimethyldecanethiol, 1-dodecanethiol, 1-tetradecanethiol and 1-oktadecanethiol. Nanoparticles (NPs) synthesized in water were precisely characterized before the phase transfer process using Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). The optical properties of AuNPs before and after the phase transfer were studied by the UV-Vis spectroscopy. Additionally, the particle size and size distribution before and after the phase transfer of nanoparticles were investigated using Dynamic Light Scattering (DLS). It turned out that the modification of NPs surface was not effective in the case of 1,1-dimethyldecanethiol, probably because of the difficult steric accessibility of the thiol functional group to NPs surface. Consequently, the effective phase transfer of AuNPs from water to toluene did not occur. In toluene the most stable were nanoparticles modified with 1-decanethiol, 1-dodecanethiol and 1-tetradecanethiol.This work was supported by FP7-NMP-2010-SMALL-4
program (HYMEC), project number 263073. Scientific
work supported by the Polish Ministry of Science and
Higher Education, funds for science in 2011–2014 allocated
for the cofounded international project
Multifunctional protein APPL2 contributes to survival of human glioma cells
Some endocytic proteins have recently been shown to play a role in tumorigenesis. In this study, we demonstrate that APPL2, an adapter protein with known endocytic functions, is upregulated in 40% cases of glioblastoma multiforme, the most common and aggressive cancer of the central nervous system. The silencing of APPL2 expression by small interfering RNAs (siRNAs) in glioma cells markedly reduces cell survival under conditions of low growth factor availability and enhances apoptosis (measured by executor caspase activity). Long‐term depletion of APPL2 by short hairpin RNAs (shRNAs), under regular growth factor availability, suppresses the cell transformation abilities, assessed by inhibited colony formation in soft agar and by reduced xenograft tumor growth in vivo. At the molecular level, the negative effect of APPL2 knockdown on cell survival is not due to the alterations in AKT or GSK3β activities which were reported to be modulated by APPL proteins. Instead, we attribute the reduced cell survival upon APPL2 depletion to the changes in gene expression, in particular to the upregulation of apoptosis‐related genes, such as UNC5B (a proapoptotic dependence receptor) and HRK (harakiri, an activator of apoptosis, which antagonizes anti‐apoptotic function of Bcl2). In support of this notion, the loss of glioma cell survival upon APPL2 knockdown can be rescued either by an excess of netrin‐1, the prosurvival ligand of UNC5B or by simultaneous silencing of HRK. Consistently, APPL2 overexpression reduces expression of HRK and caspase activation in cells treated with apoptosis inducers, resulting in the enhancement of cell viability. This prosurvival activity of APPL2 is independent of its endosomal localization. Cumulatively, our data indicate that a high level of APPL2 protein might enhance glioblastoma growth by maintaining low expression level of genes responsible for cell death induction
Versatile Phase Transfer Method for the Efficient Surface Functionalization of Gold Nanoparticles: Towards Controlled Nanoparticle Dispersion in a Polymer Matrix
In electronic devices based on hybrid materials such as nonvolatile memory elements (NVMEs), it is essential to control precisely the dispersion of metallic nanoparticles (NPs) in an insulating polymer matrix such as polystyrene in order to control the functionality of the device. In this work the incorporation of AuNPs in polystyrene films is controlled by tuning the surface functionalization of the metallic nanoparticles via ligand exchange. Two ligands with different structures were used for functionalization: 1-decanethiol and thiol-terminated polystyrene. This paper presents a versatile method for the modification of gold nanoparticles (AuNPs) with thiol-terminated polystyrene ligands via phase transfer process. An organic colloid of AuNPs (5±1 nm diameter) is obtained by the phase transfer process (from water to toluene) that allows exchanging the ligand adsorbed on AuNPs surface (hydrophilic citrate/tannic acid to hydrophobic thiols). The stability, size distribution, and precise location of modified AuNPs in the polymer matrix are obtained from UV-Vis spectroscopy, dynamic light scattering (DLS), and electron tomography. TEM tomographic 3D imaging demonstrates that the modification of AuNPs with thiol-terminated polystyrene results in homogeneous particle distribution in the polystyrene matrix compared to 1-decanethiol modified AuNPs for which a vertical phase separation with a homogeneous layer of AuNPs located at the bottom of the polymer matrix was observed.This work was supported by FP7-NMP-2010-SMALL-4 Program
(“Hybrid Organic/Inorganic Memory Elements for
Integration of Electronic and Photonic Circuitry,” HYMEC),
Project no. 263073. Eric Gonthier is acknowledged for technical
support in the preparation of hybrid thin films. Scientific
work was supported by the Polish Ministry of Science and
Higher Education Funds for Science in 2011–2014 allocated
for the cofunded international project
Diagnosis of melanoma localized in ulcer associated with diabetic foot syndrome — case report
Difficult-to-heal wounds, which include ulcers in diabetic foot syndrome (DFS), are characterized by long healing times, sometimes leading to sepsis and the need for amputation. The often months-long persistence of the ulceration creates conditions for uncontrolled proliferation of granulation tissue, which is a component of the wound, also in the direction of neoplastic lesions. The co-occurrence of such a condition with hyperglycemia can increase the risk of cancer development within the ulcer. This article presents the case of a 71-year-old man in whom a histopathological examination of a wound specimen was performed due to a lack of progress in the healing process. The patient was diagnosed with melanoma and was referred urgently to a referral centre, where a toe resection and sentinel node biopsy were performed. In addition, the article presents a diagnostic pathway that applies to patients with suspected proliferative disease in the wound associated with DFS
Detection Limits of DLS and UV-Vis Spectroscopy in Characterization of Polydisperse Nanoparticles Colloids
Dynamic light scattering is a method that depends on the interaction of light with particles. This method can be used for measurements of narrow particle size distributions especially in the range of 2–500 nm. Sample polydispersity can distort the results, and we could not see the real populations of particles because big particles presented in the sample can screen smaller ones. Although the theory and mathematical basics of DLS technique are already well known, little has been done to determine its limits experimentally. The size and size distribution of artificially prepared polydisperse silver nanoparticles (NPs) colloids were studied using dynamic light scattering (DLS) and ultraviolet-visible (UV-Vis) spectroscopy. Polydisperse colloids were prepared based on the mixture of chemically synthesized monodisperse colloids well characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), DLS, and UV-Vis spectroscopy. Analysis of the DLS results obtained for polydisperse colloids reveals that several percent of the volume content of bigger NPs could screen completely the presence of smaller ones. The presented results could be extremely important from nanoparticles metrology point of view and should help to understand experimental data especially for the one who works with DLS and/or UV-Vis only
Transfer międzyfazowy nanocząstek złota pozwalający na ich implementację w tuszach do wytwarzania hybrydowych organiczno/nieorganicznych układów elektronicznych
Pracę naukową zrealizowano w ramach międzynarodowego projektu badawczego
7 Programu Ramowego UE: Hybrydowe organiczno-nieorganiczne elementy pamięci
wykorzystujące zintegrowane układy elektroniczne i fotoniczne (HYMEC)
Printed Nonvolatile Resistive Memories Based on a Hybrid Organic/Inorganic Functional Ink
Organic memories are increasingly being considered as promising candidates for a number of novel consumer applications, such as smart labels and smart packaging devices. Indeed, organic memories can be fabricated on highly flexible substrates at low temperatures from liquid phase, employing for instance printing techniques. In this work, a nonvolatile resistive memory element conceived for large-area processing and operation in ambient conditions is presented. In particular, a functional ink made out of an air stable organic semiconductor, namely ActivInk N1400, and gold nanoparticles (NPs) is developed and optimized for the fabrication of high performance memories through inkjet printing. The ink formulation is varied in order to explore the influence of Au NPs concentration on the switching behavior. Devices are operated in ambient conditions with reproducible memory behavior, high ON/OFF current ratios, and low programming voltages. In depth material analysis with time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy depth profiles are carried out on operated devices to shine a light on resistive switching mechanism and to determine the average gold content and its 3D distribution in stable memories
Air-stable, non-volatile resistive memory based on hybrid organic/inorganic nanocomposites
Effect of the Alkyl Chain Length of Secondary Amines on the Phase Transfer of Gold Nanoparticles from Water to Toluene
In
the present paper we describe a phase transfer of aqueous synthesized
gold nanoparticles (AuNPs) from water to toluene using secondary amines:
dioctylamine, didodecylamine, and dioctadecylamine. The effect of
the hydrocarbon chain length and amount of amines on the transfer
efficiency were investigated in the case of nanoparticles (NPs) with
three different sizes: 5, 9, and 13 nm. Aqueous colloids were precisely
characterized before the transfer process using UV–vis spectroscopy,
dynamic light scattering (DLS), small-angle X-ray scattering (SAXS),
and transmission electron microscopy (TEM). Nanoparticles were next
transferred to toluene and characterized using UV–vis and DLS
techniques. It was found that dioctadecylamine provides the most effective
transfer of nanoparticles. No time-dependent changes in the NP size
were observed after 12 days, showing that the dioctadecylamine-stabilized
nanoparticles dispersed in toluene were stable. This indicates that
long hydrocarbon chains of dioctadecylamine exhibit sufficiently hydrophobic
properties of nanoparticles and consequently their good dispersibility
in nonpolar solvent