Synthesis and Bioactivity of Polymer‐Based Synthetic Mimics of Antimicrobial Peptides (SMAMPs) Made from Asymmetrically Disubstituted Itaconates

A series of asymmetrically disubstituted diitaconate monomers is presented. Starting from itaconic anhydride, functional groups could be placed selectively at the two nonequivalent carbonyl groups. By using 2D NMR spectroscopy, it was shown that the first functionalization step occurred at the carbonyl group in the β position to the double bond. These monomers were copolymerized with N,N‐dimethylacrylamide (DMAA) to yield polymer‐based synthetic mimics of antimicrobial peptides (SMAMPs). They were obtained by free radical polymerization, a metal‐free process, and still maintained facial amphiphilicity at the repeat unit level. This eliminates the need for laborious metal removal and is advantageous from a regulatory and product safety perspective. The poly(diitaconate‐co‐DMAA) copolymers obtained were statistical to alternating, and the monomer feed ratio roughly matched that of the repeat unit content of the copolymers. Investigations of varied R group hydrophobicity, repeat unit ratio, and molecular mass on antimicrobial activity against Escherichia coli and on compatibility with human keratinocytes showed that the polymers with the longest R groups and lowest DMAA content were the most antimicrobial and hemolytic. This is in agreement with the biological activity of previously reported SMAMPs. Thus, the design concept of facial amphiphilicity has successfully been transferred, but the selectivity of these polymers for bacteria over mammalian cells still needs to be optimized

Surface‐Attached Polymer Networks Made from Cationic Poly(diitaconates) : Synthesis, Surface Characterization, and Bioactivity

Facially amphiphilic polymers carrying cationic and hydrophobic groups on the same repeat unit have shown promising antimicrobial activity and biocompatibility, yet they are prone to suffer from protein adhesion which may induce biofilm formation. To overcome this problem, poly(diitaconate)-based copolymers with cationic/hydrophobic and protein-repellent/charge-neutral repeat units are synthesized. The bioactivity profile of surface-attached polymer networks made from these copolymers depends on the ratio of the cationic and charge-neutral repeat units. In all cases, the protein adhesion is substantially reduced compared to purely cationic polymers. At a 50:50 ratio, the polymer coatings are partially protein-repellent and antimicrobial, yet slightly cell toxic. At an intermediate composition of 30:70, they are still antimicrobial and the cell compatibility is substantially improved. The long-term stability of these materials still has to be determined to judge their suitability for medical applications

A facile method for the preparation of bifunctional Mn:ZnS/ZnS/Fe3O4 magnetic and fluorescent nanocrystals

Bifunctional magnetic and fluorescent core/shell/shell Mn:ZnS/ZnS/Fe3O4 nanocrystals were synthesized in a basic aqueous solution using 3-mercaptopropionic acid (MPA) as a capping ligand. The structural and optical properties of the heterostructures were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), UV–vis spectroscopy and photoluminescence (PL) spectroscopy. The PL spectra of Mn:ZnS/ZnS/Fe3O4 quantum dots (QDs) showed marked visible emission around 584 nm related to the 4T1 → 6A1 Mn2+ transition. The PL quantum yield (QY) and the remnant magnetization can be regulated by varying the thickness of the magnetic shell. The results showed that an increase in the thickness of the Fe3O4 magnetite layer around the Mn:ZnS/ZnS core reduced the PL QY but improved the magnetic properties of the composites. Nevertheless, a good compromise was achieved in order to maintain the dual modality of the nanocrystals, which may be promising candidates for various biological applications

Industria del cemento: ¿cuál sería el efecto de los impuestos a sus emisiones de carbono?

Este producto forma parte de una serie de infografías de divulgación científica que buscan reseñar algunas de las investigaciones más importantes en las que ha tenido participación la Universidad EAFIT, publicadas en las revistas especializadas más prestigiosas del mund

Differential regulation of cell death pathways by the microenvironment correlates with chemoresistance and survival in leukaemia

Glucocorticoids (GCs) and topoisomerase II inhibitors are used to treat acute lymphoblastic leukaemia (ALL) as they induce death in lymphoid cells through the glucocorticoid receptor (GR) and p53 respectively. Mechanisms underlying ALL cell death and the contribution of the bone marrow microenvironment to drug response/resistance remain unclear. The role of the microenvironment and the identification of chemoresistance determinants were studied by transcriptomic analysis in ALL cells treated with Dexamethasone (Dex), and Etoposide (Etop) grown in the presence or absence of bone marrow conditioned media (CM). The necroptotic (RIPK1) and the apoptotic (caspase-8/3) markers were downregulated by CM, whereas the inhibitory effects of chemotherapy on the autophagy marker Beclin-1 (BECN1) were reduced suggesting CM exerts cytoprotective effects. GCs upregulated the RIPK1 ubiquitinating factor BIRC3 (cIAP2), in GC-sensitive (CEM-C7-14) but not in resistant (CEM-C1-15) cells. In addition, CM selectively affected GR phosphorylation in a site and cell-specific manner. GR is recruited to RIPK1, BECN1 and BIRC3 promoters in the sensitive but not in the resistant cells with phosphorylated GR forms being generally less recruited in the presence of hormone. FACS analysis and caspase-8 assays demonstrated that CM promoted a pro-survival trend. High molecular weight proteins reacting with the RIPK1 antibody were modified upon incubation with the BIRC3 inhibitor AT406 in CEM-C7-14 cells suggesting that they represent ubiquitinated forms of RIPK1. Our data suggest that there is a correlation between microenvironment-induced ALL proliferation and altered response to chemotherapy

Heterostructured Photocatalysts Associating ZnO Nanorods and Ag-In-Zn-S Quantum Dots for the Visible Light-Driven Photocatalytic Degradation of the Acid Orange 7 Dye

Heterostructured photocatalysts associating ZnO nanorods (NRs) sensitized by quaternary Ag-In-Zn-S (AIZS) quantum dots (QDs) were prepared by depositing AIZS QDs at the surface of ZnO NRs followed by thermal treatment at 300 °C. The ZnO/AIZS catalysts were characterized by X-ray diffraction, electron microscopy, UV-vis diffuse spectroscopy and by photoelectrochemical measurements. Their photocatalytic activity was evaluated for the bleaching of the Acid Orange 7 (AO7) dye under visible light irradiation. Results show that the association of ZnO NRs with 10 wt% AIZS QDs affords the photocatalyst the highest activity due to the enhanced visible light absorption combined with the improved charge separation. The ZnO/AIZS(10) photocatalyst degrades 98% AO7 in 90 min under visible light illumination, while ZnO NRs can only decompose 11% of the dye. The ZnO/AIZS(10) photocatalyst was also found to be stable and can be reused up to eight times without significant alteration of its activity. This work demonstrates the high potential of AIZS QDs for the development of visible light active photocatalysts

Aqueous synthesis of highly fluorescent and color-tunable Ag + -doped Cd x Zn 1-x S quantum dots

International audienceFacile and low cost syntheses of 3-mercaptopropionic acid-capped Ag:CdxZn1-xS and of core/shell Ag:CdxZn1-xS/ZnS quantum dots (QDs) are presented. The effects of the Ag+ doping concentration and of the Cd/Zn ratio on the structural and optical properties of the dots were investigated. Core Ag:CdxZn1-xS QDs have an average diameter of ca. 4.5 nm and their photoluminescence (PL) emission can be tuned from 478 to 610 nm by varying the dopant concentration or the composition of the CdxZn1-xS host material. The highest PL quantum yield (25%) is obtained when using 2 or 3.5% doping in Ag+. The PL quantum yield increased substantially (44%) after capping the Ag:CdxZn1-xS core with a ZnS shell. Due to their high photostability and long excited-state lifetimes (1–2 μs), Ag:CdxZn1-xS QDs are of high potential as nanophosphors or as fluorescent probes for bio-imaging

Aqueous synthesis of Cu-doped CdZnS quantum dots with controlled and efficient photoluminescence

International audienceWe report here a facile, mild and low cost aqueous-based synthesis for the production of high quality CdZnS and Cu-doped CdZnS quantum dots (QDs). We demonstrate that the photoluminescence (PL) of the Cu-doped CdZnS nanocrystals could be tuned in the whole visible spectrum via the stoechiometric ratio of Cd/Zn precursors in the host CdZnS QDs and by tuning the particle size. By optimization of the experimental conditions (Cd/Zn ratio, reaction time, pH,…) and by varying the surface ligand, pure and highly emissive Cu:CdZnS QDs could be prepared. Moreover, by the growth of a ZnS shell around the Cu:CdZnS core, Cu:CdZnS/ZnS QDs with a PL quantum yield (PL QY) of 42% were constructed, which is the highest PL QY reported to date for Cu-doped CdZnS QDs prepared in aqueous solution. The optical properties and structure of the obtained dots were characterized by UV–visible spectroscopy, steady-state and time-resolved PL spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Cu:CdZnS/ZnS QDs were subjected to various treatments such as long-term UV illumination, storage in biological buffers or pH changes, which are usually detrimental to QDs PL. No marked deterioration in PL properties during the previously described degradation processes was observed, thus indicating the high stability of the dots prepared. Due to their good water dispersibility and stability, the Cu:CdZnS/ZnS QDs developed herein can be a promising candidate for biolabelling applications

Highly Luminescent and Photostable Core/Shell/Shell ZnSeS/Cu:ZnS/ZnS Quantum Dots Prepared via a Mild Aqueous Route

International audienceAn aqueous-phase synthesis of 3-mercaptopropionic acid (3-MPA)-capped core/shell/shell ZnSeS/Cu:ZnS/ZnS QDs was developed. The influence of the Cu-dopant location on the photoluminescence (PL) emission intensity was investigated, and the results show that the introduction of the Cu dopant in the first ZnS shell leads to QDs exhibiting the highest PL quantum yield (25%). The influence of the Cu-loading in the dots on the PL emission was also studied, and a shift from blue-green to green was observed with the increase of the Cu doping from 1.25 to 7.5%. ZnSeS/Cu:ZnS/ZnS QDs exhibit an average diameter of 2.1 ± 0.3 nm and are stable for weeks in aqueous solution. Moreover, the dots were found to be photostable under the continuous illumination of an Hg-Xe lamp and in the presence of oxygen, indicating their high potential for applications such as sensing or bio-imaging