Anisotropy in Antimicrobial Bottle Brush Copolymers and Its Influence on Biological Activity

Antimicrobial polymers are a promising alternative to conventional antibiotics in the fight against antimicrobial resistance. Cationic bottle brush copolymers have shown to be superior to linear topologies in previous studies. Herein, the aspect ratio of such polymers is varied creating differently shaped confined unimolecular structures with varying degrees of side chain mobility. Using reversible addition-fragmentation chain-transfer (RAFT) polymerization, bottle brushes are produced in a one-pot procedure. The morphology is confirmed by atomic force microscopy. The hydrophobicity, as determined via high performance-liquid chromatography (HPLC) analysis, is drastically influenced by the topology. Using Fourier-transform infrared (FTIR) spectroscopy, it is found that polymers with a high side chain mobility and increased global hydrophilicity, are less hydrated, and have stronger intramolecular hydrogen bonds. A phase segregated morphology leading to unimolecular micellization is assumed. Biological tests reveal increased antimicrobial activity for such segregated polymers. Their excellent hemocompatibility results in highly selective antimicrobial polymers whose adaptability seems to be a key feature in their excellent performance. This study highlights the tremendous importance of structural control in antimicrobial polymers.     

Deposition of thin titanium–copper films with antimicrobial effect by advanced magnetron sputtering methods

The antibacterial effect of thin titanium–copper (Ti–Cu) films combined with sufficient growth of human osteoblastic cells is reported in the paper. Thin Ti–Cu films were prepared by three different plasma-assisted magnetron sputtering methods: direct current magnetron sputtering (dc-MS), dual magnetron sputtering (dual-MS) as well as dual high power impulse magnetron sputtering (dual-HiPIMS). The antimicrobial effect is caused by copper released from the metallic Ti–Cu films, which was measured by atomic absorption spectroscopy (AAS). The copper release is influenced by the chemical and physical properties of the deposited films and was investigated by X-ray diffractometry and X-ray reflectometry (GIXD and XR) techniques. It was found that, within the first 24 h the amount of Cu released from dual-HiPIMS films (about 250 μg) was much higher than from dc-MS and dual-MS films. In vitro planktonic growth tests on Ti–Cu surfaces for Staphylococcus epidermidis and S. aureus demonstrated the killing of both bacteria using the Ti–Cu films prepared using the dual-HiPIMS technique. The killing effects on biofilm bacteria were less obvious. After the total release of copper from the Ti–Cu film the vitality of exposed human osteoblast MG-63 cells increased significantly. An initial cytotoxic effect followed by the growth of osteoblastic cells was demonstrated. The cytotoxic effect combined with growth of osteoblastic cells could be used in joint replacement surgery to reduce the possibility of infection and to increase adoption of the implants.     

Applying Web accessibility to Internet portals

Internet portals are becoming a very popular entry point to the Web. Users utilise them because of the large amount of information available. This paper aims to highlight the major hurdles disabled and/or older users encounter in Web portals, and to issue recommendations for portals layout and structure, based upon the results of a user requirements collection carried out by the authors. The findings point out that provision of a powerful search engine is essential for successful information retrieval. Moreover, due to the diverse and sometimes contradictory needs of the user groups under consideration, the customisation of information presentation plays an important role in ensuring accessibility and usability of Internet portals. The paper also includes a brief overview of the results in relation to the actual working draft of the Web Content Accessibility Guidelines 2.0.

Impact of Azidohomoalanine Incorporation on Protein Structure and Ligand Binding

The impact of the incorporation of a non‐natural amino acid (NNAA) on protein structure, dynamics, and ligand binding has not been studied rigorously so far. NNAAs are regularly used to modify proteins post‐translationally in vivo and in vitro through click chemistry. Herein, structural characterisation of the impact of the incorporation of azidohomoalanine (AZH) into the model protein domain PDZ3 is examined by means of NMR spectroscopy and X‐ray crystallography. The structure and dynamics of the apo state of AZH‐modified PDZ3 remain mostly unperturbed. Furthermore, the binding of two PDZ3 binding peptides are unchanged upon incorporation of AZH. The interface of the AZH‐modified PDZ3 and an azulene‐linked peptide for vibrational energy transfer studies has been mapped by means of chemical shift perturbations and NOEs between the unlabelled azulene‐linked peptide and the isotopically labelled protein. Co‐crystallisation and soaking failed for the peptide‐bound holo complex. NMR spectroscopy, however, allowed determination of the protein–ligand interface. Although the incorporation of AZH was minimally invasive for PDZ3, structural analysis of NNAA‐modified proteins through the methodology presented herein should be performed to ensure structural integrity of the studied target.     

Distribution of quercetin-3,4′-O-diglucoside,quercetin-4′-O-monoglucoside,and quercetin in different parts of the onion bulb (Allium cepa L.) influenced by genotype

Flavonoids have gained much attention because of their proposed positive effects for human health. Onions are a rich source of flavonoids, consisting mainly of the major flavonols quercetin-3,4′-O-diglucoside (QDG) and quercetin-4′-O-monoglucoside (QMG) in the bulb and the aglycone quercetin in the outer scales. In this study, distribution of these three flavonoids was determined in 16 onion cultivars (Allium cepa) using HPLC–DAD. Three different parts of the onion bulb, the inner layers, the middle layers and the outer scales were analysed. The analysis showed varietal differences in the selected onion cultivars. The cultivars with the highest total flavonoid content were the red skinned ‘Red Baron’ and the yellow skinned cultivars ‘Ailsa Craig’ and ‘Prilep’. The distribution of the total flavonoid content in the different parts of the onion bulb showed the following order: middle layers > outer scales > inner layers. In the inner layers QDG was the major flavonoid, while in the middle layers QDG and QMG were in equal amounts. In the outer scales quercetin was the major flavonoid prior to QMG.     

Imidazole Analogs of Vascular-Disrupting Combretastatin A-4 with Pleiotropic Efficacy against Resistant Colorectal Cancer Models

Specific targeting of the tumoral vasculature by vascular-disrupting agents (VDA), of which combretastatin A-4 (CA-4) is a main representative, has been considered a new therapeutic strategy against multidrug-resistant tumors. In addition, CA-4 and analogs are tubulin-targeting agents and can exert direct antitumor effects by different mechanisms. Herein, we analyzed a series of synthetic CA-4 analogs featuring N-methylimidazole-bridged Z-alkenes with different halo- or amino-substituted aryl rings in vitro and in vivo, focusing on models of colorectal cancer. Combined in vitro/in vivo structure–activity relationship studies using cell lines and xenograft tumors susceptible to VDA-induced vascular damage demonstrated a clear association of cytotoxic and vascular-disrupting activity with the ability to inhibit tubulin polymerization, which was determined by specific substitution constellations. The most active compounds were tested in an extended panel of colorectal cancer (CRC) cell lines and showed activity in CA-4-resistant and chemotherapy-resistant cell lines. The bromo derivative brimamin was then compared with the known fosbretabulin (CA-4P) by activity tests on DLD-1- (multidrug-resistant) and HT29- (CA-4-resistant) derived xenograft tumors. Treatment did not induce pronounced vascular-disrupting effects in these tumors. Histological analyses revealed distinct tumor substructures and vessel compositions of DLD-1/HT29 tumors, which clearly differed from the tumor models susceptible to VDA treatment. Even so, brimamin effectively retarded the growth of DLD-1 tumors, overcoming their resistance to standard treatment, and it inhibited the outgrowth of disseminated HT29 tumor cells in an experimental metastasis model. In conclusion, combretastatin analogous N-methylimidazoles proved capable of inducing vascular-disrupting effects, comparable to those of CA-4P. In addition, they showed antitumor activities in models of drug-resistant colorectal cancer, independent of vascular-disrupting effects.     

In vivo examination of the local inflammatory response after implantation of Ti6Al4V samples with a combined low-temperature plasma treatment using pulsed magnetron sputtering of copper and plasma-polymerized ethylenediamine

Copper (Cu) could serve as antibacterial coating for Ti6Al4V implants. An additional cell-adhesive layer might compensate Cu cytotoxicity. This study aimed at in vitro and in vivo evaluation of low-temperature plasma treatment of Ti6Al4V plates with Ti/Cu magnetron sputtering (Ti6Al4V–Ti/Cu), plasma-polymerized ethylenediamine (Ti6Al4V–PPEDA), or both (Ti6Al4V–Ti/Cu–PPEDA). Ti6Al4V–Ti/Cu and Ti6Al4V–Ti/Cu–PPEDA had comparable in vitro Cu release and antibacterial effectiveness. Following intramuscular implantation of Ti6Al4V–Ti/Cu, Ti6Al4V–PPEDA, Ti6Al4V–Ti/Cu–PPEDA and Ti6Al4V controls for 7, 14 and 56 days with 8 rats/day, peri-implant tissue was immunohistochemically examined for different inflammatory cells. Ti6Al4V–PPEDA had more mast cells and NK cells than Ti6Al4V, and more tissue macrophages, T lymphocytes, mast cells and NK cells than Ti6Al4V–Ti/Cu–PPEDA. Ti6Al4V–Ti/Cu had more mast cells than Ti6Al4V and Ti6Al4V–Ti/Cu–PPEDA. Results indicate that PPEDA-mediated cell adhesion counteracted Cu cytotoxicity. Ti6Al4V–Ti/Cu–PPEDA differed from Ti6Al4V only for mast cells on day 56. Altogether, implants with both plasma treatments had antibacterial properties and did not increase inflammatory reactions.