Polyelectrolyte-assisted preparation of gold nanocluster-doped silica particles with high incorporation efficiency and improved stability

Abstract

In this paper, we reported an approach for efficient incorporation of glutathione-capped gold nanoclusters (GSH-Au NCs) into silica particles with the assistance of a polyelectrolyte, poly-diallyldimethyl-ammoniumchloride (PDDA). In this approach, the negatively charged GSH-Au NCs were firstly mixed with the positively charged PDDA to form PDDA–Au NC complexes. Then, the complexes were added into a pre-hydrolyzed Stöber system to get the Au NCs-doped silica particles. With increased ratio of PDDA in the complexes, the negative charges on surface of the Au NCs were neutralized gradually and finally reversed to positive in presence of excess PDDA, which facilitated the incorporation of the Au NCs into the negatively charged silica matrix. Under the optimal amount of PDDA in the complexes, the incorporation efficiency of Au NCs could be as high as 88%. After being incorporated into the silica matrix, the Au NCs become much robust against pH and heavy metal ions attributed to the protection effect of silica and PDDA. This approach was also extendable to highly efficient incorporation of other negatively charged metal nanoclusters, such as bovine serum albumin-capped Cu nanoclusters, into silica matrix.

http://ift.tt/2ubLTeD

Comparing naturally occurring glycosylated forms of proline rich antibacterial peptide, Drosocin

Abstract

Antimicrobial peptides (AMPs) are key players of innate immunity. Amongst various classes of AMPs, proline rich AMPs from insects enjoy special attention with few members of this class bearing O-glycosylation as post-translational modification. Drosocin, a 19 amino acid glycosylated AMP is a member of proline rich class, synthesized in the haemolymph of Drosophila melanogaster upon bacterial challenge. We report herein the chemical synthesis of drosocin carrying disaccharide (β-Gal(1 → 3)α-GalNAc) and comparison of its structural and functional properties with another naturally occurring monoglycosylated form of drosocin i.e. α-GalNAc-drosocin as well as with non-glycosylated drosocin. The disaccharide containing drosocin exhibited lower potency compared to monoglycosylated drosocin against all the tested Gram negative bacteria, suggesting the role of the distal sugar or increase in the sugar chain length on the activity. Circular dichroism studies failed to demonstrate the differential effect of sugars on the overall peptide conformation. Haemolytic and cytotoxic properties of drosocin were not altered due to an increase in the sugar chain length. In addition, we have also evaluated the effect of differentially glycosylated drosocins on two pro-inflammatory cytokines secreted by murine macrophages or LPS stimulated macrophages. All the drosocin forms tested, neither could stimulate the secretion of TNF-α and IL-6 nor could modulate LPS-induced levels of TNF-α and IL-6 in murine macrophages. This study provides insights about naturally occurring two different glycosylated forms of drosocin.

http://ift.tt/2sbRhl7

Responses of Wetland Plant Carex vulpina to Copper and Iron Nanoparticles

Abstract

Currently, the use of nanotechnologies is in rapid expansion, which entails increasing risks of environmental contamination by nanoparticles. Many studies describe the toxic effects on human cells, but little is known about the possible adverse effects on plants. Currently, various nanoparticles are often detected in streams, wastewater, and sewage due to widespread nanoparticle uses. We studied the accumulation and the effect of metal oxide nanoparticles together with their bulk counter particles and soluble metal salts on the growth of a wetland plant species true fox-sedge (Carex vulpina L.). The concentration 100 mg/l of copper nanoparticles significantly affected the growth of the plants, roots characteristics, and content of the photosynthetic pigments in leaves, while the same concentration of iron nanoparticles did not reduced any of the measured items. Using the bulk materials, the effect was very similar.

http://ift.tt/2sWb3hT

Biogeochemical Cycle of Mercury and Methylmercury in Two Highly Contaminated Areas of Tagus Estuary (Portugal)

Abstract

Mercury (Hg) dynamics was evaluated in contaminated sediments and overlying waters from Tagus estuary, in two sites with different Hg anthropogenic sources: Cala Norte (CNOR) and Barreiro (BRR). Environmental factors affecting methylmercury (MMHg) production and Hg and MMHg fluxes across sediment/water interface were reported. [THg] and [MMHg] in solids (0.31–125 μg g⁻¹ and 0.76–201 ng g⁻¹, respectively) showed high variability with higher values in BRR. Porewater [MMHg] (0.1–63 ng L⁻¹, 0.5–86% of THg) varied local and seasonally; higher contents were observed in the summer campaign, thus increasing sediment toxicity affecting the sediment/water Hg (and MMHg) fluxes. In CNOR and BRR sediments, Hg availability and organic carbon were the main factors controlling MMHg production. Noteworthy, an upward MMHg diffusive flux was observed in winter that was inverted in summer. Although MMHg production increases in warmer month, the MMHg concentrations in overlying water increase in a higher proportion compared to the levels in porewaters. This opposite trend could be explained by different extension of MMHg demethylation in the water column. The high concentrations of Hg and MMHg and their dynamics in sediments are of major concern since they can cause an exportation of Hg from the contaminated areas up to ca. 14,600 mg year⁻¹ and an MMHg deposition of up to ca. 6000 mg year⁻¹. The results suggest that sediments from contaminated areas of Tagus estuary should be considered as a primary source of Hg for the water column and a sink of MMHg to the sedimentary column.

http://ift.tt/2sc7t5U

Acute disseminated encephalomyelitis in an elderly patient

http://ift.tt/2sVRztH

Biomarkers that Predict Response to Neoadjuvant Chemoradiation in Locally Advanced Rectal Cancer

Abstract

Neoadjuvant chemoradiation has been a standard of care for locally advanced rectal cancers. Recent reports suggest that a pathologic complete response to neoadjuvant treatment correlates to improved overall survival. In addition, some series suggest that patients who have a complete response to neoadjuvant therapy may safely defer surgery in favor of a "watch and wait" approach, therefore avoiding the potential complications and adverse bowel function associated with surgery. It is therefore important to understand the clinical and biologic factors which affect the response of rectal cancers to chemoradiation. This review highlights the current literature examining the biomarkers of tumor response to chemoradiation.

http://ift.tt/2thsFI2

Treatment of Hyperkalemia in Heart Failure

Abstract

Purpose of Review

The aim of this paper is to discuss strategies for prevention and management of hyperkalemia in patients with heart failure, including the role of novel therapies.

Recent Findings

Renin-angiotensin-aldosterone system (RAAS) antagonists, including angiotensin-converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), and mineralocorticoid receptor antagonists (MRA) decrease mortality and morbidity in heart failure but increase the risk of hyperkalemia, especially when used in combination. Prevention of hyperkalemia and its associated complications requires careful patient selection, counseling regarding dietary potassium intake, awareness of drug interactions, and regular laboratory surveillance. Recent data suggests that the risk of hyperkalemia may be further moderated through the use of combined angiotensin-neprilysin inhibitors, novel MRAs, and novel potassium binding agents.

Summary

Clinicians should be mindful of the risk of hyperkalemia when prescribing RAAS inhibitors to patients with heart failure. In patients at highest risk, such as those with diabetes, the elderly, and advanced chronic kidney disease, more intensive laboratory surveillance of potassium and creatinine may be required. Novel therapies hold promise for reducing the risk of hyperkalemia and enhancing the tolerability of RAAS antagonists.

http://ift.tt/2tfiCma