Layer-by-layer electrostatic entrapment of protein molecules on superparamagnetic nanoparticle: new strategy to enhance adsorption capacity and maintain biological activity

There is a recent interest to use inorganic-based magnetic nanoparticles as a vehicle to carry biomolecules for various biophysical applications, but direct attachment of the molecules is known to alter their conformation leading to attenuation in activity. In addition, surface immobilization has been limited to monolayer coverage. It is shown that alternate depositions of negatively charged protein molecules, typically bovine serum albumin (BSA) with a positively charged aminocarbohydrate template such as glycol chitosan (GC) on magnetic iron oxide nanoparticle surface as a colloid, are carried out under pH 7.4. Circular dichroism (CD) clearly reveals that the secondary structure of the entrapped BSA sequential depositions in this manner remains totally unaltered which is in sharp contrast to previous attempts. Probing the binding properties of the entrapped BSA using small molecules (Site I and Site II drug compounds) confirms for the first time the full retention of its biological activity as compared with native BSA, which also implies the ready accessibility of the entrapped protein molecules through the porous overlayers. This work clearly suggests a new method to immobilize and store protein molecules beyond monolayer adsorption on a magnetic nanoparticle surface without much structural alteration. This may find applications in magnetic recoverable enzymes or protein delivery.

Biological and chemical assessment of zinc ageing in field soils

As zinc (Zn) is both an essential trace element and potential toxicant, the effects of Zn fixation in soil are of practical significance. Soil samples from four field sites amended with ZnSO4 were used to investigate ageing of soluble Zn under field conditions over a 2-year period. Lability of Zn measured using 65Zn radioisotope dilution showed a significant decrease over time and hence evidence of Zn fixation in three of the four soils. However, 0.01 M CaCl2 extractions and toxicity measurements using a genetically modified lux-marked bacterial biosensor did not indicate a decrease in soluble/bioavailable Zn over time. This was attributed to the strong regulatory effect of abiotic properties such as pH on these latter measurements. These results also showed that Zn ageing occurred immediately after Zn spiking, emphasising the need to incubate freshly spiked soils before ecotoxicity assessments. Ageing effects were detected in Zn-amended field soils using 65Zn isotopic dilution as a measure of lability, but not with either CaCl2 extractions or a lux-marked bacterial biosensor.

Sulfation of genistein alters its antioxidant properties and its effect on platelet aggregation and monocyte and endothelial function

Soy isoflavones have been extensively studied because of their possible benefits to human health. Genistein, the major isoflavone aglycone, has received most attention; however, it undergoes extensive metabolism (e.g. conjugation with sulfuric acid) in the gut and liver, which may affect its biological proper-ties. This study investigated the antioxidant activity and free radical-scavenging properties of genistein, genistein-4'-sulfate and genistein-4'-7-disulfate as well as their effect on platelet aggregation and monocyte and endothelial function. Electron spin resonance spectroscopy (ESR) and spin trapping data and other standard antioxidant assays indicated that genistein is a relatively weak antioxidant compared to quercetin and that its sulfated metabolites are even less effective. Furthermore, genistein-4'-sulfate was less potent than genistem, and genistein-4'-7-disulfate even less potent, at inhibiting collagen-induced platelet aggregation, nitric oxide (NO) production by macrophages, and secretion by primary human endothelial cells of monocyte chemoattractant protein 1 (MCP-1), intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1). The current data suggest that sulfation of genistein, with the associated loss of hydroxyl groups, decreases its antioxidant activity and its effect on platelet aggregation, inflammation, cell adhesion and chemotaxis. (C) 2004 Elsevier B.V All rights reserved.

Sulfation of genistein alters its antioxidant properties and its effect on platelet aggregation and monocyte and endothelial function

Soy isoflavones have been extensively studied because of their possible benefits to human health. Genistein, the major isoflavone aglycone, has received most attention; however, it undergoes extensive metabolism (e.g. conjugation with sulfuric acid) in the gut and liver, which may affect its biological proper-ties. This study investigated the antioxidant activity and free radical-scavenging properties of genistein, genistein-4'-sulfate and genistein-4'-7-disulfate as well as their effect on platelet aggregation and monocyte and endothelial function. Electron spin resonance spectroscopy (ESR) and spin trapping data and other standard antioxidant assays indicated that genistein is a relatively weak antioxidant compared to quercetin and that its sulfated metabolites are even less effective. Furthermore, genistein-4'-sulfate was less potent than genistem, and genistein-4'-7-disulfate even less potent, at inhibiting collagen-induced platelet aggregation, nitric oxide (NO) production by macrophages, and secretion by primary human endothelial cells of monocyte chemoattractant protein 1 (MCP-1), intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1). The current data suggest that sulfation of genistein, with the associated loss of hydroxyl groups, decreases its antioxidant activity and its effect on platelet aggregation, inflammation, cell adhesion and chemotaxis. (C) 2004 Elsevier B.V All rights reserved.

Antioxidant properties of carotenoids in vitro and in vivo

Carotenoids are a class of natural pigments familiar to all through the orange-red to yellow colors of many fruits, vegetables, and flowers, as well as for the provitamin A activity that some of them possess. A body of scientific evidence suggests that carotenoids may scavenge and deactivate free radicals, acting thereby as antioxidants both in food systems (in vitro) and in the human organism (in vivo). Overall, epidemiological evidence links higher carotenoid intakes and tissue concentrations with reduced cancer and cardiovascular disease risk. However, research has also shown that the antioxidant activity of carotenoids may shift to a prooxidant character depending mainly on the biological environment in which they act. A summary of the antioxidant potential of natural carotenoids both in oil model systems and in vivo is presented in this article.

Chemical, physical, and sensory properties of dairy products enriched with conjugated linoleic acid

Recent studies have illustrated the effects of cis-9, trans-11 conjugated linoleic acid (CLA) on human health. Ruminant-derived meat, milk and dairy products are the predominant sources of cis-9, trans-11 CLA in the human diet. This study evaluated the processing properties, texture, storage characteristics, and organoleptic properties of UHT milk, Caerphilly cheese, and butter produced from a milk enriched to a level of cis-9, trans-11 CLA that has been shown to have biological effects in humans. Forty-nine early-lactation Holstein-British Friesian cows were fed total mixed rations containing 0 (control) or 45 g/kg ( on dry matter basis) of a mixture (1:2 wt/wt) of fish oil and sunflower oil during two consecutive 7-d periods to produce a control and CLA-enhanced milk, respectively. Milk produced from cows fed the control and fish and sunflower oil diets contained 0.54 and 4.68 g of total CLA/100 g of fatty acids, respectively. Enrichment of CLA in raw milk from the fish and sunflower oil diet was also accompanied by substantial increases in trans C18:1 levels, lowered C18: 0, cis-C18:1, and total saturated fatty acid concentrations, and small increases in n-3 polyunsaturated fatty acid content. The CLA-enriched milk was used for the manufacture of UHT milk, butter, and cheese. Both the CLA-enhanced butter and cheese were less firm than control products. Although the sensory profiles of the CLA-enriched milk, butter, and cheese differed from those of the control products with respect to some attributes, the overall impression and flavor did not differ. In conclusion, it is feasible to produce CLA-enriched dairy products with acceptable storage and sensory characteristics.

Extra virgin olive oil phenolics: absorption, metabolism, and biological activities in the GI tract

Olive oil, a typical ingredient of the Mediterranean diet, possesses many beneficial health effects. The biological activities ascribed to olive oil consumption are associated in part to its phenolics constituents, and mainly linked to the direct or indirect antioxidant activity of olive oil phenolics and their metabolites, which are exerted more efficiently in the gastrointestinal (GI) tract, where dietary phenolics are more concentrated when compared to other organs. In this regard, we present a brief overview of the metabolism, biological activities, and anticancer properties of olive oil phenolics in the GI tract. Toxicology and Industrial Health 2009; 25: 285-293.

The Ferritin-like superfamily: evolution of the biological iron storeman from a rubrerythrin-like ancestor

Background: The Ferritins are part of the extensive ‘Ferritin-like superfamily’ which have diverse functions but are linked by the presence of a common four-helical bundle domain. The role performed by Ferritins as the cellular repository of excess iron is unique. In many ways Ferritins act as tiny organelles in their ability to secrete iron away from the delicate machinery of the cell, and then to release it again in a controlled fashion avoiding toxicity. The Ferritins are ancient proteins, being common in all three domains of life. This ubiquity reflects the key contribution that Ferritins provide in achieving iron homeostasis. Scope of the review: This review compares the features of the different Ferritins and considers how they, and other members of the Ferritin-like superfamily, have evolved. It also considers relevant features of the eleven other known families within the Ferritin-like superfamily, particularly the highly diverse rubrerythrins. Major conclusions: The Ferritins have travelled a considerable evolutionary journey, being derived from far more simplistic rubrerythrin-like molecules which play roles in defence against toxic oxygen species. The forces of evolution have moulded such molecules into three distinct types of iron storing (or detoxifying) protein: the classical and universal 24-meric ferritins; the haem-containing 24-meric bacterioferritins of prokaryotes; and the prokaryotic 12-meric Dps proteins. These three Ferritin types are similar, but also possess unique properties that distinguish them and enable then to achieve their specific physiological purposes. General significance: A wide range of biological functions have evolved from a relatively simple structural unit.

The mechanical properties of amniotic membrane influence its effect as a biomaterial for ocular surface repair

The human amniotic membrane (AM) is a tissue of fetal origin and has proven to be clinically useful as a biomaterial in the management of various ocular surface disorders including corneal stem cell transplantation. However, its success rate displays a degree of clinical unpredictability. We suggest that the measured variability inAMstiffness offers an explanation for the poor clinical reproducibility when it is used as a substrate for stem cell expansion and transplantation. Corneal epithelial stem cells were expanded upon AM samples possessing different mechanical stiffness. To investigate further the importance of biological substrate stiffness on cell phenotype we replaced AM with type I collagen gels of known stiffness. Substrate stiffness was measured using shear rheometry and surface topography was characterized using scanning electron microscopy and atomic force microscopy. The differentiation status of epithelial cells was examined using RT-PCR, immunohistochemistry and Western blotting. The level of corneal stem cell differentiation was increased in cells expanded upon AM with a high dynamic elastic shear modulus and cell expansion on type I collagen gels confirmed that the level of corneal epithelial stem cell differentiation was related to the substrate’s mechanical properties. In this paper we provide evidence to show that the preparatory method of AM for clinical use can affect its mechanical properties and that these measured differences can influence the level of differentiation within expanded corneal epithelial stem cells.

A comparison of the anticancer properties of isoxanthohumol and 8-prenylnaringenin using in vitro models of colon cancer

The hops plant (Humulus lupulus L.) is an essential ingredient in beer and contains a number of potentially bioactive prenylflavonoids, the predominant being the weakly estrogenic isoxanthohumol (Ix), which can be converted to the more strongly estrogenic 8-PN by the colonic microbiota. The aim of this study was to investigate the biological activity of 8-PN and Ix using in vitro models representing key stages of colorectal carcinogenesis, namely cell growth and viability (MTT assay), cell-cycle progression (DNA content assay), DNA damage (Comet assay), and invasion (Matrigel assay). A significant decrease in Caco-2 cell viability was noted after both 8-PN and Ix treatments at the higher doses (40 and 50 μM, respectively) although the impact on cell cycle differed between the two compounds. The decreased cell viability observed after Ix treatment was associated with a concentration-dependent increase in G2/M and an increased sub-G1 cell-cycle fraction, whereas treatment with 8-PN was associated with an elevated G0/G1 and an increased sub-G1 cell-cycle fraction. Significant antigenotoxic activity was noted at all 8-PN concentrations tested (5-40 μM). Although significant antigenotoxic activity was also noted with Ix treatment at ≤25 μM, at a higher dose, Ix itself exerted genotoxic activity. In a dose-dependent manner, both compounds inhibited HT115 cell invasion with reductions up to 52 and 46% for Ix and 8-PN, respectively, in comparison to untreated cells. This study demonstrated that both Ix and its gut microbial metabolite 8-PN exert anticancer effects on models of key stages of colon tumourigenesis.

Inactivation of the antibacterial and cytotoxic properties of silver ions by biologically relevant compounds

There has been a recent surge in the use of silver as an antimicrobial agent in a wide range of domestic and clinical products, intended to prevent or treat bacterial infections and reduce bacterial colonization of surfaces. It has been reported that the antibacterial and cytotoxic properties of silver are affected by the assay conditions, particularly the type of growth media used in vitro. The toxicity of Ag+ to bacterial cells is comparable to that of human cells. We demonstrate that biologically relevant compounds such as glutathione, cysteine and human blood components significantly reduce the toxicity of silver ions to clinically relevant pathogenic bacteria and primary human dermal fibroblasts (skin cells). Bacteria are able to grow normally in the presence of silver nitrate at >20-fold the minimum inhibitory concentration (MIC) if Ag+ and thiols are added in a 1:1 ratio because the reaction of Ag+ with extracellular thiols prevents silver ions from interacting with cells. Extracellular thiols and human serum also significantly reduce the antimicrobial activity of silver wound dressings Aquacel-Ag (Convatec) and Acticoat (Smith & Nephew) to Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli in vitro. These results have important implications for the deployment of silver as an antimicrobial agent in environments exposed to biological tissue or secretions. Significant amounts of money and effort have been directed at the development of silver-coated medical devices (e.g. dressings, catheters, implants). We believe our findings are essential for the effective design and testing of antimicrobial silver coatings.