Plasmodium falciparum ligand binding to erythrocytes induce alterations in deformability essential for invasion

The most lethal form of malaria in humans is caused by Plasmodium falciparum. These parasites invade erythrocytes, a complex process involving multiple ligand-receptor interactions. The parasite makes initial contact with the erythrocyte followed by dramatic deformations linked to the function of the Erythrocyte binding antigen family and P. falciparum reticulocyte binding-like families. We show EBA-175 mediates substantial changes in the deformability of erythrocytes by binding to glycophorin A and activating a phosphorylation cascade that includes erythrocyte cytoskeletal proteins resulting in changes in the viscoelastic properties of the host cell. TRPM7 kinase inhibitors FTY720 and waixenicin A block the changes in the deformability of erythrocytes and inhibit merozoite invasion by directly inhibiting the phosphorylation cascade. Therefore, binding of P. falciparum parasites to the erythrocyte directly activate a signaling pathway through a phosphorylation cascade and this alters the viscoelastic properties of the host membrane conditioning it for successful invasion

Mapping Valley Bottom Confinement at the Network Scale

In this article, we demonstrate the application of a continuous confinement metric across entire river networks. Confinement is a useful metric for characterizing and discriminating valley setting. At the reach scale, valley bottom confinement is measured and quantified as the ratio of the length of channel confined on either bank by a confining margin divided by the reach length. The valley bottom is occupied by the contemporary floodplain and/or its channel(s); confining margins can be any landform or feature that makes up the valley bottom margin, such as bedrock hillslopes, terraces, fans, or anthropogenic features such as stopbanks or constructed levees. To test the reliability of calculating confinement across entire networks, we applied our geoprocessing scripts across four physiographically distinct watersheds of the Pacific Northwest, USA using freely available national datasets. Comparison of manually digitized and mapped with modeled calculations of confinement revealed that roughly one‐third of reaches were equivalent and about two‐thirds of the sites differ by less than ±15%. A sensitivity analysis found that a 500 m reach segmentation length produced reasonable agreement with manual, categorical, expert‐derived analysis of confinement. Confinement accuracy can be improved (c. 4% to 17% gains) using a more accurately mapped valley bottom and channel position (i.e. with higher‐resolution model inputs). This is particularly important when differentiating rivers in the partly confined valley setting. However, at the watershed scale, patterns derived from mapping confinement are not fundamentally different, making this a reasonably accurate and rapid technique for analysis and measurement of confinement across broad spatial extents

The removal of meat exudate and escherichia coli from stainless steel and titanium surfaces with irregular and regular linear topographies

Bacterial retention and organic fouling on meat preparation surfaces can be influenced by several factors. Surfaces with linear topographies and defined chemistries were used to determine how the orientation of the surface features affected cleaning efficacy. Fine polished (irregular linear) stainless steel (FPSS), titanium coated fine polished (irregular linear) stainless steel (TiFP), and topographically regular, linear titanium coated surfaces (RG) were fouled with Escherichia coli mixed with a meat exudate (which was utilised as a conditioning film). Surfaces were cleaned along or perpendicular to the linear features for one, five, or ten wipes. The bacteria were most easily removed from the titanium coated and regular featured surfaces. The direction of cleaning (along or perpendicular to the surface features) did not influence the amount of bacteria retained, but meat extract was more easily removed from the surfaces when cleaned in the direction along the linear surface features. Following ten cleans, there was no significant difference in the amount of cells or meat exudate retained on the surfaces cleaned in either direction. This study demonstrated that for the E. coli cells, the TiFP and RG surfaces were easiest to clean. However, the direction of the clean was important for the removal of the meat exudate from the surfaces

Surface Topography on the Distribution, Density, Dispersion and Clustering of Differently Organised Coccal-Shaped Bacteria

The topographic features of surfaces are known to affect bacterial retention on a surface, but the precise mechanisms of this phenomenon are little understood. Four coccal-shaped bacteria, Staphylococcus sciuri, Streptococcus pyogenes, Micrococcus luteus, and Staphylococcus aureus, that organise in different cellular groupings (grape-like clusters, tetrad-arranging clusters, short chains, and diploid arrangement, respectively) were used. These differently grouped cells were used to determine how surface topography affected their distribution, density, dispersion, and clustering when retained on titanium surfaces with defined topographies. Titanium-coated surfaces that were smooth and had grooved features of 1.02 µm-wide, 0.21 µm-deep grooves, and 0.59 µm-wide, 0.17 µm-deep grooves were used. The average contact angle of the surfaces was 91°. All bacterial species were overall of a hydrophobic nature, although M. luteus was the least hydrophobic. It was demonstrated that the 1.02 µm-wide featured surface most affected Strep. pyogenes and S. sciuri, and hence the surfaces with the larger surface features most affected the cells with smaller dimensions. The 0.59 µm featured surface only affected the density of the bacteria, and it may be suggested that the surfaces with the smaller features reduced bacterial retention. These results demonstrate that the size of the topographical surface features affect the distribution, density, dispersion, and clustering of bacteria across surfaces, and this is related to the cellular organisation of the bacterial species. The results from this work inform how surface topographical and bacterial properties affect the distribution, density, dispersion, and clustering of bacterial retention

The effect of surface properties on bacterial retention: a study utilising stainless steel and TiN/25.65at.%Ag substrata

The requirement for antimicrobial surfaces to control microorganisms for use in the food industries is increasing. A TiN/25.65at.%Ag coating and a stainless steel (304 2R) surface were characterised for roughness parameters, chemistry and physicochemistry (PC). Microbiological analysis was performed to determine the antimicrobial efficacy and retention of Staphylococcus aureus and Escherichia coli on the surfaces. Zone of inhibition assays were successful against only E. coli on the TiN/25.65at.%Ag coating. A bacterial respiratory assay demonstrated that the TiN/25.65at.%Ag coating was antimicrobial against both bacteria. Retention assays demonstrated that the physicochemistry of the bacteria and surfaces influenced bacterial retention. Multifractal analysis of the retained bacteria demonstrated that the surface properties affected the spread and clustering, but not the density of the bacteria. This work suggests that surface properties influenced specific species: surface interactions and therefore surfaces need to be tailored to specific requirements depending on the environment and microorganisms to be targeted. This work may aid in the production of coatings or surfaces that may provide more hygienic conditions

Quantifying the pattern of microbial cell dispersion, density and clustering on surfaces of differing chemistries and topographies using multifractal analysis

The effects of surface topography on bacterial distribution across a surface are of extreme importance when designing novel, hygienic or antimicrobial surface coatings. The majority of methods that are deployed to describe the pattern of cell dispersion, density and clustering across surfaces are currently qualitative. This paper presents a novel application of multifractal analysis to quantitatively measure these factors using medically relevant microorganisms (Staphylococcus aureus or Staphylococcus epidermidis). Surfaces (medical grade 316 stainless steel) and coatings (Ti–ZrN, Ti–ZrN/6.0%Ag, Ti–ZrN/15.6%Ag, TiZrN/24.7%Ag) were used in microbiological retention assays. Results demonstrated that S. aureus displayed a more heterogeneous cell dispersion (∆αAS < 1) whilst the dispersion of S. epidermidis was more symmetric and homogeneous (∆αAS ≥ 1). Further, although the surface topography and chemistry had an effect on cell dispersion, density and clustering, the type of bonding that occurred at the surface interface was also important. Both types of cells were influenced by both surface topographical and chemical effects; however, S. aureus was influenced marginally more by surface chemistry whilst S. epidermidis cells was influenced marginally more by surface topography. Thus, this effect was bacterially species specific. The results demonstrate that multifractal analysis is a method that can be used to quantitatively analyse the cell dispersion, density and clustering of retained microorganisms on surfaces. Using quantitative descriptors has the potential to aid the understanding the effect of surface properties on the production of hygienic and antimicrobial coatings

The effect of surface properties of polycrystalline, single phase metal coatings on bacterial retention

In the food industry microbial contamination of surfaces can result in product spoilage which may lead to potential health problems of the consumer. Surface properties can have a substantial effect on microbial retention. The surface characteristics of chemically different coatings (Cu, Ti, Mo, Ag, Fe) were defined using white light profilometry (micro-topography and surface features), atomic force microscopy (nano-topography) and physicochemical measurements. The Ag coating had the greatest topography measurements and Fe and Mo the least. Mo was the most hydrophobic coating (lowest γAB,γ+, γ−) whilst Ag was the most hydrophilic (greatest γAB,γ+, γ−). The physicochemical results for the Fe, Ti and Cu coatings were found to lie between those of the Ag and Mo coatings. Microbiological retention assays were carried out using Listeria monocytogenes, Escherichia coli and Staphylococcus aureus in order to determine how surface properties influenced microbial retention. It was found that surface chemistry had an effect on microbial retention, whereas the shape of the surface features and nano-topography did not. L. monocytogenes and S. aureus retention to the surfaces were mostly affected by surface micro-topography, whereas retention of E. coli to the coatings was mostly affected by the coating physicochemistry. There was no trend observed between the bacterial cell surface physicochemistry and the coating physicochemistry. This work highlights that different surface properties may be linked to factors affecting microbial retention hence, the use of surface chemistry, topography or physicochemical factors alone to describe microbial retention to a surface is no longer adequate. Moreover, the effects of surface parameters on microbial retention should be considered individually for each bacterial genus

Titania coating of mesoporous silica nanoparticles for improved biocompatibility and drug release within blood vessels

Blood vessel disease is a major contributor to cardiovascular morbidity and mortality and is hallmarked by dysfunction of the lining endothelial cells (ECs). These cells play a significant role in vascular homeostasis, through the release of mediators to control vessel diameter, hence tissue perfusion. Mesoporous silica nanoparticles (MSNs) can be used as potential drug delivery platforms for vasodilator drugs. Here, using an ex vivo model of vascular function, we examine the use of titania coating for improved biocompatibility and release dynamics of MSN loaded sodium nitroprusside (SNP). MSNs (95 ± 23 nm diameter; pore size 2.7 nm) were synthesised and fully characterised. They were loaded with SNP and coated with titania (TiO2), using the magnetron sputtering technique. Pre-constricted aortic vessels were exposed to drug loaded MSNs (at 1.96 × 1012 MSN mL−1) and the time course of vessel dilation observed, in real time. Exposure of viable vessels to MSNs lead to their internalization into the cytoplasm of ECs, while TiMSNs were also observed in the elastic lamina and smooth muscle cell layers. We demonstrate that titania coating of MSNs significantly improves their biocompatibility and alters the dynamics of drug release. A slow and more sustained relaxation was evident after uptake of TiMSN-SNP, in comparison to uncoated MSN-SNP (rate of dilation was 0.08% per min over a 2.5 h period). The use of titania coated MSNs for drug delivery to the vasculature may be an attractive strategy for therapeutic clinical intervention in cardiovascular disease