Transcatheter Aortic Valve Thrombogenesis: A Foreign Materials Perspective.

PURPOSE: The initiation of thrombus formation in transcatheter aortic valves (TAVs) is not well understood. The foreign material components of a TAV may play a key role in TAV thrombogenesis. The goal of this study was to evaluate the thrombogenic potential of a TAV (entire valve) and its stent (with skirt). METHODS: Blood was collected from eight human donors with citrate anticoagulation and later reconstituted with calcium chloride. A low-volume steady flow loop (flow rate = 0.8 L/min) was designed to facilitate three separate conditions (experimental duration = 1 h) per donor blood: (1) control (n = 8), (2) stent-with-skirt (leaflets removed from a 23 mm SAPIEN XT valve; n = 8) and (3) entire valve (an intact 23 mm SAPIEN XT valve; n = 8). Samples were collected at the start and end of each experiment. Serum D-Dimer and thrombin-antithrombin (TAT) concentrations were measured as markers of thrombogenicity. RESULTS: There was no significant change in serum D-Dimer and TAT concentration with time for the control group. An increasing trend in D-Dimer and TAT concentration was observed with time for the stent-with-skirt group. Interestingly, there was a decreasing trend in serum D-Dimer and TAT concentration with time for the entire valve (leaflet dominating) group. Moreover, changes in D-Dimer and TAT concentration were significantly different between the stent-with-skirt and entire valve (leaflet dominating) groups. CONCLUSION: Stent-with-skirt was found to impart the most prominent thrombogenic effect, indicating the significance of blood-stent and blood-skirt interactions in TAV thrombosis.

Selenium nanoparticle-enriched biomass of Yarrowia lipolytica enhances growth and survival of Artemia salina.

Controlling disease outbreaks is a major challenge in aquaculture farms and conventional methods are often ineffective. Nutritional supplementation and probiotic preparations help in reducing severity of such infections. The generally regarded as safe yeast (Yarrowia lipolytica) was used in the current study. A marine strain of Y. lipolytica exhibited tolerance towards sodium selenite and formed cell associated selenium nanoparticles (SeNPs). The synthesized nanoparticles were characterized by UV-vis spectroscopy, X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FE-SEM) observations. Fourier transform infra-red (FTIR) spectroscopy indicated the role of carboxylic and amine groups in the synthesis of nanoparticles. This SeNP-enriched biomass was used as feed for the model aquaculture system, Artemia salina and compared with normal feed, baker's yeast (Saccharomyces cerevisiae). A. salina fed with SeNP-enriched biomass, showed increased survival rates (96.66%) as compared to those fed with S. cerevisiae (60.0%). The size of the larvae fed with SeNP-enriched biomass of Y. lipolytica was also found to be larger. Additionally, larval groups fed with SeNP-enriched biomass were better protected (70.0% survival) against V. harveyi infection when compared with groups fed with S. cerevisiae (24.44%). This combination of selenium in the nanoparticle form associated with the biomass of Y. lipolytica has potential application in improving health of aquaculture species in farms.

Biogenic Nanoparticles from Schwanniomyces occidentalis NCIM 3459: Mechanistic Aspects and Catalytic Applications.

When cells of Schwanniomyces occidentalis NCIM 3459 were incubated with 1 mM tetrachloroauric acid (HAuCl4) or silver nitrate (AgNO3), cell-associated nanoparticles were obtained. Their presence was confirmed by scanning electron microscope observations. The cell-free supernatant (CFS) of the yeast mediated the synthesis of gold nanoparticles. On account of the difficulties associated with the use of cell-bound nanoparticles, further work was restricted to extracellular nanoparticles. It was hypothesized that the CFS contained thermostable biomolecule(s) that mediated metal reduction reactions. Extraction of the CFS with chloroform/methanol (2:1) and subsequent separation by preparative thin layer chromatography led to the activity-guided purification of a glycolipid. The glycolipid was hydrolyzed and the glycone (glucose) and aglycone components (palmitic acid and oleic acid) were identified by gas chromatography-mass spectrometry. The purified glycolipid mediated the synthesis of gold and silver nanoparticles that were characterized by using an X-ray diffractometer and transmission electron microscope (TEM). The extracellular nanoparticles displayed catalytic activities and reduced 4-nitroaniline to benzene-1,4-diamine. This paper thus highlights nanoparticle synthesis by a hitherto unreported yeast culture, identifies the biomolecules involved in the process, and describes a potential application of the nanostructures.

Monitoring and trend mapping of sea surface temperature (SST) from MODIS data: a case study of Mumbai coast.

Sea surface temperature (SST) is one of the most important parameters in monitoring ecosystem health in the marine and coastal environment. Coastal ecosystem is largely dependent on ambient temperature and temperature fronts for marine/coastal habitat and its sustainability. Hence, thermal pollution is seen as a severe threat for ecological health of coastal waters across the world. Mumbai is one of the largest metropolises of the world and faces severe domestic and industrial effluent disposal problem, of which thermal pollution is a major issue with policy-makers and environmental stakeholders. This study attempts to understand the long-term SST variation in the coastal waters off Mumbai, on the western coast of India, and to identify thermal pollution zones. Analysis of SST trends in the near-coastal waters for the pre- and post-monsoon seasons from the year 2004 to the year 2010 has been carried out using Moderate Resolution Imaging Spectro-radiometer (MODIS) Thermal Infra-red (TIR) bands. SST is calculated with the help of bands 31 and 32 using split window method. Several statistical operations were then applied to find the seasonal averages in SST and the standard deviation of SST in the study area. Maximum variation in SST was found within a perpendicular distance of 5 km from the shoreline during the study period. Also, a warm water mass was found to form consistently off coast during the winter months. Several anthropogenic sources of thermal pollution could be identified which were found to impact various locations along the coast.

Yarrowia lipolytica and pollutants: Interactions and applications.

Yarrowia lipolytica is a dimorphic, non-pathogenic, ascomycetous yeast species with distinctive physiological features and biochemical characteristics that are significant in environment-related matters. Strains naturally present in soils, sea water, sediments and waste waters have inherent abilities to degrade hydrocarbons such as alkanes (short and medium chain) and aromatic compounds (biphenyl and dibenzofuran). With the application of slow release fertilizers, design of immobilization techniques and development of microbial consortia, scale-up studies and in situ applications have been possible. In general, hydrocarbon uptake in this yeast is mediated by attachment to large droplets (via hydrophobic cell surfaces) or is aided by surfactants and emulsifiers. Subsequently, the internalized hydrocarbons are degraded by relevant enzymes innately present in the yeast. Some wild-type or recombinant strains also detoxify nitroaromatic (2,4,6-trinitrotoluene), halogenated (chlorinated and brominated hydrocarbons) and organophosphate (methyl parathion) compounds. The yeast can tolerate some metals and detoxify them via different biomolecules. The biomass (unmodified, in combination with sludge, magnetically-modified and in the biofilm form) has been employed in the biosorption of hexavalent chromium ions from aqueous solutions. Yeast cells have also been applied in protocols related to nanoparticle synthesis. The treatment of oily and solid wastes with this yeast reduces chemical oxygen demand or value-added products (single cell oil, single cell protein, surfactants, organic acids and polyalcohols) are obtained. On account of all these features, the microorganism has established a place for itself and is of considerable value in environment-related applications.

Psychrotrophic yeast Yarrowia lipolytica NCYC 789 mediates the synthesis of antimicrobial silver nanoparticles via cell-associated melanin.

A psychrotrophic marine strain of the ascomycetous yeast Yarrowia lipolytica (NCYC 789) synthesized silver nanoparticles (AgNPs) in a cell-associated manner. These nanostructures were characterized by UV-Visible spectroscopy and scanning electron microscope-energy dispersive spectrometer (SEM-EDS) analysis. The brown pigment (melanin) involved in metal-interactions was obtained from the cells. This extracted pigment also mediated the synthesis of silver nanoparticles that were characterized by a variety of analytical techniques. The melanin-derived nanoparticles displayed antibiofilm activity. This paper thus reports the synthesis of AgNPs by the biotechnologically important yeast Y. lipolytica; proposes a possible mechanism involved in the synthetic process and describes the use of the bio-inspired nanoparticles as antibiofilm agents.

3, 4-dihydroxy-L-phenylalanine-derived melanin from Yarrowia lipolytica mediates the synthesis of silver and gold nanostructures.

BACKGROUND: Nanobiotechnology applies the capabilities of biological systems in generating a variety of nano-sized structures. Plants, algae, fungi and bacteria are some systems mediating such reactions. In fungi, the synthesis of melanin is an important strategy for cell-survival under metal-stressed conditions. Yarrowia lipolytica, the biotechnologically significant yeast also produces melanin that sequesters heavy metal ions. The content of this cell-associated melanin is often low and precursors such as L-tyrosine or 3, 4-dihydroxy-L-phenylalanine (L-DOPA) can enhance its production. The induced melanin has not been exploited for the synthesis of nanostructures. In this investigation, we have employed L-DOPA-melanin for the facile synthesis of silver and gold nanostructures. The former have been used for the development of anti-fungal paints. METHODS: Yarrowia lipolytica NCIM 3590 cells were incubated with L-DOPA for 18 h and the resultant dark pigment was subjected to physical and chemical analysis. This biopolymer was used as a reducing and stabilizing agent for the synthesis of silver and gold nanostructures. These nanoparticles were characterized by UV-Visible spectra, X-ray diffraction (XRD) studies, and electron microscopy. Silver nanoparticles were evaluated for anti-fungal activity. RESULTS: The pigment isolated from Y. lipolytica was identified as melanin. The induced pigment reduced silver nitrate and chloroauric acid to silver and gold nanostructures, respectively. The silver nanoparticles were smaller in size (7 nm) and displayed excellent anti-fungal properties towards an Aspergillus sp. isolated from a wall surface. An application of these nanoparticles as effective paint-additives has been demonstrated. CONCLUSION: The yeast mediated enhanced production of the metal-ion-reducing pigment, melanin. A simple and rapid method for the extracellular synthesis of nanoparticles with paint-additive-application was developed.