11 research outputs found
Nanoscale-Specific Reaction in a Precursor Film: Mixing Sodium Carbonate, Calcium Chloride, and an Organic Thiol to Produce Crystals of Calcium sulfate
Lipid ratios as a marker for red blood cell storage quality and as a possible explanation for donor gender differences in storage quality
Background and objectives
Red blood cells that are stored for transfusions as red cell concentrates (RCCs) undergo changes during the storage period, culminating in the lysis of the cells. The goal of this work is to find markers that are linked to high haemolysis, in order to explain the inter‐donor variability that is known to occur in storage quality, and also the known differences between RCCs from male and female donors.
Materials and methods
The relative amounts of lipids at the end of the storage period were compared for one group of low haemolysis samples (24 units, all ≤0·15% haemolysis), and one group of high haemolysis samples (26 units, all ≥0·5% haemolysis). Representative lipids were analysed from different lipid classes, including cholesterol, phosphatidylcholine, phosphatidylethanolamine, sphingomyelin and ceramide. Whole membrane preparations were analysed with one mass spectrometry technique, and lipid extracts were analysed with a second mass spectrometry technique.
Results
The ratio of palmitoyl‐oleoyl phosphatidylcholine (POPC) to sphingomyelin was different for the high and low haemolysis groups (P = 0·0001) and for the RCCs from male and female donors (P = 0·0009). The ratio of cholesterol to phospholipids showed only minimal links to haemolysis. Higher relative amounts of sphingomyelin were associated with lower haemolysis, and higher relative amounts of ceramides were associated with increased haemolysis.
Conclusion
The level of sphingomyelinase activity and the resulting ratio of sphingomyelin to POPC is proposed as a possible marker for RCC storage quality
Hemolysis Pathways during Storage of Erythrocytes and Inter-Donor Variability in Erythrocyte Morphology
Cholesterol Organization in Phosphatidylcholine Liposomes: A Surface Plasmon Resonance Study
material
Nanoscale-Specific Reaction in a Precursor Film: Mixing Sodium Carbonate, Calcium Chloride, and an Organic Thiol to Produce Crystals of Calcium sulfate
Poly(dimethylsiloxane)-Coated Sensor Devices for the Formation of Supported Lipid Bilayers and the Subsequent Study of Membrane Interactions
Simultaneous Measurement of Mechanical and Surface Properties in Thermoresponsive, Anchored Hydrogel Films
Hydrogel films have been used extensively in the preparation
of
biosensors and biomedical devices. The characteristics of the aqueous
interface of the polymer layer are significant for the biosensor or
device function; likewise, the changing mechanical properties of thermoresponsive
polymers are an important feature that affects the polymer behavior.
Atomic force microscopy was used here to characterize both the surface
and the mechanical properties of polymeric hydrogel films prepared
from a thermoresponsive terpolymer of <i>N</i>-isopropylacrylamide
and acrylic acid with benzophenonemethacrylate as a photoreactive
cross-linker comonomer. The force–distance curves thus obtained
were analyzed to assess both the surface forces and the mechanical
response that were associated with the hydrogel. These properties
were investigated as a function of temperature, in water and in Tris
buffer, for different degrees of polymer cross-linking. For samples
in water, the distance over which the surface forces were effective
was found to remain constant as the temperature was increased from
26 to 42 °C, even though the mechanical response indicated that
the samples had been heated past the lower critical solution temperature,
or LCST. The bulk of the polymer becomes less soluble above the LCST,
although this does not seem to affect the surface properties. This
may be due to the segregation of the acrylic acid-rich polymer segments
near the gel surface, which is in agreement with reports for related
systems
Chain Length and Grafting Density Dependent Enhancement in the Hydrolysis of Ester-Linked Polymer Brushes
Poly(<i><i>N</i>,<i>N</i></i>-dimethylacrylamide)
(PDMA) brushes with different grafting density and chain length were
grown from an ester group-containing initiator using surface-initiated
polymerization. Hydrolysis of the PDMA chains from the surface was
monitored by measuring thickness of the polymer layer by ellipsometry
and extension length by atomic force microscopy. It was found that
the initial rate of cleavage of one end-tethered PDMA chains was dependent
on the grafting density and chain length; the hydrolysis rate was
faster for high grafting density brushes and brushes with higher molecular
weights. Additionally, the rate of cleavage of polymer chains during
a given experiment changed by up to 1 order of magnitude as the reaction
progressed, with a distinct transition to a lower rate as the grafting
density decreased. Also, polymer chains undergo selective cleavage,
with longer chains in a polydisperse brush being preferentially cleaved
at one stage of the hydrolysis reaction. We suggest that the enhanced
initial hydrolysis rates seen at high grafting densities and high
chain lengths are due to mechanical activation of the ester bond connecting
the polymer chains to the surface in association with high lateral
pressure within the brush. These results have implications for the
preparation of polymers brushes, their stability under harsh conditions,
and the analysis of polymer brushes from partial hydrolysates
Pulse mode shear horizontal-surface acoustic wave (SH-SAW) system for liquid based sensing applications
In this work, we describe a novel pulse mode shear horizontal-surface acoustic wave (SH-SAW) polymer coated biosensor that monitors rapid changes in both amplitude and phase. The SH-SAW sensors were fabricated on 36degrees rotated Y-cut X propagating lithium tantalate (36 YX.LT). The sensitivity of the device to both mass loading and visco-elastic effects may be increased by using a thin guiding layer of cross-linked polymer. Two acoustic modes are excited by the electrodes in this crystalline direction. Metallisation of the propagation path of the 36 YX.LT devices allows the two modes to be discriminated. Successive polymer coatings resulted in the observation of resonant conditions in both modes as the layer thickness was increased. Using the 36 YX.LT devices, we have investigated the application of a novel pulse mode system by sensing a sequence of deposition and removal of a biological layer consisting of vesicles of the phospholipid POPC. A continuous wave system was used to verify the accuracy of the pulse mode system by sensing a series of poly(ethylene glycol) (PEG) solutions. The data clearly demonstrates the ability of the 36 YX.LT pulse mode system to provide rapid measurements of both amplitude and phase for biosensing applications
Quantitative Determination of Size and Shape of Surface-Bound DNA Using an Acoustic Wave Sensor
DNA bending plays a significant role in many biological processes, such as gene regulation, DNA replication, and chromosomal packing. Understanding how such processes take place and how they can, in turn, be regulated by artificial agents for individual oriented therapies is of importance to both biology and medicine. In this work, we describe the application of an acoustic wave device for characterizing the conformation of DNA molecules tethered to the device surface via a biotin-neutravidin interaction. The acoustic energy dissipation per unit mass observed upon DNA binding is directly related to DNA intrinsic viscosity, providing quantitative information on the size and shape of the tethered molecules. The validity of the above approach was verified by showing that the predesigned geometries of model double-stranded and triple-helix DNA molecules could be quantitatively distinguished: the resolution of the acoustic measurements is sufficient to allow discrimination between same size DNA carrying a bent at different positions along the chain. Furthermore, the significance of this analysis to the study of biologically relevant systems is shown during the evaluation of DNA conformational change upon protein (histone) binding