We review a powerful regularization method, known as CONTIN, for obtaining the size distribution of colloidal suspensions from dynamic light scattering data. We show that together with the so-called ...L-curve criterion for selecting the optimal regularization parameter, the method correctly describes the average size and size distribution of microgel suspensions independently characterized using small-angle neutron scattering. In contrast, we find that when using the default regularization process, where the regularizer is selected via the "probability to reject" method, the results are not as satisfactory.
We study ionic microgel suspensions composed of swollen particles for various single-particle stiffnesses. We measure the osmotic pressure π of these suspensions and show that it is dominated by the ...contribution of free ions in solution. As this ionic osmotic pressure depends on the volume fraction of the suspension ϕ, we can determine ϕ from π, even at volume fractions so high that the microgel particles are compressed. We find that the width of the fluid-solid phase coexistence, measured using ϕ, is larger than its hard-sphere value for the stiffer microgels that we study and progressively decreases for softer microgels. For sufficiently soft microgels, the suspensions are fluidlike, irrespective of volume fraction. By calculating the dependence on ϕ of the mean volume of a microgel particle, we show that the behavior of the phase-coexistence width correlates with whether or not the microgel particles are compressed at the volume fractions corresponding to fluid-solid phase coexistence.
Label-Free Biosensing with Hydrogel Microlenses Kim, Jongseong; Singh, Neetu; Lyon, L. Andrew
Angewandte Chemie (International ed.),
February 20, 2006, Letnik:
45, Številka:
9
Journal Article
Recenzirano
Soft lenses: Reversible antibody–antigen cross‐links at the surface of a hydrogel microlens allow focal tuning of the microlens in response to soluble antigens (see picture; PBS=phosphate‐buffered ...saline) to form the basis of a label‐free biosensor/bioassay technique, whose sensitivity can be tuned by controlling the number of cross‐links required to effect a specific swelling response.
We investigate the phase behavior of suspensions of poly(N-isopropylacrylamide) (pNIPAM) microgels with either bimodal or polydisperse size distribution. We observe a shift of the fluid-crystal ...transition to higher concentrations depending on the polydispersity or the fraction of large particles in suspension. Crystallization is observed up to polydispersities as high as 18.5%, and up to a number fraction of large particles of 29% in bidisperse suspensions. The crystal structure is random hexagonal close-packed as in monodisperse pNIPAM microgel suspensions. We explain our experimental results by considering the effect of bound counterions. Above a critical particle concentration, these cause deswelling of the largest microgels, which are the softest, changing the size distribution of the suspension and enabling crystal formation in conditions where incompressible particles would not crystallize.
We describe a touchscreen method that satisfies a proposed ‘wish-list’ of desirables for a cognitive testing method for assessing rodent models of schizophrenia. A number of tests relevant to ...schizophrenia research are described which are currently being developed and validated using this method. These tests can be used to study reward learning, memory, perceptual discrimination, object-place associative learning, attention, impulsivity, compulsivity, extinction, simple Pavlovian conditioning, and other constructs. The tests can be deployed using a ‘flexible battery’ approach to establish a cognitive profile for a particular mouse or rat model. We have found these tests to be capable of detecting not just impairments in function, but enhancements as well, which is essential for testing putative cognitive therapies. New tests are being continuously developed, many of which may prove particularly valuable for schizophrenia research.
This article is part of a Special Issue entitled ‘Schizophrenia’.
► We describe a touchscreen method for assaying cognition in rodent models. ► A number of tests relevant to schizophrenia research are described. ► The tests can be used to study multiple aspects of cognition. ► The tests can be combined in a flexible battery to establish a cognitive profile. ► The tests are capable of detecting both impairments and enhancements in function.
Surface plasmon resonance (SPR) biosensing using colloidal Au enhancement is reported. Immobilization of ∼11-nm-diameter colloidal Au to an evaporated Au film results in a large shift in plasmon ...angle, a broadened plasmon resonance, and an increase in minimum reflectance. The incorporation of colloidal Au into SPR biosensing results in increased SPR sensitivity to protein−protein interactions when a Au film-immobilized antibody and an antigen−colloidal Au conjugate comprise the binding pair. A highly specific particle-enhanced analogue of a sandwich immunoassay is also demonstrated by complexing the Au particle to a secondary antibody. A tremendous signal amplification is observed, as addition of the antibody−Au colloid conjugate results in a 25-fold larger signal than that due to addition of a free antibody solution that is 6 orders of magnitude more concentrated. Picomolar detection of human immunoglobulin G has been realized using particle enhancement, with the theoretical limits for the technique being much lower. Finally, a quasi-linear relationship between particle coverage and plasmon angle shift is presented, thereby providing for a direct correlation between plasmon shift and solution antigen concentration. Together, these results represent significant advances in the generality and sensitivity of SPR as it is applied to biosensing.
Background Previous studies have demonstrated an association between hyperoxia and increased mortality in various patient groups. Critically unwell and injured patients are routinely given high ...concentration oxygen in the pre-hospital phase of care. We aim to investigate the incidence of hyperoxia in major trauma patients receiving pre-hospital emergency anesthesia (PHEA) in the pre-hospital setting and determine factors that may help guide clinicians with pre-hospital oxygen administration in these patients. Methods A retrospective cohort study was performed of all patients who received PHEA by a single helicopter emergency medical service (HEMS) between 1 October 2014 and 1 May 2019 and who were subsequently transferred to one major trauma centre (MTC). Patient and treatment factors were collected from the electronic patient records of the HEMS service and the MTC. Hyperoxia was defined as a PaO.sub.2 > 16 kPA on the first arterial blood gas analysis upon arrival in the MTC. Results On arrival in the MTC, the majority of the patients (90/147, 61.2%) had severe hyperoxia, whereas 30 patients (20.4%) had mild hyperoxia and 26 patients (19.7%) had normoxia. Only 1 patient (0.7%) had hypoxia. The median PaO.sub.2 on the first arterial blood gas analysis (ABGA) after HEMS handover was 36.7 IQR 18.5-52.2 kPa, with a range of 7.0-86.0 kPa. SpO.sub.2 pulse oximetry readings before handover were independently associated with the presence of hyperoxia. An SpO.sub.2 greater than or equai to 97% was associated with a significantly increased odds of hyperoxia (OR 3.99 1.58-10.08), and had a sensitivity of 86.7% 79.1-92.4, a specificity of 37.9% 20.7-57.8, a positive predictive value of 84.5% 70.2-87.9 and a negative predictive value of 42.3% 27.4-58.7 for the presence of hyperoxemia. Conclusion Trauma patients who have undergone PHEA often have profound hyperoxemia upon arrival at hospital. In the pre-hospital setting, where arterial blood gas analysis is not readily available a titrated approach to oxygen therapy should be considered to reduce the incidence of potentially harmful tissue hyperoxia. Keywords: Hyperoxia, Hyperoxemia, Ventilation, Trauma, Emergency medical services, Oxygen therapy, Pre-hospital anesthesia
Thermoresponsive, core−shell poly-N-isopropylacrylamide (p-NIPAm) nanoparticles (microgels) have been synthesized by seed and feed precipitation polymerization, and the influence of chemical ...differentiation between the core and shell polymers on the phase transition kinetics and thermodynamics has been examined. The results suggest that the core−shell architecture is a powerful one for the design of colloidal “smart gels” with tunable properties. To examine these materials, differential scanning calorimetry (DSC), 1H NMR, and temperature-programmed photon correlation spectroscopy (TP-PCS) have been employed. These measurements show that the addition of small concentrations of a hydrophobic monomer (butyl methacrylate, BMA) into the particle shell produces large decreases in the rate of thermo-induced particle collapse. Conversely, these low levels of hydrophobic modification do not perturb the thermodynamics of the particle phase transition. When these results are examined in light of previous studies of macroscopic hydrogels, they suggest that the formation of a thin, stable skin layer at the particle exterior during the early stages of particle collapse is the rate limiting factor in particle deswelling. Finally, the hydrophobicity (BMA content) of the shell determines the magnitude of the hydrogel collapse rate, while the thickness of the BMA containing region does not impact the observed kinetics. Together, these results suggest that control over the kinetics of microgel deswelling events can be accomplished simply by modification of the particle periphery, and therefore do not require homogeneous modification of the entire polymer structure.
Soft Nanotechnology with Soft Nanoparticles Nayak, Satish; Lyon, L. Andrew
Angewandte Chemie (International ed.),
December 2, 2005, Letnik:
44, Številka:
47
Journal Article
Recenzirano
The last decade of research in the physical sciences has seen a dramatic increase in the study of nanoscale materials. Today, “nanoscience” has emerged as a multidisciplinary effort, wherein ...obtaining a fundamental understanding of the optical, electrical, magnetic, and mechanical properties of nanostructures promises to deliver the next generation of functional materials for a wide range of applications. While this range of efforts is extremely broad, much of the work has focused on “hard” materials, such as Buckyballs, carbon nanotubes, metals, semiconductors, and organic or inorganic dielectrics. Meanwhile, the soft materials of current interest typically include conducting or emissive polymers for “plastic electronics” applications. Despite the continued interest in these established areas of nanoscience, new classes of soft nanomaterials are being developed from more traditional polymeric constructs. Specifically, nanostructured hydrogels are emerging as a promising group of materials for multiple biotechnology applications as the need for advanced materials in the post‐genomic era grows. This review will present some of the recent advances in the marriage between water‐swellable networks and nanoscience.
A swell idea: Research on hydrogel nanoparticles confirms the huge application potential of soft nanomaterials. Such nanoparticles can be made to swell and contract in response to changes in their environment. They could find uses as bioresponsive sensors, drug‐delivery systems, implantable biomaterials, biotesting, and targetable chemotherapy agents. The picture shows HeLa cells containing core–shell nanoparticles as fluorescent markers.
An analytical benchmark for high-sensitivity cardiac troponin (hs-cTn) assays is to achieve a coefficient of variation (CV) of ≤ 10.0 % at the 99th percentile upper reference limit (URL) used for the ...diagnosis of myocardial infarction. Few prospective multicenter studies have evaluated assay imprecision and none have determined precision at the female URL which is lower than the male URL for all cardiac troponin assays.
Human serum and plasma matrix samples were constructed to yield hs-cTn concentrations near the female URLs for the Abbott, Beckman, Roche, and Siemens hs-cTn assays. These materials were sent (on dry ice) to 35 Canadian hospital laboratories (n = 64 instruments evaluated) participating in a larger clinical trial, with instructions for storage, handling, and monthly testing over one year. The mean concentration, standard deviation, and CV for each instrument type and an overall pooled CV for each manufacturer were calculated.
The CVs for all individual instruments and overall were ≤ 10.0 % for two manufacturers (Abbott CVpooled = 6.3 % and Beckman CVpooled = 7.0 %). One of four Siemens Atellica instruments yielded a CV > 10.0 % (CVpooled = 7.7 %), whereas 15 of 41 Roche instruments yielded CVs > 10.0 % at the female URL of 9 ng/L used worldwide (6 cobas e411, 1 cobas e601, 4 cobas e602, and 4 cobas e801) (CVpooled = 11.7 %). Four Roche instruments also yielded CVs > 10.0 % near the female URL of 14 ng/L used in the United States (CVpooled = 8.5 %).
The number of instruments achieving a CV ≤ 10.0 % at the female 99th-percentile URL varies by manufacturer and by instrument. Monitoring assay precision at the female URL is necessary for some assays to ensure optimal use of this threshold in clinical practice.
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