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John L. Brash - One of the best experts on this subject based on the ideXlab platform.
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Polyethylene oxide surfaces of variable chain density by chemisorption of PEO-thiol on gold: adsorption of proteins from plasma studied by radiolabelling and immunoblotting.
Biomaterials, 2005Co-Authors: Larry D. Unsworth, Heather Sheardown, John L. BrashAbstract:Abstract The mechanisms involved in the inhibition of protein adsorption by polyethylene oxide (PEO) are not completely understood, but it is believed that PEO chain length, chain density and chain conformation all play a role. In this work, surfaces formed by chemisorption of PEO-thiol to gold were investigated: the Effects of PEO chain density, chain length (600, 750, 2000 and 5000 MW) and end-group (–OH, –OCH 3 ) on protein adsorption from plasma are reported. Similar to previous single protein adsorption studies (L.D. Unsworth et al., Langmuir 2005;21:1036–41) it was found that, of the different surfaces investigated, PEO layers formed from solutions near the cloud point adsorbed the lowest amount of fibrinogen from plasma. Layers of hydroxyl-terminated PEO of MW 600 formed under these low solubility conditions showed almost complete suppression (versus controls) of the Vroman Effect, with 20±1 ng/cm 2 adsorbed fibrinogen at the Vroman peak and 6.7±0.6 ng/cm 2 at higher plasma concentration. By comparison, Vroman peak adsorption was 70±20 and 50±3 ng/cm 2 , respectively, for 750-OCH 3 and 2000-OCH 3 layers formed under low solubility conditions; adsorption on these surfaces at higher plasma concentration was 16±9 and 12±3 ng/cm 2 . Thus in addition to the Effect of solution conditions noted previously, the results of this study also suggest a chain end group Effect which inhibits fibrinogen adsorption to, and/or facilitates displacement from, hydroxyl terminated PEO layers. Fibrinogen adsorption from plasma was not significantly different for surfaces prepared with PEO of molecular weight 750 and 2000 when the chain density was the same (∼0.5 chains/nm 2 ) supporting the conclusion that chain density may be the key property for suppression of protein adsorption. The proteins eluted from the surfaces after contact with plasma were investigated by SDS-PAGE and immunoblotting. A number of proteins were detected on the various surfaces including fibrinogen, albumin, C3 and apolipoprotein A-I. The blot responses were zero or weak for all four proteins of the contact system; some complement activation was observed on all of the surfaces studied.
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Interaction of IgG and albumin with functionalized silicas
Colloids and Surfaces B: Biointerfaces, 1995Co-Authors: S. Khamlichi, Jacqueline Jozefonvicz, A. Serres, D. Muller, John L. BrashAbstract:Abstract Studies of the adsorption of IgG and albumin to modified silica particles are reported. The silica particles were functionalized with so-called thiophilic and other groups designed to promote the specific adsorption of IgG according to Oscarrson and Porath, (in T.T. Ngo (Ed.), Molecular Interactions in Bioseparations, Plenum, New York, 1993, pp. 403–414). Porous silica beads were first coated with dextran which had been substituted with a calculated amount of positively charged diethylaminoethyl (DEAE) functions. This treatment was designed to “passivate” the silica, i.e. to minimize nonspecific protein adsorption via the silanol groups. The DEAE-dextran coated silica was functionalized with 2-mercaptoethanol via the coupling agent divinylsulfone. This treatment provides the thiophilic groups of Oscarrson and Porath. Ligands consisting of cysteine methyl ester and divinylsulfone residues were also coupled to the passivated silica to provide related chemical functions. The adsorption isotherms of human IgG to these materials from buffer were determined. All the functionalized materials showed an increase in adsorption of IgG in comparison with the passivated silica. The apparent affinities of the functionalized materials for IgG binding were all similar, thus demonstrating the importance of the sulfone group in the so-called thiophilic interaction. The adsorption of IgG from serum onto the functionalized materials showed the same specificity of IgG for these materials but the amounts of adsorbed IgG were lower than from buffer, indicating that other proteins in serum compete with IgG. IgG adsorption from serum also showed the Vroman Effect, i.e. a maximum in adsorption as a function of serum dilution, indicating that initially adsorbed IgG is displaced by proteins of higher affinity. Human albumin adsorption from buffer showed an increase compared to the control surface on only one of the functionalized materials, i.e. the thiophilic material. Of the three derivatized materials, the cysteine methyl ester material shows the greatest binding capacity for IgG both from buffer and serum, and essentially no specificity for albumin binding. It would thus probably be the most Effective of the materials studied for chromatography of IgG.
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Interactions of plasminogen and fibrinogen with model silica glass surfaces: adsorption from plasma and enzymatic activity studies.
Journal of biomedical materials research, 1994Co-Authors: K.a. Woodhouse, Jeff Weitz, John L. BrashAbstract:The adsorption of fibrinogen and plasminogen from plasma to silica glass, sulfonated silica glass, and lysinederivatized silica glass has been investigated. The data indicate that the sulfonated material has a high affinity for both fibrinogen and plasminogen, but that the ratio of plasminogen to fibrinogen is greater on the lysinederivatized surface. The adsorption data also suggest plasminogen as a possible contributor to the fibrinogen Vroman Effect, whereby initially adsorbed fibrinogen is displaced from the surface. The plasmin activity of plasminogen adsorbed to the lysine-derivatized silica glass and its sulfonated precursor was assessed by both a chromogenic substrate assay and a radioimmunoassay for the plasmin cleavage product of fibrinogen, the Bβ 1–42 peptide. The data indicate that (1) the adsorbed plasminogen is not inherently plasmin-like; (2) the enzymatic activity associated with the bound plasminogen is significantly enhanced on both surfaces in the presence of activator; and (3) in the presence of activator, the plasmin activity per mole of bound plasminogen on the lysinized material is approximately a factor of two greater than on the sulfonated material based on the chromogenic substrate assay, and a factor of four greater based on the Bβ 1–42 radioimmunoassay. The lysinized material thus exhibits several properties that are different from its sulfonated precursor. It adsorbs more plasminogen relative to fibrinogen after the Vroman peak, and this adsorbed plasminogen appears to be in a conformation that is more readily activated to plasmin. Once activated, the surface bound plasmin shows enhanced ability to cleave either a low molecular weight chromogenic substrate or a macromolecular substrate. These properties appear to be directly related to lysine residues on the surface and may be the result of specific conformational changes occurring when plasminogen engages its lysine binding sites. © 1994 John Wiley & Sons, Inc.
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Fibrinogen and albumin adsorption from human blood plasma and from buffer onto chemically functionalized silica substrates
Colloids and Surfaces B: Biointerfaces, 1993Co-Authors: P.w Wojciechowski, John L. BrashAbstract:Abstract Monolayers of silanes having a variety of chemical functionality were attached to pure silica tubes or plates. These model surfaces were characterized by X-ray photoelectron spectroscopy and advancing water contact angles. The adsorption of albumin and fibrinogen to these surfaces was studied using the radioiodinated proteins. In single protein systems neither albumin nor fibrinogen adsorption was found to be strongly correlated with wettability, although a slight increase in initial rate of adsorption with increasing wettability was noted. Fibrinogen adsorption was most strongly correlated with surface chemistry such that the presence of sulfur coincided with increased adsorption and nitrogen with decreased adsorption. Fibrinogen adsorption from blood plasma exhibited the Vroman Effect to varying extents, and was found to be directly correlated with adsorption from buffer on most surfaces. On those surfaces which suppressed the Vroman Effect, both sulfonate and amine groups were present.
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Protein adsorption studies on 'standard' polymeric materials.
Journal of biomaterials science. Polymer edition, 1993Co-Authors: John L. Brash, P. Ten HoveAbstract:Adsorption of fibrinogen from buffer as a single protein and from plasma to four materials has been studied. The two NIH-NHLBI primary reference standards, filler free polydimethylsiloxane and low density polyethylene, were used along with polyvinylcholoride and cellulose materials supplied by the IUPAC Working Party. The materials were examined in both film and tubing form, except for polydimethylsiloxane which was studied only in tubing form. Adsorption was measured at room temperature using 125I-labelled fibrinogen. The order of adsorbed amounts in the single protein experiments was found to be: cellulose < PVC < PE = PDMS. Apparent adsorption affinities are in the same order. In plasma, all surfaces except cellulose showed maxima in adsorption as a function of plasma concentration after 5 min contact. This is indicative of initial adsorption followed by displacement of fibrinogen (the Vroman Effect). Cellulose showed very low adsorption of fibrinogen from plasma. The Vroman maxima were more pronounced on the tubing samples than on the films, and, as for the single protein experiments, adsorption was found to be less on tubing than on film samples. A tentative interpretation of the Vroman Effect data suggests that the order of procoagulant activity of the materials may be: PDMS = PE < PVC < cellulose.
Junseok Chae - One of the best experts on this subject based on the ideXlab platform.
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Probing thyroglobulin in undiluted human serum based on pattern recognition and competitive adsorption of proteins
Applied Physics Letters, 2014Co-Authors: Ran Wang, Shuai Huang, Junseok ChaeAbstract:Thyroglobulin (Tg) is a sensitive indicator of persistent or recurrent differentiated thyroid cancer of follicular cell origin. Detection of Tg in human serum is challenging as bio-receptors, such as anti-Tg, used in immunoassay have relatively weak binding affinity. We engineer sensing surfaces using the competitive adsorption of proteins, termed the Vroman Effect. Coupled with Surface Plasmon Resonance, the “cross-responsive” interactions of Tg on the engineered surfaces produce uniquely distinguishable multiple signature patterns, which are discriminated using Linear Discriminant Analysis. Tg-spiked samples, down to 2 ng/ml Tg in undiluted human serum, are sensitively and selectively discriminated from the control (undiluted human serum).
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detection of copper ions in drinking water using the competitive adsorption of proteins
Biosensors and Bioelectronics, 2014Co-Authors: Ran Wang, Wei Wang, Junseok ChaeAbstract:Abstract Heavy metal ions, i.e., Cu 2+ , are harmful to the environment and our health. In order to detect them, and circumvent or alleviate the weaknesses of existing detecting technologies, we contrive a unique Surface Plasmon Resonance (SPR) biosensor combined with competitive adsorption of proteins, termed the Vroman Effect. This approach adopts native proteins (albumin) as bio-receptors that interact with Cu 2+ to be denatured. Denaturation disrupts the conformation of albumin so that it weakens its affinity to adsorb on the sensing surface. Through the competitive adsorption between the denatured albumins and the native ones, the displacement occurs adjacent to the sensing surface, and this process is real-time monitored by SPR, a surface-sensitive label-free biosensor. The affinities of native albumin is significantly higher than that of denatured albumin, demonstrated by measured K D of native and denatured albumin to gold surafce, 5.8±0.2×10 −5 M and 5.4±0.1×10 −4 M, respectively. Using our biosensor, Cu 2+ with concentration down to 0.1 mg/L is detected in PBS, tap water, deionized water, and bottled water. The SPR biosensor is characterized for 5 different heavy metal ions, Cu 2+ , Fe 3+ , Mn 2+ , Pb 2+ , and Hg 2+ , most common heavy metal ions found in tap water. At the maximum contaminant level (MCL) suggested by the United States Environmental Protection Agency (EPA), the SPR biosensor produces 13.5±0.4, 1.5±0.4, 0, 0, and 0 mDeg, respectively, suggesting the biosensor may be used to detect Cu 2+ in tap water samples.
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A High-Quality-Factor Film Bulk Acoustic Resonator in Liquid for Biosensing Applications
Journal of Microelectromechanical Systems, 2011Co-Authors: Xu Zhang, Seokheun Choi, Junseok ChaeAbstract:We report a high-quality-factor (Q) film bulk acoustic resonator (FBAR) operating in liquid environments. By integrating a microfluidic channel to a longitudinal-mode FBAR, a Q of up to 150 is achieved with direct liquid contacting. A transmission line model is used to theoretically predict the Q behavior of the FBAR. The model suggests an oscillatory pattern of Q as a function of the channel thickness and the acoustic wavelength in the liquid, which is experimentally verified by precisely controlling the channel thickness. This FBAR biosensor is characterized in liquids for the real-time in situ monitoring of the competitive adsorption/exchange of proteins, the Vroman Effect. The FBAR offers a minimum detectable mass of 1.35 ng/cm2 and is successfully implemented in a Pierce oscillator as a portable sensing module.
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Characterization of a high-Q in-liquid longitudinal-mode film bulk acoustic resonator for real-time in-situ monitoring of competitive protein adsorption
2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010Co-Authors: Seokheun Choi, Wencheng Xu, Xu Zhang, Junseok ChaeAbstract:We report the characterization results of in-liquid longitudinal-mode FBAR (L-FBAR) for real-time in-situ monitoring of the Vroman Effect, a competitive adsorption and exchange of proteins on a surface. The change of resonant frequency of the L-FBAR, ~1.55 GHz, is a direct function of the proteins' molecular weight, and thus we monitor the resonant frequency shifts to estimate the adsorption and exchange behavior. A low molecular weight (LMW) protein, albumin, initially covers the surface and is displaced by a high molecular weight (HMW) protein, IgG; sequentially, the highest molecular weight protein, fibrinogen displaces IgG. However, the reverse sequence does not occur.
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Thyroglobulin detection using competitive protein adsorption
2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010Co-Authors: Seokheun Choi, Junseok ChaeAbstract:We report a unique sensing mechanism based on competitive proteins' adsorption/exchange reaction, namely Vroman Effect, for detecting a cancer biomarker, thyroglobulin (Tg). Implemented in a microfluidic system, the target protein, Tg, displaces a pre-adsorbed weak-affinity protein, IgG, on one surface, while a pre-adsorbed strong-affinity protein, fibrinogen, is not displaced by Tg on the other surface. Differential measurement using SPR (Surface Plasmon Resonance) allows the detection of Tg; the SPR angle changes offer a quantitative analysis of concentration of Tg in a sample. Using this technique, we demonstrate the selective detection of Tg in a protein mixture of albumin, haptoglobin, IgG and Tg.
Agneta Askendal - One of the best experts on this subject based on the ideXlab platform.
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Lens-on-surface method for investigating adhesion of Staphylococcus aureus to solid surfaces incubated in blood plasma.
Journal of Biomedical Materials Research, 1994Co-Authors: Hans Elwing, Agneta AskendalAbstract:Adhesion of Staphylococcus aureus was investigated on flat silicon oxide surfaces that had been incubated in human plasma at different concentrations. Adhesion of bacteria did not occur at high incubation concentrations of plasma or when the surface had been incubated in egg albumin. However, significant adhesion was observed when plasma was diluted. With the use of antibody method, it was noted that the adhesion of the bacteria coincided with adsorbed fibrinogen, and possibly also with IgG. We also investigated the Effect of "narrow space" on the adsorption of blood plasma and subsequent adhesion of S. aureus. In these experiments, blood plasma was incubated under a convex lens placed upside-down on the silicon oxide surface. This method creates a continuous gradient of space from the contact point of the lens and outward. After rinsing off the plasma and the lens, the surface was incubated with a suspension of S. aureus followed by quantification of the attached bacteria by means of optical methods. Adhesion of bacteria occurred in several circular zones that were easily detectable with the naked eye or by the means of simple optical methods. In addition, in these experiments, adhesion coincided with adsorbed fibrinogen or IgG at the surfaces. The increased bacterial adhesion to surfaces incubated in diluted plasma, or plasma incubated in narrow space, is a variant of the so-called "Vroman Effect." With a model protein system consisting of fibrinogen and IgG and the corresponding antibodies, we demonstrate that "dilution" and "incubation in narrow space" are two phenomenologically similar methods.(ABSTRACT TRUNCATED AT 250 WORDS)
Seokheun Choi - One of the best experts on this subject based on the ideXlab platform.
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A High-Quality-Factor Film Bulk Acoustic Resonator in Liquid for Biosensing Applications
Journal of Microelectromechanical Systems, 2011Co-Authors: Xu Zhang, Seokheun Choi, Junseok ChaeAbstract:We report a high-quality-factor (Q) film bulk acoustic resonator (FBAR) operating in liquid environments. By integrating a microfluidic channel to a longitudinal-mode FBAR, a Q of up to 150 is achieved with direct liquid contacting. A transmission line model is used to theoretically predict the Q behavior of the FBAR. The model suggests an oscillatory pattern of Q as a function of the channel thickness and the acoustic wavelength in the liquid, which is experimentally verified by precisely controlling the channel thickness. This FBAR biosensor is characterized in liquids for the real-time in situ monitoring of the competitive adsorption/exchange of proteins, the Vroman Effect. The FBAR offers a minimum detectable mass of 1.35 ng/cm2 and is successfully implemented in a Pierce oscillator as a portable sensing module.
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Characterization of a high-Q in-liquid longitudinal-mode film bulk acoustic resonator for real-time in-situ monitoring of competitive protein adsorption
2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010Co-Authors: Seokheun Choi, Wencheng Xu, Xu Zhang, Junseok ChaeAbstract:We report the characterization results of in-liquid longitudinal-mode FBAR (L-FBAR) for real-time in-situ monitoring of the Vroman Effect, a competitive adsorption and exchange of proteins on a surface. The change of resonant frequency of the L-FBAR, ~1.55 GHz, is a direct function of the proteins' molecular weight, and thus we monitor the resonant frequency shifts to estimate the adsorption and exchange behavior. A low molecular weight (LMW) protein, albumin, initially covers the surface and is displaced by a high molecular weight (HMW) protein, IgG; sequentially, the highest molecular weight protein, fibrinogen displaces IgG. However, the reverse sequence does not occur.
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Thyroglobulin detection using competitive protein adsorption
2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010Co-Authors: Seokheun Choi, Junseok ChaeAbstract:We report a unique sensing mechanism based on competitive proteins' adsorption/exchange reaction, namely Vroman Effect, for detecting a cancer biomarker, thyroglobulin (Tg). Implemented in a microfluidic system, the target protein, Tg, displaces a pre-adsorbed weak-affinity protein, IgG, on one surface, while a pre-adsorbed strong-affinity protein, fibrinogen, is not displaced by Tg on the other surface. Differential measurement using SPR (Surface Plasmon Resonance) allows the detection of Tg; the SPR angle changes offer a quantitative analysis of concentration of Tg in a sample. Using this technique, we demonstrate the selective detection of Tg in a protein mixture of albumin, haptoglobin, IgG and Tg.
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Surface plasmon resonance biosensor based on Vroman Effect : Towards cancer biomarker detection
2009 IEEE 15th International Mixed-Signals Sensors and Systems Test Workshop, 2009Co-Authors: Seokheun Choi, Junseok ChaeAbstract:We report a new sensing technique of proteins using the Vroman Effect in a microfluidic device. The sensor relies on the competitive nature of protein adsorption onto a surface, directly depending upon protein's adsorption strength. The sensor uses SPR (surface plasmon resonance) for highly sensitive biomolecular interactions detection and the Vroman Effect for highly selective detection. A target protein displaces a pre-adsorbed weak-affinity protein; however a pre-adsorbed strong-affinity protein is not displaced by the target protein. In a microfluidic device, we engineer two gold surfaces covered by two known proteins. The sensor allows selective protein detection by being displaced by a target protein on only one of the surfaces. The SPR sensorgrams show that four different human serum proteins, albumin (Alb), immunoglobulin G (IgG), fibrinogen (Fib), and thyroglobulin (Tg) have different adsorption strengths to the surface and the competitive adsorption of individuals controls the exchange sequence. Based on the exchange reaction, we demonstrate that the sensor has a high selectivity for Tg which is a thyroid cancer biomarker. By using the technique, we bypass having to rely on bio-receptors and their attachment to transducers, a process known to be complex and time-consuming.
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Surface plasmon resonance protein sensor using Vroman Effect.
Biosensors & bioelectronics, 2008Co-Authors: Seokheun Choi, Yongmo Yang, Junseok ChaeAbstract:We report a new surface plasmon resonance (SPR) protein sensor using the Vroman Effect for real-time, sensitive and selective detection of protein. The sensor relies on the competitive nature of protein adsorption onto the surface, directly depending upon protein's molecular weight. The sensor uses SPR for highly sensitive biomolecular interactions detection and the Vroman Effect for highly selective detection. By using the Vroman Effect we bypass having to rely on bio-receptors and their attachment to transducers, a process known to be complex and time-consuming. The protein sensor is microfabricated to perform real-time protein detection using four different proteins including aprotinin (0.65 kDa), lysozyme (14.7 kDa), streptavidine (53 kDa), and isolectin (114 kDa) on three different surfaces, namely a bare-gold surface and two others modified by OH- and COOH-terminated self-assembled monolayer (SAM). The real-time adsorption and displacement of the proteins are observed by SPR and evaluated using an atomic force microscope (AFM). The sensor can distinguish proteins of at least 14.05 kDa in molecular weight and demonstrate a very low false positive rate. The protein detector can be integrated with microfluidic systems to provide extremely sensitive and selective analytical capability.
K.a. Woodhouse - One of the best experts on this subject based on the ideXlab platform.
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Interactions of plasminogen and fibrinogen with model silica glass surfaces: adsorption from plasma and enzymatic activity studies.
Journal of biomedical materials research, 1994Co-Authors: K.a. Woodhouse, Jeff Weitz, John L. BrashAbstract:The adsorption of fibrinogen and plasminogen from plasma to silica glass, sulfonated silica glass, and lysinederivatized silica glass has been investigated. The data indicate that the sulfonated material has a high affinity for both fibrinogen and plasminogen, but that the ratio of plasminogen to fibrinogen is greater on the lysinederivatized surface. The adsorption data also suggest plasminogen as a possible contributor to the fibrinogen Vroman Effect, whereby initially adsorbed fibrinogen is displaced from the surface. The plasmin activity of plasminogen adsorbed to the lysine-derivatized silica glass and its sulfonated precursor was assessed by both a chromogenic substrate assay and a radioimmunoassay for the plasmin cleavage product of fibrinogen, the Bβ 1–42 peptide. The data indicate that (1) the adsorbed plasminogen is not inherently plasmin-like; (2) the enzymatic activity associated with the bound plasminogen is significantly enhanced on both surfaces in the presence of activator; and (3) in the presence of activator, the plasmin activity per mole of bound plasminogen on the lysinized material is approximately a factor of two greater than on the sulfonated material based on the chromogenic substrate assay, and a factor of four greater based on the Bβ 1–42 radioimmunoassay. The lysinized material thus exhibits several properties that are different from its sulfonated precursor. It adsorbs more plasminogen relative to fibrinogen after the Vroman peak, and this adsorbed plasminogen appears to be in a conformation that is more readily activated to plasmin. Once activated, the surface bound plasmin shows enhanced ability to cleave either a low molecular weight chromogenic substrate or a macromolecular substrate. These properties appear to be directly related to lysine residues on the surface and may be the result of specific conformational changes occurring when plasminogen engages its lysine binding sites. © 1994 John Wiley & Sons, Inc.
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Adsorption of plasminogen from plasma to lysine-derivatized polyurethane surfaces.
Biomaterials, 1992Co-Authors: K.a. Woodhouse, John L. BrashAbstract:Abstract The adsorption of plasminogen, the principal protein of the fibrinolytic pathway in blood, to a number of solid surfaces from plasma was investigated. This study forms part of a larger project to develop a fibrinolytic surface for blood-contacting applications. Polyurethanes incorporating lysine residues were developed in an attempt to promote selective adsorption of plasminogen from plasma through lysine-binding sites in the plasminogen molecule. The adsorption of plasminogen to these surfaces as well as to glass, ‘conventional’ polyurethanes and precursor sulphonated polyurethanes was investigated. Adsorption from citrated human plasma diluted with isotonic Tris buffer (pH 7.4) was measured under static conditions at room temperature using radioiodinated plasminogen. The following trends were observed. (1) Adsorption increases monotonically with increasing plasma concentration and there is no suggestion of transient adsorption (Vroman Effect) on any of the surfaces studied. (2) Sulphonate groups appear to have a strong Effect on plasminogen adsorption as was found previously for adsorption from buffer. (3) The lysine-derivatized material having the highest lysine content may show a slight increase in plasminogen binding affinity compared to its sulphonated precursor.
