Biomedical subjects

B Lassen

Publications and source records attributed to B Lassen.

7 recordsLinked to original sources

PubMed1997

Sequential Adsorption of Human Serum Albumin (HSA), Immunoglobulin G (IgG), and Fibrinogen (Fgn) at HMDSO Plasma Polymer Surfaces

The sequential adsorption of human serum albumin (HSA), immunoglobulin G (IgG), and fibrinogen (Fgn) at hexamethyldisiloxane (HMDSO) plasma polymer surfaces was investigated with ellipsometry and total internal reflection fluorescence spectroscopy (TIRF) as a function of adsorption time, pH, and excess electrolyte concentration. HSA was found to self-exchange very slowly ( approximately hours) at pH 7.2, irrespective of adsorption time in the range 90 s to 90 min. Preadsorbed HSA was exchanged by Fgn and IgG only to a limited extent irrespectively of pH (5 </= pH </= 8) and excess electrolyte concentration (5 mM </= Cs </= 150 mM). At an excess electrolyte concentration of 150 mM, the sequential adsorption of Fgn and IgG was dramatically reduced by HSA preadsorption, irrespective of pH. At an excess electrolyte concentration of 5 mM, on the other hand, there were indications of second-layer adsorption of Fgn and IgG. Copyright 1997Academic Press

Journal Article↗

PubMed1997

Competitive Protein Adsorption at Plasma Polymer Surfaces

Competitive adsorption from a ternary mixture of human serum albumin (HSA), human IgG, and human fibrinogen (Fgn) at concentrations corresponding to blood plasma diluted 1/100 was investigated with the combination of Total Internal Reflection Fluorescence spectroscopy (TIRF) and ellipsometry. As substrates, three different plasma polymer surfaces, representing different surface charge and surface energy, were prepared from hexamethyldisiloxane (PP-HMDSO), acrylic acid (PP-AA), and 1,2-diaminocyclohexane (PP-DACH). In addition, adsorption from single and binary protein systems was investigated with ellipsometry. At the hydrophobic PP-HMDSO little or no displacement of any of the proteins was observed. The adsorbed layer was dominated by HSA and IgG, although Fgn was also present to a smaller extent. On PP-DACH and PP-AA, representing positively and negatively charged hydrophilic surfaces, respectively, Fgn completely dominated the adsorbed layer while HSA was almost absent and IgG was present only at a very low level.

Journal Article↗

PubMed1996

Effects of Hydrophilization and Immobilization on the Interfacial Behavior of Immunoglobulins.

The adsorption and immobilization of rabbit anti-human immunoglobulin (rabbit IgG), as well as the effects of rinsing with buffer and addition of bovine serum albumin (BSA) or human IgG on the amount and reactivity of bound rabbit IgG, were investigated with ellipsometry, total internal reflection fluorescence spectroscopy (TIRF), and enzyme immuno assay (EIA). It was found that although rabbit IgG readily adsorbs at hydrophobic hexamethyldisiloxane (HMDSO) plasma polymer surfaces, a substantial fraction of the adsorbed protein molecules is desorbed upon rinsing with buffer. BSA was found to adsorb readily at the surfaces obtained after rinsing, although also this protein desorbed to a large extent (about 60%) upon further rinsing with buffer. The adsorption of BSA causes a further reduction in the amount of rabbit IgG adsorbed. Immobilization of rabbit IgG to acrylic acid (AA) plasma polymer surfaces, achieved by covalent coupling via a strongly adsorbed PEG-PEI copolymer, was found to overcome the problem of the desorption of rabbit IgG upon rinsing with buffer or addition of BSA. Furthermore, nonspecific adsorption was virtually absent after immobilization. However, covalently bound rabbit IgG reacted strongly with human IgG, as observed by ellipsometry, TIRF, and EIA. The immobilization of rabbit IgG to hydrophilized surfaces was found to facilitate the interpretation of EIA results.

Journal Article↗

PubMed1996

Transporting.

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Ambulances↗

PubMed1994

Adsorption of fibrinogen and some other proteins from blood plasma at a variety of solid surfaces.

Enzyme linked immunosorbent assay (ELISA) was used for the estimation of protein adsorption from blood plasma at some model solid surfaces. The majority of those surfaces were made in the wells of microtiterplates of polystyrene commonly used for ELISA purposes. Three of the model surfaces were made by radio frequency plasma discharge polymerization (RFPD) of the microtiterplates of polystyrene. The monomers we used were diaminocyclohexane, hexamethylenedisiloxane, and acrylic acid. Other surfaces investigated were: unmodified polystyrene, oxidized polystyrene, hydrophilic silicon oxide, and methylized silicon oxide. Two substances, Tween and bovine serum albumin (BSA), for the prevention of unintended adsorption of ELISA conjugate were also tested and the BSA method was found to be superior for this kind of investigation. Human blood plasma at different dilutions was incubated in the surface-modified microtiterplates followed by incubation of rabbit antibodies against fibrinogen (FG), fibronectin (FN), human serum albumin (HSA), complement factor 3 (C3), and immunoglobulin G (IgG). Visualization of bound antibodies was then made by standard ELISA procedure. At low blood plasma concentrations (plasma dil 1/1000), anti-IgG and anti-HSA were detected at high levels at the majority of surfaces. At high blood plasma concentration (plasma dil 1/10), anti-FG dominated at most surfaces. ELISA activity of FN and C3 were low at most of the surfaces at both plasma concentrations. An 'optimum' plasma dilution for the detection of surface bound FG (the Vroman effect) was not found with the use of the ELISA on any of the surfaces except for the silicon oxide surface. This is in contrast to findings by others who had used isotope-labelled fibrinogen diluted in plasma. However, 'false' Vroman effects occurred if nonionic surfactant was used for the prevention of unspecific binding in the ELISA.

Adsorption↗

PubMed1994

The chemiluminescence response of neutrophils on polymer surfaces made by glow discharge plasma polymerization.

Polypropylene tubes were coated with different polymers made by glow discharge plasma polymerization. Isolated human blood neutrophils were allowed to interact with the polymer surface and the chemiluminescence response of the cells was recorded as a measure of oxidative activation. The polymers represented surfaces that differed markedly with respect to charge, hardness, and wettability. We found that all polymers stimulated the chemiluminescence response in neutrophils differently; when preincubation with human serum albumin (HSA) there was a general reduction of the chemiluminescence response particularly on one of the positively charged surface 1,2-diamino-cyclohexane (DACH). Addition of a soluble stimulus, the chemoattractant formylmethionyl-leucylphenylalanine (FMLP), to the cells caused a dramatic increase in the response on one of the hydrophobic surface hexamethylene-disiloxane (HMDSO). However, there was also a pronounced reduction in the response on polymers with acrylic acid (AA). The response was normalized after addition of HSA. Taken together, the chemiluminescence response of the neutrophils interacting with the polymer surfaces differed with regard to the type of surfaces. When HSA and FMLP were added a larger difference in the response was found. Our results showed that the activation of human neutrophil granulocytes influenced by different polymer surfaces, followed unspecific different patterns which were someway related to the specific characteristics of the polymer and from this point we came to similar conclusions made by Kaplan et al. (J. Biomater. Res. 28, 377 (1994)), that it is difficult to extrapolate any activation mechanisms from one material to another.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylates↗

PubMed1992

RF-plasma-modified polystyrene surfaces for studying complement activation.

Five different plasma modified surfaces were made for studying different aspects of biocompatibility. These surfaces were: 1,2-diaminocyclohexane (DACH), acrylic acid (AA), Hydroxyethylmethacrylate (HEMA), methane and hexamethylene-disiloxane (HMDSO). In addition a polyethylene-glycol (PEG) was made by grafting aldehyde functional PEG to the DACH surface. PEG and HMDSO which are the most hydrophilic and the most hydrophobic surface shows the lowest amount of adsorbed protein of the three proteins studied here (albumin, IgG and C3). Methane, HMDSO and HEMA was found to activate via the classical (complement activation) pathway while the others activated via the alternative pathway.

Adsorption↗