Effect of pH on the adsorption of immunoglobulin G on anionic poly(vinyltoluene) model latex particles

Influence of surface charge on adsorption of fibrinogen and/or albumin on a rotating disc electrode of platinum and carbon

The adsorption of fibrinogen on to platinum and carbon and of albumin on to carbon was investigated for various changes of the surface by recording the variations of the double-layer capacitance of the electrochemical interface during adsorption, as a function of time. The rate of the second step of the adsorption decreased with increasing negative charge on to platinum but was charge-independent on to carbon. In contrast, on both surfaces, the rate of the first step and the area of the electrode surface in close contact with adsorbed proteins were both found to increase with increasing negative charge of the surface, although at pH 7.4 albumin and fibrinogen are negatively charged. The hypothesis of ion coadsorption inside the proteic layer has been proposed to account for this result.

Analysis of colloidal gold probes by isoelectric focusing in agarose gels

Colloidal gold particles of different size (3-20 nm in diameter) were prepared by tannic acid-citrate and citrate reduction methods. From these colloids, different probes were prepared using sheep anti-rabbit antiserum, sheep anti-rabbit IgG, bovine serum albumin, polyethylene glycol, and protein A as the primary stabilizers and polyethylene glycol and/or bovine serum albumin as secondary and tertiary stabilizers, in different combinations. The probes were analyzed by isoelectric focusing in agarose gels, which allow the migration of particles in the size range 3-20 nm. (P. Sewer and S. J. Hayes, 1986, Anal. Biochem. 158, 72-78). Isoelectric focusing revealed that the surface charge of colloidal gold probes is dependent upon the size of the gold particle, the reduction method used, the primary ligand, and the pH at which this is adsorbed, as well as upon the secondary and tertiary stabilizers used. It is proposed that such differences in surface charge may underlie the different results which may sometimes be observed in colloidal gold labeling, especially when novel ligands are used.

Fundamental study on latex reagents for agglutination tests

Competitive adsorption of Fab and Fc fragments on to particles revealed that the main driving forces for the adsorption of Fab and Fc fragments are ionic and hydrophobic forces, respectively. Latex particles were sensitized with antihuman C-reactive protein-antibody under a condition where ionic binding force was suppressed, and hence antibody was supposed to attach to the particles predominantly at the Fc site. The resulting latex indicated a high efficiency for the determination of C-reactive protein. Among the latexes used, a partially hydrolysed styrene-acrylamide copolymer latex was the best with respect to test efficiency and storage stability.

Particle agglutination assays for rapid detection of fibronectin, fibrinogen, and collagen receptors on Staphylococcus aureus

Latex beads (0.8-micron diameter; Difco Laboratories) were coated with fibronectin, fibrinogen, collagen type I, or denatured collagen (gelatin) and evaluated in a particle agglutination assay (PAA) for the rapid detection of fibronectin, fibrinogen, or collagen binding to Staphylococcus aureus. These assays were compared with a commercial test for detecting the binding of fibrinogen and immunoglobulin G (Staphaurex). Bacterial cells (approximately 10(10) cells per ml) suspended in 0.02 M potassium phosphate buffer (pH 6.8) caused the clumping of standard fibronectin, collagen, gelatin, and fibrinogen latex suspensions within 2 min on glass slides. The test results were scored semiquantitatively from strongly positive ( ) to weakly positive (+) and negative (-) reactions. The negative PAA reactions corresponded to a median value of 11.5% relative to the binding of 125I-labeled protein to strain Cowan 1, indicating the high sensitivity of the test. The reactions with fibronectin and fibrinogen latex suspensions and with Staphaurex were optimal for cells grown on tryptic soy and brain heart infusion broth media. Blood agar was optimal for reactions with collagen and gelatin latex suspensions. Media containing high salts (mannitol salt agar and staphylococcus medium 110) enhanced the tendency of cells to autoaggregate. These assays were also clinically evaluated on 187 S. aureus isolates. The PAA reagents were stable, and the assays were highly specific, sensitive, and reproducible, thus making PAA suitable for the rapid screening of the binding of various bacterial pathogens to serum and connective-tissue proteins.

Immunoaffinity chromatography of lymphocyte subpopulations using tert-amine derived matrices with adsorbed antibodies

New polymeric solid-phase matrices for cell affinity chromatography were prepared and their advantageous characteristics compared with conventional matrices were highlighted. These new matrices are derivatives of poly(2-hydroxyethyl methacrylate) (PHEMA) containing a slight quantity of amino compounds as a co-monomer. They were applied to immunoaffinity selection between IgG+ and IgG- lymphocytes of the rat mesenteric lymph node. Simple physical adsorption was sufficient for anti-rat IgG antibodies to be immobilized on these matrices, allowing us to omit the laborious procedure of covalent-linking of antibodies on a matrix. As these matrices themselves showed extremely low non-specific adsorption of lymphocytes, a very dilute solution of antibody (0.02-0.08 mg/ml) was enough for column conditioning. This separation method gave IgG- lymphocytes of more than 90% purity and almost 95% yield within as short a time as 7 min. Further, IgG+ lymphocytes were obtained in good yield (80-90% of loaded number) by recovering the adsorbing cell fraction from the column by gentle pipetting of the matrix.

Endothelialization of polymer surfaces

The role that substrate surface properties play in influencing the extent of endothelialization of polymer surfaces has been investigated. For a wide range of polymer surfaces, the degree of endothelialization for both porcine and bovine endothelial cells is directly related to polymer surface tension: increased endothelialization occurring with increasing substrate surface tension. As a result of adsorption of the proteins in the culture media, the surface properties of the polymers are altered considerably. The protein-coated polymers were characterized by means of liquid-liquid contact angle measurements under non-denaturing conditions. A striking correlation is observed between the degree of endothelialization and the measured dextran contact angle. The degree of endothelial cell spreading is not related to polymer surface tension. Cell morphology and extracellular matrix production, however, are influenced by substrate surface properties.

Adsorption of proteins from solution at the solid-liquid interface

The purpose of this article is to present some general principles and rules for the adsorption of proteins from aqueous solution on solid surfaces, emphasizing conformational and reversibility aspects. Special attention is paid to the relation between structural properties of the protein molecule and its adsorption behavior and to the role of small ions in the overall adsorption process. Thermodynamic analysis reveals that, under many conditions, the adsorption is driven by an entropy increase that is (partly) related to changes in the structure of the protein molecules.

Turbidimetric latex immunoassay for serum ferritin

A sensitive immunoassay based on latex particle agglutination (latex immunoassay) has been developed for the determination of serum ferritin. Polystyrene particles (0.8 micron) to which anti-ferritin antibody is adsorbed are incubated with serum for 30 min with shaking or 60 min without shaking. The resulting agglutination is quantified by measuring the decrease of absorbance of the latex suspension at 360 nm. Pretreatment of the serum is required to prevent interference from complement, rheumatoid factor and chylomicrons. The lowest detectable concentration of ferritin in serum is about 5 micrograms/l. Within-runs and between-runs coefficients of variation, based on analysis of samples containing 14-820 micrograms/l ferritin, ranged from 3.6 to 13.8%. A correlation coefficient of 0.95 between latex immunoassay and radioimmunoassay was obtained for the determination of ferritin in 46 sera.