Biomedical subjects

Per Ola Andersson

Publications and source records attributed to Per Ola Andersson.

3 recordsLinked to original sources

PubMed2006

A label-free continuous total-internal-reflection-fluorescence-based immunosensor.

In this study, we continuously monitored, second-by-second, concentration changes of two different carbohydrates (maltose and panose) by using monoclonal antibodies in an optical immunosensor based on total internal reflection fluorescence. Earlier studies have demonstrated that these antibodies increase their intrinsic tryptophan fluorescence upon binding of carbohydrate antigens. Using the four immobilized monoclonal antibodies with low affinities (K(d)>10(-6)M), fast kinetics (k(off)>1s(-1)), and high reversibility gave opportunities for developing a continuous immunosensor without any need for regeneration. Since intrinsic fluorescence was used, no extrinsic labeling was necessary. Sensitivity was in the range of 1-5 microM for panose, and 10-15 microM for maltose and the loss of intensity was as low as 3.5% per hour during measurements. Calculations of DeltaH degrees and DeltaS degrees from the temperature dependence of K(d) indicated an enthalpic driven antigen-antibody binding event that is diminished upon antibody immobilization. We feel certain that weakly interacting antibodies can be used in future applications for continuous monitoring where there is a need to achieve instantaneous information on the concentration of an analyte.

Antibodies, Monoclonal↗

PubMed2005

Chemometric models of template--molecularly imprinted polymer binding.

This report provides the first example of the use of chemometrics to describe and predict the extent of template binding to molecularly imprinted polymers. The binding of bupivacaine to imprinted and reference polymers was examined in different solvent mixtures and at various temperatures using equilibrium binding studies. Data were fitted to third-degree equations using partial least-squares regression, resulting in chemometric models describing template binding in this system. The mathematical models demonstrated good correlation (R = 0.72-0.98) and predictive ability (Q = 0.54-0.99), and binding could be described in terms of temperature and dielectric constant. Binding in a nonpolar, aprotic solvent was unaffected by temperature whereas in more polar solvent mixtures temperature had a greater influence. This was explained by changes in the balance between electrostatic and hydrophobic interactions. Moreover, the results demonstrate that temperature has a greater influence on the nonspecific portion of binding, particularly in water-containing solvent mixtures.

Journal Article↗

PubMed2005

Analysis of the specificity and thermodynamics of the interaction between low affinity antibodies and carbohydrate antigens using fluorescence spectroscopy.

The purpose of this work has been to examine whether fluorescence spectroscopy can be used to investigate weak or transient binding between monoclonal antibodies and carbohydrate antigens. In earlier studies we have demonstrated that the three monoclonal antibodies 39.4 (IgG2b), 39.5 (IgG2b) and 61.1(IgG3) bind weakly to the glycosidic alpha(1-4) bond present in e.g. maltose and panose. In this study these antibodies showed an enhancement in the fluorescence intensity of tryptophan upon binding in solution to these two carbohydrate antigens. Using a structural analog to maltose, cellobiose, no fluorescence intensity change was induced. Dissociation constants for these antibodies at different temperatures (5-40 degrees C) were obtained in the range of 0.003-0.2 mM and they were in accordance with earlier data from studies on affinity chromatography and surface plasmon resonance. Almost a doubling of the dissociation constants was observed for every 10 degrees C increase in temperature, giving an exothermal reaction with standard enthalpy change of -51 kJ/mol, for the association between antibody and carbohydrate antigen. It was seen that the extra glycosyl ring in panose increased the affinity more than eight times for the monoclonal antibody 39.5. A standard entropy increase of 21%, probably due to hydrophobic effects, is introduced by the extra glycosyl ring, while the enthalpy stays unaffected. This direct fluorescence approach to measure the binding and thermodynamics of an interacting antigen-antibody pair is simple and accurate since measurements are performed in solution and no immobilization or fluorophore labeling of the components is required. Introduction of fluorescence techniques will be a useful complement to current procedures to measure interaction of antibody with antigen and in particular they will offer solutions to detect transiently binding antigens.

Animals↗