Biomedical subjects

M Natesan

Publications and source records attributed to M Natesan.

3 recordsLinked to original sources

PubMed2000

Implementation of force differentiation in the immunoassay.

A technique has been developed to apply force to the antibody-antigen complex in a solid-phase immunoassay. Force was applied to the immunochemical complex by labeling the secondary antibody with a magnetically susceptible, micrometer-size particle and placing the assay chamber in a magnetic field of defined magnitude and orientation. The force was strong enough to displace weakly bound particles but was not strong enough to rupture the immunochemical complex. The number of particles bound to the surface after applying the differentiation force was related to the analyte concentration, thus an optical detection scheme was developed for counting the number of particles on the surface. The sensitivity of the force differentiation assay was demonstrated to be one to two orders of magnitude higher than conventional solid-phase immunoassay techniques for model protein, virus, and bacterial analytes, with 99% specificity. The enhanced sensitivity of this assay appears to result from lowering the assay background through the identification of weakly adhesive, nonspecific interactions.

Antigen-Antibody Complex↗

PubMed1998

A biosensor based on magnetoresistance technology.

We are developing a biosensor that will measure, at the level of single molecules, the forces that bind DNA-DNA, antibody-antigen, or ligand-receptor pairs together. The Bead Array Counter (BARC) will use these interaction forces to hold magnetic microbeads to a solid substrate. Microfabricated magnetoresistive transducers on the substrate will indicate whether or not the beads are removed when pulled by magnetic forces. By adapting magnetoresistive computer memory technology, it may be possible to fabricate millions of transducers on a chip and detect or screen thousands of analytes. The multi-analyte capability of this portable sensor would be ideal for on-site testing, while the potential to directly gauge intermolecular interaction strengths suggests drug discovery applications.

Biosensing Techniques↗

PubMed1996

Costimulation of IL-4 production by murine B7-1 and B7-2 molecules.

We have examined the capacity of murine B7-1 and B7-2 to costimulate the production of IL-4 by murine CD4+ T lymphocytes. Cloned and freshly isolated T cells were incubated with the anti-CD3 mAb 145-2C11 in the presence of Chinese hamster ovary (CHO) cells that stably express murine B7-1 and B7-2 at comparable levels. IL-4 protein levels were measured in culture supernatants by the CT.4S bioassay, and levels of IL-4 mRNA were determined by semiquantitative reverse transcription-PCR. Both B7-1- and B7-2-transfected CHO cells, but not CHO control transfectants, were able to costimulate IL-4 production. Similarly, both B7-1 and B7-2 could up-regulate IFN-gamma mRNA levels. Cell fractionation experiments on freshly isolated CD4+ T lymphocytes revealed that the costimulatory potential of B7-1 and B7-2 for IL-4 production was restricted to CD44high T cells, i.e., the subpopulation that contains recently activated and memory cells. CD44low, naive CD4+ T lymphocytes, could only be induced to produce IL-4 by repeated stimulation with B7 transfectants. In summary, we have not detected qualitative differences in the capacities of murine B7-1 and B7-2 to induce IL-4 production. The results of our experiments, therefore, argue against the recent hypothesis that precursor Th cells are directed toward the Th2 phenotype by B7-2 and toward the Th1 phenotype by B7-1.

Animals↗