Esch, M.B.; Bäumner, A.; Durst, R.A. “Rapid Visual Detection of Viable Cryptosporidium parvum on Test Strips using Oligonucleotide-tagged Liposomes” Analytical Chemistry, 2001, 73(13), 3162-3167

Paper-based microfluidics are the basis for pregnancy test strips that detect hormones via antibodies that are immobilized on a paper test strip. We employed the same principle to detect the RNA of a pathogen (Cryptosporidium parvum).  We immobilized synthetic DNA that is complementary to the RNA and placed it on the test strip. While the sample moves up the strip via capillary forces, the RNA in the sample comes into very close contact with the immobilized DNA. In our assay, the RNA competes with a second dye-conjugated synthetic DNA with the same sequence. This dye-conjugated DNA was initially added to the sample. In this competitive assay format, no color on the strip means the pathogen RNA was present.

Esch, M.B.; Sukhorukov, V.L.; Kürschner, M.; Zimmermann, U. “Dielectric Properties of Alginate Beads and Bound Water Relaxation Studied by Electrorotation” Biopolymers, 1999, 50, 227-237

The association of water with polysaccharides is the basis for the survival of cells within hydrogels. Hydrogel-encapsulated cells are important because they could replace native cells that have experienced a loss of function, for example insensitivity to insulin-needs of the body. Here we proved experimentally that water is bound non-covalently to hydrogels. To prove this, we used four microelectrodes to create a rotating electric field in which we placed 400 micrometer large alginate beads. We measured how fast the beads rotated in fields of varying frequency and in medium of varying conductivity. A broad internal dispersion of the hydrogel centered between 20 and 40 MHz. We attribute this dispersion to the relaxation of water bound to the polysaccharide matrix of the beads.