We have developed a new microsystem for fast, automated studies of reaction
s and kinetics of single cells with biochemical or pharmacological agents.
A cell spins in an external rotating electric field and the frequency depen
dence characterises the passive dielectric properties of membrane and cytop
lasm. We use a planar microelectrode chip with microchannel (easily covered
with a removable slip) for the application of frequencies exceeding 250 MH
z to determine cytoplasmic properties in low and high conductivity electrol
yte solutions. The laser tweezers serve as a bearing system, rotation is in
duced by microelectrodes and rotation speed is recorded automatically. This
opens up new possibilities in biotechnology, e.g. for drug screening as de
monstrated by measuring the influence of ionomycin on the passive dielectri
c properties of T-lymphoma cells. Additionally, a possible infrared-induced
long-term cell damage could be observed by electrorotation and is discusse
d. (C) 2000 Elsevier Science B.V. All rights reserved.