Abstract

Electromagnetic waves at microwave frequencies (1 Gigahertz – 300 Gigahertz) allow an unshielded view into the interior of biological cells, which is not obstructed by the cell membrane polarization and by scattering of the electromagnetic waves. The microwave dielectric properties of the cell interior is largely determined by the amount and state of water, and therefore the technique provides a means of fast single cell characterisation dependent solely on their physiological properties, without the need of expensive and complex labelling processes. We have developed and optimised a cavity-coupled thin metal film double-split-ring resonator which is fully integrated into a disposable PDMS microfluidic chip. This system enables fast measurements of the dielectric properties of the interior of a single cell at ca. 10 Gigahertz, which allows to determine the average water content of a flowing cell in a microfluidic channel. Potential applications are cancer monitoring by a “liquid biopsy” of blood, urine or pancreatic fluid samples and label-free detection of circulating tumour cells.

As a complementary lab-on-chip approach for cancer diagnostics, we have developed a low-cost microfluidic liquid sensor based on a functionalized graphene field-effect transistor, which was optimized for detection of exosomes. Both approaches may complement each other and pave the way to low cost multi-sensor lab-on-chip systems for comprehensive and safe cancer diagnostics based on sole bio-liquid analysis.