Three-dimensional in vitro reaggregates of embryonic cardiomyocytes: a potential model system for monitoring effects of bioactive agents.

To understand the physiological effects of substances used in drugs and therapies on heart muscle tissue, model systems that mirror the in vivo situation of living tissues are required. Therefore, the creation of 3-dimensional (3D) cell aggregates provides an improved and refined in vitro model as a link between cell-free or single cells and organs or whole organisms in vivo. Here we have characterized a stable contracting in vitro tissue model, which consists of embryonic chicken cardiomyocytes. For establishing a cell-based test system, the 3D in vitro cardiomyocyte spheres were characterized according to messenger RNA expression of special cardiac cell types and protein expression pattern of functional markers such as connexin-43. Finally, the in vitro spheroid model was used for investigating the effect of isoproterenol, a *-adrenergic receptor agonist, on the contractibility mediated by the ligand receptor interaction.

A more aggressive breast cancer spheroid model coupled to an electronic capillary sensor system for a high-content screening of cytotoxic agents in cancer therapy: 3-dimensional in vitro tumor spheroids as a screening model.

One major problem in cancer therapy is the immortality of tumor cells showing an active telomerase, which is responsible for the elongation of the telomeres after each cellular division and the knocking down of apoptotic suppressors. A further phenomenon occurring during cancer therapies is the problem of multicellular resistance. To develop therapeutic anticancer approaches inducing cellular apoptosis, gene-modified biological in vitro systems were established and evaluated for drug screening in a capillary system for a real-time, impedimertic monitoring. Multicellular spheroids of the human breast cancer cell line T-47D clone 11 were transfected with 1) antisense caspase-3 cDNA expression vectors for knocking down the main cell death molecule and 2) sense Bcl-xl cDNA expression vectors for overexpressing the apoptotic suppressor, resulting in more aggressive tumor models. These gene-modified tumor spheroids less sensitive for apoptosis were developed for screening drugs such as methotrexate in tumor spheroid-based biosensor systems via impedance spectroscopy. In this report, it is demonstrated that this could successfully exhibit that this real-time monitoring system with tumor spheroids positioned in a capillary system with a 4-electrode configuration is the most efficient high-content screening module for impedimetric measurements of physiological alterations during gene modification and drug application.

Evaluation of impedance spectroscopy for the characterization of small biological samples in tissue-based test systems.

Marker free techniques are needed for the construction of efficient tissue-based test and sensor systems. In principle biological tissue can be characterized by impedance spectroscopy. In this paper we investigate by simulation how sensitive parameters of small biological tissue samples can be determined by impedance spectroscopy under optimal measurement conditions. Further, we experimentally evaluate whether the effects of different clinical relevant radio therapy variants on 3D in vitro tumor models are determinable and distinguishable by impedance spectroscopy using a tissue-based test system. The simulations demonstrate that changes in tissue parameters related to the extracellular space are determinable with a high sensitivity. The experiments show that the effect of different radiation dose levels on 3D in vitro tumor models can be determined and distinguished by using a capillary measurement system and impedance spectroscopy. These results are relevant for the development of tissue-based test and sensor systems using impedance spectroscopy to evaluate personalized therapy variants or new therapy approaches.