Jan Hornung

Characterisation of cell movement by impedance measurement on fibroblasts grown on perforated Si-membranes

Mouse fibroblasts grown on perforated Si-membranes (pore diameter approximately 10 microns have been studied to clarify cell locomotive ability. The cell motility was microscopically monitored by a time-lapse video system and, simultaneously, the impedance of the growing cells was measured every 5 s. The correlations between observed cell activities and measured impedance events are discussed and classified. The method is sensitive and allows discrimination between signals arising from translocation of single cells and those arising from filopodia activities. Both cell and filopodia motion could be detected. Designs of microdevices fabricated in semiconductor technology are presented.

Influence of polylysine on adhesion of fibroblasts to glass substrates visualized by total internal reflection microscopy

The cell adhesion topography of mouse fibroblasts growing on glass substrates has been investigated. In order to compare cell adhesion on covered and uncovered glass, substrates were partly exposed to a solution with 0.1 mg/ml polylysine (300 kDa) for 15 min before incubation with cell suspension. After cultivation for 1, 3, 6, and 24 h their adhesion was visualised by total internal reflection microscopy. In the presence of polylysine, cells incubated for 1 h were strongly attracted to the substrate, leading to a typical cell adhesion topography characterised by round concavities under the ventral cell membrane with an approximate diameter of 1 μm. The cavity-surrounding rims were tightly bound to the glass surface. During further cell cultivation, the topography changed into a well-organised adhesion pattern with focal contact areas on the periphery of the cells. In contrast to the polylysine-mediated adhesion, cells growing on untreated surfaces did not exhibit the cavity-like topography at any stage of cultivation, but a more point spread adhesion with a dense clustering of contact-forming areas.

Holographic microscopy with conjugated reconstruction for the investigation of deformations of surfaces

It is necessary to use a magnifying system for the investigation of very small diffusely reflecting objects by holographic interferometry. The influence of imaging errors as well as fringe localization in holographic interferometric microscopy with conjugated reconstruction was investigated in previous papers. In this paper we describe the possibility of applying the phase shifting technique in holographic microscopy with conjugated reconstruction. The phase shifting is a well known technique in interferometry for the investigation of phase distributions. By using digital image processing for the suppression of speckles it is possible to measure deformations of rough surfaces at sub-millimeter objects.

Holographic interference microscope for the investigation of surface-mounted devices

Holographic interferometry is a widely used tool for nondestructive testing of mechanical deformations. In connection with microscopy, it is also possible to investigate very small objects. However, due to the imaging system used to magnify the object, the visibility of the interference pattern is disturbed. This disturbance still remains even if the conjugated reconstruction is applied. To decrease the influence of the imaging system, the aperture must be of small size. To suppress the speckle effect, the hologram should be made as an image plane hologram.