Monitoring of laser micromanipulated optically trapped cells by digital holographic microscopy.

For a precise manipulation of particles and cells with laser light as well as for the understanding and the control of the underlying processes it is important to visualize and quantify the response of the specimens. Thus, we investigated if digital holographic microscopy (DHM) can be used in combination with microfluidics to observe optically trapped living cells in a minimally invasive fashion during laser micromanipulation. The obtained results demonstrate that DHM multi-focus phase contrast provides label-free quantitative monitoring of optical manipulation with a temporal resolution of a few milliseconds.

Inverted microcontact printing on polystyrene-block-poly(tert-butyl acrylate) films: a versatile approach to fabricate structured biointerfaces across the length scales.

The combination of the recently introduced soft lithographic technique of inverted microcontact printing (i-muCP) and spin-coated films of polystyrene- block-poly( tert-butyl acrylate) (PS 690- b-P tBA 1210) as a reactive platform is shown to yield a versatile approach for the facile fabrication of topographically structured and chemically patterned biointerfaces with characteristic spacings and distances that cross many orders of magnitude. The shortcomings of conventional muCP in printing of small features with large spacings, due to the collapse of small or high aspect ratio stamp structures, are circumvented in i-muCP by printing reactants using a featureless elastomeric stamp onto a topographically structured reactive polymer film. Prior to molecular transfer, the substrate-supported PS 690- b-P tBA 1210 films were structured by imprint lithography resulting in lateral and vertical feature sizes between >50 microm-150 nm and >1.

Integral refractive index determination of living suspension cells by multifocus digital holographic phase contrast microscopy.

A method for the determination of the integral refractive index of living cells in suspension by digital holographic microscopy is described. Digital holographic phase contrast images of spherical cells in suspension are recorded, and the radius as well as the integral refractive index are determined by fitting the relation between cell thickness and phase distribution to the measured phase data. The algorithm only requires information about the refractive index of the suspension medium and the image scale of the microscope system.

Investigation of living pancreas tumor cells by digital holographic microscopy.

Digital holographic microscopy provides new facilities for contactless and marker-free quantitative phase contrast imaging. In this work, a digital holographic microscopy method for the integral refractive index determination of living single cells in cell culture medium is presented. Further, the obtained refractive index information is applied to full field thickness and shape determination of adherent pancreas tumor cells, as well as for analysis of drug-induced dynamic changes of a single cell's cytoskeleton.

Oxygen preference of Daphnia magna is influenced by Po2 acclimation and biotic interactions.

Oxygen preference of the planktonic crustacean Daphnia magna was observed within an oxygen gradient. Long-term acclimation to specific oxygen conditions determined the preferred oxygen tension. Animals from hypoxic acclimation stayed in oxygen-poor water at first.

Differential haemoglobin gene expression in the crustacean Daphnia magna exposed to different oxygen partial pressures.

The quantity and quality of the haemoglobin (Hb) of Daphnia magna is related to oxygen partial pressure in the water. Both the dynamics of hypoxia-induced Hb gene transcription, as well as Hb properties in animals incubated long-term at hyperoxia, normoxia and hypoxia, were investigated. Examination of Hb gene (dhb1-dhb3) transcription showed the expression of dhb2 and especially dhb3 to increase markedly approximately one hour after the onset of hypoxia, whereas dhb1 was expressed more or less constitutively.