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. The results demonstrate that digital holographic microscopy is a quantitative phase contrast technique for living cells under conventional laboratory conditions.

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. The specific digital holographic microscopy advantage of subsequent focus correction allows a simultaneous investigation of cells in different focus planes. Results obtained from human pancreas and liver tumor cells show that the integral cellular refractive index decreases with increasing cell radius.

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. At an incubation close to anoxia, an onset of dhb3 transcription was found already after two minutes. In long-term incubated animals, concentration and oxygen affinity of Hb were lower at higher oxygen partial pressures. With decreasing oxygen availability, the subunit composition of Hb macromolecules changed. The share of the dhb2-encoded subunit, DHbF, increased already during moderate hypoxia. The increase of dhb3 mRNA (encoding DHbC) may be related to a transient increase of DHbC in the first days of hypoxia and/or to an additional coding of dhb3 for DHbD. The rise of DHbD, and particularly DHbA, only at severe hypoxia coincided with the increase of Hb oxygen affinity. The dhb1-encoded subunits DHbB and DHbE showed either a relatively moderate increase or even a decrease in concentration at hypoxia. In small animals with restricted homeostasis capabilities such as Daphnia, adaptation of the protein equipment seems to be a more effective strategy than allosteric modulator control.

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Highly localized, selective deprotection chemistry and efficient grafting reactions in microcontacts between elastomeric stamps and reactive polystyrene‐block‐poly(tert‐butyl acrylate) (PS690‐b‐PtBA1210) diblock copolymer films are developed. The procedure yields well‐defined protein–poly(ethylene glycol) (PEG) nanopatterns (see figure), which may find applications in, for example, cancer‐cell–surface interaction studies.