Dr. Lerche KG

Berlin, Germany

Dr. Lerche KG

Berlin, Germany
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Kestens V.,European Commission | Coleman V.A.,Australian National Measurement Institute | De Temmerman P.-J.,Coda Research | Minelli C.,National Physical Laboratory United Kingdom | And 2 more authors.
Langmuir | Year: 2017

Line-start incremental centrifugal liquid sedimentation (disc-CLS) is a powerful method to determine particle size based on the principles of Stokes' law. Because several of the input quantities of the Stokes equation cannot be easily determined for this case of a rotating disc, the disc-CLS approach relies on calibrating the sedimentation time scale with reference particles. To use these calibrant particles for establishing metrological traceability, they must fulfill the same requirements as those imposed on a certified reference material, i.e., their certified Stokes diameter and density value must come with a realistic measurement uncertainty and with a traceability statement. As is the case for several other techniques, the calibrants do not always come with uncertainties for the assigned modal diameter and effective particle density. The lack of such information and the absence of a traceability statement make it difficult for the end-user to estimate the uncertainty of the measurement results and to compare them with results obtained by others. We present the results of a collaborative study that aimed at demonstrating the traceability of particle size results obtained with disc-CLS. For this purpose, the particle size and effective particle density of polyvinyl chloride calibrants were measured using different validated methods, and measurement uncertainties were estimated according to the Guide to the Expression of Uncertainty in Measurement. The results indicate that the modal Stokes diameter and effective particle density that are assigned to the calibrants are accurate within 5% and 3.5%, respectively, and that they can be used to establish traceability of particle size results obtained with disc-CLS. This conclusion has a great impact on the traceability statement of certified particle size reference materials, for which the traceability is limited to the size and density values of the calibrant particles. © 2017 American Chemical Society.


Endres M.,TransTissue Technologies GmbH | Endres M.,Charité - Medical University of Berlin | Wenda N.,Dr. Lerche KG | Woehlecke H.,Dr. Lerche KG | And 6 more authors.
Acta Biomaterialia | Year: 2010

The application of stem cells is a promising therapeutic approach for cartilage regeneration. For cell therapies, a biocompatible injectable carrier, which improves retention and cell distribution and enables cell differentiation, is a prerequisite. In this study, Ca-alginate microcapsules containing human subchondral cortico-spongious progenitor cells were prepared and the chondrogenic differentiation potential was verified by real-time reverse transcription-polymerase chain reaction analysis of typical chondrogenic marker genes. The results confirmed that these cells were able to differentiate along the chondrogenic lineage when encapsulated in Ca-alginate microcapsules with a mean diameter of 600-700 μm and stimulated with TGF-beta3. Chondrogenic marker genes type II collagen, aggrecan and cartilage oligomeric matrix protein were induced together with type I collagen, whereas adipogenic and osteogenic marker genes showed no induction over 14 days. After 28 days, proteoglycans and type II collagen were evident histochemically and immunohistochemically. Mechanical stability as well as permeability of Ca-alginate capsules were analysed over the course of cultivation and found to be qualified for stable cell immobilization and sufficient exchange of solutes. Therefore, from the cell biology point of view, Ca-alginate, an established hydrogel scaffold material is suited for regenerative therapies of cartilage defects based on the injection of progenitor cells. © 2009 Acta Materialia Inc.


Linke B.,Humboldt University of Berlin | Schroder K.,Humboldt University of Berlin | Arter J.,Humboldt University of Berlin | Gasperazzo T.,Humboldt University of Berlin | And 2 more authors.
BioTechniques | Year: 2010

Here we report that dehydrated ethanol is an excellent medium for both in situ preservation of nucleic acids and cell disruption of plant and yeast cells. Cell disruption was strongly facilitated by prior dehydration of the ethanol using dehydrated zeolite. Following removal of ethanol, nucleic acids were extracted from the homogenate pellet using denaturing buffers. The method provided DNA and RNA of high yield and integrity. Whereas cell wall disruption was essential for extraction of DNA and large RNA molecules, smaller molecules such as tRNAs could be selectively extracted from undisrupted, ethanol-treated yeast cells. Our results demonstrate the utility of absolute ethanol for sample fixation, cell membrane and cell wall disruption, as well as preservation of nucleic acids during sample storage.

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