Rational design of dendritic thermoresponsive nanogels that undergo phase transition under endolysosomal conditions.

In the last few decades, the synthesis of nanodevices has become a very active research field with many applications in biochemistry, biotechnology, and biomedicine. However, there is still a great need for smart nanomaterials that can sense and respond to environmental changes. Temperature- and pH-responsive nanogels (NGs), which are prepared in a one-pot synthesis from N-isopropylacrylamide (NiPAm) and a Newkome-type dendron (ABC) bearing carboxylic acid groups, are being investigated as multi-responsive drug carriers. As a result, NGs have been developed that are able to undergo a reversible volume phase transition triggered by acidic conditions, like the ones found in endolysosomal compartments of cancer cells. The NGs have been thoroughly characterized using dynamic light scattering and spectroscopies, such as infrared, nuclear magnetic resonance, UV-visible, and stimulated Raman. Strong hydrogen bonds have been detected when the ABC moieties are deprotonated, which has led to changes in the transition temperatures of the NGs and a reversible, pH-dependent aggregation. This pH-dependent phase change was exploited for the effective encapsulation and sustained release of the anticancer drug cisplatin and resulted in a faster release of the drug at endolysosomal pH values. The cisplatin-loaded NGs have exhibited high toxicities against A549 cells in vitro, while the unloaded NGs have been found to be not cytotoxic and hemocompatible.

Studies for improved understanding of lipid distributions in human skin by combining stimulated and spontaneous Raman microscopy.

Advanced Raman techniques, such as stimulated Raman spectroscopy (SRS), have become a valuable tool for investigations of distributions of substances in biological samples. However, these techniques lack spectral information and are therefore highly affected by cross-sensitivities, which are due to blended Raman bands. One typical example is the symmetric CH2 stretching vibration of lipids, which is blended with the more intense Raman band of proteins. We report in this work an approach to reduce such cross-sensitivities by a factor of 8 in human skin samples. This is accomplished by careful spectral deconvolutions revealing the neat spectra of skin lipids. Extensive Raman studies combining the complementary advantages of fast mapping and scanning, i.e. SRS, as well as spectral information provided by spontaneous Raman spectroscopy, were performed on the same skin regions. In addition, an approach for correcting artifacts is reported, which are due to transmission and reflection geometries in Raman microscopy as well as scattering of radiation from rough and highly structured skin samples. As a result, these developments offer improved results obtained from label-free spectromicroscopy provided by Raman techniques. These yield substance specific information from spectral regimes in which blended bands dominate. This improvement is illustrated by studies on the asymmetric CH2 stretching vibration of lipids, which was previously difficult to identify due to the strong background signal from proteins. The advantage of the correction procedures is demonstrated by higher spatial resolution permitting to perform more detailed investigations on lipids and their composition in skin.

[In vitro studies into the influence of ochratoxin A on the production of tumor necrosis factor alpha by the human monocytic cell line THP-1]. / In vitro-Untersuchungen zum Einfluss von Ochratoxin A auf die Tumornekrosefaktor alpha-Produktion der humanen Monozytenzelllinie THP-1.

The influence of pure OTA and an Aspergillus-ochraceus crude toxin on the intracellular expression and the secretion of tumor necrosis factor (TNF) alpha by the monocytic cell line THP-1 was studied in vitro. After 4 hours exposure, the secretion of TNF alpha was inhibited to 50% by pure OTA in a concentration of 400 ng/ml and by crude toxin in a concentration of 100 ng/ml. The same concentrations of mycotoxins impaired the mitochondrial activity of THP-1 cells only marginally. The intracellular expression of TNF alpha was not disturbed by pure OTA in the concentrations tested, whereas crude toxin showed an inhibitory effect. The possible reasons for these findings are discussed.

[Not Available]. / Modulation der zytotoxischen Aktivität von humanen natürlichen Killerzellen durch Ochratoxin A und C.

The effect of ochratoxin A (OTA) and C (OTC) on the cytolytic activity of natural killer cells (NK cells) was studied using a fluorescence based bioassay with the cell line NK-92 as effector cell line and K-562 as target cell line. Different OTA and OTC preparations were included in the study. After exposure to very low toxin concentrations (1-10 ng/ml) a slight stimulation of NK cell activity was noted, whereas after addition of higher toxin concentrations (100-1000 ng/ml) NK cell function was suppressed. Preparations containing OTC showed a stronger effect than those containing OTA.

[Not Available]. / Beeinflussung der Zytokinsekretion von Maus-Thymom-Zellen (EL-4) durch Ochratoxin A.

The murine thymoma cell line EL-4 was used as an in vitro T-cell model to assess the immunomodulating effect of pure Ochratoxin A (OTA) and an Aspergillus ochraceus raw toxin preparation. Cytokine production (IL-2, IL-4, IL-5, IL-6) and cell viability of PMA-stimulated EL-4 cells were investigated in the presence of OTA. The cytotoxic effect of the raw toxin could be observed at lower concentrations than pure OTA. The IC50 values were 3 µg/ml and 11 µg/ml, respectively. Increasing concentrations of both OTA preparations caused an inhibition of cytokine production, but the inhibition effect of the raw toxin was stronger than of pure OTA. This is supposed to be the effect of further up to now not characterized substances in the raw toxin. Differences in the susceptibility of the mechanisms of production and regulation of each cytokine are indicated by the different concentrations for inhibition effects. Both toxin preparations showed also stimulating effects on some cytokines (IL-2 and IL-6) while others (IL-4 and IL-5) were depressed at these OTA concentrations. This indicates the immunomodulating properties of the toxin.