Translocation of positively and negatively charged polystyrene nanoparticles in an in vitro placental model.

To obtain insight in translocation of nanoparticles across the placental barrier, translocation was studied for one positively and two negatively charged polystyrene nanoparticles (PS-NPs) of similar size in an in vitro model. The model consisted of BeWo b30 cells, derived from a human choriocarcinoma grown on a transwell insert forming a cell layer that separates an apical from a basolateral compartment. PS-NPs were characterized with respect to size, surface charge, morphology and protein corona. Translocation of PS-NPs was not related to PS-NP charge. Two PS-NPs were translocated across the BeWo transwell model to a lower extent than amoxicillin, a model compound known to be translocated over the placental barrier to only a limited extent, whereas one PS-NP showed a slightly higher translocation. Studies on the effect of transporter inhibitors on the translocation of the PS-NPs indicated that their translocation was not mediated by known transporters and mainly dependent on passive diffusion. It is concluded that the BeWo b30 model can be used as an efficient method to get an initial qualitative impression about the capacity of NPs to translocate across the placental barrier and set priorities in further in vivo studies on translocation of NPs to the fetus.

Bioavailability and biodistribution of differently charged polystyrene nanoparticles upon oral exposure in rats.

The likelihood of oral exposure to nanoparticles (NPs) is increasing, and it is necessary to evaluate the oral bioavailability of NPs. In vitro approaches could help reducing animal studies, but validation against in vivo studies is essential. Previously, we assessed the translocation of 50 nm polystyrene NPs of different charges (neutral, positive and negative) using a Caco-2/HT29-MTX in vitro intestinal translocation model. The NPs translocated in a surface charge-dependent manner. The present study aimed to validate this in vitro intestinal model by an in vivo study. For this, rats were orally exposed to a single dose of these polystyrene NPs and the uptake in organs was determined. A negatively charged NP was taken up more than other NPs, with the highest amounts in kidney (37.4 µg/g tissue), heart (52.8 µg/g tissue), stomach wall (98.3 µg/g tissue) and small intestinal wall (94.4 µg/g tissue). This partly confirms our in vitro findings, where the same NPs translocated to the highest extent. The estimated bioavailability of different types of NPs ranged from 0.2 to 1.7 % in vivo, which was much lower than in vitro (1.6-12.3 %). Therefore, the integrated in vitro model cannot be used for a direct prediction of the bioavailability of orally administered NPs. However, the model can be used for prioritizing NPs before further in vivo testing for risk assessment.

Cloning and characterization of a tuberous root-specific promoter from cassava (Manihot esculenta Crantz).

In order to obtain a tuberous root-specific promoter to be used in the transformation of cassava, a 1,728 bp sequence containing the cassava granule-bound starch synthase (GBSSI) promoter was isolated. The sequence proved to contain light- and sugar-responsive cis elements. Part of this sequence (1,167 bp) was cloned into binary vectors to drive expression of the firefly luciferase gene. Cassava cultivar Adira 4 was transformed with this construct or a control construct in which the luciferase gene was cloned behind the 35S promoter. Luciferase activity was measured in leaves, stems, roots and tuberous roots. As expected, the 35S promoter induced luciferase activity in all organs at similar levels, whereas the GBSSI promoter showed very low expression in leaves, stems and roots, but very high expression in tuberous roots. These results show that the cassava GBSSI promoter is an excellent candidate to achieve tuberous root-specific expression in cassava.

Quantitative structure-activity relationship modeling of the toxicity of organothiophosphate pesticides to Daphnia magna and Cyprinus carpio.

Within the REACH regulatory framework in the EU, quantitative structure-activity relationships (QSAR) models are expected to help reduce the number of animals used for experimental testing. The objective of this study was to develop QSAR models to describe the acute toxicity of organothiophosphate pesticides to aquatic organisms. Literature data sets for acute toxicity data of organothiophosphates to fish and one data set from experiments with 15 organothiophosphates on Daphniamagna performed in the present study were used to establish QSARs based on quantum mechanically derived molecular descriptors. The logarithm of the octanol/water partition coefficient, logK(ow,) the energy of the lowest unoccupied molecular orbital, E(lumo), and the energy of the highest occupied molecular orbital, E(homo) were used as descriptors. Additionally, it was investigated if toxicity data for the invertebrate D. magna could be used to build a QSAR model to predict toxicity to fish. Suitable QSAR models (0.80