3 research outputs found
Titanium Dioxide Nanoparticles Disturb the Fibronectin-Mediated Adhesion and Spreading of Pre-osteoblastic Cells
In the context of rapid development of nanoparticles
(NPs) for
industrial applications, the question of their toxicity and biological
effects must be considered. In this work, we have assessed the influence
of titanium dioxide NPs on the adhesion and spreading of MC-3T3 pre-osteoblasts
by using a cell subclone that does not produce its own extracellular
matrix. Petri dishes were coated with the important adhesion protein
fibronectin (Fn). By incubating these Fn-coated surfaces with different
amounts of TiO<sub>2</sub> NPs, we have shown that the adhesion of
pre-osteoblasts is disturbed, with an important decrease in the number
of adherent cells (from 40 to 75% depending upon the concentration
and type of NPs). Petri-dish surfaces were analyzed with environmental
scanning electron microscropy (ESEM), with images showing that TiO<sub>2</sub> NP aggregates are bound to the layer of adsorbed Fn molecules.
The cells cultured on these Fn/NP surfaces adopted an irregular shape
and an aberrant organization of actin cytoskeleton, as revealed by
fluorescence microscopy. Most importantly, these results, taken together,
have revealed that the actin cytoskeleton forms abnormal aggregates,
even on top of the nucleus, that coincide with the presence of large
aggregates of NPs on top of cells. On the basis of these observations,
we propose that some Fn molecules are able to desorb from the Petri
dish surface to coat TiO<sub>2</sub> NPs. Fn/NP complexes are not
attached firmly enough on the surface to allow for normal cell adhesion/spreading
and the development of tense actin fibers. These results stress the
paramount need for the assessment of the toxicology of NPs, with special
attention to their interactions with biomolecules
Topological Effects and Binding Modes Operating with Multivalent Iminosugar-Based Glycoclusters and Mannosidases
Multivalent
iminosugars have been recently explored for glycosidase
inhibition. Affinity enhancements due to multivalency have been reported
for specific targets, which are particularly appealing when a gain
in enzyme selectivity is achieved but raise the question of the binding
mode operating with this new class of inhibitors. Here we describe
the development of a set of tetra- and octavalent iminosugar probes
with specific topologies and an assessment of their binding affinities
toward a panel of glycosidases including the Jack Bean Ī±-mannosidase
(JBĪ±Man) and the biologically relevant class II Ī±-mannosidases
from <i>Drosophila melanogaster</i> belonging to glycohydrolase
family 38, namely Golgi Ī±-mannosidase ManIIb (GM) and lysosomal
Ī±-mannosidase LManII (LM). Very different inhibitory profiles
were observed for compounds with identical valencies, indicating that
the spatial distribution of the iminosugars is critical to fine-tune
the enzymatic inhibitory activity. Compared to the monovalent reference,
the best multivalent compound showed a dramatic 800-fold improvement
in the inhibitory potency for JBĪ±Man, which is outstanding for
just a tetravalent ligand. The compound was also shown to increase
both the inhibitory activity and the selectivity for GM over LM. This
suggests that multivalency could be an alternative strategy in developing
therapeutic GM inhibitors not affecting the lysosomal mannosidases.
Dynamic light scattering experiments and atomic force microscopy performed
with coincubated solutions of the compounds with JBĪ±Man shed
light on the multivalent binding mode. The multivalent compounds were
shown to promote the formation of JBĪ±Man aggregates with different
sizes and shapes. The dimeric nature of the JBĪ±Man allows such
intermolecular cross-linking mechanisms to occur
Correction to āTopological Effects and Binding Modes Operating with Multivalent Iminosugar-Based Glycoclusters and Mannosidasesā
Correction
to āTopological Effects and Binding
Modes Operating with Multivalent Iminosugar-Based Glycoclusters and
Mannosidases